Maataloustieteellinen Aikakauskirja
Vol. }2: 49}-}O4. 1980

The effect of selenium fertilizers on the selenium content of barley,
spring wheat and potatoes

JOHAN KORKMAN

Kemira Oy, 00101 Helsinki 10, Finland

Abstract When Se-cnriched fertilizers were given to barley and spring wheat on fine sand soils in Southern
Finland the Se content in the grain was raised as follows: 50 g Sc/ha increased the Se content by around 50
fig/kg; 250 g Sc/ha by appr. 400 U g/kg; and 500 g Sc/ha by a little more than 900 fA g/kg.

The selenium content of potatoes rose to Se/kg dry matter when the soil was enriched with 500 g
Se in the form of Na 2 per hectare. The selenium content ofpotatoes was found to be very low when no ad-
ded selenium was given. The selenium content of potatoes did not fall when the potatoes were boiled.

Introduction

Selenium is not an indispensable nutrient for crops. Nevertheless, there have
been experimental attempts at raising the selenium content of agricultural produce;
in the USA (CARY and ALLAWAY 1973), in New Zealand (GRANT 1965, DAVIES
andWATKINSON 1966), and in Denmark (GISSEL-NIELSEN 1971, 1975). TheSe
quantities used in the experiments have varied greatly, ranging from a few grammes
when crops were sprayed (GISSEL-NIELSEN 1971) to several kilogrammes per
hectare when transmitted through the soil (CARY and ALLAWAY 1973). When the
selenium has been transmitted through the soil, selenium fertilizer quantities in the re-
gion of 100 g Se/ha have proved sufficient to give the desired Se level for fodder
crops and hay, 50—100 u g Se/kg (GRANT 1965, GISSEL-NIELSEN 1977). It has
been found that much smaller Se quantities give the same results when crops are
sprayed if the spraying is done at the right time (GISSEL-NIELSEN 1977).

Pure selenium, selenate and selenite were used in the experiments to increase the
selenium content of the fertilizers. GISSEL-NIELSEN (1977) has conducted many
experiments and he holds that selenite is the best source, even though selenate may
be more effective than selenite for raising the selenium content of crops. The same re-
searcher has also demonstrated (GISSEL-NIELSEN 1977) that the sulphate content
of the soil has a much greater influence on how selenate is transmitted than on how
selenite is transmitted.

The present study made use of selenite only. The selenite was employed to raise
the selenium content of the fertilizers and for crop spraying purposes. The study aims

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496

at reaching a preliminary assessment of the manner in which the selenium content of
barley, spring wheat and potatoes is raised when selenite fertilizers are sprayed and
transmitted through the soil. The selenium-enriched barley obtained as a result of
spraying has been used in feed tests on chickens, pigs and horses (KÄÄNTEE and
KURKELA 1980a, and 1980b).

Materials and methods

The fertilizers used in the experiments were prepared at the small factory of Ke-
mira Oy’s research plant. Ordinary commercial products were used as raw material;
the fertilizers were granulated by being sprinkled with NajSeOj-JHjO solute. The
Se content aims for the fertilizers were 0.01 % Se, 0.05 % Se and 0.10 % Se and
these levels were realized.

A tractor spray was used for carrying out the selenium spraying: a solution of
sodium selenite in 400 litres of water was used over one hectare.

The field tests were carried out at the Kotkaniemi experimental farm at Vihti.
The fertilizers which were meant to be transmitted through the soil were placed with
a combined drilling machine.

The Kemira Oy Oulu research plant conducted the selenium analyses. The hy-
dridemethod was used (SAARI and PAASO 1 980).

Results

1 Spraying

Suvi barley (sown 17. 5. 1978) growing on sandy loam was sprayed on 21. 6.
1978. The barley was being grown for experimental fodder and was just beginning

to sprout when the spraying was carried out. Follow-up samples of the Suvi barley
were taken the next year.

The spraying treatment was repeated on another plot of sandy loam in the sum-
mer of 1979. The Aapo barley had been sown on 17—18. 5. and the spraying was
carried out on 21. 6. 1979 when the barley was sprouting. The initial selenium con-
tent of the plot sprayed in 1979 was slightly higher than the soil sprayed the year
before.

