Journal of the Scientific Agricultural Society of Finland
Voi. 45: 121-215 1973
Maataloustieteellinen Aikakauskirja

SULPHUR STATUS IN FINNISH CULTIVATED SOILS
Selostus: Suomen viljelysmaiden rikkitila

JOHAN KORKMAN

Department of Agricultural Chemistry, University of Helsinki

Academic dissertation

TO BE PRESENTED, WITH THE PERMISSION OF

the Faculty of Agriculture and Forestry

of the University of Helsinki, for public

criticism in Auditorium XII on May 16, 1973,
at 12 o’clock

SUOMEN MAATALOUSTIETEELLINEN SEURA HELSINKI

https://www.c-info.fi/en/info/?token=2e13BWwKxEj7Z0sq.7I7P2n2e2kpnx5s_gfd_zg.rZhcULFXKpz1027S6kkvxFtzAyvbf4qkIhi28AiNR6jCs69Suo71tbUZU3NwTu8q8dIbwl70tQazEPUBWm32xhYmvNWmem1ABj2HntdhqyPLHJhGlXboCCx77BnCozLjgrPJ5vrhkgFYG2MbV5vUIfGOVmE1eAPMjoBw




123

Preface

This study was carried out at the Department of Agricultural Chemistry, University of
Helsinki. I owe a debt of gratitude to my teacher. Professor Armi Kaila, Head of the Depart-
ment, for the support she gave me in my work over a long period of time.

It is my pleasure to thankProfessors Viljo Puustjärvi and Helge Gyllenberg for check-
ing my work and giving me valuable, constructive criticism.

The field experiments were established in cooperation with Dr. Paavo Elonen and Dr. Osmo
Kara in southern Finland and with Veli Tuomikoski, M. Sc., in northern Finland. I wish to
thank these colleagues for their productive cooperation.

The translation of the Swedish manuscript into English was made by a working team consist-
ing of Karl-Johan Ahlsved, B. Sc., Paul Erlewein and Marxyn Summerhill. The Finnish
summary was checked by Dr. Antti Jaakkola. I want to express my appreciation for their
work.

In the practical laboratory work I was assisted in a praiseworthy manner by Miss Oili
Tanska during the whole study.

I have received financial aid for this studyfrom the Rikkihappo Oy :n tutkimussäätiö (Research
Foundation of Rikkihappo Ltd). During the period Sept. 1971 Dec. 1972 I was ex-
clusively making research work on the strength of these grants-in-aid. The translation was
aided by the Svenska Vetenskapliga CentralrAdet (Swedish Scientific Central Board in Finland).
A travel grant from the Agronomien Yhdistys (Finnish Association of Agricultural Graduates)
made it possible for me to visit research institutes in the Nordic Countries in 1969. Among all
persons I met during my trip, I especially wish to thank Professor M. odelien at NLH, Norway,
for his valuable advice.

Finally, I am grateful to the Scientific Agricultural Society of Finland for accepting my
paper for inclusion in its series of publications.

Helsinki, March 1973
Johan Korkman





125

CONTENTS

INTRODUCTION 127
Sulphur research in plant husbandry and soil science 128

ANALYTICAL METHODS 131
A. Determination of sulphur in solutions 131

I. Determination of sulphate sulphur 131
a. Gravimetric determination of sulphate sulphur 132

Procedure of analysis 132
b. Titrimetric determination of sulphate sulphur 132

1. Procedure of analysis 133
2. Reliability of method 133

c. Turbidimetric determination of sulphate sulphur 135
1. Procedure of analysis 135

2. Reliability of method 135
11. Determination of sulphide sulphur 136

Procedure of analysis 137
B. Analytical methods for soil and plant samples 137

I. Pretreatment in laboratory 137
11. Determination of the total suphur in soil and plant samples 138

1. Procedure of analysis 138
2. Reliability of method 140

111. Determination of elemental sulphur in soil 142
1. Procedure of analysis 142

2. Reliability of method 143
IV. Determination of various criteria of soil sulphur available to plants 143

a. Determination of the sulphur extractable with 1 % NaCl 144
1. Procedure of analysis 144
2. Reliability of method 144

b. Determination of the sulphur extractable with 0.03 M NaH2P04
• 2H a O in a 2 N

acetic acid 145
1. Procedure of analysis 145
2. Reliability of method 146

c. Determination of the sulphur extractable with ammonium acetate of
pH 4.65 147
Procedure of analysis 147

C. Other laboratory methods 147
SULPHUR BALANCE OF THE SOIL 149
A. Sulphur emission into the atmosphere 149
B. The absorption of atmospheric sulphur into the soil 152
C. The sulphur in the precipitation 153
D. Sulphur in fertilizers 156
E. Leaching of sulphur 159
F. Sulphur consumption by plants 162



126

G. Sulphur balance of cultivated soils in Finland 163
SULPHUR IN THE SOIL 166
A. Chemical survey of the sulphur situation in cultivated soils in Finland 167

I. Series of soil samples providing the basis of the survey 167
11. Total sulphur and elemental sulphur 169

111. Chemical criteria for sulphur available to plants 173
a. Sulphur extractable with NaCl, NaHaP0 4-CH3COOH and CH3COONH4 173
b. Mobilization and immobilization of extractable sulphur at incubation under

laboratory conditions 175
B. Supply of sulphur in pot experiments 176

I. Pot experiment technique 177
11. Yields and their dependency on the characteristics of the soil 178

C. Sulphur supply in field experiments 182
I. Experimental results from North Finland 182

11. Experimental results from South Finland 184
D. Comparison between field and pot experiments 188

DEPENDENCE OF THE AVAILABILITY OF SULPHUR TO THE PLANTS
UPON THE SUPPLY OF CERTAIN OTHER NUTRIENTS 190
A. Relationship between sulphur and nitrogen 190

I. Physiological effect of ammonium nitrogen and nitrate nitrogen on the sulphur
supply 190

11. Dependence of yield upon the N/S ratio of the substrate 192
B. Pot experiment with sulphur and phosphorus as variables 197
C. Pot experiment with sulphur and molybdenum as variables 199

DISCUSSION 202

SUMMARY 204
REFERENCES 206

APPENDIX 211
SELOSTUS 214



127

Korkman, J. 1973. Sulphur status in Finnish cultivated soils. J. Sclent.
Agric.- Soc. Finl. 45: 121—215.

Abstract. A method for determining total sulphur in plant material and soil samples using
the induction furnace technique and subsequent turbidimetric determination of sulphate
sulphur was discussed. A procedure for extracting sulphur from soil samples with ammonium
acetate (pH 4.65), the interference of the organic matter being reduced by oxidation of the
extract with H 2Oa, was proposed.

Sulphur balance in Finnish cultivated soils was estimated by taking into account the average
amounts of emitted (8 kg S/ha/yr.), precipitated (8 kg S/ha/yr.) and leached (8 kg S/ha/yr.)
sulphur. The actual situation in the cultivated soils seems thus to be depending, on an average,
on the uptake by plants and the sulphur applied (12 kg S/ha/yr. in the early 19705).

In 104 samples of cultivated soil, the content of total sulphur showed a slight correlation
with the content of organic carbon. The amounts of sulphur extracted in various ways were
not predictable by means of the soil characteristics used (pHCaCi 2, org. C and texture). Ex-
tracted sulphur did not correlate sufficiently with the development and sulphur uptake of plants.

Under field conditions in northern Finland, sulphur application produced a relatively dis-
tinct result in respect both to the ley yields on Carex peat, and their sulphur content. On mineral
soils in southern Finland the yields were unaffected by supplementary fertilization with sulphur.
In the pot experiments performed a fairly close relationship between sulphur and nitrogen was
demonstrated.

Introduction

Sulphur is essential to plant development. The sulphur supply situation
of cultivated plants in Finland is examined in the present work.

A thorough study of methods is necessary on account of the absence of
analytic methods sufficiently tested in Finland, particularly in respect of soil
analysis. However, the reported methods are of a provisional character insofar
as they concern the sulphur in cultivated soil available to plants, and further
investigations are required in order that the methods may provide results
that are reliable and more easily interpreted.

The considerable supplement that plants and soil obtain from the atmosphere
and from precipitation is a significant feature of the sulphur economy. Within
the scope of the present work it will consequently be necessary to estimate
the amount of sulphur supplied in this manner. Impoverishment of the sulphur



128

supply in the soil through leaching also contributes towards making the sulphur
situation in the soil more unstable than is the case with most other plant nu-
trients.

Sufficient information about the sulphur contents of cultivated soils in Fin-
land did not exist, and an inventory was consequently made in the present
study with the intention of providing a preliminary notion of the sulphur
contents of these soils and the solubility of the sulphur. The importance to
cultivated plants of this solubility is investigated by comparing the results of
the chemical analysis with sulphur uptakes in pot experiments. The uptake
of sulphur in ley and cereal was investigated in a few field experiments.

The need of an investigation of the type envisaged in this work arises out
of an essential change in the fertilization practices which has taken place since
the beginning of the 19605. During the whole of that period in which super-
phosphate was the dominant phosphorus fertilizer and also was used as the
phosphorus component in the NPK fertilizers, soils received large amounts of
sulphur in connection with the phosphorus fertilization, for superphosphate
contains some 12 per cent of sulphur in the form of gypsum. The switch to
NPK fertilizers based on phosphoric acid, with a consequent sharp decline in
the use of sulphur and a concurrent sharp increase in fertilization with nitrogen,
phosphorus and potassium, has caused a complete change in the situation in
a few years. It is of interest at the present stage to discover how low the use
of sulphur may be allowed to fall in relation to the use of other nutrients before
the shortage of sulphur limits the yield.

Sulphur research in plant husbandry and soil science

The use of gypsum (CaSO 4
• 2HaO) as a fertilizer has very old traditions. Its

use has apparently been long known in China, and Pliny (Honcamp 1931, p. 5)
mentions that gypsum was a substance that the Romans employed for improve-
ment of the soil. The first actual field experiment with results saved for
posterity was one performed by Mayer at Kupferzel in Switzerland in 1768
(Alway 1940). Field experiments with gypsum were also carried out in the
United States of America. Benjamin Franklin initiated a famous experiment
in which, along a road leading to Washington, D.C., gypsum was spread out
on a field so as to form the words »This has been plastered». Some time later
passers-by could read this text clearly in the form of a rich growth. The agri-
cultural chemists of that day did not quite know what the effect of gypsum
depended upon (odelien 1957), and sulphur research was to experience a number
of vicissitudes.

Sulphur was referred to as an indispensable plant nutrient as early as the
middle of last century, by Justus von Liebig in his classical work on the use
of chemistry in agriculture (1862, p. 86). Liebig’s view was largely based upon
results of plant analyses and observations on plant and animal physiology.
Sulphur research experienced a period of success at the end of the 19th century
and very beginning of the 20th century, when encouraging results were reported
concerning experimental cultivations with a great number of plants of various



129

species (Bogdanov 1899, Duley 1916, Ames and Boltz 1919). Sulphur fer-
tilization appears to have produced a particularly great increment in yield in
those cases in which organic residuals such as blood meal and cattle manure
were coincidently applied to the soil (Vermorel and Danthony 1913).

The use of sulphur fertilizers such as gypsum (CaSO4
• 2H2 0) and flowers

of sulphur (S 8) experienced a sharp increase in commercial farming during
that time. In Norway, for instance, 7.4 times as much sulphur as nitrogen
was added to the soil with artificial fertilizers in 1908 (odelien 1970). It soon
became obvious, however, that yields could not continually be increased with
sulphur alone, without the simultaneous addition of other nutrients too (Fian-
netto 1912). The dominant position of superphosphate among the fertilizers
made the secondary use of sulphur fairly great also.

By means of a pot experiment the Japanese Daikuhara (1907) had already
shown that the concentrations of sulphate sulphur which are required in the
soil in order that plants might develop normally are rather small. In many
experiments the yield increase produced with sulphur fertilization was low,
and some research workers doubted whether it was expedient to employ sulphur
at all (Söderbaum 1919).

The indirect effects of the sulphur doses in the soil then began to attract
attention. Sulphur seemed to increase the availability of phosphorus in the soil,
at least in soils rich in lime (Lipman et al. 1916, Tottingham and Hart 1921,
Chapman 1936). Sulphur addition increased the mineralization of nitrogen
from organic material (Scott and Robertson 1926). There was an increase
in the weathering of minerals, and potassium (Shedd 1926) and also magnesium
(Scott and Robertson 1926) were released. Micronutrients are frequently
fixed in forms not easily available to plants when the soil is highly alkaline.
It is consequently possible to correct a disturbed balance of micronutrients in
soils rich in lime by adding substances with acid reaction such as flowers of
sulphur. A certain flocculation of colloidal soil particles seemed to be of benefit
to the soil structure (Scott and Robertson 1926).

Lyon and Bizzell (1918, pp. 72 78) devoted attention long ago to the
relatively high mobility of the sulphate ion in the soil. By means of lysimeter
experiments these research workers (Lyon and Bizzell 1936, pp. 21—22)
found that in humid conditions leaching was a far bigger factor in the consump-
tion of sulphur than was the uptake by plants. The vegetation and the lime
situation were found to have a certain effect on the leaching propensity.

It was realized that a considerable fallout of sulphurous matter occurred
along with precipitation (Erdman 1922, Johnson 1925, Wilson 1926, Vincent
et al. 1935). The stated amounts of sulphate sulphur must be regarded as being
relatively great even today. Erdman (1922) estimates the annual sulphur
quantity in precipitation to have been about 17 kg/ha in the lowa countryside
in the early years of the 19205. On average the fallout is probably not greater
in the countryside today. Other data, too, indicate a rather intensive emission
of sulphur dioxide into the atmosphere. A comparison with more recent results
of analysis is difficult, however, on account of changes in laboratory and sam-
pling techniques. Alway, Marsh and Methley (1937) warn against the risk of
contamination which exists when use is made of ordinary galvanized rain gauges.



130

It was also demonstrated that both plant and soil were able to absorb
sulphur dioxide directly from the air (Alway et al. 1937).

Sulphur research today still proceeds from the fixed points referred to above.
There has been a considerable development in the research equipment, in the
purely analytical as well as the mathematical, but the basic problems of the
sulphur economy of the plant and the sulphur balance of the soil remain the
same. Although more than 1500 scientific articles dealing with sulphur from
an agricultural viewpoint are mentioned in available bibliographies, the research
input in this area is relatively speaking rather modest. The small and uncertain
yield increments produced through sulphur fertilization in experiments during
the 1920 s and 1930 s and later must have contributed to making interest rather
lame.



131

Analytical methods

The determination of sulphur in soil and plant material received most of
the analytical interest in the present work. Every method in these cases has
been the subject of some form of study of the method of analysis before being
approved for use on an extensive scale. The other characteristics of the plant
material and soil samples were generally determined in accordance with instruc-
tions in the literature and are consequently described in main outline only.

The determination of sulphur in soil and plants is often regarded as being
laborious and difficult analytical work. There are two reasons for this state
of things. First, the isolation and conversion of the sulphur fraction into a
determinable form is usually time-consuming and may lead to losses of sulphur.
Second, the determination of the converted and isolated fraction is laborious
when conventional methods are employed. The analysis is often susceptible
to disturbances when the determined concentrations are low.

A. Determination of sulphur in solutions

The sulphur can be determined in a great number of ways, many of which
have been employed for different purposes. This is because none of the existing
methods is definitely superior to the others in terms of sensitivity, reproducibility
or facility. In the great majority of the current methods the sulphur is first
converted into sulphate (S04

=

) or sulphide (S =

) form.

I. Determination of sulphate sulphur

Relatively large amounts of sulphate sulphur are often most reliably de-
termined by gravimetry (Beaton et al. 1968). In practical analytical work
sulphur quantities of approximately I—s mg can be determined depending
upon the sensitivity of the weighing scales used. Quantities below 1 mg of
S0 4-S can be determined by turbidimeter, colorimeter or titration. For large
amounts of sulphur there are a number of simple methods of determination
such as indirect determination by atomic absorption or infrared spectroscopy.

In the present study the sulphate sulphur was determined 1) gravimetrically
from fertilizer extract, 2) titrimetrically from soil extract, and 3) turbidi-
metrically in determination of total sulphur by combustion gas analysis and
from certain soil extracts.



132

a. Gravimetric determination of sulphate sulphur

A barium chloride solution is added to the solution in which the sulphate
sulphur is to be determined, and barium sulphate is precipitated.

Only 2.2 and 4.1 mg of barium sulphate are soluble per litre of water at 18° C
and 100° C respectively (Handbook of chemistry and physics 49th ed.,
1968—1969). In solutions that are slightly acid the solubility of barium sulphate
is somewhat higher (Kolthoff and Sandell 1950, p. 329), but in order to avoid
the precipitation of barium phosphate, barium carbonate or barium hydroxide,
however, the precipitation reaction should be carried out in acid conditions.
Calcium and trivalent iron also precipitate easily together with barium sulphate,
causing uncertainty and error in the analysis. Filtration, washing of the pre-
cipitate and weighting are causes of errors which, when the amounts of sulphur
are low, have to be taken into account (Freney 1958).

Pure barium sulphate does not break up into barium oxide and sulphur
trioxide until the temperature reaches 1400° C, but in order to dry the pre-
cipitate and destroy the filter paper it is not usually desirable to raise the tem-
perature beyond 800—900° C, for a higher temperature than this may lead
to partial decomposition if certain impurities are present.

Procedure of analysis (according to Kolthoff and Sandell 1950, pp. 329 339)

Hydrochloric acid is added to a measured volume of the clear extract con-
taining more than Img of S0 4-S to give an HCI concentration of c. 0.05 N.
In order to obtain larger crystals in the precipitate, the solution is heated and
a sufficient quantity of BaCla solution then added. The suspension is allowed
to cool overnight, and the barium sulphate precipitate is recovered on a filter
paper for fine precipitates. The precipitate is dried and the paper destroyed
at 800° C, the weighing being done at an accuracy of 0.1—0.01 mg.

b. Titrimetric determination of sulphate sulphur

For small quantities of sulphur occurring, for instance, in soil extracts,
use is often made of titrimetric or colorimetric methods based upon precipitation
of sulphate sulphur with barium chromate with a consequent determinable
excess of dissolved chromate ions (Hirst and Greaves 1922, Canting 1946,
Saalbach et al. 1962).

Barium chromate may partly coprecipitate with sulphate precipitation, which
must be avoided in the gravimetric method but is of no account when the
excess of free chromate ions is determined. Small quantities of calcium, mag-
nesium, sodium, potassium, chloride, nitrate, carbonate or bicarbonate (< 25
100 mg per sample) do not interfere with the analysis (Canting 1946). The
phosphate ion may be precipitated before the addition of barium chromate in
order that the precipitation of barium phosphate may be avoided.



133

1. Procedure of analysis (Saalbach et al. 1962)

200 ml of the liquid is pipetted into a 250 ml graduated flask. 5 ml of iron
chloride solution is added in order to reduce the risk of the barium being pre-
cipitated by the phosphate ions in the liquid, and the conditions are made
alkaline through the addition of a few drops of concentrated NH 4OH. Iron
(Ill)phosphate, which is sparingly soluble in a basic solution, is coprecipitated
with iron(lll)hydroxide and organic matter. The flask is kept in a water bath
for an hour in order that the precipitation may be as complete as possible. The
cooled bottle is then filled to the volume mark with water and the precipitate
filtered off. The precipitation of sulphate with barium chromate must be carried
out in an acid solution, but as the chromate solution is an acid one, a suitable
quantity can be added directly to the alkaline filtrate. 200 ml of the filtrate
is put into a 250 ml graduated flask and 25 ml of the acid solution of barium
chromate is added. The flask is allowed to stand for an hour but should be shaken
by hand from time to time. Concentrated NH4OH is then added in drops
until the solution turns alkaline, when the colour will change from orange to
greenish yellow. The flask is then filled to the volume mark and is allowed
to stand for 20—3O minutes before the liquid is filtered through a small-pored
filter paper (MN64Od). The first 30 ml of filtrate is poured off in order to re-

duce the risk that fine particles of barium chromate may enter into the titration,
when the addition of acid would dissolve the chromate and cause a positive
error. 200 ml of the filtrate is put into a conical flask, and 0.5 g of potassium
iodide and 5 ml of hydrochloric acid (25 %) are added. The amount of iodine
set free is titrated ten minutes later with thiosulphate until the added starch
(1 ml) loses its blue colour.

The flask must be washed with HCI after each analysis to remove any
adsorbed barium chromate.

2. Reliability of method

Performed in this manner the method is a warning example of how the
results of an analysis are affected by factors other than those for which the
analysis is intended. A known quantity of potassium sulphate (0.64 mg S)
was added to extracts from 5 surface soils and 5 subsurface soils before the
phosphate and hydroxide impurities were precipitated. The same amount of
sulphur was also added to a pure extraction liquid, and potassium dihydro-
phosphate (0.64 mg P) was further added in one experiment in order to de-
termine the interfering effect of the phosphate ion. Every extract was analysed
in three replicates. The soil extracts were further analysed without the addition
of sulphur, also in three replicates. When these values were subtracted from
the results of the analyses obtained after the addition of sulphur, the difference
constituted a measure of the recovered amount. This amount is shown in Table
1 as a percentage of the total added amount. In those cases in which sulphur
was added to a pure extraction liquid with or without phosphate content, the
total analysed quantity is given as a percentage of the added amount.



134

Table 1. Sulphate sulphur as determined with the barium chromate method using titration
with thiosulphate. The results are presented as the determined amount in per cent of the
calculated.

S = 0.64 mg S as K 2S0 4 P = 0.64 mg P as KH 2P04

min. max. average
% % 0//o

NaCl + S 220 290 250
NaCl + S + P 115 140 125
NaCl extract of surface soil + S 25 100 66
NaCl extract of subsoil + S 115 190 155

Carried out in the indicated manner, the method has a very strong tendency
to give results that are too high (Table 1). This tendency is opposed by other
factors in the extracts. The phosphorus content of the extracts may have
some effect at this stage. The effect of the organic matter in the surface soils
is probably not decisive, because the colouring of the extracts that is easily
caused by the organic matter has been reduced by treatment with activated
carbon, and the rest precipitated by treatment with FeCl 3 . This assumption
is supported by the fact that the minimum value among the surface soils
and the maximum value among the subsoils originate in the extracts of the
peat soil which constituted the experimental series together with four mineral
soils.

The explanation of the variation is assumed to be as follows. The method
has a certain propensity to produce a positive error because some chromate
in excess of the amount corresponding to the sulphate enters into the determi-
nation. This error is compensated for in the extracts of surface soils, even to
too high a degree, through the effect of some unidentified factor which is
present only to a lesser extent in the subsoil extracts. This factor might be the
quantity of easily soluble phosphorus, which in these cultivated soils is probably
higher in the surface layer than it is in the subsoil (cf. Kaila 1963). If this
is the case, it means that some of the sulphate may have become coprecipitated
with the phosphate during the treatment with trivalent iron. The observations
showed, however, that some of the phosphate had not been precipitated during
the treatment with iron chloride but it was precipitated in the form of ammo-
nium phosphate during the treatment with alkali. There is a risk, then, that
some of the excess chromate will accompany the precipitate.

As we have seen, the results of the analyses are of practically no relevance
in absolute terms. The results would probably require correction in respect
of some other factor in the soil extract, perhaps of easily soluble phosphorus.
That a difference may just as well depend on a variation in the phosphorus
content as on one in the sulphur content is very regrettable.



135

c. Turbidimetric determination of sulphate sulphur

Concentrations of sulphate sulphur between 1 and 100 mg per litre can be
determined turbidimetrically. When use is made of a sample of 20 ml, as was
the case in the present work, it means that the determinable quantities of
sulphur are those between 0.02 and 2 mg.

The method is based on the precipitation of barium sulphate, which in
finely divided form can be retained in the suspension by means of a stabilizer
such as gelatin (Dodgson 1961), glycerol (Steinbergs 1953) or gum arabic
(Chesnin and Yien 1951). The optic density is measured by colorimeter with
the use of blue light. The greater the amount of barium sulphate precipitated,
the more turbid will the suspension be and the smaller the transmission of light.

1. Procedure of analysis

In order to obtain results with good reproducibility it is of importance
that the precipitation in the various analyses should take place under identical
conditions. A great number of factors, such as the amount and the particle
size of the crystals of barium chloride, the shaking period and the intensity
of shaking, the temperature and the volume of the flask, have an effect upon the
results. The procedure of analysis used in the present work was, in detail, as
follows:

20 ml of the liquid to be analyzed was pipetted into a cylindrical flask of
100 ml. 20 ml of an acetate buffer solution (pH 4.8) and 2 ml of gum arabic
solution were added. After stirring, 1.0g of barium chloride crystals were poured
into the flask, whereupon the flask was immediately shaken in a »Desaga»
mechanical shaker set at its highest speed of revolution for a period of three
minutes. The measurement of the transmission of the suspension was done
by a »Lange J» colorimeter 20 minutes later, with a blue filter and a 50 ml
cuvette.

2. Reliability of method

When the control series was done in water, the curve became somewhat
S-shaped but fully acceptable in other respects. The time between the shaking
and the measurement was not very critical, although a 20 minute period of
waiting seemed to be the minimum. When the control series was done in a
phosphate solution, the transmission became greatly altered depending on the
length of time it stood. The turbidimetric method as such proved to be unre-
liable with soil extracts and phosphate solutions.

It is necessary that any interfering agents should be reduced in one way
or another. A great improvement can be produced by performing a control
series dissolved in the extraction liquid and allowing it to undergo the same
pre-treatment with H 202 as that undergone by the soil extracts. In the example
shown in Table 2, soil extracts were produced by shaking 10 g of soil (23b)



136

in 100 ml of KH 2P04 solution containing 100 mg of phosphorus per litre for
30 minutes. 25 ml of the filtered extract was thereafter treated with 5 ml
of 15 % H 202 for an hour on a hot water bath. Imlof 20 % HCI was then
added to the cooled extract and allowed to react for one hour, during which
time the extracts became clear. The control series was treated in the same
manner.

Table 2. Turbidimetrically determined recovery of sulphur added to a KH2P04 (100 ppm P)
extract of a loamy clay. The extracts were treated with H 202 and HCI prior to analysis.

Added Analyzed Difference
mg S mg S mg S

O 0.25
0.04 0.29 O
0.08 0.33 O
0.12 0.38 + 0.01
0.16 0.43 + 0.02
0.20 0.48 + 0.03
0.30 0.57 + 0.02
0.50 0.76 + 0.01

As appears from Table 2, quite acceptable results can be obtained by the
oxidation method. The saving in labour involved in this pre-treatment in com-
parison, for instance, with the ion exchange technique (Nydahl and Gustafsson
1953) is the reason for the selection of this method. Probably, it is primarily
the interfering effect of the organic matter that is eliminated in this way. Un-
fortunately disturbances may still occur on account of other factors in the soil
extracts.

11. Determination of sulphide sulphur

Determination of elemental sulphur and sulphide sulphur in the soil is most
easily effected by analysis of the quantity of hydrogen sulphide, which can be
drawn off under reducing and/or acid conditions. In some cases, when very
small amounts of sulphur are concerned, there may also be cause first to reduce
other sulphur compounds into a sulphide form and then to determine the
hydrogen sulphide that develops (Johnson and Nishita 1952). In the present
work, however, sulphide determination was employed only for elemental sulphur
in soil samples.

The method utilized herein has been described by Barrow (1968) and is
based on titration of the hydrogen sulphide collected in an alkaline solution with
mercury (II) ions and with dithizon as indicator. As long as the solutioncontains
sulphide ions, the mercury (II) ions will not adhere to the dithizon molecule
C 6H 5 —N=N—CS— NH NH C 6H 5 . When all the HgS has been precipitated,
the dithizon and Hg2+ will form a thio-enol complex of a bright red colour
under the prevailing highly alkaline conditions.



It is important that the titration is performed under reducing conditions
for two reasons. Firstly, the sulphide sulphur may be oxidized if air should
enter, and secondly, the indicator turns into diphenylthiocarbodiazon, which
lacks complex-forming characteristics. To avoid this, hydroxylaminhydrochlor-
ide is added (Milton and Waters 1949, p. 47) or the titration is performed in
a nitrogen atmosphere (Barrow 1968).

Procedure of analysis

The hydrogen sulphide released in various ways from the reaction vessel
is absorbed in 10 ml of 1 N NaOH which has been pipetted into a measuring
cylinder of 50 ml. When all the sulphur is released, the delivery tube is dis-
connected from the rest of the apparatus and is left in the absorption liquid.
10 ml of acetondithizon reagent (1 mg dithizon/100 ml glass-distilled acetone)
is added in such a way that the tube will simultaneously be rinsed internally.
The liquid is stirred by letting a weak stream of purified nitrogen gas bubble
into the vessel, and titration with 0.001 N HgCl2 is performed until the dirty
yellow colour at the point of equivalence becomes a bright red. The change
in colour is distinct, although when the amounts of sulphur are large (more
than 0.3 mg S) troubles may occur with a great precipitation of mercury sulphide.

1 mMol HgCl2 is the equivalent of 1 mMol S. As 0.5 ml is reckoned to be the
smallest volume that can be titrated with sufficient precision, 0.015 mg S in
such conditions will be the lower limit for the sensitivity of the method, while
the upper limit runs at 0.3—0.4 mg S for reasons stated above.

B. Analytical methods for soil and plant samples

I. Pretreatment in laboratory

The soil samples comprised some 15 kg. They were spread out to dry at
room temperature (c. 23° C) in thin layers, and the samples were allowed to
dry until there was a balance between the humidity of the laboratory atmosphere
and that of the soil samples. The dried soil was divided up into two portions,
the smaller portion of which was ground in a rotating crusher in which all
particles of diameter greater than 2 mm were broken up. The ground samples
were stored in cardboard boxes to be used at chemical analysis. The unground
portion was used in pot experiments after being passed by hand through a
sieve with square apertures of 0.25 cm 2

.

The plant samples were dried immediately upon being collected, in a »Horo»
drying cabinet equipped with a fan. The drying temperature was 50° C, and
drying usually took approximately 24 hours. The period of drying, however,
proved to be somewhat dependent on the amount of plant samples concurrently
in the drying cabinet, and on the consistency of the material to be dried. After
being dried the samples were milled in a »Culatti» hammer mill. In some cases,
for instance for the wood and bark samples, a more powerful mill was required,
however. A »Janke & Kunkel» pulverizer was used in such cases.

2 137



138

11. Determination of the total sulphur in soil and plant samples

The sulphur in the soil consists of many different components that vary
a great deal from one another in characteristics. There are various forms of
sulphur bound to organic matter, inorganic sulphur in difficultly soluble form,
sorbed sulphate sulphur and, finally, sulphate sulphur dissolved in the soil
solution (Wiklander 1957). It is obvious that extraordinarily effective methods
will be necessary in a case such as this, in order that all these fractions may
be converted into a dissolved form that is determinable in analysis. The total
sulphur in the soil (as in plant samples) was determined in the present work
through combustion in a closed system, in a flow of oxygen gas by means of
an induction furnace. Induction furnaces are in quite common use nowadays,
for they require a relatively small amount of work (Jensen 1964, Searle
1968, Lavkulich et al. 1970).

The induction furnace used in this work was manufactured by the »Labora-
tory Equipment Corporation» of Michigan, U.S.A., and was reliable in operation
so far as its vital parts are concerned. With careless use, however, there is a
risk of explosion in respect of the glass and quartz components.

In the furnace the sample is inserted into a high-frequency field within an
induction coil. Magnetic materials are heated in this field through electro-
magnetic induction. Non-magnetic materials such as soil and plant samples
do not heat up unless mixed with magnetic iron powder. In that event the sample
is heated indirectly through the prior heating and melting of the iron. The
manufacturer states that the temperature will rise to above 1600° C.

Round the induction furnace itself auxiliary equipment is mounted for the
purification of the gaseous oxygen and for the absorption of the combustion
gases which are released from the induction chamber (Figure 1). The gas-
purification section consists of there columns, one with concentrated sulphuric
acid, followed by one with »ascarit» and »drierit» and one with a rotometer to
measure the speed of flow of the gas. The absorption section consists of a glass
tube wound inside a heating tape (HT 301, 100 W), which keeps the temperature
at the surface of the delivery tube at about 100° C. The delivery tube is fixed
with a short plastic pipe to a tube with the lower end fitted with a sinter (sinter
density GO) that is inserted into the solution which is to absorb the sulphur
released at combustion.

1. Procedure of analysis

500 mg of finely ground mineral soil (200 mg of organogenic soil or plant
material) are weighed out in a crucible (Leco 528—35 or 528—25, which, however,
has a greater tendency to deform at high temperatures). Approximately 1.5 g
of powdered iron with a low content of sulphur (Leco 501 —78) is added. After
thorough mixing with the aid of a thin glass rod, the crucible is covered with
a porous quartz cover (Leco 528 42).

The current is switched on roughly 15 minutes before use, in order that the
temperature of the heating tape may rise sufficiently. The induction furnace



139

A, gas flow control and gas washing
ar needle valve
a 2. moisture trap with concentrated H2S0 4
a 3. column with ascarite and drierite
a 4. rotometer

B. combustion
br combustion tube (quartz)
b 2. crucible for the sample
b 3. induction coil

C. absorption of combustion gases
Cj. delivery tube with heating tape
c 2. gas washing tube
c 3. vessel for absorption liquid

itself requires a mere 45 seconds of heating, and cannot be turned on until
after that period.

The absorption liquid, 60 ml of 2 % H 202, is measured in the absorption
chamber. The oxygen valve is opened, and the flow velocity is adjusted to 1
litre of 02 per minute.

The combustion is allowed to continue for 12 minutes. The absorption liquid

Figure 1. The most important parts of the induction furnace.



s then removed and put into a beaker of 250 ml, and the unheated part of the
delivery tube is washed with 2% H 202 . The beaker with the gases absorbed
in the hydrogen peroxide is placed on a hot water bath and the liquid is evap-
orated to dryness. The beakers should not be touched with the bare hand
at this stage, for some condensation of excess H 202 may occur up to the upper
rims of the beakers.

The residues after evaporation are dissolved in 10 ml of water, which is
emptied into a flask that is suitable for turbidimetric determination of sulphate
sulphur. The beaker is thereafter washed with a further 10 ml of water, which
is combined with the previous portion. The sulphur is thereafter determined
turbidimetrically in the ordinary manner.

The sinter tube in the absorption chamber should be washed in 1 N NaOH
after some 10 burnings of mineral soils and after three samples of peat or plant
material. If the sinter tube has become blocked for any reason, there is an ob-
vious risk of explosion. Peat samples seem to have a greater propensity than
plant samples not to ignite until the temperature is relatively high.

2. Reliability of method

a. The completeness of absorption was investigated by
covering the first absorption chamber and conducting the gases that bubbled
through into a second, identical absorption chamber and thence to a third.
Sulphate determinations from all the chambers, however, showed that the
sulphur quantities that may have entered chambers 2 and 3 were so small that
they lay below the sensitivity of analysis, which is approximately 0.005 mg of
sulphur per sample.

b. The completeness of combustion was investigated partly
by means of theburning of pure chemicals and partly by the burning of mixtures
of soil and chemicals. Table 3 shows the results that were obtained in a series
with different kinds of chemicals.

Table 3. Recovery of sulphur (%) added as sulphanilic acid, sulphosalicylic acid and potassium
aluminium sulphate in the dry combustion process.

Analyzed amount Recovery
C 6H 4NH 2S0 3 H C 7H 606 S • 2H20 KAI(SO4) 2

• 12H2 0
mg % % %

2.5 94 118 76
5 74 105 69
7.5 92 91 93

10 87 80 90
15 99 86 93
20 74 108 109
30 99 86 97
40 100 98 92
50 99 95 102
mean 1) 91±8 96±9 91±9

l) means ± s-- t 0 05
140



141

Despite the great variation in Table 3, the method was approved primarily
on account of the labour saving allowed. These results indicated a certain need
for a correction factor with a value of approximately 1.1 if account is taken
of the averages in Table 3. However, as there are values that are too high as
well as values that are too low, the introduction of this factor is not warranted
in the opinion of the author. The values that are given in various connections
for the amount of total sulphur are uncorrected. It seems that the uncertainty
would increase when the sulphur quantities get very small, but here too the error
is both positive and negative, and a correction by quantity is consequently
not possible.

As shown in Table 4, the situation is largely the same in those cases in which
the known quantities of sulphur were blended into the soil samples.

Table 4. Recovery of sulphur added as potassium aluminium sulphate to a finesaud soil
(la, 500 mg).

Added Analyzed Recovery
mg mg %

0 0.091
0.081 0.155 80
0.135 0.226 100
0.270 0.345 94
0.405 0.432 84

Investigations showed that there is no reason to make use of accellerators
or »catalysts» other than iron powder. Tin was tried without success, among
the accellerators and molybdenum trioxide and chromium trioxide among the
catalysts (cf. Searle 1968). This is a step that is thought questionable by
Tabatabai and Bremner (1970) too. The great variation that these researchers
complain of in the induction combustion method conforms with the experience
in the present work.

c. The completeness of dissolution after evaporation was
investigated by thorough cleaning of the beakers used in routine analyses. The
sulphur content of the liquid utilized for the cleaning was then determined.
It proved, however, that the sulphur at this stage is very easily soluble, for even
in those cases in which the evaporation pattern could be clearly discerned after
the routine procedure, the sulphur determinations gave no reading.

d. The necessary number of parallel analyses and the
calculation of the results were tested in 32 analyses of equivalent plant material.
In chronological order the results of the analyses were as follows (in mg S/g
plant material): 1.64, 1.13, 1.73, 1.70, 2.12, 1.82, 1.60, 1.72, 1.80, 1.68, 1.72,
1.73, 1.75, 1.61, 1.70, 1.51, 1.10, 1.77, 1.96, 1.62, 2.28, 1.66, 2.24, 1.65, 1.79,
1.67, 1.68, 1.58, 1.73, 1.83, 1.86, and 1.76. The arithmetic mean as well as the
median of the material was 1.72 mg S/g plant material. The moving averages
and the medians for 3, 5 and 15 parallel determinations were calculated on this
material.



142

Coefficients of variation = 100 ~=r% j for the concentration of sulphur calculat-Table 5.

ed from 3,5, and 15 analytical replicates.

replicates
3 5 15

%% %

Arithmetic average 8.25 5.93 1.71
Median 7.40 3.74 1.20

As shown in Table 5, the variation of the medians is smaller than that of the
arithmetic means for all the classes of replication. The reason is that on account
of chance interference the method of analysis may produce results that have
nothing at all in common with the other results. If, on some occasion, the
combustion does not get started, the concentration of sulphur in the matter will
appear to be very low. Contamination of the atmosphere of the laboratory,
of the reaction vessels or of the cuvettes may temporarily produce very high
results. In order that such totally unsuccessful analyses should affect the final
results as little as possible, there may according to Table sbe some reason to
carry out at least three parallel analyses of which the median should be noted.

111. Determination of elemental sulphur in soil

Through examination of soil samples of high sulphur content, Purokoski
(1958) was able to demonstrate the great tendency of sulphide sulphur to oxi-
dize upon contact with the atmosphere. There simultaneously occurred an
accumulation of elemental and sulphate sulphur. A year subsequent to the
beginning of exposure to the air 15 per cent of the inorganic sulphur of the
samples was still in elemental form, while practically the whole of the remainder
was in the form of sulphate. The relative stability of the elemental sulphur
may prompt an analysis of this sulphur fraction for practical purposes too.
The elemental sulphur was analyzed in the present work from a few air-dried
soil samples according to a method worked out by Barrow (1968).

1. Procedure of analysis

50 g of soil is weighed out into an extraction flask and 100 ml of chloroform
is added. The flask is sealed with a plastic stopper or with a cork covered with
plastic film, and is shaken for 30 minutes. 25 ml of clear extract is pipetted
into the reduction flask and is allowed to evaporate on a water bath. When the
extract has evaporated, 2 ml of acetone, 2 ml of chloroform and c. 200 mg of
Fe powder are added.

The flask is connected to the reduction apparatus, the air is expelled from
the apparatus together with the nitrogen gas, and a 50 ml graduated flask



143

with 10 ml of 1 N NaOH as absorption liquid is connected to the gas delivery
tube. 10 ml of HCI (1: 1) is poured into the reduction flask, and the flask is
heated on an electric plate (set at 310°C in the present work) for 15 minutes.

The last part of the gas delivery tube is then disconnected and the tube
is washed with 10 ml of dithizon reagent which is pipetted into the graduated
flask. Titration is carried out immediately in the graduated flask with 0.001 M
HgCl2 . At the point of equivalence, which is easy to discern, the dirty yellow
colour becomes a clear red.

2. Reliability of method

In a simple investigation of method, 3 mg of S 8 was mixed into a finesand
sample (lb) and directly into the extraction liquid respectively before shaking
(Table 6). All treatments had 3 replicates, and in the present modest material
the reliability of the mean was i 6 P er cent with a probability of 95 per cent
when the variance for all treatments was assumed to be identical. In both
cases the recovery of the added sulphur remained at c. 85 per cent. As Barrow
(1968) very correctly pointed out when presenting the method, it will conse-
quently be necessary to calibrate the HgCl2 solution against sulphur samples
that have gone through the entire process of extraction and reduction.

Table 6. An example of the recovery of added elemental sulphur obtained with Barrow s
(1968) method.

Quantity of soil

g finesand (la)
Added
mg S 8

Analyzed
mg S

Recovery
%

50 - 0.08
50 3.00 2.62 85

3.00 2.62 87

Barrow (1970 b) himself reported an unsatisfactory extraction of elemental
sulphur, which is held to be the result of the formation of a protective envelope
of water around the sulphur, which makes it inaccessible to the organic solvent
when the moisture of the soil sample is high.

IV. Determination of various criteria of soil sulphur available to plants

Great efforts have been made to provide a chemical method of estimating
the sulphur reserves of the soil which are available to plants. Criteria for these
are then used indirectly to determine the need for a sulphur increment through
fertilization. Methods for direct determination of the quantitative shortage
have not been reported in respect of sulphur.

All the methods proceed from the extraction of a soil sample with a liquid
free from sulphur which, on account of its ion exchange characteristics, of its



144

acidity or alkalinity or its oxidation capacity, extracts a greater or smaller
quantity of sulphur. The methods by which rather much of the nutrient is
dissolved, frequently give too rough a picture of the possibility the plant has
of taking up the substance from the soil; while weak extractants may cause
technical difficulties in analysis and differences which are too small and unre-
liable between samples of different characteristics.

In order to determine the sulphur in the soil »available to plants» use has
been made of the following extractants at least: water (Freney 1958, Seim
et al. 1969), boiling water and successive treatment with NaCl and Ha 02 (Wil-
liams and Steinbergs 1959, Saalbach et al. 1962, Cooper 1968), 0.005 M
MgCl2 and 0.1 M LiCl (Roberts and Koehler 1968), 1 % NaCl (Saalbach
et al. 1962), 0.15 % (Williams and Steinbergs 1959) and 0.02 N CaCl2 (Salo-
nen et al. 1965), 0.001 N HCI (Lowe 1964), KH2P0 4 (Ensminger 1954,
Williams and Steinbergs 1964), 0.5 M (K 2HPO4 + KH 2 P04 ) pH 7 (Lowe
1964), Ca(H 2PO 4 ) 2 (Rehm and Caldwell 1968, Seim et al. 1969), 0.5 M NaHC03

pH 8.5 (Kilmer and Nearpass 1960), CaC0 3 (Williams and Steinbergs

1964), 1.0 N NH 4-acetate (Rehm and Caldwell 1968), 1.0 N NH 4-acetate pH
7.0 (McClung et al. 1959), 0.5 N NH 4-acetate + 0.25 N H-acetate (Seim et al.
1969), Morgan’s solution = Na-acetate pH 4.8 (Chesnin and Yien 1951, Neller
1959) and 0.3 M NaH2P04

• 2H20 in 2 N H-acetate (Cooper 1968).

a. Determination of the sulphur extractable with
1 % NaCl

1. Procedure of analysis (Saalbach et al. 1962)

50 g of air-dried soil is weighed out in a 0.5 litre plastic flask. 250 ml of 1 %

NaCl solution is added, and the flask is shaken in a mechanical shaker (in the,
present study, of make Desaga) for one hour. 3g of active carbon is then added
and the shaking is continued for a further 2—3 minutes. After filtration, the
sulphate sulphur is determined in accordance with the barium chromate method.

2. Reliability of method

The reproducibility for the sodium chloride extraction and the subsequent
sulphate determination was investigated by performing extractions on 5 surface
soils and 5 subsoil samples with three replicates of each (Table 7). The analytic
average was calculated for the analyzed quantities, no account being taken of
the fact that a smaller quantity of soil was analyzed for soil No. 3 than for the
others.

No statistically significant differences occurred between the replicates of
the analysis, which is an indication that the great variation (x ± 9.5% for
t 0 05 ) is not necessarily due to inferior work in analysis, but rather to pure
chance or to the low number of analyzed samples.



145

Table 7. Analyzed amounts of sulphate sulphur in the case of three analytic replicates.

Sample Soil type
Nr

I II 111 Average
mg S mg Smg S mgS mg S

la finesand 0.63 0.54 0.53 0.57
lb finesand 0.33 0.38 0.35 0.35
2a loam 0.75 0.74 0.61 0.70
2b loam 0.53 0.48 0.47 0.49
3a Carex peat 0.75 0.72 0.69 0.72
3b Carex peat 0.58 0.53 0.55 0.55
4a finesand 0.46 0.56 0.43 0.48
4b finesand 0.57 0.53 0.54 0.55
5a finer finesand 0.90 1.04 1.03 0.99
5b finer finesand 0.71 0.70 0.67 0.69

b. Determination of the sulphur extractable with
0.03 M NaH 2 P0 4 -2H 2 0 in a 2N acetic acid

This extraction liquid was first used by Bardsley and Lancaster (1960)
to extract »soil sulphur» from heated samples. Cooper, however, made use
later on (1968) of the same extractant for direct extraction from soil samples,
and found a close connection between these results of analysis and observations
of symptoms of sulphur deficiency in the field. The method differs from most
others in the sense that extraction and filtration are followed by oxidation of
dissolved organic compounds, which means that the determined fraction con-
sists of dissolved sulphate sulphur, part of fixed sulphate sulphur (phosphate
extraction) and an acid soluble part of the initially carbon-bound sulphur
(acetic acid + oxidation with H 202).

1. Procedure of analysis

10 g of air-dried mineral soil or 3 g of peat soil is weighed out into a 100 ml
extraction flask, and 50 ml of 0.03 M NaH2P04 ■ 2HaO +2 N CH 3COOH is
added. After 30 minutes of shaking, the sample is filtered through dense paper.
25 ml of the filtrate is taken to a 100 ml beaker, and smlof 15 % H 202 is added.
The beaker is left on a hot water bath for one hour. The beaker is then taken
off the bath, and 1 ml of 20 % HCI is added and allowed to react for one hour,
whereupon the solution should become perfectly clear.

The clear solution is poured into a 20 ml graduated measuring glass, and the
beaker is washed with small quantities of water which are then poured into
the glass. Finally, the measuring glass is filled up to 20 ml. From the solution
thus obtained, the sulphate sulphur is determined turbidimetrically but with
the omission of the gum arabic additive.



146

2. Reliability of method

As the turbidimetric determination of sulphate is quite sensitive to small
variations in pH, etc., there is cause to investigate the extent to which the
character of the extraction liquid and the other chemicals needed in the pre-
treatment of the soil samples affect the sulphate determination.

Standard solutions of sulphur with 0.1 mg of S0 4-S/ml (0.4246 g of CaS04/l)
were prepared both in water and in NaH2P04-acetic acid. With these solutions,
standards were prepared containing 0.1, 0.2, 0.3, 0.4 and 0.5 mg of S which
were introduced in the course of analysis before and after the treatment with
hydrogen peroxide. The results (Figure 2) show that it is necessary to use a
standard series dissolved in NaH2P04-acetic acid. Hydrogen peroxide treatment
should also be done on the standard series, as this seems to raise the readings
slightly, perhaps because of a small content of sulphur or through activation

Figure 2. Interference of extractantand H 202 treatment on the turbidimetric sulphate sulphur
determination.



147

of impurities containing sulphur on the glassware. The reproducibility of the
method is not among the best. All the soil samples in the present work were
analyzed with three replicates, and the confidence interval of the average
was as much as % at the 95 per cent level of confidence, provided that the
variance was identical in the analyses in respect of all the soils.

c. Determination of the sulphur extractable with
ammonium acetate of pH 4.65

In view of practical analytical work it was of interest to investigate the sul-
phur quantities extracted with ammonium acetate pH 4.65, as this extractant
is utilized to determine soil fertility in practical agriculture in Finland (Vuori-
nen and Mäkitie 1955).

Procedure of analysis

The procedure of analysis in this case is the same as that in extraction with
0.03 M NaH2P04 in 2 N CH 3COOH. According to accepted practice, however,
the ratio between soil and liquid is measured in units of volume, usually 20 ml
of soil in 200 ml of liquid. Shaking time is one hour.

The extraction liquid is a mixture of c. 62 ml of concentrated acetic acid
(99—100 %) and 45 ml of 25 % ammonia per litre. Control of the pH is
necessary, and correction can be effected through the cautious addition of either
component.

Gravimetric determination of the sulphate with or without hydrogen per-
oxide treatment of the extract did not give satisfactory results. The sulphate
sulphur was consequently determined in this case, too, by turbidimetry after
peroxide oxidation.

In detail, the analysis is carried out as follows. 50 ml of extract is poured
into a 100 ml beaker, 10 ml of 15 % H 202 is added and the mixture is evaporated
on a hot water bath. 1 ml of 20 % HCI is added to the cooled evaporation residue
and is allowed to react for one hour. The content of the beaker is then washed
with small quantities of distilled water into a graduated measuring glass which,
finally, is filled to the 20 ml mark. This liquid is poured into the flask for
turbidimetric determination of the sulphate sulphur which is carried out in
the ordinary way but with the omission of the solution of gum arabic.

C. Other laboratory methods

The determination of nitrate nitrogen is done with an »Orion»
nitrate specific electrode. In these tasks the measurements were made within
the range of concentration of 1-100 mg of N0 3-N/1 extract. For the plant
material the extraction ratio of 1: 125 between plant material and water was
employed. The shaking period was 10 minutes and the solutions were filtered



148

in all cases before determination. The nitrate content of the soil samples was
determined in some cases from different extracts. No steps were taken to
reduce the interfering HC0 3

~ or Cl“. For a detailed study of the possibilities
of the nitrate electrode, reference is made to Myers and Paul (1968),
Paul and Carlson (1968), Mahendrappa (1969), oien and Selmer-Olsen
(1969), Mack and Sanderson (1971).