2 Fertilisers transmitted through the soil

Grain

The selenium fertilizer experiments conducted in 1978—79 were carried out on
coarse mineral soil. Barley and spring wheat were treated with experimental fertili-
zers which were enriched with Na2Se0 3 . Half of the experiment site was limed with
5 t/ha of agricultural lime before the experiment was instigated. The mean analysis
results of the soil samples taken on 1 1. 5. 1978 before liming and fertilizing were as
follows;



497

Table 1. The effect of Na 2 Sc0 3 spraying on the Se content of barley, 1978—79.

barley grain Se content 11 g/kg dry matter

1978 spraying residual effect
in 1979

1. untreated 10 10
2 0.1 kg/ha Se in the form of Na2 SeO, 170 10
3. 0.5 " " " 680 20
4. 1.0

" " " 1000 10

Table 2. The effect of Na2 ScO s spraying on the Sc content of barley, 1979

barley grain Sc content jj, g/kg dry matter

1 untreated 40
2. 0.1 kg/ha Se in the form of Na 2 SeOj
3. 0,5

500
1100

4 1.0 2500

soil type

pH H 2 O

coarse sand
6,0

Ca NH 4 Ac
K NH 4 Ac
P NH 4 Ac
Mg NH 4Ac

B hot water

824 mg/1 soil

154
6,5

80
0,5

Cu 2M HCI

Mn MgS04

5,1

4,4

Four fertilizer types were prepared for the grain experiments. The main nutrient
and boron content of each type was the same: N 15, P 8.7, K 1 2.4 and B 0.03 %.

Selenium content was regulated to four levels with Na2Se0 3 : 0.00, 0.01, 0.5, and
0.10 % Se. The quantity of fertilizer with which the grain was treated was 500
kg/ha.

The spring wheat (Tähti variety) harvest was very low both years. The mean
1978 wheat harvest was 1790 kg grain/ha. The 1979 figure was as low as 1310

kg grain/ha. The barley harvest was satisfactory: an average of 4975 kg/ha was ob-
tained in 1978, and an average of 3255 kg/ha in 1979. Neither year’s spring whe-
at crop was affected by the Se fertilizing. Halving with liming had no significant ef-
fect on the grain harvest either.

Soil samples were taken in the spring of 1979 after the first year of tests in or-
der that selenium analyses might be made.

Following the first year of tests the experiment site was divided into two. One
half of the site was re-treated with the same Se-enrichcd fertilizer, whereas the other
half was treated with normal, seleniumless fertilizer. The type of fertilizer used was
the same as that which had been employed the previous year. Liming was not repea-
ted.



498

Table 3. The effect of the selenium content of fertilizers on the selenium content of grain, 1978.The same letter
in the vertical column = no significant deviation of figures (p = 0.05).

grain selenium content Sc (I g/kg
spring wheat barley

fertilizer limed unlimed limed unlimed
Se content kernel middle husk kernel middle husk

1 0.00%5e 170a 175a 117a 100a 105a 137a 40a 50a

2 0.01 %Se 135a 210ab 247a 135a 153a 197a 130b 130a

3 0.05 %Se 467 b 600bc 765 b 290 b 435 b 575 b 450c 480 b
4 0.10%5e 737 b 840 c 1032 b 970 c 1050c 132 5 c 1110 d 1200c

Table 4. The quantities of water soluble selenium of soil samples after one test year.

fertilizer Sc content water soluble Se mg/1

limed unlimed

1 0.00 %Se 0.0063 0.0068
2 0.01 %Se 0.005 3 0.0060
3 0.05 %Sc 0.0058 0.0065
4 0.10%5e 0.0090 0.0090

Tabic 5. The effect of selenium content of fertilizers on the selenium content of spring wheat grains, 1979. The
same letter in the vertical column = no significant deviation of figures (p = 0.05).

fertilizer grain selenium content Se*) fl g/kg
Sc content limed unlimcd

1979 1978 kernel middle husk kernel middle husk mean

1 0.00%5e 0.00 %Se 60 55 75 60 65 75 65 a

2a 0.00%5c 0.01 %Sc 40 50 50 90 95 60 64 a

3a 0.00%5c 0.05%5e 70 70 60 110 115 75 83a

4a 0.00%5e 0.10%5e 170 200 160 120 120 150 153a

2b0.01%5c 0.01%5e 135 195 195 190 235 210 193a

3b0.05%5e 0.05%5c 415 470 560 410 495 625 496 b
4b 0.10%5e 0.10%5e 1150 1400 1800 1100 1750 1800 1500c

*) limed/unlimed F = 0.51 i.c. liming has no significant effect

Table 6. The effect of the selenium content of fertilizers on the selenium content of barley grains, 1979. The sa-
me letter in the vertical column = no significant deviation of figures (p = 0.05).