Determination of the total nitrogen content of the plant
matter was performed with the Kjeldahl method in concentrated sulphuric
acid with copper sulphate as catalyst and potassium sulphate to raise the
boiling point of the acid sufficiently.

The total nitrogen content of the soil samples was
determined by means of a modification (Bremner and Shaw 1958) of the
Olsen method. It proved necessary to use quite small quantities of soil and
large Kjeldahl flasks with the facility of great dilution before alkali addition
at distillation, in order to avoid an all too violent neutralization reaction at
that stage.

The total phosphorus in the plant matter was released
from the organic compounds through heating in a furnace up to 550° C. The
ash was dissolved in 0.2 N HCI and the phosphorus was determined with vana-
date reagent (Quinlan and DeSesa 1955).

The total molybdenum in the plant material was
determined from an ash extract in which the ash was dissolved in 6.5 N HCI
containing 0.5 g of FeCl 3

■ 6H20/litre. The molybdate was determined through
rodanide dyeing by colorimeter after concentration through absorption into
a small quantity of isoamyl alcohol carbon tetrachloride solution (Johnson
and Arkley 1954). For measurement, use was made of a Hitachi Perkin-Elmer
UV-VIS spectrophotometer set at a wavelength of 470 nm.

The content of organic carbon in the soil samples
was determined through oxidation with potassium dichromate (Graham 1948).
The change in the colour of the chromate was measured with the colorimeter
referred to in the previous paragraph and a wavelength of 645 nm.

The pH of the soil samples was measurep in a 1: 2.5 soil 0.02
N CaCl2 suspension. The measuring was carried out with a »Beckman» potentio-
meter and a glass electrode.

The bulk density of the soil was calculated by means of weighing
three parallel samples of 20 ml of ground air-dried soil (Erviö 1971).

The texture of the soil samples was determined by the pipette
method with the pre-treatment recommended by Elonen (1971).

The approximations for field capacity were determined in
the laboratory from ground samples. In this method, the water is sucked arti-
ficially out of the soil samples for 15 minutes, by placing the soil samples in
a 1 cm layer in a Buchner funnel attached to a suction flask.



149

Sulphur balance of the soil

The sulphur situation of the soil and the access of sulphur to plants follow
a slightly more complicated pattern than is the case with most other nutrients.
This is mainly due to two factors. Firstly, the soil receives a considerable in-
crement of sulphur from the atmosphere through precipitation which contains
sulphur, and through absorption from the air. Secondly, plants are not ex-
clusively dependent upon the sulphur supply in the soil, for they are able in
some degree, at least, to satisfy their own needs through sulphur uptake directly
from the atmosphere.

The importance of the sulphur in the atmosphere will be discussed more
closely below, with respect to the sulphur emission into the atmosphere and
the sulphur content in the precipitation. It is further necessary to study the
processes that the soil sulphur may undergo. As in the case of most other nu-
trients, absorption by plants is only one part of the loss of nutrients, while
the leaching with drainage and discharge water and the evaporation stand
for the rest of the loss.

A. Sulphur emission into the atmosphere

On the input side of the sulphur balance of the soil, the fallout with the rain
occupies a significant portion. It is consequently of interest to investigate the
sources from which the sulphur in the atmosphere originates.ln the combustion
of fossil fuels and organic matter containing sulphur compounds, sulphur di-
oxide and sulphur trioxide of varying ratios are formed, depending on the com-
bustion temperature, air supply and presence of soot with catalytic effect in
the combustion chamber (Tikkanen and Yläsaari 1972). However, the
formation of sulphur dioxide seems to be dominant. It has not been definitively
established to what extent and at what reaction speed the conversion takes
place in the atmosphere from S02 to S0 3 and, subsequent to the absorption of
water vapour, to H2S0 4 . At a very high temperature sulphur is emitted from
inorganic substances, this occurring in natural conditions in volcanic areas.
Reduced gaseous sulphur compounds may occur in environments low in oxygen,
such as in mud on the beds of watercourses, in flooded areas and in peat soils
(Takai and Asami 1962).

The sulphur content of the oils used as fuel for heating and power is more
or less completely converted into gaseous form at combustion. The quantities



150

of sulphur that enter the atmosphere in this way are rather big, as can be seen
in Table 8. Refinery products »lighter» than diesel oil contain only very small
amounts of sulphur and are consequently left out of Table 8.

Table 8. Use of oil products in Finland and their sulphur contents.1)

Total use Sulphur content Sulphur amount
1000 tons % 1000 tons

1970 1971 1972 1970 1971 1972

Diesel oil 740 753 788 0.40-0.45 3 3 3
Light oil 3300 3271 3478 0.60 20 20 21
Heavy oil 4300 4538 5110 2.5 108 113 128

Total 131 136 152

•) Laiho, A, 1972. Neste Oy. Personal communication.

With even distribution over the 33.7 million hectares that make up the total
area of Finland, the fallout per hectare originating in the combustion of oil
would have been 3.9 kg of Sin 1970 and 4.5 kg of Sin 1972. There is information,
however, which indicates that a great deal of the sulphur reaches the ground
quite close to the site of emission (Johansson 1959). The true distributionof the
sulphur originating in the various combustion processes is dependent, in other
words, upon the wind and precipitation conditions.

The utilization of coal and coke products is admittedly on the decline at the
moment, but some types are still being used in large quantities in energy supply
and industry (Table 9).

Table 9. Use of coal products in Finland and their sulphur contents.1)

Total use Sulphur content Sulphur amount
1000 tons % 1000 tons

1970 1971 1972 1970 1971 1972

Anthracite 118 96 104 0.95-2.0 2 2 2
Pit coal 267 235 122 0.60-1.8 3 3 2
Slack 2836 2575 2435 0.60-1.5 30 27 26
Coke (imported) 792 665 659 1.0 8 7 7
Crushed coke 51 71 65 1.0 111

Total 44 40 38

*) Imported amounts from Customs Statistics 1972. Sulphur contents stated by the im-
portiny company GHH. 1972.

The sulphur quantities in Table 9 were calculated by multiplying the con-
sumed amounts with the estimated average sulphur content for the various
products. When an estimate is made of the quantities that entered the atmos-
phere, it must be remembered that a early average of 200,000 tons of the pit



151

coal was used to produce 150,000 tons of coke as well as gas. The sulphur in the
gas is recovered in the production process and consequently does not enter the
atmosphere. At a low combustion temperature a proportion of the sulphur
which is difficult to ascertain may, too, remain in the ashes or slag.

In the countryside use is still mainly made of wood for heating and cookinb ,

while industry burns some wood, and some older buildings in population centres
are also still heated by means of wood stoves. In order to get a rough picture
of the sulphur quantities that may be emitted by the fuelwood, a few sulphur
analyses of wood and bark samples were made. The results in Table 10, however,
should be regarded merely as being guidelines, as only two samples of pine and
spruce, one of birch and three of other deciduous trees (aspen, alder and rowan)
were analyzed, with three replicates. The calculations were also complicated
by the fact that the bark component contains considerably more sulphur than
the wood component. In the analyzed samples the ratio between bark weight
and wood weight was 1: 5.6 and this ratio was employed in the calculation of
the sulphur contents given in Table 10 for the various types of fuelwood. The
consumption of fuelwood indicated in cubic metres of solid measure is based
on a preliminary estimate by the Forest Research Institute1), and for the
conversion into weight units the coefficients mentioned in the forest calendar
were applied. The estimated total consumption of fuelwood was thus estimated
to 4.2 million tons in 1972.

Table 10. Use of fuelwoods in Finland and their sulphur contents.

Total use Sulphur content Sulphur amount
1000 m' 1000 tons % 1000 tons

solid volume

1970 1971 1972 1970 1971 1972 1970 1971 1972

Pine 730 701 666 394 379 360 0.010 0.04 0.04 0.04
Spruce 754 729 700 369 357 343 0.015 0.06 0.05 0.05
Birch 4950 4778 4572 3168 3058 2926 0.010 0.32 0.31 0.29
Other hardwoords . 1255 1170 1142 628 585 571 0.011 0.07 0.06 0.06

Total 0.49 0.46 0.44

At a low combustion temperature some of the sulphur may remain in an
ungasified form in the ash. The sulphur in the fuelwood is thus a very insig-
nificant source in raising the sulphur content of the atmosphere.

A large number of industrial processes cause emission of sulphurous com-
pounds into the atmosphere. In its report (1973: 6) the Committee for Air
Conservation and Noise Abatement, estimated the emissions of sulphur
into the atmosphere to be as shown in Table 11, the estimate being based on
data provided by industry.

vj Huttunen, T. 1973. Forest Research Institute, Helsinki. Personal communication.



152

Table 11. Sulphur emission from industrial processes in Finland in 1970. Sulphur from oil
and coal products omitted.

Emitted sulphur
1000 tons

Sulphite cellulose industry 57
Sulphate cellulose industry 13
Oil refineries 28
Fertilizer industry 8
Iron and steel industry 2

Total 108

The great emission by the sulphite pulp industry is primarily a result of the
fact that a very large portion of the sulphite waste liquor is burned. The sulphur
emission from the oil refineries is likely to decrease somewhat in the next few
years, as projected desulphurising plants are taken into use.

Gaseous sulphur compounds might be emitted from peatlands and flooded
areas. Under extremely reduced conditions, when all the dissolved oxygen
has been consumed, all the nitrate and nitrite nitrogen reduced, all four-valent
manganese converted into two-valent form and all dissolved three-valent iron
become two-valent, the sulphate sulphur (S 8+ ) begins to be reduced to sul-
phide sulphur (S2 ~) (Koyama and Tomino 1970). H2S is then first formed,
and it is easily dissolved in the soil solution in large concentrations, especially
when the temperature is low. The sulphide sulphur is then gradually precipitated
in the form of various metal sulphides. The emission of free hydrogen sul-
phide is consequently slight (Takijima et al. 1962).

Methyl mercaptan (CH 3SH) is formed at microbiological decomposition of
the sulphur-bearing amino-acids methionine and cystine, but may under cer-
tain circumstances be formed from hydrogen sulphide and fermentation prod-
ucts from the decomposition of organic substances (Takai and Asami 1962).

In the atmosphere the reduced gaseous sulphur compounds are soon oxi-
dized, and it is consequently impossible to distinguish these sulphur impurities
in the atmosphere from those entering in a different fashion. It seems that
nobody has ventured an estimation of the sulphur quantities in question, and
the relative importance of these phenomena in the local or global sulphur
balance. In as marshy a country as Finland it would be interesting to inves-
tigate such questions as well as the gas emission from peatlands in general,
together with the importance thereof. Oden (1968, p. 12) suggests that there
is a conversion of the sulphate sulphur in fertilizers into hydrogen sulphide in
ordinary cultivated soils too a question that may well deserve further study.

B. The absorption of atmospheric sulphur into the soil

The soil surface absorbs some sulphur from the air beyond the amounts that
fall out with precipitation. Sulphur dioxide, a gas easily soluble in water, is
pressed by the turbulence of the atmosphere against the soil surface and is



dissolved into the soil moisture. A dry surface may thus be expected to absorb
less sulphur than would a wet one, and a covered surface less than a bare one.
It must certainly be the microclimate that ultimately determines what amount
of sulphur is absorbed. Johansson gives some estimates of this amount in his
thesis of 1959. He demonstrates how the absorption of sulphur from the air
in cultivated pots provides a greater sulphur increment than does precipitation.
The directly absorbed amount was relatively highest when the amount of
atmospheric sulphur was at its greatest, which may be an expression of the
importance of the constant contact between the atmosphere and the soil surface,
while the contact between raindrops or snowflakes in the precipitation and the
very lowest layers of the atmosphere, in which sulphur pollution is at its most
intensive, is naturally very brief and occasional.

Some of the sulphur that the plants absorb from the atmosphere may be
carried to the roots and excreted into the soil, which may thus indirectly obtain
an increment of sulphur from the atmosphere through the plant (deCoßMis
1968). In other words, it has not been unequivocally established whether a
bare soil or an overgrown soil fixes more atmospheric sulphur.

C. The sulphur in the precipitation

The sulphur emission from various sources results in a certain sulphur content
in the atmosphere. How high this content is, depends on the closeness to the
source of emission (Johansson 1959), but also has a certain connection with
the total emission in our entire continent (Oden), as some of the sulphur that
has entered the atmosphere may be transported over long distances with the
global movements of the higher atmospheric layers. A marked local increase
in the deposition of sulphur can be traced only for a distance of a few kilometres
from its source (Johansson 1959). On the other hand, the sulphur emissions
in the industrial regions of Western Europe are held to influence the basic
level of sulphur fallout even in the Nordic countries (Oden 1968).

The results reported in the present work are based upon analyses and sam-
pling performed by the Institute of Marine Research in Helsinki. The processed
material covers the period December 1, 1965 to November 30, 1970, i.e., a period
of five years. The precipitation was collected for a month at a time at a total
of 10 sampling sites in various parts of Finland. Representative samples of
the precipitation of the month were sent to the Central Laboratory of the In-
stitute of Marine Research for analysis. Unfortunately, the amount of sulphate
sulphur is determined by means of precipitation of the sulphate with barium
chromate and a colorimetric recording of the change in the colour of the chromate,
and here, too, allowance must be made for a possible interference of phosphorus.

In the present work statistical processing was carried out on the previously
unprocessed material consisting of the quantities of precipitation and the
sulphur content in the precipitation. Of the total of 600 precipitation samples
that were analyzed, the sulphur content of 15 had remained undetermined.
The commonest reason for this omission was that the amount of rain during

3 153



154

the period had been small (o—l 9 mm). On account of this the 15 samples
were given the value of 0 for sulphur fallout in the calculations.

Table 12 shows the sulphur fallout during the successive twelve-month
periods for the various sampling sites.

Table 12. Sulphur amounts in precipitation. Mean values for the five twelve-month periods
between Dec. 1, 1965 and Nov. 30, 1970.

Position Sulphur in precipitation
S kg/ha per year 1)N E

Helsinki 60°11' 24°58' 18,5 C

Tvärminne 59°54' 23°12' 11.2b

Sodankylä 67°22' 26°39' 8,8 ab

Kuopio 63°00' 27°44' 7.8ab

Punkaharju 61°48' 29°20' 7.0ab

Jyväskylä 62°24' 25°40' 6.6ab
Kuolio 65°48' 28°35' 5.9a

Kauhava 63°06' 23°03' 5.7a

Hailuoto 65°00' 24°45' 5.5a

Pudasjärvi 65°24' 26°55' 5.0a

1) Means followed by a common letter do not differ at P = 0.05.

The averages of Table 12 were treated with the Duncan (1955) test to
ascertain any differences between the various periods and the various places.
The indices show that Helsinki experienced a significant increase in sulphur
fallout in comparison with the other sampling sites. In Helsinki it is the settle-
ment of population and industry that have been responsible for the emission
of sulphur into the atmosphere. Tvärminne research station on the peninsula
of Hangö seems also to have had a slightly higher fallout of sulphate sulphur
than some of the other sampling sites at least. It must certainly have been the
sea foam drifting in over the coast that influenced the sulphur content of the
precipitation there. A sulphur fallout of approximately 5 kg per hectare yearly
seems to be expected in relatively sparsely settled non-industrialized parts,
too, such as Pudasjärvi and Kuolio.

Treatment of the entire material reveals no significant differences between
the various periods of twelve months. The total period of sampling is also too
short to indicate any rising or declining trend. Nor could any significant differ-
ences among the months be obtained from the material when the total period
was divided into months with the various years as replicates. This situation
is to be expected in those cases in which no local sources of emission can be
assumed to contribute to the fallout. By contrast, the local emission of sulphur
is dependent on such things as the intensity of combustion during the respective
period (Johansson 1969). For a closer study of any monthly variation, the
results of analysis for Helsinki were processed (Table 13) in a separate statistical
test.

The results did not unambiguously indicate that the fallout was highest
during the winter months. The location of the town, on a headland in the Gulf



155

Table 13. Monthly sulphur content in rainwater collected in Helsinki during the period
Dec. 1, 1965 - Nov. 30, 1970.

Sulphur content
S kg/ha1)

January 1.3abc

February 1.0ab

March 1.2abc
April 2.3 C

May 1.2abc

June 0.8a

July I.Babc
August 1.2abc

September 1,6abo
October 2.2bc
November 2.0abc
December 1.9abc

*) Means followed by a common letter do not differ at P = 0.05

of Finland, makes the atmospheric pollution generally slight. The fallout of
sulphur with precipitation was markedly greater in April than in February
and June and markedly greater in October than in June. Whether the absence
of the expectedly great fallout for the coldest period, from December to March,
is due to chance or might have something to do with other factors, was not
settled within the scope of the present study. A factor worth investigating in
the future might be the tendency of sulphur pollutions to become absorbed in
rain and in snow respectively. In other words, investigations should be made
on the question whether rainfall cleanses the atmosphere better than does the
same amount of precipitation in the form of snow.

There is plenty of information in the literature about sulphur fallout in
precipitation in various parts of the world. For a thorough study of these ques-
tions, reference in made to the excellent paper by Coleman (1966). It may be
pointed out in a quite general sense that the fallout in industrialized zones may
rise extremely high while the fallout in sparsely populated areas in Germany
and Denmark seems to fluctuate around 10 kg of S per hectare per annum, in
Sweden between 5 and 10 kg of S per hectare per annum and in the Swedish
fells in the north some 2—3 kg of S. The lowest recorded amounts (less than
1 kg of S per hectare per annum) are reported from Australia, New Zealand
and Kenya.

The quantities of sulphur recorded for Finnish conditions in the present
work fit the picture quite well. Encouraging, too, is the fact that sulphur
quantities that are high in international terms were not recorded even in in-
dustrialized and densely settled areas. The calculated fallout is nevertheless
on the high side rather than on the low side, if the discussion is strictly limited
to the sulphur conveyed to the soil with the precipitation. This is due to the
fact that solid particles containing sulphur may be deposited on the collecting
vessel even during drought. Some of the very high readings for months of low



156

precipitation seem to speak in favour of this assumption. As it is difficult to
draw the mentioned distinction between the sulphur really dissolved in the pre-
cipitation and the solid particles of soot and dirt deposited on the collecting
vessel and dissolved in the collected rainwater, it is probable that most if not
all the values stated in the literature are recorded in the same way. This pro-
cedure is advantageous for the determination of the importance to cultivated
plants of the sulphur content of the precipitation, because the solid particles
can be as easily dissolved in the soil as in the reservoir of the water gauge.

D. Sulphur in fertilizers

A large proportion of the sulphur utilized by cultivated plants is that added
to the soil by fertilizers. Although intentional fertilization with sulphur on a
field scale has not been carried out to any great extent in Finland, sulphur
has been added to the cultivated soil over the years in large amounts in the
form of impurity and accompanying ion in nitrogen, phosphorus and potassium
fertilizers. An estimate of the annual sulphur dose in the fertilizers was worked
out in the present study from the import and sales statistics collated by the
Market Research Department of the Pellervo Society and from resjilts of analy-
sis from Kemira Oy. In this estimate the deficiency in information concern-
ing the sulphur content, especially before 1945, is probably a greater source
of error than that concerning the amounts employed.

The sulphur content is of little importance from a sales point of view, and
it is consequently possible to offer a product for sale under a single trade-name
and with identical contents of nitrogen, phosphorus and potassium but with
highly varying contents of other agents such as sulphur. Where the older types
of fertilizer are concerned, it was impossible to determine the variation. To
give an example of the kind of variation that may be concerned, and to eluci-
date the cause of the difference between various production batches, a closer
description is provided here only of one certain compound fertilizer
(15—8.8—12.5), which is the dominant type of fertilizer at this moment.

It is reckoned that during the first years of production the whole domestic
output was of a type low in sulphur, of which it contained 0.4 per cent. Since
1968, however, two different production processes have been in concurrent use
for the manufacturing of the abovementioned compound fertilizer. The »DORR»
process gives a product with approximately 2.1 per cent of sulphur, while the
»PEC» process gives one with at least 0.4 per cent. A product containing 4.6
per cent of sulphur has been occasionally produced. The difference in sulphur
content is the result of a varying use of ammonium sulphate in the production
process. In Table 14 the sales during 1968—7l are distributed according
to sulphur content.

The type low in sulphur has thus been the commonest type on the market.
The minimum sulphur content of fertilizer of this type should consequently
always be stated as the most probable content on trade descriptions. In this
connection it gives a misleading impression to state the sulphur content in the
form of an average weighed according to the sales statistics, which has also
been practiced.



157

Table 14. Sale of a certain compound fertilizer (15 8.8 12.5) during the period 1968 —7l
divided according to the sulphur content of the product.

Sulphur content Sale
1000 tons

S% 1968 1969 1970 1971 Total

0.4 148 196 228 198 770
2.1 59 133 112 90 394
4.6 (4.3 in 1971) 0 20 1 88 109

In order to determine the variation in sulphur content within one and the
same process, samples taken at various times from the same production unit
were ordered from the Finnish producer. Four samples from the DORR process
and four from the PEC process were received. After pulverization these samples
were dissolved in 6.5 N HCI, and the dissolved sulphate sulphur was determined
gravimetrically. The sulphur content in both processes slightly exceeded the
declared minimum content: the product from the PEC process contained 0.44
0.58 per cent of sulphur with an average of 0.52 per cent in the dry fertilizer,
while that from the DORR process contained 2.6—2.9 per cent with an average
of 2.8 per cent of sulphur in the dry fertilizer. These variations must be re-
garded as being surprisingly small.

However, the situation becomes more confusing when consideration is given
to the fact that fertilizers are imported into Finland, too, and then sold
in packings identical with those used for Finnish fertilizer. 10 samples of older
types of compound fertilizer (15—8.8—12.5 (11.6)) were collected from a few
farms. The question was one of remaining quantities from the period 1965
71 the origin of which could not, unfortunately, be traced at the time. These
samples were analyzed for their sulphur content in the same way as in the pre-
vious case. The sulphur content proved to lie between 0.65 and 5.9 per cent
with a fairly even spread between these two extreme values. At least that fer-
tilizer with the highest content of sulphur was probably imported.

The total use of sulphur in Finland from the year 1920 to June 1972,
calculated on the grounds described above, is recorded in Figure 3. Throughout
practically the whole of that period the dosage of sulphur was of the same order
of magnitude as the dosages of nitrogen, phosphorus or potassium, which were
inserted into the figure for the sake of comparison. During the years 1955
57 the cultivated soil was supplied with more sulphur than with any of the
other mentioned nutrients. The transition from simple fertilizers to compound
fertilizers and the introduction of fertilizers based on phosphoric acid instead
of ones based on superphosphate have, however, caused a sharp decline in the
use of sulphur in recent years. The sulphur dosage dropped by one half between
1965 and 1972, while the utilization of nitrogen almost doubled during that
period. In the fertilization year of 1970 71, nitrogen and sulphur were utilized
in the ratio of N: S = 5.2: 1. During that time the cultivated acreage amounted
to 2.55 million hectares, and the sulphur utilization amounted to 12.3 kg of
S per hectare when account is taken of the fact that 1,131 tons of the total amount
of 32,453 tons of S were employed in forest fertilization.



158

Figure
3.
Use
of

sulphur,
nitrogen,

phosphorus,
and
potassium
in
fertilizers
in

Finland
during
the
period

1920
1972.



159

E. Leaching of sulphur

The leaching of sulphur compounds, primarily sulphate sulphur, has been
the subject of intensive research. The movement of sulphur in the soil is de-
pendent upon physical factors such as the total volume and distribution of the
soil pores, which factors together characterize the hydraulic conductivity, and
the amount of precipitation and its distribution. The soil structure and texture
have an indirect influence through their effects on the porosity.

The texture affects the leaching also through the fact that there is greater
chemical activity in the finest fractions. The fixation of sulphate to the soil
particles is the stronger the lower the pH value (Barrow 1970 a). The depen-
dence on the pH is held to be valid for both main types of sulphate-adsorbing
material in the soil, i.e., for the positive charges of the clay minerals at the
surfaces of fracture and for the iron and aluminium oxides (Aylmore et al.
1967). In respect of the aluminium oxides, however, an adsorption maximum
could be found at pH 4 (Chao et al. 1964).

The leaching conditions in Finland were estimated in the present work with
the guidance of the results of analysis published by Laaksonen (1969, 1970).
It is an investigation of watercourses made by the Water Pollution Control
Authority, which is performed in respect of all the most important watercourses
in Finland. During 1962—68 sampling took place at above 160 different
sites on average. Samples were extracted four times a year: in the beginning
of March, in the middle of May and of August, and at the end of October. The
estimated proportion of waste water is indicated for the various sampling sites
(Laaksonen 1969). For the purposes of the present work it was necessary
to exclude those samples in which a stated high sulphur content might be due
to a large amount of waste and not to effective leaching. According to the data
supplied by Laaksonen (1969) only 47 sampling sites were absolutely free of
a wastewater load. In order to extend the number of sampling sites taken into
account, if such is possible, the correlation between sulphur content and waste
quantity was| tested in those cases in which the proportion of waste water was
between 0.3 and 1 per thousand.

The total linear correlation coefficient between sulphur content and waste
load for these 47 sampling sites was 0.02, i.e. nonexistent, and these sampling
sites were consequently included in the tests for leaching. The total number
of sampling sites with no or with an insignificant load of waste was consequently
94.