fertilizer Sc content

1979 1978
grain selenium content

limed*) unlimed

1 0.00% Sc 0.00% Sc 40a 75a

2a 0.00% Sc 0.01% Sc 5 5 a 60a

3a 0.00% Sc 0.05 % Se 70 ab 85 ab
4a 0.00% Sc 0.10 %Sc 105bc 130 b
2b 0.01 %Se 0.01 %Se 110c 95b
3b 0.05 %Se 0.05 %Se 370 d 390c

4b 0,10% Sc 0.10 % Sc 1100c 1300d

') limed/unlimcd F = 5.97 x, i.e. the Se content on limed soil is significantly lower



499

Potatoes

The selenium fertilizer experiments conducted in 1978—79 were carried out on
coarse mineral soil. Rekord potatoes were treated with experimental fertilizers which
were enriched with Na 2Se0 3 . Half of the experiment site was limed with 5 t/ha of
agricultural lime before the experiment was instigated. The mean analysis results of
the soil samples taken on 22. 5. 1978 before liming and fertilizing were as follows:

soil type fine sand

pH 6.15

Ca NH 4Ac 1400 mg/1 soil

K NH 4 Ac 167

P NH 4 Ac 17
Mg NH 4 Ac 158

B hot water 0.8

Cu 2M HO 7.6 "

Mn MgSQ 4 6.8

Four batches of fertilizer were prepared for the experiment. Apart from the sele-
nium content, all the batches had identical nutrient contents: N 8.0, P 10.5, K
11.6, S 10.7, Mg 2.5, Cu 0.4, Mn 0.7, Zn 0,03, Mo 0.02 and B 0.1 5%. The qu-
antity of fertilizer with which the potatoes were treated was 1000 kg/ha.

The Se fertilizer treatment was not repeated in 1979 on test plots which were
treated with selenium-enriched fertilizer in, 1978 (cp. the section on grain). Instead,
a control experiment was set up on another spot on the same plot. The mean analysis
results for this area prior to liming and fertilizing were as follows:

soil type coarse fine sand
pH H 2 O 60

Ca NH 4 Ac 1640 mg/1 soil
K NH 4 Ac 164

P NH 4 Ac 16
Mg NH 4 Ac 102

B hot water 0. 5
Cu 2M HCI 8.1
Mn MgS04 12.6

Se water 0.0136 "

The same fertilizer type was used in the 1979 potato fertilizing experiments as
had been employed the year before.



500

Table 7. Potato crop, 1978 and 1979.

potato crop kg/ha
fertilizer Se content 1978 1979

1978 1979 limed unlimed limed unlimed

1 0.00 %Se 0.00 %Se 28 570 29 810 21 400 25 120
2 0.01 %Se 0.00 %Se 37 170 33 400 24 830 26 100
3 0.03 %Sc 0.00 %Se 34 790 31 950 26 240 23 450
4 0.10 %Sc 0.00 %Se 35 100 26 640 23 980 21 260

1978 1979
F
s x
F
s x

Se fertilizing 2.91 0.01
5.6% 4.4%

liming 2.24 0.78
4.3% 6.2%

Table 8. The effect of the selenium content of fertilizers on the selenium content ofpotatoes in 1978, and the re-
sidual effect in 1979. The same letter in the vertical column = no significant deviation of figures (p =

0.05)

potato Sc content Se fl g/kg dry matter
1978 1979fertilizer Se content 1979

1978 1979 limed unlimed limed unlimcd

1 0.00 %Se 0.00 %Sc <■ 10a <c 10a <r 10a <. 10a

2 0.01 %Se 0.00 %Sc 10a < 10a
< 10a < 10a

3 0.05 %Sc 0.00%5e 103b 87b 23a 13a

4 0.10 %Se 0.00 %Se 160c 203c 33a 27a

Table 9. The potato crop and the selenium content of potatoes in the experiment instigated in 1979.

fertilizer Se content potato crop kg/ha selenium content of potatoes
(peeled) Se /I g/kg dry matter 1 )

limed unlimed limed unlimed

1 0.00 %Sc 27 670 24 380 < 10a 10a

2 0.01 %Se 28 290 23 430 23a 27a

3 0.03 %Sc 28 690 27 500 110 b 100b
4 0.10 %Se 27 980 24 640 190c 2 ) 213 C

') The same letter in the vertical column = no significant deviation of figures (p = 0.05)

2
) corresponding peels contained 297 u g Sc/kg dry matter

Food preparation tests

A few barley samples were used to bake unleavened bread. The loaves were ba-
ked in an oven at a temperature of 200°C. The Se content of the baked loaves is gi-
ven in Table 10.