The annual leaching of sulphur per hectare was calculated by taking into
account the average content of sulphur, the average runoff and the size of run-
off area. The relationship between the sulphur leaching per hectare (1) and
the relative areas of cultivated land (2), peatland (3) and lake (4) in the run-off
area was tested by means of linear correlation analysis. The coefficients of
correlation

r l2 = o.43***
ri3

= -0.16
rl4

= 0.29**



160

show a positive although weak influence of the ratio of the area of cultivated
land upon the leaching of sulphur. This can be assumed to be due to cultivation
techniques, and also to a certain effect of settlement and of animal hus-
bandry, the results of increased cultivated acreage. The acreage of peatland
is unrelated to the leaching of sulphur. A weak negative tendency might suggest
some fixation of sulphur in peat soil, but may also be due to other factors such
as the location of the vast peatlands in the northern parts of Finland, where
the sulphur fallout from the atmosphere is at its lowest. In sharp contrast
to the result obtained by Laaksonen (1970) for the whole of the material, a
separate processing of those watercourses that are not recipients of waste
produces a weakly negative correlation between the sulphur and the lake acreage
of the run-off area.

As shown in Figure 4, the differences between various parts of the country
are great. The average leaching was calculated with account being taken of the
total size of the run-off areas (316,300 km2 ) and the total leaching in the investi-
gated areas (218,000 tons of S per annum), and an average was thus obtained
of 6.9 kg per hectare per year. When the four northernmost watercourses were
not taken into account as there were no collection stations for rainwater analy-
ses, an average of 8.1 kg per hectare per year was obtained. The leaching that
actually occurred from the land areas was calculated for that area in the follow-
ing way. From the total area of 198.300 km 2 the water area of 27,300 km2

was subtracted. The quantity of sulphur that fell with precipitation directly
into the watercourses was obtained by multiplying the water area by the sulphur
fallout per unit of area (0.836 tons of S per km 2 per annum), which was taken
from the investigation of precipitation. The sulphur quantity thus obtained
was subtracted from the total amount of sulphur carried off (160,000 tons of
S per annum). When the amount of sulphur thus obtained was distributed over
the land area, the value of 8.0 kg of S per hectare per year was produced, a figure
that will be employed in the discussion on the sulphur balance of the soil in the
next section.

As can be seen, it is difficult to calculate an average for the whole country
from the present material. The difficulty is increased on account of the inad-
equacy of information about a number of areas in southern and western Finland.
The reason for this is that none of the sampling sites on the watercourses in these
areas were sufficiently free of waste load to provide information on natural
leaching from forest and field. The watercourses marked out in southern and
south-western Finland in Figure 4 are probably also relatively more loaded
with rural waste than are the watercourses in other more sparsely settled parts
of the country.

The highest values for leaching come from areas with large stretches that
were sedimented during the period of the Litorina Sea. It has been calculated
that large amounts of sulphur run off every year especially in the western coastal
region. The highest value, one of 91 kg of S per hectare per year, was obtained
for the river Laihia. In his inventory of the sulphur-containing soils of the
coastal regions Purokoski (1959) came to the conclusion that there are nearly
20,000 hectares of sulphate soils in that area. The leached quantities of sulphur
decrease markedly farther to the north, and no similarity can be seen to the



161

Figure 4. Calculated leaching of sulphur (kg S/ha/yr.). Dark areas are omitted because of
waste water interference on the results obtained.



162

vast sulphur-rich areas of which Purokoski (1959) writes. It was unfortunately
necessary to exclude a few interesting rivers of these regions, such as those of
Lapua and Pyhäjoki, and the sulphur-rich areas in question may consequently
be located primarily along these watercourses.

The values for leaching assessed in this manner are relatively low as compared
with the estimates that have been made in Germany (Buchner 1958) and
Norway (odelien 1965). In those studies, however, the question was partly
concerned with lysimeter investigations in which leaching might be somewhat
higher than normal on account of loosening of the soil, and partly with field
observations on well-drained and well-fertilized cultivated soils with a relatively
great run-off of drainage water. odelien (1965) unequivocally demonstrated
that leaching is dependent on the intensity of sulphur fertilization. When forest,
peatland and mountains are included in addition to cultivated land, as is the
case in the present study, the average leaching is bound to be low.

F. Sulphur consumption by plants

It is relatively easy to determine how much sulphur is annually removed
from cultivated lands together with the harvest. Table 15 is taken from the
compilations published by Coleman (1966) and Beaton (1966). The information
on grasses and clover appears to match fairly well with the sulphur uptake
calculated according to the datapublished by Salonen et al. (1965) from Finnish
field experiments (7—14 kg of S per hectare per annunt).

Table 15. Sulphur content of certain crops.

Yield Sulphur content
tons/ha kg/ha

Wheat 2.7 10-13
Clovers 10 17-22
Grasses 10 9-11
Potato 20-22 8-11
Cabbage 40 21-42
Turnips 50 28 30
Onions 40 20-22

It is far more difficult to decide how much the plants actually have taken up
from the soil in various conditions and how much comes from the air directly.
That the importance of atmospheric sulphur should not be exaggerated is shown
by the very numerous field experiments by which increased yields have been
produced through fertilization with sulphur in many parts of the world and
on widely different crops (Beaton 1966). In experimental conditions in which
natural precipitation has been excluded and irrigation carried out with distilled
water, the yield is very highly dependent on the sulphur deposits in the soil
and on sulphur fertilization. This indicates that absorption of sulphur through
the root system in the form of sulphate is the dominant process, at least for
crops with rapid development and high but brief uptake of sulphur.



163

The sulphur in the atmosphere may occur in solid form, as dust and particles
of soot, or dissolved in microscopic droplets of liquid, or in the form of gas
such as sulphur dioxide, hydrogen sulphide and other sulphurous gases. When,
however, the proportion of sulphur dioxide is the highest, it is the uptake of
that gas that has aroused the interest of the researcher. The uptake of hydrogen
sulphide, mercaptans and other gaseous sulphur compounds through leaf and
stem, however, is quite possible and actually likely.

A very high concentration of S0 2 in the atmosphere may cause damage
to plant tissues, with consequent necrosis and defoliation. An atmosphere
with 0.5 —1.5 mg of S02 per cubic metre seems to approach the harmful con-
centration (Faller 1971 a). The concentration of sulphur dioxide is normally
between 10 and 100 times as low as this; and at such levels the uptake by plants
of S02 from the air is an important increment in the sulphur supply (Olsen
1957). In the experiment by Olsen (1957) cotton plants with an unsatisfactory
supply of sulphur in the substrate absorbed far more than half their sulphur
content from the atmosphere. Even when there was a sufficient supply of sul-
phur in the substrate, almost 30 per cent of the total sulphur in theplant came
from the atmosphere. In other experiments with the same isotope technique
(Jensen 1963) the proportion of total sulphur in barley, oats, lucerne (alfalfa),
red clover, turnip and sugar beet which originated in the atmosphere varied
between 13 and 36 per cent. The lowest percentages were obtained at an early
stage of development and with a good supply of sulphate to the root system.
No genuine differences can be discerned between various types of plant.

Plants take up sulphur from the atmosphere in direct proportion to the
sulphur concentration (deCoßMis 1968). Under normal conditions, atmos-
pheric sulphur does not suffice to meet the need of plants (Olsen 1957), be-
cause a high S0 2 content may damage the tissue before a concentration high
enough for the sulphur balance is attained. Plants hardy to S0 2, such as
tobacco, are particularly able to utilize artificially increased sulphur dioxide
as their only source of sulphur (Faller 1971 b).

It would seem that hardiness to sulphur dioxide would be related to the
sulphur uptake of various plants. Cabbage and oil plants, in particular, which
seem able to stand a great deal of S0 2 in the atmosphere, also require large
amounts of sulphur in order to develop.

G. Sulphur balance of cultivated soils in Finland

Input. As seen from the above, calculations have shown that the
fallout of sulphur in precipitation is roughly of the same magnitude
as the emission from utilized fuels and industrial processes. In both these
cases the quantities are in the region of 8 kg of S per hectare per year. A more
important finding than the average fallout, however, is the fact that the »basic
level» of the fallout of sulphur in the rural districts of relatively large parts
of Finland appears to occur approximately in the amount of 5 kg of S per
hectare per annum.



164

Among the fertilizers the decisive role is played by the artificial
fertilizers. It is calculated that the cultivated soil was supplied with approxi-
mately 12 times as much sulphur in artificial fertilizer (12.3 kg of S per
hectare per annum) as in farmyard manure (total of farmyard manure 2.5
million tons of dry matter of a sulphur content estimated at 1 kg per ton gives
roughly 1 kg of S per hectare of cultivated soil per annum).

Take o u t. The basic level of leaching, which was estimated above
at 8 kg per hectare per annum, corresponds with the amount of sulphur in the
precipitation. It is probable that far larger amounts will have to be calculated
with, on account of applied sulphur, when land is more intensively cultivated.
The leaching out of small annual doses may be at a low level during the growing
season, but there is a risk of effective leaching of unutilized fertilizer sulphur
in autumn and spring. The results of odelien (1965) from lysimeter investigati-
ons with radio-active sulphur indicate very strong leaching of applied sulphate
sulphur from fallow land. The poor capacity of soils to fix sulphur makes it
impossible to bring about a long-term increase in the sulphate sulphur content
of the soil through the utilization of easily soluble sulphate compounds. An
assessment of the total extent of leaching in various situations is made yet
more difficult by the fact that some soils nevertheless possess a considerable
capacity to bind sulphate sulphur (Hogg 1966). This applies primarily to clay
mineral of 1: 1 type, in which the positive charge and frequently, too, a con-
tamination with colloidal iron and aluminium oxides possessing anion fixing
properties, are greater than in 2: 1 minerals (Harward and Reisenauer 1966).
The clay minerals in Finland would seem, however, to consist mostly of 2: I
minerals of the illite type, and the sulphate fixation is in consequence probably
rather weak.

The uptake of sulphur by plants depends on the type of plant.
A cereal crop may, roughly speaking, be reckoned to take up 10 kg of S per
hectare per annum; a ley crop between 15 and 20 kg; and a root crop 20—30
kg. The highest amount of sulphur is required by cultivated plants of the
families Cruciferae and Liliaceae, in which sulphur is necessary not only for
protein synthesis but also for the formation of various isothiocyan esters and
organic sulphides, which give these plants their characteristic taste and smell.

It is very difficult to estimate the amounts of direct gas emission from the
soil and direct absorption of sulphur by the soil. In an article (1962) Freney,
Barrow and Spencer, who are all authorities on sulphur, estimated the di-
rect uptake at less than 0.1 kg of S per hectare annually and assumed that the
emission of H 2S may be of importance only in waterlogged stretches and, for
example, in shallow salt-water bays that are uncovered at low tide. The ques-
tion is consequently one of factors of little importance to the total sulphur
balance. Johansson (1959) has put the direct absorption rather high, but
fallout of solid sulphurous particles may have caused an abnormal in crease
in the amount of sulphur in the soil in that case. The sulphur addition from
pesticides, fungicides and insecticides is very small because the quantities
used per unit of area are very low.

Under the outlined conditions, it is the sulphur in fertilizers that must
equilibrate the uptake by plants of sulphur from the soil. Temporarily the



165

weathering of mineral sulphur of the soil may also keep the sulphur supply
at an acceptable level. In such cases fertilization with sulphur is likely to lead
to increased leaching. It would seem that the sulphur reserves of the soil
are often quite large, and that sulphur fertilization might be superfluous for
long periods of time. A reliable estimate by chemical means of the sulphur
situation of the soil would consequently be of importance in Finland as else-
where.



166

Sulphur in the soil

The most important sulphurous minerals of the soil are pyrite FeS 2, pyr-
rhotite FeS-Fe 5S6 , chalkopyrite CuFeS2, pentlandite (Fe, Ni)9SB and bornite
Cu5FeS 4 . Of these, pyrrhotite, pentlandite and chalkopyrite mostly occur in
basic rocks such as gabbro, while pyrite is common in acidic rocks. The sulphur
content of the acidic rocks which are common in Finland is lower than that of
the basic rocks, as can be seen in the following compilation out of the text-
book by Rankama and Sahama (1964, pp. 743 755):

S
g per ton

Gabbro 2000
Granite 500
Alkali pyroxenite 2000
Pyroxenite 3000
Peridotite 2500

Weathered sulphide minerals and volcanic activity may, perhaps, when
very long periods of time are in question, have been of extremely great import-
ance to the global circulation of sulphur, but nowadays most of the »active»
sulphur in the soil occurs in an organic or in an inorganic form that is not min-
eral-fixed (Nelson 1964), and it is consequently the availability in these that
is of special interest.

The organic sulphur of the soil occurs in two main types (Freney et al.
1970). They are a) organic sulphur bound directly to carbon, reducible to S 2~

with Raney’s nickel, and b) covalent bound sulphate sulphur, which can be
reduced to hydrogen sulphide by hydriodic acid. The former group includes
compounds of the same type as cysteine, cystine and methionine, while the
latter group comprises sulphate esters.

The non-mineral-bound inorganic sulphur consists mostly of sulphate sulphur.
In some analyzed soil samples from pastures in Australia the absorbed and
easily soluble sulphate sulphurs together made up 6 per cent of the totalsulphur,
while the more reduced forms of the inorganic sulphur made up 1 per cent
(Freney 1961). In oxygen-poor conditions, however, a relatively large part
of this »active» inorganic sulphur may occur in the form of sulphide and elemen-
tal sulphur. In his thesis (1958) Purokoski showed how easily the sulphide
compounds are oxidated when the soil is kept moistened but in good contact
with the air. In a sulphide clay with approximately 9 g of S per kg of dry soil.



167

a good 60 per cent was originally in sulphide form while 4 per cent occurred
as S0 4 -S, 15 per cent as SB -S and above 20 per cent as organic sulphur. One
month later the sulphide form was almost totally absent, while the proportion
of sulphate had increased to more than 40 per cent, that of the elementary
sulphur to almost 35 per cent, sulphite sulphur occurred to an amount of 5
per cent of the total amount of sulphur, and the organic sulphur had remained
constant.

The redisposition of the sulphur compounds of the soil into sulphate sulphur
does not require any extreme conditions. A reduction of sulphate, however,
does not occur except under highly reducing circumstances;

S0 4
2 + H2O +2 e = S03

2 +2 OH (redox potential = 0.92 V)
(DcVries 1968).

As the redox potential of the soil usually lies between —0.5 and -fO.B
(Jackson 1956, p. 652), the sulphate sulphur tends to become the dominant
and practically only form of the non-mineral-bound inorganic sulphur in the
soil.

A. Chemical survey of the sulphur situation in cultivated soils in Finland

I. Series of soil samples providing the basis of the survey

To get an idea of the sulphur situation in cultivated land in Finland, a series
of soil samples was collected during the summer of 1969. The samples, taken
from the two depths of 0— 25 cm and 25—5O cm, obtained from fields in culti-
vation, form a sparse network covering the southern and central parts of Finland
(Figure 5). The sampling locality was determined in advance from the map,
while the precise sampling site was selected with a view to obtaining the most
representative sample possible of the dominant soil in the locality. Appendix

1 gives a few important general characteristics of the series of soil samples
obtained in this manner. The total number of samples was 104, of which 62
were surface soil and 42 subsoil, taken from 62 different localities.

The sampling localities 1—44 were selected exclusively with a view to sur-
veying the sulphur situation, while sampling localities 45 —62 were selected
partly according to other criteria. 45a is a sample from a zero plot of a long-
term experiment on fertilization and soil improvement at Leteensuo, an ex-
perimental station, later disbanded, of the Peat Cultivation Society. 46a
is from an unfertilized plot of a field experiment of 1969 while 47a and 48a
were taken primarily for use in pot experiments. 49a —62 a are sulphur-unfer-
tilized surface soil samples from field experiments with sulphur fertilization
combined in most cases with field-scale irrigation. The quartz sand was used
in pot experiments.

Of the soil samples, 21 are organogenic, 22 are clay soils, 18 silt and the rest
coarse mineral soils. The weight per volume varies between 0.18 and 1.54 kg
per litre of air-dried soil. The average for the peat soils is 0.32, and for the min-
eral soils 1.06, a fact worth bearing in mind when various extraction methods



168

Figure 5. Map of the sampling localities.



are being developed. The choice between an extraction ratio based on volume
and one based on weight becomes difficult if identical criteria are desired for
organogenic and mineral soils.

The pH of the samples varied between 3.3 and 6.4 with 80 per cent of all
readings being between 4.0 and 5.4 and the median pH being 4.8. Such a distri-
bution of pH values seems to be natural for Finnish conditions and probably
fairly well represents the pH situation of the country as a whole.

The proportion of oxidizable carbon in the peat samples varies between
29.1 and 50.4 per cent. The latter extremely pure peat is a sample of subsoil.
Generally, very many cultivated peatlands have a substantial depth of soil
in which the carbon content increases with increasing depth. The situation on
mineral soils is the reverse, of course, the subsoil containing on average a mere
1.0 per cent of organic carbon while the variation is great in the surface layer,
an arithmetic mean thereof providing little information.

11. Total sulphur and elemental sulphur

Two criteria for soil sulphur are stated in the present work, i.e., totalsulphur
and elemental sulphur, which appear to be clearly defined chemically. The
analyzed quantities of total sulphur are shown in Appendix 1. The primary
results are brought together in Tables 16 and 17. Sample 57a was not included
in the compilation because it was much too specific.

Table 16. Amounts of total sulphur grouped according to soil type and sampling depth.
Values given in mg S/kg air-dry soil.

Number of Total sulphur
samples min. max. mean1)

All satupies
mould, peat 21 530 2160 1180+220
clay soils 22 120 1140 450 ± 94
silt, loam 18 120 760 410±100
finesand. sand 42 130 700 310± 43

Surface samples
mould, peat 14 530 1810 1130±240
clay soils 15 310 1140 480±110
silt, loam 10 330 760 520 ±l2O
finesand, sand 22 130 660 350 ± 61

Subsoil samples
mould, peat 7 740 2160 1290±550
clay soils 7 120 790 370±210
silt, loam 8 120 500 280±120
finesand, sand 20 140 700 270± 60

!) means ± Sj • t 0 05 .

4 169



170

For the purposes of a survey of the sulphur supply in the cultivated lands
of Finland the results shown in Table 16 do not provide a clear picture of the
probable occurrence of total sulphur in various soils and at various depths.
The wide limits of confidence indicate that neither classification by type of
soil nor classification by sampling depth will give a reliable picture of the sul-
phur situation. Yet it should be obvious that the organic and peat soils gen-
erally contain rather a lot of total sulphur per unit of weight.

In order to get an idea of the reasons for the variations, the results of analy-
sis for total sulphur were compared with the general properties that had
been determined in the series of soil samples (Appendix 1), the comparison
being done by means of linear correlation analysis. The most important of the
factors that could not be taken into account in this manner are probably the
geological age and origin of the soil samples and the prevailing intensity of
cultivation. Sedimentation during the Litorina period, with high sulphur
content as a result, is assumed to be the case with at least three of the samples,
in which the subsoil contained a surprisingly large amount of sulphur (samples
13b from Purmo, 23b from Karhula and 43b from Rantsila). Samples 13b
and 43b of these were taken several miles from the present coastline of the
Gulf of Bothnia, which shows the immensity of the land elevation in those
parts. Sample 57a, from Perniö, taken from a shoreline pasture more or less at
the same level as the present surface of the sea, possesses a very high sulphur
content originating from a rather recent time. This soil sample, which on account
of its exceptionality was not included in the compilations, shows that the sulphur
contents in the soils which are still being uncovered through land elevation may
rise very high. The high sulphur content in soil sample 60a, from Hausjärvi,
is by contrast probably due to intensive cultivation. Any other explanation
is, in any event, difficult to provide.

In the entire material the total sulphur shows a relatively close correlation
with the amount of organic carbon (r = o.B3***). When the results of the
samples were distributed among mineral and organic soils, however, there oc-
curred a decrease in that part of the variation which could be explained in terms
of differences in the contents of the organic matter. The results of the analyses
on the mineral soils and the regression line for the relationship to the organic
carbon are marked out in Figure 6. The soil samples discussed above have been
ringed in. The content of total sulphur in the mineral soils shows a relatively
close correlation with the organic carbon (r = o.64***). This correlation would
become still closer if a few soil samples with marked character of sulphate soil
were excluded from the material (the ringed-in points in Fig. 6). In the organic
and peat soils the correlation between the total sulphur and the oxidizable
carbon is low (Fig. 7).

No clear correlation between sulphur content and soil reaction could be
demonstrated in the present material despite the fact that a few samples taken
in the coastal regions seem to show in a dried condition a low pH value typical
of sulphate soils and a relatively high content of sulphur (e.g. samples 13b
and 23b).

The elementalsulphur (Table 17) appears to occur in soils in which the content
of the total sulphur is high. The analyzed sulphur, however, may in this case



171

be a pure laboratory product formed at the drying of the samples through
interrupted sulphide oxidation. However, the conclusion drawn is that the
elemental sulphur is not likely to be of any practical importance in surface
soils in the field which are occasionally exposed to drying.

Scattered notes from a number of countries (Johansson 1959, Saalbach
et al. 1962, Jensen 1964, Lowe 1964, 1965, Searle 1968, Seim et al. 1969)
show that the total sulphur situation in Finland does not diverge from that
in other countries.

Figure 6. Relation between the contents of total sulphur and organic carbon in mineral soils.



172

Table 17. Amounts of elemental sulphur in subsoil samples grouped according to soil type
Values given in mg S/kg air-dry soil.

Number of
samples

Elemental sulphur
min. mean1)max.

Mould, peat 5 0.3 5.4 1.9±2.8
Clay soils 7 0.3 7.6 1.7±2.4
Silt, loam 8 0.2 1.1 0.7±0.3
Finesand, sand 20 0.2 2.1 0.6±0.3

*) means ±Sj • tOO5 .

Figure 7. Relation between the contents of total sulphur and organic carbon in mould and
peat soils.



173

111. Chemical criteria for sulphur available to plants

a. Sulphur extractable with NaCl,
NaH 2 P O 4 -C H 3 C OO H and CH 3 COONH 4

The extracted sulphur fractions shown in Table 18 indicate, as does the total
sulphur, a great variation; and a classification by type of soil and depth of sam-
pling hardly facilitates the interpretation of the results. Of these extraction
liquids the NaH2P04-CH 3COOH solution (»PA») has usually been able to extract
the largest quantities of sulphur, and the acid ammonium acetate solution
the smallest, also when the bulk density is taken into account. Extrac-

Table 18. Amounts of NaCl-, NaH2P0 4-CH3COOH-, and NH4 Ac-extractable sulphur grouped
according to soil type and sampling depth. Values for the former two extractants given in mg
S/kg air-dry soil and for the last-mentioned extractant in mg S/T air-dry soil.

No. of NaCl-extractable NaH2P0 4-CH 3 COOH-extr. ClI:I COONH,-extr.
samples min. max. mean 1) min. max. mean1) min. max. mean1)

mould, peat . 21 19 180 82±24 40 350 150±36 2 24 7± 3
clay soils 22 13 120 36±10 14 110 47 +lO 0 180 18±17
silt, loam .... 18 18 180 64±24 15 240 76±37 0 250 34±36
finesand, sand 42 14 120 37± 7 17 160 62±10 1 57 10± 4

Surface samples
mould, peat . 14 24 180 90±35 64 350 160±51 2 24 8± 5
clay soils 15 19 53 32± 7 31 74 49± 8 0 22 8± 3
silt, loam .... 10 18 180 74±39 36 240 91±54 1 250 35±54
finesand, sand 22 14 77 38± 9 28 120 59±11 1 41 7± 4

Subsoil samples
mould, peat . 7 19 130 69±38 40 160 110±36 2 12 5± 4
clay soils 7 13 120 46±35 14 110 43±31 2 180 39±59
silt, loam ....

8 18 110 51±26 15 230 58±59 0 210 33±60
finesand, sand 20 14 120 41 ±l2 17 160 66±19 1 57 13± 7

i) means ± s- • tO .o 5 -

tion by means of these solutions differs in principle from extraction with so-
dium chloride in that the two former, on account of the hydrogen peroxide
treatment of the extracts, also takes off the most easily extractable organic
sulphur while the extraction with NaCl is merely aimed at ascertaining the
amount of soluble sulphate sulphur. It consequently appears strange, initially,
that sodium chloride should have given higher results than extraction with
PA in some cases. This is probably because the 1 per cent NaCl solution, de-
spite the low fixation propensity of the chloride ion, was more effectively able
to release fixed sulphate sulphur than was the weak phosphate solution employed
in the PA method.



174

The NaCl-soluble sulphate sulphur showed a certain correlation with the
total sulphur (r = o.B2***) and, on average, made up 9.5 per cent of the latter.
The correlation with the organic carbon of the soil samples (r = o.s4***) is
completely eliminated when the effect of the total sulphur is reduced. This
material gives no opportunity of ascertaining whether the sulphate thus ex-
tracted was bound in a higher degree with the organic matter or with the min-
eral particles.

That the question is one of a chemically diffuse sulphur fraction which is
extracted in the PA method is shown in the loose relationship with the total
sulphur (r = o.63***). The results were affected by the content of organic
carbon (r = o.6o***), as in the NaCl method, indirectly through an increase
in the content of total sulphur.

The ammonium acetate extraction is interesting insofar as it could easily
be introduced as a routine method, for the same extractant is already being
used for the determination of easily soluble phosphorus, potassium and calcium
in the routine analyses performed to determine the need for fertilization in
commercial farming in Finland. It is important to observe that this method,
in contrast to the previous methods, has an extraction ratio between soil and
liquid that is based on units of volume. When studying the data on bulk
density in Appendix 1, it will be noticed that in this way a 3—7 times greater
weight of mineral soil than of the peat soils will be analyzed. The amount of
sulphur extracted by the ammonium acetate method was quite independent of
the content of organic matter. In the present study this is regarded as being
an advantage, as nothing suggests that the organic matter is of any primary
importance to the sulphur supply of plants.

Sulphur soluble in ammonium acetate constitutes too small a fraction ana-
lytically. Most of the results lie between 2 and 10 mg of S per litre of soil, and
the differences are easily covered by small variations in the techniques of
analysis and in sampling. The low values are also sensitive to agents that may
interfere with the determination of the sulphur. The method seems to give
the most reliable results for soils that contain relatively large amounts of sul-
phur. The extraction seemed to be particularly sensitive to the sulphur in the
soils of sulphate-soil type. In samples 23b, 43a and 43b more sulphur was
extracted with ammonium acetate than with either of the other methods, when
account is taken of the bulk density.

Saalbach, Kessen and Judel (1962) state slightly lower values for extrac-
tion with NaCl than those obtained in the present study, which is probably
due to the higher content of organic matter in the Finnish soils. As shown in
the study of method, the difference may also be due to quite different factors,
such as a higher content of easily soluble phosphorus in the German soils.
The values stated by Cooper (1968) for extraction with NaH2P0 4-acetic acid
in New Zealand also seem low. As the carbon content of the soils in question
is not stated, it can only be assumed that they were rather poor in humus. It
also seems that the soil samples were mainly taken in areas known to be low
in sulphur.



175

b. Mobilization and immobilization of extractable
sulphur at incubation under laboratory
conditions

In order that a single extraction may provide an idea of the chances of plants
to take up a nutrient from a specific soil during the growing period under con-
ditions that are satisfactory in other respects, the method of extraction should
fulfil the following criteria:

1. The extracted fraction must be absorbable in entirety or in determinable
proportion.

2. The quantity of substance mobilized during the growing season must be
closely correlated with the original extracted quantities, or there should
be no mobilization at all.

3. The absorbable non-extractable and non-mobilizing quantity of substance
must stand in determinable relationship with the extracted quantity or
must be entirely absent.
It is consequently only in those cases in which the »intensity factor» in point

1 stands in known relationship with the »capacity factor» in points 2 and 3 that
a single extraction value may provide acceptable information. The part of the
nutrient deposit in the soil mentioned under point 3 is the fraction which,
analytically regarded, is the one most difficult to define. Consequently, the
choice is often made of extraction media that are relatively effective in order
that the absorbable non-extracted fraction should be of as little importance
as possible. In those cases in which an immobilization reaction takes place
instead of mobilization, it must suffice to ascertain whether there is a close
relationship between the value of analysis before immobilization and that after
immobilization.

In order to investigate how the methods used to extract soluble sulphur
relate to point 2 above, an investigation was performed in the laboratory in
the following way. 200 ml of soil was placed in each of a number of 400 ml
beakers and moistened to field capacity. The beakers were stored for 20 days
in a dark room at a temperature of +2o° C. In order to avoid too great a drying-
up in the dry air of the laboratory (relative humidity c. 50 %) the samples were
re-moistened every third day. The number of incubated samples was 97. Sam-
ples 3b, 29a, 30b, 31a, 34a, 38a and 48a had to be excluded, as the amount of
soil in stock was insufficient.

The mobilization that occurred during the period of incubation was deter-
mined in terms of the difference between the extraction results for soil kept
humid for 20 days and those for soil kept dry all the time. Extraction with
ammonium acetate was performed on all the soil samples, while 19 of the soils
(3a, 7a, 7b. 13a, 13b, 17a, 17b, 23a, 23b, 27a, 27b, 33a, 33b, 37a, 37b, 43a,
43b, 47a and 53a) were selected for extraction with 1 % NaCl and 0.03 M
NaH2P04 in 2 N acetic acid. The incubated samples were dried before analysis.

The change during the period1) of incubation proved to be rather small

*) The primary results can be seen in the Department of Agricultural Chemistry, University
of Helsinki.



176

where the extraction with NaCl was concerned. The highest
mobilization and the highest immobilization were 10 mg of S per kg of soil.
On average 2 mg of S per kg of soil was mobilized in the present material, in
which the average for sulphur extracted with NaCl was 67 mg of S per kg.
The amount of mobilization or of immobilization did not stand in any close
relationship with the original extracted amounts.

The extraction with NaH 2 P0 4 tended to produce lower
values after incubation than without incubation. The immobilization in all
the organic and peat soils was high both absolutely and relatively. A certain
equalization of the values of analysis seemed to occur during the incubation.
This might have been the result of changes occurring during extended storage
of the soil samples, even in dry conditions. On average a good 20 per cent of
the extractable sulphur in the peat soils but only 3 per cent of that in the other
soils were immobilized during the 20 days on which the samples were kept
moist. In view of the practical importance of the method of extraction, it was
in any event of interest that the values of analysis before incubation correlated
closely with those after incubation (r = o.97***).

The extraction with acid ammonium acetate showed
no definite correlation between mobilization and original value of analysis.
On average the result of the analysis increased after incubation by one third,
but there were great variations in either direction.

Thus none of the methods of extraction met the criterion under point 2
according to which the mobilization should stand in a known relationship with
the original extracted quantity of substance. As the question of the availability
to plants of the extracted amount of sulphur could not be unequivocally ana-
lyzed, either, the choice of extraction method, for instance extraction with
acid ammonium acetate, must be regarded as being a provisional one pending
further results of research on the chemical status of sulphur in the soil and the
ability of plants to absorb various sulphur compounds (cf. Jones et al. 1972).

B. Supply of sulphur in pot experiments

The only thing that justifies a method of extraction is the attempt to
simulate the nutrient-solving effect of the substances excreted by the plant
roots, the ion exchange occurring between plant roots and soil particles and the
mobilization processes occurring in the soil on account of biological and chemical
activity. The results of the chemical analyses were compared in the present
study with the development and sulphur absorption of the plants in pot and
field experiments in order to ascertain the reliability of the information provided
by the various extraction procedures about the sulphur situation of the soil
samples.



177

I. Pot experiment technique

Pot experiments were carried out in greenhouse and in pot-experiment garden
at premises of the University of Helsinki at Viikki. The area lies in the geo-
graphic centre of the urban district of Helsinki but is not surrounded by any
particularly dense or air-polluting built-up sections. As all the experiments
were performed under roof, the sulphur content of rainwater was eliminated
while absorption directly from the atmosphere might naturally occur. The
pot-experiment garden, for instance, only had netted walls, and the change of
air must have been very effective there at least. The greenhouse department
had automatic aeration in the roof and manual aeration in the walls. The
temperature was adjusted to 20° C by thermostat, but during sunny summer
days this normal temperature was regularly exceeded by s—lo° C.

The vessels, which could hold 0.5 litres of soil, lacked drainage, and leaching
from these pots was thus out of the question. In order to facilitate the exchange
of gases between the atmosphere and the bottom layer in the airproof plastic
pots, a plastic tube of suitable stiffness and width was bent in such a way that
both ends were above the soil while the tube in the soil made a loop towards
the bottom of the pot. In that part of the tube which was to run towards the
bottom a number of large holes were cut to allow the exchange of gases and
liquids. This tube made it possible to water the pots from the surface as well
as from the bottom. It may be a good idea not to have to expose the surface
to the flow of water, especially when the plants are small and the stems weak.

Irrigation was done with water that had been pressed through an ion-
exchange column and then allowed to warm up in a large fibreglass basin under
the glass roof. The requisite amount of water was determined through weighing.
The field capacity for all the soils had been determined in advance in the
laboratory. It was the field capacity thus obtained that was the primary object
of the irrigation. During the most intensive growing period the pots were irri-
gated daily.

Fertilization was administered by means of a single application at the es-
tablishment of the experiments. Table 19 shows the basic quantities of the
various nutrients and the compounds used.

The experiment was started on April 20, 1970 with 87 test soils (soils la-48a
with the exception of Bb, 19b and 21b). All the soils received basic quantities
of all nutrients except sulphur. As the amount of soil available for the exper-
iment was limited, only four pots of each soil could be included. Two of these
pots were fertilized with sulphur (Na 2SO 4 ) while two were left without. Each
pot was sown with twelve kernels of Otra barley. They were cut just before
coming into ear, on June 22, 1970. 14 soil samples (soils 49a —62 a and 21b)
were subsequently added, and these were cultivated together with the repeats of
the older series in an identical experiment between January 20 and March 3,1971.

The stalks were cut right at ground level and were then dried and weighed.
At the later cutting, on March 3, 1971, two persons independently assessed the
effect of the sulphur fertilization according to a scale of 0—4. The differences
in colour, which would not have been taken into account if only weighing had
been performed, were thus recorded.



178

Table 19. »Normal') amounts of nutrients in the pot experiments, and compounds applied in
fertilizing and liming.

chemical compoundmg/1 soil

N 215 Ca(NO 3) 2 • 4H a O
K 125 KCI
P 20 Ca(H2P0 4 ) 2 • H 2 O
Mg 25 MgCl2 ■ 6H2 0
S 20 Na„SO 4
Mn 10 MnCl2
Cu 2 CuCl2 • 2H2 0
B 1 H 3B03
Fe 0.5 Fe-EDTA
Mo 0.3 Na 2Mo0 4

• 2H.X>
Zn') 0.7 Zn-EDTA
CaCOj 1) 895 CaC03

Only in sand cultures.

11. Yields and their dependency on the characteristics of the soil

The yield from the various soil samples varied a great deal on account of
the diversified physical conditions of the soils. The weight of the dried yield
in the first cultivation, without fertilization with sulphur, varied between
0.29 and 9.11 g per pot. The highest yields, with sulphur fertilization, were
about 14 g per pot. Appendix 2 1) shows the primary yield results and the up take
of sulphur in each case separately. In the first cultivation the sulphur fertiliz-
ation produced the greatest decrease in a soil of sulphate-soil character (43a)
and the greatest increase in a Carex peat soil (38a). The dosage of sulphur
produced on average a yield increment of 22 per cent or 0.58 g per pot. In the
pots in which the cultivation was repeated the total yield was mostly somewhat
lower than it had been in the first cultivation, and the dependency on sulphur
was usually unchanged.

The great differences in the produced plant material had the result that the
yield of plant material and sulphur did not, as such, provide sufficient infor-
mation about the sulphur situation in the sampled soils. Instead, the sulphur
situation was assessed on the basis of the increase or the decrease in the yield
of plant matter and sulphur that the fertilization with sulphur caused.

When the averages for the dry matter yield and the sulphur absorption were
tested by t-test, it appeared that in 38 soils (la, 6a, 6b, 7a, 7b, 9b, 11b, 14b,
15a, 20a, 20b, 21a, 25a, 25b, 26a, 26b, 27a, 30b, 33a, 33b, 35b, 37a, 37b,
38a, 39a, 41b, 42a, 42b, 47a, 49a, 50a, 51a, 52a, 54a, 55a, 56a, 61a and
62a) the fertilization with sulphur had caused a signicant increase either in the
yield of plant material or in the uptake of sulphur.

*) Appendix 2 can be seen in the Department of Agricultural Chemistry, University of
Helsinki.



179

An evaluation of the statistical significance of the change in yield was
made impossible in some cases, on account of the fact that the soil sample
was insufficient for more than two pots and no replicate could thus be done,
or on account of the yield being too small for analysis, or for other reasons.
Of these instances, however, a few of the soil samples (Ba, 15b, 46a and 48a)
were thought to have given a positive result from fertilization with sulphur, in
spite of the fact that this could not be statistically demonstrated although it
appeared to be quite obvious.

A total of 42 of the 101 test soils, then, reacted positively to the sulphur
fertilization in the pot experiment with the 0.5 litre pot. Distributed into classes
of soil, these soils are brought together in Table 20 and the averages for the
chemical extraction methods for this »sulphur-dependent» group calculated.

Table 20. Extractable sulphur in soils benefiting from sulphur application in pot experiments.

Number of NaCl-extract. NaH 2P04-CH3COOH-extr. CH3COONH4-extr.
samples mg S/kg soil1) mg S/kg soil 1) mg S/l soil 1)mg S/kg soil 1) mg S/l soil 1 )

Mould, peat 13 100±37 150±42 4± 2
Clay soils 13 26± 5 39±11 6± 3
Silt, loam 5 4l± 7 29±13 6± 3
Finesand, sand .11 30 ± 9 63 ±26 8 ±lO

') means ±s H • t 0

When the averages given in Table 20 are compared with those in Table 18,
which concern all the soil samples, it will be seen that the averages for the soils
that gave a positive reaction to the fertilization with sulphur are in most cases
lower than the average for the respective complete group of soil samples. The
NaCl and PA methods, however, produced an increased or unchanged average
for the organic and peat soils, and this must be regarded as an expression of the
unsuitability of these methods for the analysis of such soils. The PA method
moreover gave an implausible result for the finesand and sand soils.

In order to provide a closer study of the conformity between the results
of analysis and those of yields, the results were distributed according to sulphur
content and to type of soil. The results were converted into volume units by
multiplying the original results by the bulk density given in Appendix 1, be-
cause the same volume of soil was employed in all cases in the pot experiment.
For the extraction with 1 % NaCl the results of analysis, grouped according
to size and soil and compared with the effect of the fertilization with sulphur
in pot experiments, obtained the appearance: 1 = individual soil sample,/
= significant increment in yield of dry matter and/or sulphur.



180

S mg/l soil sand, finesand silt, loam clay soils mould, peat

Ui0-10
n-20 iiii i nami iin
21-30 HHimiiiin im HH iin
3i-4o Hi i i Himi i
41-50 Hun iin Hum H
51-60 Hi in i
61-70 1111 i
71-80 in
si- mi inn i

The conversion into units of volume was necessary for the results of the
extraction with NaCl of the peat soils to be collated into the same classes of
size as the mineral soils. The coarser mineral soils seem to be able largely to
satisfy the needs of the plants also when they contain rather little sulphur
according to the extraction with NaCl.

Classified according to size and soil, the results of the extraction by PA
compared with the effect of the fertilization with sulphur obtained the appear-
ance (symbols as in the results of the extraction with NaCl):

S mg/l soil sand, finesand silt, loam clay soils mould, peat
0- 15.

u an mat16- 30 11
31- 45 HHnn HHn Uintiin UH
46- 60 Hunnini Hm in in
61- 75 Hill 11 Hll Hi
76- 90 Hill i
91-120 11l 1 Hi

121-180 fill! 1
181- i 11

The distribution of the results for the extraction with 0.03 M NaH2P04
2 N CHgCOOH resembles the distribution for the extraction with NaCl. In
this case, too, the extraction seems to provide some information concerning
the clay soils, but here, too, there are examples of dependency on sulphur despite
relatively high results of analysis.

The analysis with acid ammonium acetate as solvent provides directly
similar distributions of results for mineral soils and for organic soils, probably
because of the extraction ratio based on volume (symbols as in previous tabu-
lations):

S mg/l soil sand, finesand silt, loam clay soils mould, peat

o- 3 iUiiiininni tlm Hillin 111Hillin
4- 7 illlllllllllll ll 111 11
8-11 . 11l Itll ll 111

12-15 11l 1 Hill i1 Hill
16-19 tl 11
20-23 1 1 11 11
24-27 1 • 1
28-31
32- til 11 11



181

Few examples of effect of sulphur at high value of analysis give some hope
that the method might be of some importance for the assessment of the sulphur
situation of the soil. In 54 per cent of the mineral soils and 82 per cent of the
organic soils of lowest class, of o—3 mg of S per litre of soil, the fertilization
with sulphur had a positive effect. Especially where the coarse mineral soils
are concerned, there seems to be a need to increase the selectivity of the analysis
as the lowest class, too, contains many samples of finesand and sand in which
the fertilization with sulphur caused no increase either in yield of plant material
or in uptake of sulphur.

The visual assessment of the plants is compared in Table 21 with the results
of the extraction with ammonium acetate.

Table 21. Ammonium-acetate extractable sulphur in soils compared with the visible sulphur
deficiency symptoms in plants.

Number of Positive effect of S applicationGroup
mg S/l soil soils number 0//o

O- 3 40 26 65
4- 7 21 12 57
8-11 11 5 45

12-15 10 3 30
16-19 4 1 25
20- 15 1 7

When assessing the classification provided in Table 21, it must be borne
in mind that the visual assessment was carried out in greenhouse conditions at
a pot experiment with relatively small pots, and consequently with efficient
nutrient uptake. The connection between the various classes and the effect
of the fertilization with sulphur seems obvious nevertheless. Yet it is evident
that the lowest class, too mg of S per litre of soil), contains many soils
in which no improvement of the amount or quality of yield can be obtained
with sulphur fertilization.

On the basis of extensive field experiments Odelien (1965) assumes that
plants can utilize some of the sulphate sulphur that is not extracted by the
ammonium acetate solution used by him. Unfortunately, the pH value of that
solution is not given, but it was probably in the region of 5.8. The higher pH
value (cf. Chang and Thomas 1963) and the wider extraction ratio may have
produced slightly higher quantities of sulphur than those obtained in the pres-
ent study. It might be conceivable, on the other hand, that a lowering of the
pH value of the extraction liquid may be justified in order that the propensity
of the soil to fix sulphate may be raised and the extracted fraction thus con-
fined to the most easily available part. In soils dominated by hydrous
aluminium oxide in the anion-fixing colloidal fraction, a fixation maximum
has been discovered at a pH of 4.0 (Chao, et al. 1964). (How such a soil pH
was measured is not stated, but the question is probably one of soil-water
suspension.) There might be reason not to go under this value in the choice of



182

acidity of extraction liquid. Byrne and Hanley (1970) also obtained the
most reliable results with an extraction liquid with a pH value of 4.8 (Na acet-
ate) when a comparison was made with some other common extraction liquids
(NH 4Ac, CaCl2, Na 2C03 and Ca(H 2PO 4 ) 2).

C. Sulphur supply in field experiments

Without chemical soil analyses and pot experiments it is often difficult to
forecast and explain various occurrences in field conditions. For commercial
farming the results obtained in field experiments in natural conditions, however,
are those of greatest interest. As the experiments arranged in connection with
this investigation of sulphur made use of quite varied experimentation tech-
niques for practical reasons, the technique employed will be described in the
context of the respective series of experiments.

I. Experimental results from North Finland

In 1969 a few field experiments were arranged at Kuusamo, where a peculiar
indifference to increased nitrogen and compound fertilization for ley had been
observed during preceding years. These experiments were established by
Typpi Oy, which had already received complaints in 1968 from fertilizer users
at Taivalkoski and Posio, too, that the compound fertilizers of the manufac-
turer gave poor yields of hay with continued dressings on peat soils. As these
types of compound fertilizer were practically free of sulphur at that time, it
was natural that a deficiency in sulphur should be suspected as being the cause
of the loss in yield.

With the experiments of 1969 there was determination to get an idea of the
causes of the troubles with fertilization, and a very large number of treatments
were consequently included (36 treatments in all), 14 of which had identical
fertilization with nitrogen, phosphorus and potassium and could be used for
comparison of the effect of sulphur. The experiments were in the nature of
demonstrations and consequently lacked local replicates, but they were repeated
at two separate localities (experimental sites 37 and 38), which are regarded
as being replicates in the statistical calculations.

The field experiment was established on timothy leys on Carex peat where
wintering had been as even as possible. The plots were manually fertilized on
June 7. The harvest was movn on July 30 and during the first days in August.
The weather conditions during the experimental period were fairly good, which
can be seen from the results given for the observation station at Kuusamo in
Table 22. The effect of the topdressing was obviously improved by a slight
rain on June 12—13.

In the experiments 216 kg of N per hectare was applied, in the form of ni-
trate and also partly in the form of ammonium. 90 kg of P per hectare was
applied, partly in the form of superphosphate and partly in the form of nitro-
phosphate based compound fertilizer. 108 kg of K per hectare was applied.



183

Table 22. Monthly averages of daily mean temperatures 1 ) and precipitation at some meteoro-
logical stations situated in the vicinity of the experimental fields.

May June July August
°C mm °C mm °C °C mm

1969
Kuusamo 1.9 10.3 14.1 13.3

9.7 34.5 44.3 54.2

1970
Helsinki, Airport 9.9 17.2 16.6 15.8

25.1 11.5 136.1 21.7

Hyvinkää 9.5 16.5 16.0 14.7
30.1 10.2 100.8 30.9

Lauttakylä 9.7 17.1 15.9 14.6
11.8 2.7 124.2 25.8

Salo 9.9 17.1 16.4 15.1
24.0 9.8 133.8 41,9

') Mean temperature 1/4 (tO2+1 09 +t14+t2()) +k, where the empirical correction term
(k) has the following values in various months:

I II 111 IV V VI VII VIII IX X XI XII
-0.04 +O.Ol +0.17 0.00 -0.12 -0.07 -0.15 -0.11 +O.OB +0.05 -0.03 -0.03

either in the form of 60 % potassium salt or as compound fertilizer. The sulphur
was applied partly in the form of gypsum in simple form or in the superphos-
phate, and partly in the form of magnesium sulphate or copper sulphate. As
the yield was not affected by magnesium, copper or boron, the plots in which
the addition of any of these agents caused a changed situation in sulphur
fertilization were included in Table 23 in such a way as if all the effect had
derived from sulphur.

The amount and sulphur content of the timothy yield increased through
fertilization with sulphur. 10 kg of S/ha already seemed to have been enough
to relieve the deficiency fairly well, but a larger dosage of sulphur produced
a further increment in the sulphur content. It is a pity that there were no
sulphur levels between 10 and 54 kg of S/ha, as it is conceivable that the Optimum
dosage of sulphur might lie within theseThmits, considering the intensity of the
rest of the fertilization.

The relatively clear dependency of the yield upon the amount of sulphur
in the fertilizer was expected, although the result is probably the first of its
kind in field conditions in Finland. The surface layer of both experimental
fields had a content of sulphur extractable with ammonium acetate of only
3 mg per litre of soil. There were no local sources of emission of airborne sulphur,
and the fairly intensive cultivation of leys had in the preceding years been car-
ried out with the utilization of fertilizers completely free of sulphur. Other
field experiments of the nature of demonstrations which were performed at



184

Table 23. Yield of timothy grass and its sulphur content in field experiments carried out in
Kuusamo in 1959 on Carex peat. 1)

Added sulphur Number of Average yield Average sulphur
fresh matter content % of

kg S/ha crops tons/ha dry matter

0 7 8.39a 0.13a

10 2 16.60ab 0.15 ab

54 6 19.10b 0.18ab
64 2 18.50b 0.21abc

96 2 17.90b 0.21abc
108 2 20.30b 0.32d

150 4 16.50b 0.25 d

162 2 20.90b 0.22bc

*) Means in each column followed by a common letter do not differ at P = 0.05.

a few other localities in the same region also seemed to show that the area of
acute sulphur deficiency on peat soil extended over the districts of Posio, Kuu-
samo and Taivalkoski. The results of the analyses from experimental sites
39 and 46 also seem to speak in favour of this statement.

11. Experimental results from South Finland.

During 1970 the experimental operations were transferred to South Finland
and comprised ten experiments in which the fertilization with sulphur was
combined with irrigation and three experiments in which the fertilization with
sulphur was combined with supplementary fertilization with nitrogen. The
experimental fields were located on farms with intensive cultivation of cereals,
as it was assumed that any deficiency in sulphur would first reveal itself on
farms where the use of other nutrients was great. On the other hand, no attempts
were made to select the locations with a view to suspected or observed de-
ficiency in sulphur.

The sulphur fertilizer consisted of industrial-grade sodium sulphate (Na 2SO 4 )

with a sulphur content of a good 22 per cent. The solubility in water of the
utilized salt was 378 g/1 at 20° C and 72 g/1 at 4° C according to performed
investigations. The relatively high solubility in water was necessary in order
that the surface-spread fertilizer might act in the soil with sufficient rapidity.
In the experiments with irrigation the fertilizer was spread between May 21
and 28 i.e., little more than a week after sowing, the spreading being done
with Juko-fertilizer placement drills of 2.5 m working width. The fertilizer
coulters were kept close to the soil in order to prevent the wind from carry-
ing off the powdery salt. In the three experiments comprising sulphur fertiliz-
ation in combination with supplementary nitrogen, both the sodium sulphate
and the ammonium nitrate limestone were spread by hand over the soil surface
about one week after sowing, i.e. about May 20.



The weather during summer 1970, expressed in quantity of rainfall and in
averages for the daily mean temperatures at four locations in South Finland, is
shown in Table 22. Helsinki Airport is the location closest to the experiment
at Pakankylä (55), and Hyvinkää may represent the conditions at locations
52, 54, 58, 59 and 60, Lauttakylä those at locations 49, 50 and 61, and Salo
those at 51, 53, 56 and 62. June was extremely dry in 1970 at all the locations,
and the rainfall only amounted to 525 per cent of the average for long-term
observations. By contrast July was rather wet, the amounts of precipitation
being 139—187 per cent of the »normal». Under such conditions the surface
spreading of the fertilizers was an unsatisfactory method. Observations out
in the field, and the degree of ripeness of the harvested product, also indicated
that the broadcast fertilizers were not washed down into the root zone and
could not be taken up by the plants until July.

In the field experiments in which the fertilization with sulphur was combined
with an increased dosage of nitrogen, the idea was that an intensified growth
would speed up the emergence of symptoms of sulphur defiency on account of
the nitrogen supplement. The basic fertilization consisted of 400 kg of com-
pound fertilizer (15—8.8—12.5) per hectare drilled in before sowing. This quan-
tity of fertilizer contained less than 2 kg of S per hectare. Increments of nitrogen
(54 kg of N/ha in the form of ammonium nitrate limestone) or of sulphur (40
kg of S/ha) or of both were applied with four replicates at each experimental
location. The experimental plots were 48 m 2 at two of the locations and 28.8 m 2
at one. The plant was Ruso spring wheat at location 52, Ingrid barley at lo-
cation 55 and Sisu oats at location 56. The nitrogen produced a large number
of green secondary shoots on account of the unfavourable weather conditions,
as appears in Table 24, in the high moisture contents in the cereal from the plots
fertilized with nitrogen. Perhaps it was this that resulted in the absence of
effect of sulphur and interaction between sulphur and nitrogen. At location
56 in Perniö the oats grew so well without supplementary fertilization that the
nitrogen caused a decrease in yield on account of the early lodging of the crop.

Table 24. Results from three field experiments on finesand (52a), silty clay (55a), and heavy
clay (56a). Grain yields expressed in kg/ha and grain moistures in per cent at harvesting.

52a

Yield Moisture
With basic fertilizing 3240 26.2
Additional treatment

55a

Yield Moisture
3520 24.7

effect

56a
Yield Moisture

4710 26.626,6

S -60 -0,7 -10 -0.1 -160 -0.5
N +3lo* +4.o*»* +36o** +7.9*** -580** +1.4
S x N +9O -0.4 +2O -0.7 -40 -0.9

The sulphur content in the samples representatively taken at threshing did
not clearly indicate that the fertilization with sulphur had any increasing
effect. The sulphur concentration in the wheat (52) apparently varied inde-
pendently of the fertilization from 1.07 to 2.14 g of S per kg, and averaged

5 185



186

1.6 of S per kg. The respective values for the barley were 1.22 2.01 g of S
per kg, the average being 1.5 g of S per kg, and for the oats 1.3—1.6 with an
average of 1.4 g of S per kg.

In the experiments in which the fertilization with sulphur was combined
with irrigation, the aim was to maximize the nutrient consumption of the plants
by means of water increment. The experiments were established on the farms
with the basic fertilization and crop demanded by the commercial farming.
The original conditions appear in Table 25. The geographical position of the
locations appears in Figure 5, and the characteristics of the soils in Appendix 1.
The spreading of the supplementary sulphur (40 kg of S per hectare), the irri-
gation and the harvesting were carried out by the experimental personnel,
while the basic fertilization, the sowing and the plant protection measures
were performed by the farmers concerned.

Table 25. Experimental crop, basic fertilization and its sulphur content in the case of ten
field experiments on sulphur application combined with irrigation.

Basic fertilization Basic sulphur
Location „ , ~Crop kg/ha amount
number

(N-P-K %) kg S/ha

49 Barley (Karri) 750 3
(15-8.8-12.5)

50 Barley (Ingrid) 700 4
(15-11.0-8.3)

51 Wheat (Svenno) 600 42
(20-4.4-8.3)

53 Wheat (Ruso) 700 18
(20-8.8- 0)

54 Barley (Porno) 500 2
(15-8.8-12.5)

58 Oats (Ryhti) 500 4
(13-10.1-16.6)

59 Oats (Ryhti) 500 4
(13-10.1-16.6)

60 Barley (Ingrid) 600 2
(15-8.8-12.5)

61 Barley (Ingrid) 750 3
(15-8.8-12.5)

62 Barley (Karri) 500 13
(20-8.8- 0)

In order that compaction of the tractor at plots fertilized with sulphur
should not give rise to experimental error, the unfertilized plots were run over
with the same tractor. The irrigation by sprinkler was performed at an intensity
of 3—lo mm per hour. The first irrigation was done slightly more than 3 weeks
(9—16 June) after the sowing, and on the twice-irrigated plots this treatment



187

was repeated some 10 days later. As it was the intention to raise the moisture
of the soil to field capacity, the total amount of water varied from case to case.
The irrigation amounted to 39 mm per time on average.

The experimental locations individually would in no case have provided
a statistically reliable effect for sulphur on the quantity or quality of yield,
and Table 26 consequently shows the most important results as averages for
all the experimental locations. The same index mark in one and the same
column indicate that there is no significant difference.

Table 26. Average grain yield and its moisture, sulphur, and nitrogen contents. I 0 = without
irrigation, Ij = irrigated once, I 2 = irrigated twice. S 0 = without additional sulphur, S x =

40 kg S/ha added1).

Yield
kg/ha

Moisture Sulphur Nitrogen
% g S/kg D.M. g NI kg D.M.

I 0S 0 3550» 31.8" 1.13 c 22.7»
I,S, 3540» 31.5» 1.10bc 22.8»
I,S O 4340 b 27.7» 1.01» 21.6»
ItS, 4340* 27.7» 1.07b 21.6»
I S S0 4600 b 26.5» 0.99» 20.9»
I,S, 4600b 26.1» 1.08b 20.9»

f) Means in each column followed by a common letter do not differ at P = 0.05.

The increment of sulphur did not affect the amount of yield or the moisture
content of the cereal on these experimental fields. Small but noticable changes,
however, could be discerned in the sulphur content of the grains. Without
sulphur fertilization the irrigation produced a slightly decreased content of
sulphur, but this decrease could be counteracted through the fertilization. This
circumstance could be taken as indicating that although the supply of sulphur
may have been sufficient for a good yield, it was nevertheless not unlimited
and some shortage may have arisen during heavy absorption.

That the fertilization with sulphur did not produce an increased concen-
tration of sulphur without irrigation is surprising, considering that July was
very rainy and that the sodium sulphate should have become dissolved by that
month at the latest. Whether this was due to a lowered absorption of sulphur
towards the end of the growing season or to other factors could not be dis-
covered.

The experiments with the various types of spring cereal on mineral soils
in South Finland showed that under the prevailing conditions the increment
in sulphur had an insignificant effect on the development of the plants. The
sulphur content of the basic fertilization was so high in some cases that no effect
was to be expected. Even a small amount of sulphur in the fertilization can
be of importance, especially as local increments in the sulphur fallout from the
atmosphere can be counted upon in the densely settled parts of South Finland.
The cereal plants are, too, among those that require least sulphur.



188

D. Comparison between field and pot experiments

A circumstance that often throws doubt upon the use of the technique of
the pot experiment is the unclear relationship between such experiments and
the natural conditions in the field. In order to clarify this question a comparison
was made between the results of the field experiments and those of the pot
experiments with the same soils in pots of 5 and 0.5 litres. The basic fertiliz-
ation in the experimental fields had been performed by the time at which the
soils for the pot experiments were taken. The sample soils represented the
cultivated soil layer from the surface to a depth of 25 cm. In the pots the fer-
tilization was applied according to Table 19. There were two treatments, one
with sulphur and one without, while the other nutrients were added to all the
pots.

The experiment with the 5-litre pots was carried out partly indoors, in a
greenhouse with the temperature set at 20° C, and partly in a pot shed in which
the temperature corresponded rather closely with outdoor conditions. These
experiments were sown on June 26, 1970 and were harvested at the end of
August. Every treatment had three replicates, and the plant was the same as
in the respective field experiment. This comparison was performed for 12 of
the experimental locations in South Finland, where the field experiments did
not give any positive result for sulphur fertilization. Location 56a was excluded
in this connection, as it had been the subject of detailed study in another
connection1).

In the pot experiments with 5-litre pots two of the soils (55a and 61a) provided
a positive result for fertilization with sulphur in respect of the grain and the
straw yield. The other soils (49a, 50a, 51a, 52a, 53a, 58a, 59a, 60a and 62a)
by contrast provided no signs that the fertilization with sulphur had affected
the growth of the sulphur uptake in any way. In the material there was no
connection between the fertilization with sulphur and the temperature con-
ditions where the grain yield is concerned. In one of the soils, however (61a),
the sulphur in combination with the lower temperature produced the biggest
yield of straw, there being an interaction between the sulphur and the tem-
perature (cf. Herath and Ormrod 1971). It is conceivable that the rather low
temperature in field conditions in Finland may cause a greater need for sul-
phur than is the case in warmer places or in greenhouse environment.

In the smaller pots the plants seemed to be more dependent upon the added
nutrients. In six clay soils (49a, 50a, 51a, 55a, 61a and 62a), one finesand soil
(52a) and one silt soil (54a) the fertilization with sulphur caused an increase in
the uptake of sulphur in the barley plants cut when coming into ear. The silty
clay soil rich in organic matter (53a) in which the fertilization with sulphur
seems to have had a negative effect was also the soil with the highest content
of sulphur extractable with NH 4-Ac. Sulphur thus had an effect in none of
the twelve cases in the field, in two cases out of the twelve in the 5-litre pots and
in eight cases out of the twelve in the 0.5 litre pots. As the active volume of
soil in the field is calculated at 2.5 million litres per hectare, the production

*) F.RJala, M. 1971. Liejusavien rikkivaroista. Graduate work 90 pp.



189

of dry matter in the respective conditions was about 4, 8 and 12 g per litre of
soil. The differences in the production of dry matter appears to be smaller
than the differences in the dependency on sulphur. The optimum conditions
of humidity and, often, of temperature in pot experiments, however, usually
make the plants develop more quickly than they do in the field. According to
the experience provided by the present study of sulphur, this time factor
should also be taken into account when comparative experiments are being
performed. The average period of growth was 105 days in the field ex-
periments, 65 days in the 5-litre pots and 45 days in the small pots, and the
dry matter production per day is consequently 0.04, 0.12 and 0.27 g per litre
of soil in these three growing conditions respectively. This gives an intensity
ratio of 1:3: 7, which resembles the results of the experiments with sulphur.

It is obvious that a comparison of this kind between conditions of culti-
vation has many weaknesses. Firstly, the crop of the small pots was not cut
when ripe, which was the case with the field experiments and the 5-litre pots.
It might be said that a constant and even production of dry matter up to the
time of ripeness would be necessary, but this is not quite realistic. Secondly,
a supply of sulphur in the rainwater could not be prevented in the field. The
calculation nevertheless provides a picture of how different the situation may
be between field conditions and pot conditions. Such a difference is well re-
flected in the effect of sulphur fertilization on the various soils.



190

Dependence of the availability of sulphur to the plants
upon the supply of certain other nutrients

If it is assumed that the information provided by chemical analysis on the
sulphur situation of the soil is really relevant in view of the opportunities of
plants to satisfy their need for sulphur (cf. section on mobilization of sulphur),
the differences in growth observed in pot and field experiments must have their
origin in some other factor. The differences may be due to variations in the
sulphur fallout from the atmosphere on account of the geographical location,
or due to variations in leaching propensity of incremental sulphur in field con-
ditions, or due to other differences caused by the climate.

In this chapter an analysis is made of the differences that may be due to
variations in the supply of some other nutrients. The experimental technique
employed ensured that no leaching occurred, and any effect that one nutrient
has upon the leaching propensity of another may consequently be disregarded.
In field conditions, however, this is a factor that must be taken into account.
In the experiments carried out with sand cultures the substrate probably
had no nutrient-absorbing features worth mentioning. The relationships ascer-
tained in these cases are consequently held to have originated in processes
of plant physiology alone. In samples of natural soil, however, it is necessary
to take account, too, of the propensity of the soil to fix various nutrient ions.

A. Relationship between sulphur and nitrogen

Probably on account of the central role of sulphur and nitrogen in the
structure of proteins, the supplies of sulphur and nitrogen in plants are highly
integrated. O’Connor and Vartha (1969) were consequently able to demon-
strate that a large dosage of gypsum gave a reduced yield of ley when the nitro-
gen situation of the soil was unsatisfactory. Eppendorfer (1969), on the other
hand, was able to induce symptoms of sulphur deficiency by means of large
dosages of nitrogen.

Three pot experiments were established in this study in an attempt to
clarify the relationship between sulphur and nitrogen.

I. Physiological effect of ammonium nitrogen and nitrate nitrogen on the sulphur
supply

A pot experiment with in a 0.5-litre pot was performed from
July 10 to August 4, 1969 with washed quartz sand as substrate. 1 per cent
by weight of undecayed Sphagnum peat was mixed into the sand to give it



191

solidity and better water-retentiveness. Both the peat and the sand had been
treated with hydrochloric acid (HCI) prior to use, and were thereafter rinsed
with water until the leached water no longer showed any acid reaction.

In this pot experiment the fertilization was identical with that shown in
Table 19 except in respect of sulphur and nitrogen. There were three levels of
sulphur: no addition (S 0), 2.5 mg of S per litre of soil (S 4) and smgof S per litre
of soil (S 2). 107 mg of N per litre of soil was given, partly in the form of Ca(NO 3 ) 2
and partly in the form of NH 4CI. The pots were sown with 12 grains of barley
each, and were watered so that the nutrient solutions and the water would
together amount to 120 ml per pot, which amply corresponded with the field
capacity determined in laboratory. 25 days after the sowing and imraedialely
before coming into ear, the crop was harvested by cutting the barley stalks
at the surface of the soil. The roots were washed clean of soil with a jet of
water. The total sulphur was determined in the ordinary way in both stalk
and leaf samples and in root matter (Table 27).

Table 27. Shoot and root yields at various sulphur levels with ammonium and nitrate nitrogen
application, sulphur content of the plant material and sulphur uptake by the plants. x )

Shoot material Root material

Yield S content S yield Yield S content S yield
D.M. g/pot mg/g mg/pot D.M. g/pot mg/g g/pot

N0 3-N S 0 0.99b 0.80a 0.79" o.Bo° 0.63a 0.49a

S x 1.33c 1.10ab 1.48ab 0.86° 0.68ab 0.59ab

S 2 1.92c 1.60b 2.85° 1.08 d 0.74abc 0.80 ab

NH4-N S 0 0.73a 1.07ab 0.78a 0.61 a 0.99bcd 0.60 ab

Sj 1.12bc 0.96ab 1.09a 0.63ab 1.05cd 0.66ab

S 2 1.65d 1.23ab 2.05 bc 0.75 bo 1.15d 0.88b

*) Means in each column followed by a common letter do not differ at P = 0.05.

In these extreme conditions of substrate the nitrate nitrogen seemed to be
a trifle more favourable to growth than was the ammonium nitrogen. The root
mass especially proved to be smaller with NH 4-N than with NO a -N, while the
difference in stalk and leaf mass was smaller relatively. A slight tendency
to higher sulphur content in the root mass at fertilization with ammonia is
due to a sulphur concentration that is higher throughout than it is in the ni-
trate treatment. A certain competition between nitrate and sulphate ions in
the root tissue may be conceived of in the treatment with nitrate. The pH
value of the substrate probably had no effect, as it was 6.0 before the sowing
whether the fertilizer was nitrate or ammonium, and 6.9 to 7.1 at harvest
irrespective of the fertilization.

The sulphur taken up in the S 0 treatment may come from various sources
such as sulphur remaining in the substrate despite the treatment, impurities
in other added chemicals and in the irrigation water and impurities in the at-
mosphere or from sulphur in the seed. It is impossible, however, to distinguish
among these factors on the basis of this experiment or of any of the experiments



192

to be reported on later. Considering the precision at the rinsing of the soil
samples and taken account of the ion exchange of the irrigating water, the author
estimates that quite a large proportion of the sulphur originates in the atmos-
phere while a smallerproportion may have been mineralized out of the Sphagnum
peat.

The absorption of the added sulphur seems to have been just about complete
in one of the cases (NOa-N, S 2). It seems that the uptake of sulphur in the case
of the smaller sulphur dosage was also weaker in relative terms, too, than it
was from the larger dosage, which might suggest that despite its particularity
of character the substrate competes with the plants for a certain quantity of
the added nutrient.

11. Dependence of yield upon the N/S ratio of the substrate

In a pot experiment with 0.5-litre pots performed during July and August
1969 with washed quartz sand as substrate, the N/S ratio was varied between
5 and 430, while other nutrients were applied according to the basic fertilization
schedule in Table 19. By varying both the nitrogen and the sulphur dosages,
the following N/S values were achieved at the various levels of nitrogen (the
index numbers refer to the ratio to the basic amounts stated in Table 19, which
are ascribed the value of 1:

N I S
ratio by weight

N l/2 S l/8 43
» Sl/4 21
» St 5

»1 S l/20 215
• S l/2 21

N 2 Sl/20 430
» Sl/2 43

In Figure 8 the yield is related to the N/S ratio on a semilogarithmic scale.
Points for the nitrogen levels 107, 215 and 430 mg per litre of soil are indicated
with various signs. The yield pertains to the stalk and leaf of Otra barley
immediately prior to coming into ear.

The result shows that despite large variations in the amounts of added
nitrogen and sulphur, the N/S ratio is an acceptable indicator of yield. What
the N/S ratio should optimally have been under the prevailing conditions of
absorption of atmospheric sulphur and the prevailing mobilization rate for the
sulphur and nitrogen reserves in the soil, in this case minimal, remains an open
question. Clarification would have necessitated a number of experimental
harvests for an N/S ratio between 0 and 20 and perhaps especially for an N/S
ratio of between 5 and 20.

The relationship between the sulphur and the nitrogen was studied in a
second pot experiment with five cultivated surface soils, three Carex peat soils



(38a, 39a and 45a), one loamy clay soil (47a) and one finesand soil (48a). In this
experiment there were two levels of nitrogen, i.e. Nx =43 and N 2 = 215 mg
of N per litre of soil, and sulphur at the levels S 0 and Sx (20 mg of S per litre).
The N 0 factor was held to be superfluous, for a small dosage of nitrogen was
expected to give a greater return of information. All the other nutrients were
applied according to the basic level (Table 19).

Liming was omitted, however. All the treatments had three replicates and
there were consequently twelve pots of each soil. These 5-litre plastic pots were
sown with 40 Otra grains each on July 30, 1969and thinned out to 25 specimens
on August 5, 1969 and harvested on September 25, 1969, by which time all
the treatments had come into ear. The thinning-out was probably unnecessary,
as a vigorous formation of secondary shoots in the heavily fertilized treatments
in any case made the density of shoots very different in the various treatments.
The original content of 0.5 N K 2S0 4 extractable ammonium and nitrate nitrogen
and of ammonium-acetate extractable sulphur in the various experimental
soils were:

Figure 8. Yield of plant material in sand cultures with Otra barley compared with the NS
ratio.

193



194

N S
mg/1 mg/1

38a 29 3
39a 37 3
45a 39 23
47a 14 3
48a 41 1

This meant that the molar ratio between nitrogen and sulphur after fer-
tilization varied between 4.4 and 610 and the weight ratio N/S between 1.9
and 260.

Two weeks after the sowing the effect of the nitrogen could be observed in
four soils out of five. Only three days later were the first signs of sulphur
deficiency registered, on two peat soils. After four more days the symptoms
of sulphur deficiency were at their most distinct.

The symptoms of sulphur deficiency in this pot experiment were at their
most distinct I—2 weeks before the coming into ear, the differences becoming
evened out subsequently. At harvest a few weeks after coming into ear, the
sulphur shortage had apparently disappeared.

Tables 28, 29, 30 and 31 show the dry matter yield and the concentrations
of nitrate nitrogen, total sulphur and total nitrogen. The values in any one
column which possess an identical letter show no significant differences at the
95 per cent level of probability.

Table 28. Yield of shoots (D.M. g/pot) in a pot experiment with Otra barley. 1 )

Sample number
Treatment

38a 39a 45a 47a 48a

Nj S 0 22.0a 32.la 11.9ab 8.4a 17.1a

N 2 S 0 26.2b 30.6a 10.5a 18.2b 23.5 b

N 2 S 2 27.l b 36.4 b 12.9b 10.3a 16.1a

N 2 Sj 33.2° 35.l b 13.8b 19.8b 21.9b

') Means in each column followed by a common letter do not differ at P = 0.05.

Table 29. Concentration of nitrate nitrogen in shoots (g/kg D.M.) of Otra barley.1)

Sample number
Treatment

38a 39a 45a 47a 48a

Nj S 0 0.5a 0.4a 1.6a 0.1a 0.5a

N 2 S„ 0.8 b 3.6° 5.5 b 3.5 b 2.5b
Nx Sx 0.3 a 0.3a 1.3a 0.1a 0.5a

N 2 Sj 0.5 a 1.9b 2.4a 3,5 b 2.7b

1 ) Means in each columnn followed by a common letter do not differ at P = 0.05.



195

In two Carex peat soils, 38a and 39a, both of which had been obtained from
the area of Kuusamo in North Finland, the fertilization with sulphur produced
a significant increment of yield at the lower as well as the higher level of nitrogen.
The yields for the other soils showed an indistinct or nil effect of sulphur, but
in mineral soils 47a and 48a the fertilization with nitrogen produced a signifi-
cant increment of yield, as it also did in soil 38a. Heavy fertilization with
nitrogen without the addition of sulphur produced the highest concentration
of nitrate nitrogen in all the peat soils (38a, 39a and 45a). This is an expression
of the close affinity between sulphur and nitrogen in the metabolism of the
plant (cf. O’Connor and Vartha 1969). Instead of the formation of protein
there occurs under sulphur deficiency an accumulation of nitrate nitrogen.
amino-acids and amides.

Table 30. Concentration of sulphur in shoots (g/kg D.M.) of Otra barley.1)

Sample number
Treatment

38a 39a 45a 47a 48a

Nt S 0 1.7» 1.5» 3.4» 1.7» 1.8»
Nj S 0 1.7» 1.9» 3.5» 1.7» 1.6»
Nj S, 1.9b 1.7a 3.8 b 1.8a 1.9a

Na 1.9b 2.4 b 3.5a 2.4 b 1.9a

b Means in each column followed by a common letter do not differ at P = 0.05.

Table 31. Concentration of nitrogen in shoots (g/kg D.M.) of Otra barley. 1)

Sample number
Treatment

38a 39a 45a 47a

N, S 0 15.5a 13.3a 23.5 ab 15.7a

N 2 S 0 18.0a 24.9° 30.4C 34.8 b

N, Sx 16.9a 12.8a 20.4a 17.9a

N 4 Sj 18.4a 22.3 b 27.0bc 39.4°

*) Means in each column followed by a common letter do not differ at P = 0.05.

Table 30 does not provide a clear picture of the sulphur uptake. In soil
39a an increment of nitrogen in addition to that of sulphur was necessary for
the concentration of total sulphur to rise. Fertilization with sulphur in con-
ditions of nitrogen deficiency in this experiment did not produce any consistent
increase in the concentration of total sulphur. This status may be due to
metabolistic inactivity in plants when there is a deficiency of nitrogen, but
also due to the nutrient fixing conditions in the soil.

The concentration of total nitrogen in all the analyzed cases was raised
through increased dosage of nitrogen (Table 31). It seems that the nitrogen
uptake was rather independent of the sulphur situation.



196

As the results of these pot experiments only provided an opportunity for
modest conclusions, the experiment was repeated the following spring with
the same soils and the same experimental scheme but with spring rape as the
experimental plant. The experimental soils, stored in dry conditions, were
homogenized pot by pot and were fertilized in such a manner that every pot
received the same dosage of nutrients as that for the first experimental harvest.
For instance, the pots that had received S 0 treatments in the first round were
once again left without sulphur fertilizer. A certain impoverishment of the
sulphur reserves was expected to occur in consequence.

20 seeds of spring rape were sown on February 20, 1970. As the early de-
velopment of rape is rather slow, thinning out to tenspecimens was not per-
formed until one month after sowing. Two weeks later another four plants
per pot were culled. The removed plants were dried and weighed and were
analyzed for total sulphur. The final yield of seeds and stalks was harvested
4.5 months after sowing.

The poor growth of the rape during the first month had the result that no
real differences could be discovered between the various treatments until a
good month subsequent to sowing. At the time of the second thinning, however,
the differences were very obvious. The growth- inhibiting effects of nitrogen
in conditions of sulphur shortage could already be observed at that stage. Symp-
toms of sulphur deficiency could be discerned on two peat soils, on the
loamy clay and on the finesand soil, while one Carex peat (45a) produced a
weak growth throughout and showed slow development.

The analyses of the removed material showed that the sulphur concen-
tration in the youngest shoots of rape may rise to 10 g per kg. At the same time,
when there was a shortage of sulphur the concentration only amounted to about
2 g per kg. Two weeks later the sulphur contents had fallen to 4 and 0.8 g per
kg respectively. The most important results of this pot experiment are shown
in Tables 32 and 33.

All the soils except for 45a reacted to the fertilization with sulphur. The
seed yield of these other soils was poorest in those cases in which the increased
dosage of nitrogen was combined with a lack of sulphur (N 2;S O). It is clear
that the need for additional sulphur increases with increased input of nitrogen,
as an increase of nitrogen from Nx to N 2 in the S 0 treatment in these soils pro-

Table 32. Spring rape yield (g/pot) in a pot experiment with two nitrogen and sulphur levels
and five soils. 1)

Sample number
Treatment

38a 39a 45a 47a 48a

N* S 0 0.03a 3.10b 7.32a 4.25b 3.74b

N 2 S„ 0.00a 0.00 a 11.08° 0.77 a 0.06a

Nx Sj 8.15b 5.53° 7.38ab 4.20b 3.89b

N 2 Sj 16.74c 15.86d 9.26b ° 17.00° 21.25°

Means in each column followed by a common letter do not differ at P = 0.05.



197

Table 33. Spring rape straw yield (g/pot). 1)

Sample number
Treatment

38a 39a 45a 47a 48a

Nx S 0 18.7° 17.2C 10.9ab 8.5a 7.3»
N 2 S 0 1.1» 1.4a 17.lc 28.7 b 25.7b

Nj Sj 12.4b 10.1b 8.2a 8.7 a 6.9a

N 2 Sj 31.3 d 34.4 d 14.9bc 39.4° 35.lc

l) Means in each column followed by a common letter do not differ at P = 0.05.

duced a marked decrease in the seed yield. It is interesting to note how the
situation is a rather different one where the stalk yield is concerned. In two
cases on Carex peat (38a, 39a) stalk yield and seed yield go together, but on both
the loamy clay (47a) and on the finesand soil (48a) a relatively high yield of
stalk was obtained despite a total failure in seed yield. It seems that a balance
between sulphur and nitrogen was primarily needed for a good seed formation,
which is evidently induced through an effective protein synthesis, while the
vegetative part of the crop is less susceptible to an unsuitable N/S ratio.

At the lower level of nitrogen the fertilization with sulphur had no effect
on the yield of either seed or stalk on the mineral soils, in which a definite short-
age of nitrogen excluded an increase in yield. The effect of sulphur is signifi-
cant on the Carex peat soils (38a, 39a), which have a sulphur shortage. The
interesting thing, however, is that while the seed yield was positively affected,
the sulphur had a reducing effect upon the yield of stalk. This redisposition of
the very scarce nitrogen reserves may be seen as an expression of the capa-
bility of the plant to translocate nitrogen from the oldest leaves, which wither
and fall away, to the growing point. In the treatment there is a concur-
rent shortage of sulphur and nitrogen. The nitrogen caused a restriction in the
total yield of plant matter while the shortage of sulphur made the seed forma-
tion impossible. This is the reason why the seed yield brought on by the dosage
of sulphur in treatment could only be achieved through a reduction in
the stalk yield. The growth was good in treatment N 2;S 1 with an applied N/S
ratio of about 11, but an even higher yield might have been obtained with
additional nitrogen.

B. Pot experiment with sulphur and phosphorus as variables.

Sulphur and phosphorus are evidently more loosely bound to each other
in physiological terms than are sulphur and nitrogen. The stimulation of the
uptake of phosphorus which has been accomplished in some cases by means
of sulphur fertilization is chiefly due to a change in the propensity of the soil
to phosphorus, caused by the fertilization. The total phosphorus fixation in
some soils of high pH value may be directly influenced by means of sulphur
fertilizers possessing an acid effect (Kacar and Akgul 1967), such as elemental



198

sulphur and ammonium sulphate. Without any change in the fixation capacity
it is possible to imagine a limited exchange of phosphorus ions for sulphur
ions when there is a substantial addition of sulphur (Menary and Hughes

1967). In a pot experiment with a mixture of quartz sand and peat Johansson
(1959) recorded a reduced yield with sulphur fertilization when the supply
of phosphorus was scanty.

In order to investigate the physiological interaction between sulphur and
phosphorus, a pot experiment with a 0.5-litre plastic pot with washed quartz
sand as substrate was carried out between July 11 and August 4, 1969. The
plant was Otra barley, and was cut immediately before coming into ear. The
fertilization is shown in Table 19 except that there were three different levels
of sulphur, i.e., S O , Sx (2.5 mg of S per 1) and S 2 (5 mg of S per 1) and two levels
of phosphorus, i.e., Pt (4 mg of P per 1) and P 2 (20 mg of P per 1). Nitrogen
equivalent to 107 mg of N per litre was applied in the form of Ca(NO 3 ) 2

- 4H 20.
Sowing, moistening and reaping were performed as in the experiment with the
fertilization with nitrate and ammonium nitrogen. The yields from this pot
experiment are shown in Table 34.

Table 34. Shoot and root yields (D.M. g/pot) in a pot experiment with twophosphorus and
three sulphur levels in quartz sand. 1)

p p

S 0 Shoot 0.87 a 1.59bc
Root 0.86 m 1.12mn

Total 1.73s 2.71 tu

Sx Shoot 1.21ab 1.89c

Root 0.98 mn 1.19°
Total 2.19 st 3.08 uv

S 2 Shoot 1.37b 2.37 d

Root 1.06mn 1.24n

Total 2.47 stu 3.61 v

h Means for shoot, root, and total yields, respectively, followed by a common letter do not
differ at P = 0.05.

In Table 34 the stalk and leaf material was statistically processed separately
from the root material. The indices for the former values are a, b, c and d, for
the root material m and n, and for the sum s, t, u and v.

The interaction effect between the sulphur and the phosphorus was calculated
on the basis of the total stalk, leaf and root material yields. The interaction
effects of S x x P and S2 x P were lacking. The factor analysis also showed that the
effect of the sulphur was not statistically reliable at the lower level of sulphur
but was at the higher.

Statistically the factor analysis shows that the same absolute increase in
yield is obtained with the phosphorus fertilization at the different levels of
sulphur. This interesting but somewhat surprising circumstance is due in the



199

present material to the fact that the fertilization with phosphorus at the higher
levels of sulphur produced a smaller increase in the root material both absolutely
and relatively than it did at the nil level of sulphur fertilization. The factor
analysis for the yield of root material, however, does not show a statistically
reliable antagonism.

Table 35. Uptake of phosphorus in shoot and root material (mg P/pot). 1)

ft
S 0 Shoot 2.17a 4.92c

Root 0.98" 1.951
Total 3.15 5t 6.87 u

S x Shoot 2.47b 5.32d

Root 0.88 n 1.721
Total 3.35» 7.04u

S 2 Shoot 2.24 a 5.44d

Root 0.75 m 1.60°
Total 2.99s 7.04 u

0 Means for shoot, root, and total yields, respectively, followed by a common letter do not
differ at P = 0.05.

The indices for the phosphorus content of the stalk and leaf material (Table
35) start with »a» and the indices for the phosphorus yield of the root material
run from »m» and those for the sum from »s». The phosphorus content of the
root material decreases with increased sulphur input, primarily on account of
severely reduced phosphorus concentration in the root tissue at increased
fertilization with sulphur. In this experiment the sulphur prompted a distinct
redisposition of the total quantity of phosphorus taken up, especially at the
higher level of phosphorus. With decreasing supply of sulphur an increasing
proportion of the phosphorus is to be found in the root tissue. Thus at level
P x the root matter contained 45 per cent of the phosphorus in the S 0 treatment
and 34 per cent in the S 2 treatment, while at level P 2 the figures were 40 per
cent and 30 per cent respectively.

As the lack of interaction between sulphur and phosphorus reveals, it is
impossible to set an optimum ratio between P and S in fertilizer on the basis
of the experiment outlined here. There were no critical points within the limits
tested therein (P/S = 0.8—8.0).

The sulphur concentration both in the stalk and leaf material and in the
root material was nowise affected by the fertilization with phosphorus.

C. Pot experiment with sulphur and molybdenum as variables

It seems to be a generally accepted fact that sulphur fertilization results
in reduced uptake of molybdenum (Gupta 1969, Reisenauer 1963). Fertiliz-
ation with superphosphate, for instance, has an inhibiting effect in this re-



200

spect upon the uptake of molybdenum because of its content of sulphur, in spite
of the fact that it is known that phosphorus has a stimulating effect on the ab-
sorption of Mo (Gupta and Cutcliffe 1968, Jaakkola 1972). Likewise, a
shortage of sulphur may induce abnormally high, toxic contents of molyb-
denum (> 10 ppm of Mo) (Gupta 1969).

A pot experiment with quartz sand from July 11 to August 4, 1969 with
the variables S O , Sx (5 mg of S per litre) and S 2 (20 mg S/l) and Mo0 and Mo1
(3 mg Mo/1) and three replicates of each treatment produced a total of 36 ex-
perimental yields when the young Otra barley was reaped immediately be-
fore coming into ear. The dosage of nitrogen was the equivalent of 107 mg
of N per litre and was given in the form of calcium nitrate. The rest of the fer-
tilization was done in accordance with Table 19. The yields of this pot exper-
iment are shown in Table 36.

Table 36. Shoot and root yields (D.M. g/pot) in a pot experiment with two molybdenum and
three sulphur levels in quartz sand. 1)

Mo 0 Mo,
S 0 Shoot 0.85 a 0.99a

Root 0.70" 1 0.80 m

Total 1.55a 1.79s

S, Shoot 1.92b 1.92b
Root 1.22 n 1.08n

Total 3.14' 3.00'

S 2 Shoot 2.57c 2.39°
Root 1.46° 1.46°
Total 4.03u 3.85 u

f) Means for shoot, root, and total yields, respectively, followed by a common letter do not
differ at P = 0.05.

The indices for the yield of stalk and leaf run from »a», those for the yield
of root from »m» and those for the sum from »s», and as Table 36 shows, the
exclusion of fertilization with molybdenum did not affect the yield in this
experiment. Table 37 shows the concentrations of total sulphur in the same
experimental yields.

Here, too, the stalk and leaf matter was processed separately from the root
matter. The values with the indices »a», »b» and »c» are thus comparable, and
so, on the other hand, are the values for the root material with the indices
»m» and »n».

The sulphur content rises slightly with raised dosage of sulphur, while the
molybdenum dosage has no significant effect.

The molybdenum content in the yields appears in Table 38. Here, too,
the stalk and leaf yield was tested separately from the root yield, the indices
in the former case running from »a» and in the latter from »m».

Table 38 shows how easily molybdenum is translocated into the plant when



Table 37. Concentration of sulphur (g S/kg D.M.) in shoot and root material. 1)

Mo 0 Moj

S 0 Shoot l.l ab 0.8a

Root 0.8 mno 0.6 m

U"ot 10mnO 07mn

Root l.lno 1.2°

■) Means for shoots and roots, respectively, followed by a common letter do not differ at
P = 0.05.

Table 38. Concentration of molybdenum (mg Mo/kg D.M.) in shoot and root material. 1)

Mo0 Moj

S„ Shoot 1.07a 209°
Root 1.26m 291 P

Root 0.81 m 215°

S 2 Shoot 0.51 a 171b
Root 0.63 m 75 n

x ) Means for shoots and roots, respectively, followed by a common letter do not differ at
P = 0.05.

there are no fixing features in the substrate. Although the crops fertilized
with molybdenum all have a high content of molybdenum, a certain decrease
in the content can be registered with increased dosages of sulphur. It is also
interesting to note that the very large dosages of molybdenum in this experiment
and the very high content of molybdenum produced thereby seem to have no
kind of toxic effect upon the plants.

6 201



202

Discussion

The chemical determination of sulphur in samples of soil and plants and in
extracts thereof proved to be surprisingly laborious and susceptible to inter-
ference. An efficient study of the problems of sulphur on a large scale necessi-
tates a simplification and an improvement in the methods of analysis. The
difficulty consists in the fact that the quantities of sulphur to be analyzed
are relatively small, while the interfering materials, especially in the soil extracts,
occur in abundance.

The determination of the total amount of sulphur in plant and soil samples
through combustion in an induction furnace and through the turbidimetric
determination of sulphate gives a rather great variation between parallel analy-
ses on account of the many phases of work (cf. Tabatabai and Bremner
1970), and a small proportion of the sulphur will apparently remain in the fused

sample, and consequently outside the analysis. Employment of this method,
in any event, may be justified on account of its low requirement of labour.

It is difficult to develop methods for the analysis of soil extracts which
would be totally insensitive to all the other materials that may occur in such
extracts in highly varying quantities. In the present work it was possible, more
or less by chance, to demonstrate how a concentration of phosphate has a very
great influence upon the chromate determination of sulphate, but there may
certainly be a number of other impurities with similar effect. It might be
said that the determination will ultimately express the relationship between
the sulphur and the materials which interfere in various ways. Whether the
determined factor under such circumstances is called sulphur or is given some
other name and numerical value is probably a matter of indifference.

The most difficult thing in the discussion on the sulphur balance of the soil
is, without doubt, the assessment of the magnitude of leaching. The calculations
are only based on four annual samplings with simultaneous flow measurements.
Moreover, a few sampling sites not loaded with waste were in some cases used
to represent large areas where other sampling sites were excluded on account
of sulphur contamination from industry and human settlement. The included
samples were often taken from rather remote locations, and the calculated values
for leaching consequently constituted only a natural basic level that is locally
exceeded in parts with large-scale industrial industry or intensive agriculture.

It was clear that there would be a relationship between the added and the
leached quantities of sulphur (odelien 1965), but it was surprising that the
calculations should show the same numerical value for the fallout with pre-



cipitation as for the leaching. How this situation changes on account of fertilizer
application on cultivated soils regrettably remains outside the scope of the
present work. There is probably a certain risk of leaching of all the unutilized
added sulphur during the autumn and spring under Finnish conditions.

It is clear that if fertilization with sulphur merely causes an increase of
leaching, such fertilization should be avoided. Where the sulphur content in
the atmosphere and in precipitation and the spontaneous mobilization of sul-
phur in the soil are not sufficient to produce a qualitatively and quantitatively
acceptable yield, fertilization with sulphur should, by contrast, be carried
out. In the present study experiments were made with little success to predict
by chemical analysis those cases in which fertilization with sulphur may be
warranted. The risk of erroneous conclusions was great even when the most
suitable method was employed, i.e. the method of extraction with acid am-
monium acetate. Mineral soil in particular probably contains sulphur that is
not extracted by this method but is nevertheless available to plants. A high
value of analysis in extraction with ammonium acetate in any event makes it
possible to assume with rather high reliability that an increment of sulphur
is superfluous. It is more difficult to interpret the significance of low values.

A clue to why this should be so was provided by extraction with more
effective solvents. In a comparison with results obtained elsewhere by the
same methods (Kessen et al. 1962, Cooper 1968) it proved that cultivated
soils in Finland contain somewhat more firmly bound sulphur over a relatively
large extent. This state of things was assumed to be the result of the generally
rather high content of organic matter in Finnish soils.

To indicate the ratio in which various nutrients should be added in each
separate case in order that optimum biological results might be achieved with
minimum input would require a very thorough study of the needs of the re-
spective plant and the characteristics of the soil. Special attention was paid
to the ratio between added sulphur and added nitrogen. In artificial substrates
the proper ratio between these two nutrients can be determined to some ex-
tent with the aid of the analysis of a well-developed plant material, but in
natural conditions, account must also be taken of differences in the rate of
mobilization, the propensity of fixation, the evaporation and the leaching
of sulphur and nitrogen.

Although symptoms of sulphur deficiency in greenhouse conditions may
easily emerge when fertilization is unsatisfactory, the field experiments showed
that the supply of sulphur on cultivated soils in southern Finland is probably
satisfactory in general. The sulphur effect recorded on the Carex peat soils in
the region of Kuusamo in North Finland was, by contrast, probably one of the
most distinct ever observed in field conditions. The great need for sulphur
is explicable in the sense that the region lacks sources of emission of sulphur
dioxide, and that there have been many years of heavy application of NPK
fertilizers perfectly free of sulphur.

203



204

Summary

A number of chemical methods for the analysis of the sulphur content of
plant and soil samples and of extracts thereof were examined in the present
study. A method for the determination of the total sulphur of plant and soil
material was worked out, being based upon the combustion of the samples in
a Leco induction furnace and upon turbidimetric analysis of the quantity of
sulphate sulphur in the combustion gas. The great difficulties with the analysis
of soil extracts were demonstrated, and the value of the information obtained
through such determination was shown to be questionable in respect of one
of the methods (precipitation with barium chromate). A new procedure of
analysis was proposed for sulphur determination in ammonium acetate extract
(pH 4.65), the interference of the organic matter being reduced by oxidation
of the extract with H 2 02 .

The sulphur balance of the cultivated soils in Finland was investigated on
the basis of the increment in sulphur received by the soil through the atmos-
phere and through measures of cultivation, and of the loss in sulphur occurring
through leaching and through overflow into the watercourses and the uptake
by plants. The amount of sulphur falling out with precipitation, as well as the
amount of sulphur washed off into the watercourses, seemed to average about
8 kg per hectare per annum. During the 1970—7l fertilization period the sul-
phur of the fertilizers distributed over the field acreage is reckoned to have
amounted to 12 kg per hectare, which is adequate for a cereal crop but not
for crops possessing higher sulphur requirements than those of cereals.

A preliminary survey of the sulphur reserves of the cultivated soils in Fin-
land and of the availability of the soil sulphur to the plants was carried out
through the analysis of a set of soil samples and plant experiments on those
soils. The series composes a sparse network covering the land south of the line
running from Oulu to Kuusamo, there being 104 samples including 62 of sur-
face soil and 42 of subsoil.

The 21 mould and peat soils of the series of samples contained an average
of 1180 dr 220 mg of S per kg of air-dried soil (t 0 05 ), the 22 clay soils 450 d:
94, the 18 silt and loam soils 410 ± 100, and the 42 finesand and sand soils
310 dr 43. The subsoil samples of the mineral soils contained some 30 per
cent less sulphur than the surface soils on average.

The total sulphur content of the sample soils correlated rather closely with
the content of organic carbon (r = o.B3***). For sulphur extracted through
treatment with 1 % NaCl, 0.03 M NaH2P0 4 2 N CH 3COOH and a solution



205

of CH 3COONH 4 CH 3COOH with a pH of 4.65 there were no close correlations
with the criteria determined for the general characteristics of the soil (pH CaC , 2 ,

org. C and texture).
Of the various methods of extraction, that with acid ammonium acetate

gave the lowest values also when the bulk density is taken into account, while
the two other methods gave results of a roughly equal order of magnitude.
None of the methods of extraction could provide a satisfactory explanation of
the effect of fertilization with sulphur in the pot experiments. The determi-
nation of sulphur soluble in NH4

- acetate, however, did provide some information
about the sulphur situation of the soil samples. An important advantage with
this method seems to consist in the use of a volume-based extraction ratio,
which gives comparable values for mineral and for mould and peat soils.

In field experiments with ley dominated by timothy on peat soil in the Kuu-
samo region of North Finland, fertilization with sulphur in the summer of
1969 produced a relatively distinct positive result in respect both of ley yield
and of sulphur content of yield. A dosage of sulphur of 10 kg of S per hectare
was enough to raise the yield of ley to a relatively high level, and further in-
crement of the dosage had an effect almost exclusively upon the sulphur content
of the crop alone. In South Finland field experiments with spring cereal in
1970 showed that the amount of yield was not affected by supplementary fer-
tilization with sulphur.

With a view to the planning of the composition of fertilizers, an investigation
by means of pot experiments was made of the relationships between sulphur
on the one hand and nitrogen, phosphorus and molybdenum on the other. In
order to produce an optimum yield it seems that sulphur and nitrogen had
to be available in a certain ratio which would apparently lie between the limits
N/S = 5—20 for barley. With a concurrent shortage of these two nutrients
in rape, nitrogen primarily restricted the vegetative development and sul-
phur the seed formation. No definite relationship could be demonstrated
between phosphorus and sulphur in these experiments, while fertilization with
molybdenum under conditions of sulphur shortage led to a sharp increase in
the molybdenum content of the plant material.



206

REFERENCES

Alway, F. J. 1940. A nutrient element slighted in agricultural research. J. Amer. Soc.Agron.
32: 913-921.

Alway, F. J., Marsh, A. W. & Methley, W. J. 1937. Sufficiency of atmospheric sulfur for
maximum crop yields. Soil Sei. Soc. Amer. Proc. 2; 229 238.

Ames, J. W. & Boltz, G. E. 1919. Effect of sulfofication and nitrification on potassium and
other soil constituents. Soil Sci. 7: 183 195.

Aylmore, L. A. G., Karim, M. & Quirk, J. P. 1967. Adsorption and desorption of sulfate ions
by soil constituents. Soil Sci. 103: 10 15.

Bardsley, C. E. & Lancaster, J. D. 1960. Determination of reserve sulfur and soluble sulfates
in soils. Soil Sei. Soc. Amer. Proc. 24: 265 268.

Barrow, N. J. 1968. Determination of elemental sulphur in soils. J. Sci. Fd Agr. 19: 454 456.
1970 a. Comparison of the adsorption of molybdate, sulfate and phosphate by soils.
Soil Sci. 109: 282-288.
1970 b. Note on incomplete extraction of elemental sulphur from wet soil by chloroform.
J. Sci. Ed Agr. 21: 439.

Beaton, J. D. 1966. Sulfur requirements of cereals, tree fruits, vegetables, and other crops.
Soil Sci. 101: 267-282.

Beaton, J. D., Burns, G. R. & Platou, J. 1968. Determination of sulphur in soils and plant
material. Sulphur Inst. Techn. Bull. 14: 1 56.

Bogdanov, S. 1899. On the sulphur in plants. Zhur. Russ. Fiz. Khim. Obshch. 31: 471. Abs.
Bibliography of the literature on the minor elements and their relation to plant and
animal nutrition. 4th ed. 1948. New York 1037 p. Voi. 1: 871—872.

Bremner, J. M. & Shaw, K. 1958. Denitrification in soil: I. Methods of investigation. J.
Agric. Sci. 51: 22 39.

Buchner, A. 1958. Die Schwefelversorgung der westdeutschen Landwirtschaft. Landw. Forsch.
11: 79-92.

Byrne, E. & Hanley, P. K. 1970. A comparison of methods for predicting sulphur deficiencies
and uptake from Irish soils, pp. 88 106 in Sulphur, in agriculture. Dublin 226 p.

Canting, E. C. 1946. Titrimetric determination of sulfate in natural waters and soil extracts.
Soil Sci. 61: 361 368.

Chang, M. L. & Thomas, G. W. 1963. A suggested mechanism for sulfate adsorption by soils.
Soil Sei. Soc. Amer. Proc. 27: 281 283.

Chao, T. T., Harward, M. E. & Fang, S. C. 1964. Iron and aluminum coatings in relation to
sulfate adsorption characteristics of soils. Soil Sei. Soc. Amer. Proc. 28: 632 —635.

Chapman, H. D. 1936. Effect of nitrogenous fertilizers, organic matter, sulfur, and colloidal
silica on the availability of phosphorus in calcareous soils, J. Amer. Soc. Agron. 28:
135-145.

Chesnin, L. & Yien, C, H. 1951. Turbidimetric determination of available sulfates. Soil Sci.
Soc. Amer. Proc. 15: 149 151.

Coleman, R. 1966. The importance of sulfur as a plant nutrient in world crop production. Soil
Sci. 101: 230-239.

Cooper, M. 1968. A comparison of five methods for determining the sulphur status of New
Zealand soils. 9th Int. Congr. Soil Sei. Trans. 2: 263 271.



207

Cormis, L. de, 1968. Ann. Physiol. Veg. Paris 10: 99—112. Abs. Sulphur adsorption by plants
in an atmosphere containing sulphur dioxide. Soils & Fert. 32; 3019.

Daikuhara, G. 1907. Are soils containing less than 0.02 % S0 3 benefited by special manuring
with sulphates? Bull, Imp. Cent. Agr. Exp. Sta. Japan 1,2: 135 143.

Dodgson, K. S. 1961. Determination of inorganic sulphate in studies on the enzymic and non-
enzymic hydrolysis of carbohydrate and other sulphate esters. Biochem. J. 78: 312 319.

Duley, F. L. 1916. The relation of sulphur to soil productivity. J. Amer. Soc. Agron. 8: 154
160. Abs. Bibliography of the literature on the minor elements and their relation to
plant and animal nutrition. 4th ed. 1948. New York 1037 p. Voi 1: 879.

Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics 11: 1—42
Elonen, P. 1971. Particle-size analysis of soil. Acta Agr. Fenn. 122: 1 122.
Ensminger, L. E. 1954. Some factors affecting the adsorption of sulfate by Alabama soils.

Soil Sei. Soc. Amer. Proc. 18: 259 264.
Eppendorfer, W. 1969. The effects of nitrogen and sulphur on dry matter yields of barley plants,

on total-N and -S concentrations in grain and straw, and on cystine and methionine
contents of grain. Roy. Vet. Agric. Univ. Yearbook 1969: 100 116.

Erdman, L. W. 1922. The sulfur content of rainwater. Soil Sci. 14: 363 367.
Erviö, R. 1971. Volymviktens inverkan pä markkarteringsvärden. Nord. Jordbr. Forskn.

53; 216-218.
Faller, N. 1971 a. Effects of atmospheric S0 2 on plants. Sulphur Inst. J. 6,4: 5 7.

1971 b. Plant nutrient sulphur S02 vs. S0 4.
Sulphur Inst. J. 7,2: 56.

Fiannetto, F. 1912. 801. Quind. Sox. Agr. Ital. 17: 425—429. Abs. Study of sulphur as a
fertilizer. Bibliography of the literature on minor elements and their relation to plant
and animal nutrition. 4th ed. 1948. New York 1037 p. Voi 1: 882 883.

Freney, J. R, 1958. Determination of water-soluble sulfate in soils. Soil Sci. 86: 241—244.
1961. Some observations on the nature of organic sulphur compounds in soil. Austr.
J. Agric. Res. 12: 424-432.
Barrow, N. J. & Spencer, K. 1962. A review of certain aspects of sulphur as a soil
constituent and plant nutrient. Plant & Soil 17: 295 308.
Melville, G. E. & Williams, C. H. 1970. The determination of carbon bonded sulfur
in soil. Soil Sci. 109: 310-318.

Graham, E. R. 1948. Determination of soil organic matter by means of a photoelectric colorime-
ter. Soil Sci. 65: 181-183.

Gupta, U. C. 1969. S x Mo interaction in plant nutrition. Sulphur Inst. J. 5,1: 4—6.
& Cutcliffe, J. A. 1968. Influence of phosphorus on molybdenum content of Brussels
sprouts under field and greenhouse conditions and on recovery of added molybdenum
in soil. Can. J. Soil Sci. 48: 117 123.

Harward, M. E. & Reisenauer, H. M. 1966. Reactions and movement of inorganic soil
sulfur. Soil Sci. 101: 326-335.

Herath, H. M. W. & Ormrod, D. P. 1971. Temperature effects on the response to sulphur
of barley, peas and rape. Plant - & Soil 35: 635 646.

Hirst, C. T. & Greaves, J. E. 1922. Factors influencing the determination of sulfates in soil.
Soil Sci. 13: 231-249.

Hogg, D. E. 1966. Studies on leaching losses of sulphur from pumice soils, yellow brown sands
and loams. Proc. N. Z. Grassl. Ass. 1965: 123 128. Abs. Soils & Fert. 29: 3403.

Honcamp, F. 1931. Diingung und Diingemittel. pp. 1—44 in Handbuch der Pflanzenernährung
und Diingerlehre. 11. Diingemittel und Diingung. Berlin 919 p.

Jaakkola, A. 1972. Availability to plants of molybdenum in Finnish mineral soils. Acta Agr.
Fenn. 126: 1-92.

Jackson, H. L. 1956. Soil chemical analysis advanced course. Madison 991 p.
Jensen, J. 1963, Some investigations on plant uptake of sulfur. Soil Sci. 95; 63—68.

1964. Investigations concerning sulfur in Danish soils. Bth Int, Congr. Soil Sci. Trans.
4: 411-417.

Johansson, O. 1959. On sulfur problems in Swedish agriculture. Ann. Agr. Coll. Sweden 25:
57-169.
1969. Aktuelli om svavel som växtnäringsämne. Rapp, Avd. Växtnäringslära 8.



208

Johnson, E. M. 1925. Analyses of rainfall from a protected and an exposed gage for sulfur,
nitrate nitrogen, and ammonia. J. Amer. Soc. Agron. 17; 589 591.

Johnson, C. M. & Arkley, T. H. 1954. Determination of molybdenum in plant tissue. Anal.
Chem. 26: 572 574.

Johnson, C. M. & Nishita, H. 1952. Microestimation of sulfur in plant materials, soils, and
irrigation waters. Anal. Chem. 24: 736 742.

Jones, L. H. P,, Cowling, D. W. & Lockyer, D. R. 1972. Plant-available and extractable
sulfur in some soils of England and Wales. Soil Sci. 114: 104 114.

Kacar, B. & Akgul, M. E. 1967. Influence of heavy dressing of sulfur on the availability
of soil phosphorus in an alkaline calcareous soil. Yb. Fac. Agric. Univ. Ankara 1966:
33-41. Abs. Soils & Fert. 31: 840.

Kaila, A. 1963. Phosphorus conditions at various depths in some mineral soils. J. Scient. Agric.
Soc. Finl. 35: 69-79.

Kilmer, V. J. & Nearpass, D. C. 1960. The determination of available sulfur in soils. Soil
Sei. Soc. Amer. Proc. 24: 337 340.

Kolthofe, I, M. & Sandell, E. B. 1950. Textbook of quantitative inorganic analysis. Lon-
don 794 p.

Koyama, T. & Tomino, T. 1970. Influence of sea salts on the soil metabolism (I). On the be-
haviour of iron, manganese, ammonium, and carbohydrates in waterlogged soils. Soil
Sci. & Plant Nutr. 16: 69-80.

Laaksonen, R. 1969. Vesistöjen veden laadusta vuosina 1962 1968. Vesiensuojelutoimiston
tiedonantoja 47: 1 512 -f Appendixes.
1970. Vesistöjen veden laatu. Summary: Water quality in the water systems. Soil and
Hydrotechn. Inv. 17: 1 132.

Lavkulich, L. M., Dairon, P. A. & Spindler, B. von, 1970. Determination of carbon and
sulfur in soil extracts by dry combustion using a high temperature induction furnace.
Can. J. Soil Sci. 50: 95—96.

Liebig, J. von, 1862. Die Chemie in ihrer Anwendung auf Agricultur und Physiologic. 7th
ed. Braunschweig I part 469 p.

Lipman, J. G., McLean, H. C. & Lint, H. C. 1916. The oxidation of sulfur in soils as a means
of increasing the availability ot mineral phosphates. Soil Sci. 1: 533 539.

Lowe, L. E. 1964. An approach to the study of the sulphur status of soils and its application
to selected Quebec soils. Can. J. Soil Sci. 44: 176 179.
1965. Sulphur fractions of selected Alberta soil profiles of the chernozemic and podzolic
orders. Can. J. Soil Sci. 45: 297 303.

Lyon, T. L. & Bizzell, J. A. 1918. Records for tanks 1 to 12 during the years 1910 to 1914,
inclusive. Cornell Univ. Agric. Exp. Sta. Mem. 12: 1 115.
1936, Lysimeter experiments. IV, Records for tanks 17 to 20 during the years 1922
to 1933 and for tanks 13 to 16 during the years 1913 to 1928. Cornell Univ. Agric. Exp.
Sta. Mem. 194: 1-59.

Mack, A. R. & Sanderson, R. B. 1971. Sensitivity of the nitrate-ion membrane electrode in
various soil extracts. Can. J. Soil Sci. 51: 95 104.

Mahendrappa, M. K. 1969. Determination of nitrate nitrogen in soil extracts using a specific
ion activity electrode. Soi Sci. 108; 132 136.

McClung, A. C., DeFreitas, L. M. M. & Lott, W. L. 1959. Analyses of several Brazilian soils
in relation to plant responses to sulfur. Soil Sei. Soc. Amer. Proc. 23: 221—224.

Menary, R. C. & Hughes, J. D. 1967. The effect of sulphate on phosphorus availability on a
krasnozem soil. Austr. J. Exp. Agr. Anim. Husb. 7: 168 173.

Milton, R. F. & Waters, W. A. 1949. Methods of quantitative micro-analysis. London 599 p.
Myers, R. J. K. & Paul, E, A. 1968. Nitrate ion electrode method for soil nitrate nitrogen

determination. Can. J. Soil Sci. 48: 369 371.
Neller, J. R. 1959. Extractable sulfate-sulfur in soils of Florida in relation to amount of

clay in the profile. Soil Sei. Soc. Amer. Proc. 23: 346 348.
Nelson, L. E. 1964. Status and transformation of sulfur in Mississippi soils. Soil Sei. 97: 300

306.



Nydahl, F. & Gustafsson, L. A. 1953. Separation of sulphate and hydrogen sulphate ions
from interfering substances by adsorption on aluminium oxide, prior to sulphate deter-
mination. Acta Chem. Scand. 7: 143 153.

O'Connor, K. F. & Vartha, E. W. 1969. Responses of grasses to sulphur fertilisers. N. Z. J.
Agric. Res. 12: 97-118.

odelien, M. 1957. Kulturvekstenes svovelforsyning. Summary: The sulphur supply of
cultivated plants. Res. Norwegian Agr. 8; 377 387.
1965. Undersokelser over utvaskingen av sulfat fra jorda. Summary: Investigations on
the leaching of sulphate from soil. Res. Norwegian Agr. 16: 39 76.
1970. Kulturvekstenes svovelforsyning. En oversikt. Summary; The sulphur supply
of cultivated plants. A review. Res. Norwegian Agr. 21: I—2l.

OdUn, S. 1968. Nederbördens och luftens försurning dess orsaker, förlopp och verkan i olika
miljöer. Summary: The acidification of air and precipitation and its consequenses on
the natural environment. Ecolog. Res. Comm, Bull. 1: 1 86.

oien, A. & Selmer-Olsen, A. R. 1969. Nitrate determination in soil extracts with the nitrate
electrode. Analyst 94: 888 894.

Olsen, R. A. 1957, Absorption of sulfur dioxide from the atmosphere by cotton plants. Soil
Sci. 84: 107-111.

Paul, J. L. & Carlson, R. M. 1968. Nitrate determination in plant extracts by the nitrate
electrode. J. Agr. Food Chem, 16: 766 768.

Purokoski, P. 1958. Die schwefelhaltigen Tonsedimente in dem Flachlandgebiet von Liminka
im Lichte chemischer Forschung. Agrogeol. Pubi. 70: 1 88.
1959. Rannikkoseudun rikkipitoisista maista. Referat: t’ber die schwefelhaltigen Boden
an der Kiiste Finnlands. Agrogeol. Pubi. 74: 1 27.

Quinlan, K. P. & DeSesa, M. A. 1955. Spectrophotometric determination of phosphorus as
molybdovanadophosphoric acid. Anal. Chem. 27: 1626 1629.

Rankama, K. & Sahama, T, G. 1964. Geochemistry. sth ed. Chicago 912 p.
Rehm, G. W. & Caldwell, A. C. 1968. Sulfur supplying capacity of soils and the relationship

to soil type. Soil Sci. 105: 355 361.
Reisenauer, H. M. 1963. The effect of sulfur on the absorption and utilization of molybdenum

by peas. Soil Sei. Soc. Amer. Proc. 27: 553 555.
Roberts, S. & Koehler, F. E. 1968. Extractable and plant-available sulfur in representative

soils of Washington. Soil Sci. 106: 53 59.
Säalbach, E., Kessen, G. & Judel, G. K. 1962. Untersuchungen iiber die Bestimmung des

Gehaltes an pflanzenverfiigbarem Schwefel im Boden. Landvv. Forsch. 15: 6 15.
Salonen, M., Tähtinen, H., Tainio, A., Keränen, T., Barkoff, E. & Jokinen, R. 1965.

Rikkipitoisten ja rikittömien moniravinteisten lannoitteiden käyttöarvoa selvitteleviä
tutkimuksia. Summary: Comparative studies on the effect of sulphur-containing and
sulphur-free multi-nutrient fertilizers. Ann. Agric. Fenn. 4: 155 177.

Scott, P. R. & Robertson, W. C. 1926. Gypsum or copi. J. Dept. Agr. Victoria 24, 2: 65
74. Abs. Bibliography of literature on the minor elements and their relation to plant
and animal nutrition. 4th ed. 1948. New York 1037 p. Voi 1: 913.

Searle, P. L. 1968. Determination of total sulphur in soil by using high-frequency induction
furnace equipment. Analyst 93: 540 545.

Seim, E. C., Caldwell, A. C. & Rehm, G. W. 1969. Sulfur response by alfalfa (Medicago sativa
L.) on a sulfur-deficient soil. Agron. J. 61: 368 371.

Shedd, O. M, 1926. Influence of sulfur and gypsum on the solubility of potassium in soils and
on the quantity of this element removed by certain plants. Soil Sci. 22: 335 354.

Steinbergs, A. 1953. A rapid turbidimetric method for the determination of small amounts
of sulphur in plant material. Analyst 78: 47 53.

Söderbaum, H. G. 1919. Kan svavel betecknas som ett gödselmedel? K. Lantbr. Akad. Handl.
Tidskr. 58: 357-363.

Tabatabai, M. A. & Bremner, J. M. 1970. Comparison of some methods for determination
of total sulfur in soils. Soil Sei. Soc. Amer. Proc. 34: 417—420.

Takai, Y. & Asami, T. 1962. Formation of methyl mercaptan in paddy soils. I. Soil Sci. &

Plant Nutr. 8: 132-136.

209



210

Takijima, Y., Shiojima, M. & Konno, K. 1962. J. Sci. Soil Tokyo 33; 331 334. Abs. Growth-
inhibiting substances found in poorly drained peaty paddy soils. 1. Inhibition of plant
growth and soil metabolism. Soils & Fert. 26: 2755.

Tikkanen, M. H. & Yläsaari, S, 1972. Ilman saastuminen ja atmosfäärinen korroosio. Finnish

J. Chem. Ind. 29: 118-122.
Tottingham, W. E. & Hart, E. B. 1921. Sulfur and sulfur composts in relation to plant

nutrition. Soil Sci. 11; 49 73.
Vermorel, V. & Dante ony, E. 1913. Engrais 28: 1304—1306. Abs. Sulfur and iron pyrites

as fertilizers. Chem. Abs. 8 (1914): 545 546.
Wiklander, L. 1957. Om svavlets förekomst i marken. Nord. Jordbr. Forskn. 39: 399—406
Williams, C. H. & Steinbergs, A. 1959. Soil sulphur fractions as chemical indices of available

sulphur in some Australian soils. Austr. J. Agric. Res. 10: 340 352.
1964. The evaluation ol plant-available sulphur in soils. 11. The availability of adsorbed
and insoluble sulphates. Plant & Soil 21: 50 62.

Wilson, B. D. 1926. Nitrogen and sulfur in rainwater in New York. J. Amer. Soc. Agron. 18:
1108-1112.

Vincent, Sarazin & Hkrviaux, 1935. Le soufre dans les goemons, les vases marines et les
eaux de pluie en Bretagne. Compt. Rend. Acad. Agr. France 21: 1032 1034.

Vries, T. de, 1968. Potentials of electrochemical reactions at 25°C. Section D-86 in Handbook
of chemistry and physics. 49th ed. 1968 1969. Ohio.

Vuorinen, J. & Mäkitie, O. 1955. The method of soil testing in use in Finland. AgrogeoJ.
Pubi. 63: 1-44.



211

Appendix 1. Somecharacteristics of the soil samples, a= 0 —25 cm, b= 25 —5O cm

,

Amm. acet.
Clay Organic C lotal ex tractable
% %

denS,ty pHc*c'* SU,phur sulphurkg/1 mg S/kg
mg S/l

Sample
Nr Soil type

la finesand 4 2.8 1.02 5.3 450 3
lb finesand 3 0.4 1.29 5.1 400 5
2a loam 13 4.5 0.85 5.2 690 3
2b loam 11 1.5 1.00 4.9 400 3
3a Carex peat 29.1 0.47 4.5 1190 3
3b Carex peat 36.3 0.51 3.5 2160 3
4a finesand 3 2.0 1.02 5.0 180 2
4b finesand 2 0.2 1.34 5.1 210 7
5a finer finesand 8 2.3 0.97 6.4 320 3
5b finer finesand 7 0.4 1.13 5.4 230 9

6a finer finesand 13 2.6 0.85 5.1 420 2
6b finesand 7 0.6 1.10 4.9 220 3
7a silt 28 3.2 0.98 4.8 580 3
7b silty clay 33 0.6 1.13 5.4 120 2
8a Carex peat 32.6 0.39 4.5 530 2
8b Carex peat 33.5 0.40 3.8 960 2
9a mould 33 14.2 0,57 4.5 700 20
9b loam 17 0.5 1.24 4.7 120 7

10a loam 18 7.5 0.70 5.5 590 8
10b loam 9 1.0 1.13 5.0 130 0

11a loam 14 3.1 1.14 4.7 340 27
11b silt 18 1.2 1.20 5.2 230 9
12a loamy clay 33 2.8 0.96 4.7 500 10
12b loamy clay 36 1.7 0.97 4.7 460 23
13a mould 6 13.5 0.69 4.0 710 24
13b finesand 9 2.1 1.00 3.8 700 57
14a silt 23 4.6 0.90 4.5 430 16
14b silt 15 0.6 1.08 5.0 180 8
15a Carex peat 40.3 0.18 3.5 850 3
15b Carex peat 48.0 0.28 3.8 740 9
16a finer finesand 5 3.0 1.02 5.2 450 13
16b finer finesand 3 0.6 1.30 5.0 210 23
17a finesand 6 4.0 1.02 4.5 420 13
17b finesand 3 0.8 1.31 4.9 200 14
18a finesand 4 2.0 1.05 5.4 260 3

18b finesand 5 1.3 1.17 5.4 140 6
19a moraine 2 0.8 1.44 4.9 140 41
19b moraine 2 0.9 1.50 4.3 200 26
20a finesand 3 2.3 1.10 4.3 130 9
20b finesand 2 1.4 1,34 4,5 190 49

21a silty clay 49 4.2 0.90 4,9 480 4
21b heavy clay 67 2.0 1.04 5.2 270 3
22a finer finesand 12 2.6 1.13 5.1 380 3
22b finer finesand 7 0.5 1.41 5.4 160 1
23a loamy clay 39 4.3 0.90 4.4 530 22



212

Appendix 1. Some characteristics of the soil samples (continued).

Amm. acet.
Sample Clay Organic C ' extractable

Nr Soil type
% %

density pH CaCI2 sulphur su]phur
kg/l mg S/kg mg g/1

23b loamy clay 39 1.8 1.04 4.1 790 180
24a loamy clay 50 3.00.96 5.2 580 14
24b heavy clay 64 1.20.99 4.9 480 40
25a loamy clay 37 5.00.84 4.5 410 13
25b loamy clay 34 0.7 1,08 4.7 160 15

26a finesand 19 1.91.26 4.8 320 4
26b loamy clay 48 0.81.20 5.0 320 9
27a finesand 10 2.51.12 5.7 310 3
27b sand 7 0.51.43 5.4 270 5
28a moraine 4 3.71.25 4.6 660 6
28b moraine 3 1,2 1,51 5.0 460 19
29a finesand 6 6.30.90 4.7 650 5
29b finesand 3 0.81.52 5.2 340 16
30a mould 45 13.80.52 4.7 1120 9
30b mould 59 12.00.53 5.1 900 12

31a finesand 8 3.11.02 5.1 460 7
31b finer finesand 5 0,6 1.35 5,1 220 5
32a sand 3 2.01.16 4.6 280 3
32b finesand 2 0.61.44 4.7 170 2
33a Carex peat 46.80.27 4.6 980 3
33b Carex peat - 44.30.20 3.5 760 5
34a loam 7 2.60.99 4.7 350 15
34b loam 8 1.61.16 4.6 270 17
35a finesand 3 2.51.09 4.6 320 9
35b finesand 2 1.11.54 5.5 260 4

36a silt 8 5.20.67 4.9 760 21
36b silt 8 1.01.06 4.7 400 11
37a Carex peat 39.60.38 5.1 1500 3
37b Carex peat 47.10.35 4.3 1580 2
38a Carex peat 45.70.19 4.3 1530 3

39a Carex peat 46.80.20 4.3 1620 3
40a finer finesand 6 2.31.04 4.6 360 4
40b finer finesand 6 1.41.16 4.6 260 4
41a finesand 3 2.91.14 4.2 340 5
41b sand 3 2.91.10 3.9 280 2

42a Carex peat 38.90.38 4.4 1810 6
42b Carex peat 50.40.28 4.4 1960 2
43a loam 19 6.10.91 4.9 750 250
43b silt 26 0.71.25 4.1 500 210
44a mould 22 12.80.78 4.7 580 11

44b finesand 11 1.4 1,40 4.8 250 5
45a Carex peat 39.60.34 4.0 1520 23
46a Carex peat 41.10.33 4,5 1130 2
47a loamy clay 47 2.01.00 5.7 320 3
48a finesand 4 1.51.36 4.9 230 1



213

Appendix 1. Some characteristics of the soil samples (continued).

Amm, acet.
Sample Clay Organic C 1 otal

extractable
Nr Soil type 0/ 0/ density pH CaCla sulphur sul hur

k g/' ™g S/kg mg g/1

49a loamy clay 30 2.9 0.91 4.5 400 6
50a silty clay 41 2.6 0.90 4.7 330 3
51a loamy clay 47 1.9 1.00 5.7 310 5
52a finesand 6 2.1 0.91 5.8 310 3
53a silty clay 59 3.9 0.81 4.6 540 14
54a silt 23 2.8 0.86 4.7 380 1
55a silty clay 50 3.0 0.98 5.4 450 0
56a heavy clay 62 4.3 0.85 5.1 480 12
57a silty clay 56 4.5 0.72 3.3 8200 -

58a loam 22 2.8 0.89 5.9 330 4

59a finer finesand 11 3.1 0.84 5.7 360 3
60a silty clay 34 3.2 0.81 5.3 1140 3
61a loamy clay 48 3.4 0.93 6.0 430 3
62a loamy clay 34 3.1 0.96 5.6 360 3



214

SELOSTUS

Suomen viljelysmaiden rikkitila

Johan Korkman

Helsingin Yliopiston maanviljelyskemian laitos

Tässä tutkimuksessa jouduttiin aluksi rikin määritystapojen joukosta valitsemaan labora-
torion varustuksen ja maanäytteiden laadun mukaiset menetelmät. Kokonaisrikin määrittä-
miseen kehitettiin menetelmä, joka perustuu näytteen polttamiseen induktiouunissa ja sul-
faattiakin turbidimetriseen mittaukseen vetyperoksidiin imeytetystä polttokaasusta. Maa-
uutteiden analysoinnissa esille tulevat vaikeudet voitiin selvästi osoittaa. Analyysitulosten
arvo näytti yleisesti käytetyn bariumkroraaattimenetelmän kohdalla jopa kyseenalaiselta.
Rikin määrittämiseksi ammoniumasetaattiuutteesta (pH 4.65) on esitetty uusi menetelmä, jossa
eloperäisen aineksen määritystä häiritsevää vaikutusta on vähennetty käsittelemällä uutteita
vetyperoksidilla.

Suomen viljelysmaitten rikkitase arvioitiin ottamalla huomioon maahan ilmakehästä ja
viljelytoimenpiteiden seurauksena tuleva rikki sekä huuhtoutumisesta ja kasvien otosta aiheu-
tuva rikin kulutus. Sateen mukana tulevan ja vesistöihin huuhtoutuvan rikin määrät näyttivät
olevan samaa suuruusluokkaa eli noin 8 kg/ha vuodessa. Lannoitusvuonna 1970 —7l levitettiin
rikkiä lannoitteissa noin 12 kg viljeltyä hehtaaria kohti. Tämä viljasadolle riittävä määrä on
ilmeisesti liian niukka paljon rikkiä vaativille kasveille.

Alustava tutkimus Suomen viljelysmaiden rikkivaroista ja niiden käyttökelpoisuudesta kas-
veille suoritettiin analysoimalla joukko maanäytteitä ja järjestämällä näissä maissa astia- ja
kenttäkokeita. Näytteet olivat 62 kohteesta linjan Oulu-Kuusamo eteläpuolella. Näytteiden
kokonaismäärä oli 104, joista 62 pinta- ja 42 jankkonäytettä.

Näytesarjan multa- ja turvemaat (21 kpl) sisälsivät keskimäärin .11 SO - 220 mg rikkiä ilma-
kuivaa maakiloa kohti, savimaat (22 kpl, koska eräs sulfaattimaan näyte jätettiin tarkastelun
ulkopuolelle) 450±94, hiesu- ja hiuemaat (18 kpl) 410±100 ja hieta- ja hiekkamaat (42 kpl)
310±43 mg/kg (vaihtelurajat ilmoitettu 95 % luotettavuudella). Kivennäismaiden jankko sisälsi
keskimäärin 30 % vähemmän rikki kuin pintamaa.

Maanäytteiden kokonaisrikin pitoisuus oli melko hyvin korreloitunut eloperäisen aineksen
pitoisuuden kanssa (r = o.B3***). Tutkittuihin reagensseihin (1 % NaCl, 0.03 M NaH2P04-2
N CHjCOOH ja CH3COONH4 -CH3COOH, pH 4.65) uuttuva rikki sen sijaan ei juuri riippunut
määritetyistä maan yleisistä ominaisuuksista (pHCaCi2, org.C ja tekstuuri).

Tutkituista uuttoliuoksista hapan ammoniumasetaatti uutti vähiten rikkiä myös kun tila-
vuuspaino otettiin huomioon. Muut kaksi menetelmää antoivat keskenään samaa suuruus-
luokkaa olevia tuloksia. Mikään uuttomenetelmistä ei pystynyt antamaan selvää kuvaa siitä,
miten lannoiterikki vaikuttaa kasvien kehitykseen. Ammoniumasetaattiin uuttuvan rikin määrä
kuvasi kuitenkin jotenkin maan rikkitilaa. Tämän menetelmän tärkeä etu näytti olevan tila-
vuusyksikköön perustuva uuttosuhde, joka antoi vertailukelpoisia tuloksia niin kivennäis- kuin
multa- ja turvemaistakin.

Timoteivaltaisen nurmen rikkilannoitus saraturvemailla Kuusamossa lisäsi suhteellisen



215

selvästi nurmisatoa ja sen rikinottoa kesällä 1969. 10 kg rikkiä hehtaarille oli tarpeeksi nurmi-
sadon kohottamiseksi tyydyttävälle tasolle. Vielä runsaampi rikkilannoitus aiheutti melkein
yksinomaan sadon rikin pitoisuuden lisääntymisen. Etelä-Suomessa vuonna 1970 järjestetyissä
kenttäkokeissa rikkilannoitus ei vaikuttanut kevätviljojen satoihin.

Lähinnä lannoitteiden koostumuksen suunnittelua ajatellen tutkittiin astiakokein toisaalta
rikin toisaalta typen, fosforin ja molybdeenin vuorosuhteita. Tuntui ilmeiseltä, että määrältään
ja laadultaan optimaalisen sadon saavuttamiseksirikkiä ja typpeä täytyy olla kasvien käytettä-
vissä tietyssä suhteessa, joka todennäköisesti on rajojen N/S = 5-20 puitteissa. Kun rapsi kärsi
samanaikaisesti näiden kahden ravinteen puutetta, typpi rajoitti ensisijaisesti kasvin vegetatii-
vista kehitystä ja rikki siementen muodostusta. Rikki ja fosfori tuntuivat vaikuttavan kas-
vissa toisistaan riippumatta, kun taas molybdeenilannoitus rikin niukkuuden vallitessa kohotti
voimakkaasti kasviaineksen molybdeeninpitoisuutta.