A few potatoes which had formed part of the 1979 experiment were boiled.
This was done as a type of random test and the results obtained are presented in Ta-
ble 11.



501

Table 10. The Sc content of barley flour and unleavened loaves baked from it.

selenium content Se fl g/kg dry matter
limed unlimed

fertilizer Se content flour') unleavened flour 1 ) unleavened
1979 1978 loaf loaf

2b 0.01 %Se 0.01 %Se ...
90 60 60 50

3h 0.05 %Se 0.05 %Se... 340 310 320 280
4b 0.10%5c 010%5e... 980 950 1010 960

1978
1 0.00 %Se 50 60(40») 50 50 (402 )

2 0.01 %Se 120 130(90) 110 120(80)
3 0.05 %Se 390 500(450) 430 490(430)
4 0.10%5e 1040 1210(1220) 1110 1230(1150)
') repeat analyses were made of the flour used in the baking, and the figures in the column are not the same as

those in Tables 4 and 8 for this reason.

2 ) the figures in paretheses were obtained by re-analyzing the unleavened loaves after they had been deep frozen
for one year.

Table 11. The effect of boiling potatoes on their selenium content.

fertilizer Sc content peeled potato corresponding boiled and peeled
Se u g/kg dry matter potato Se // g/kg dry matter

1978 1979 limed unlimed limed unlimcd

0.10%5c 0.00%5e ... 33 27 40 37
0.10%5e ... 190 213 270 210

Discussion

The present study’s findings agree with the results of earlier experiments
(SYVÄLAHTI and KORKMAN 1978). Selenium may be given to crops by spraying
or by transmitting it through the soil. The natural selenium content of Finnish crops
is very low (cp. e.g. KOIVISTOINEN 1979) and this means that selenium fertilizers
have a marked effect on both grain and potatoes. When 50 g Se/ha (500 kg/ha of
fertilizer containing 0.01 % sodium selenite) were transmitted to crops through the
soil, the selenium content of the crops rose by a mean of 56 n g/kg during the first
year. When 2 50 g Se/ha were given, the selenium content increased by 404 u g/kg
on an average, and the content rose by a mean of 925 ,u g/kg when 500 g Se/ha
was used.

GISSEL-NIELSEN (1977) found that a Se quantity corresponding to the smallest
amount (60 g Se/ha) caused the Se content of barley to rise by 38 ,m g/kg, and the
content of wheat by 64 M g/kg. The results of these experiments and the present stu-

dy are thus of equivalent magnitude. On the other hand, the effect of the present stu-
dy on the Se content of grain was less great than earlier studies might have led one
to expect (cp. SYVÄLAHTI and KORKMAN 1978). Contrastingly, the natural
content of spring wheat in particular was higher than normal (cp. YLARANTA
1980). The reason for this was not discovered. The very low harvest figures might



502

have a bearing, but it would also appear that the soil of the experiment site had a
greater than usual amount of selenium which could be used by plants.

The present study was unable to arrive at an unequivocal conclusion as to how
liming increases selenium uptake (cp. GEERING et al. 1968). Conflicting results
have been obtained in this field: in Sippola’s study (SIPPOLA 1979) a high pH
appeared to have some slight retarding effect on the Se uptake of plants in this ti-
mothy material.

The finding that selenium is comparatively evenly distributed over the various
parts of wheat grains and does not become concentrated in the husk to the same ex-
tents as other elements was noteworthy. Whilst the most selenium is found in the
husk and the least in the kernel, differences are not great.

The selenium content of the unleavened barley loaves did not fall during baking.
The content remained constant or rose a little. The Se content of the loaves was not
affected by being deep frozen for a year. Selenium was not lost when potatoes were
boiled.

There have been very few studies made with selenium fertilizers and potatoes.
The present study demonstrated that the amount of selenium transmitted to potatoes
is proportional to the quantity of selenium given during fertilizing. An estimate was
made of the total selenium content of the dry harvest and demonstrated that potato
is unlikely to be a more efficient user of selenium than spring wheat or barley.

The same problem is inherent in selenium fertilizers as mineral micronutrient fer-
tilizers: only a very small part of the fertilizing element is transmitted to the crop
and the rest of the element is bound to the soil or placed beyond the reach of the
crop in some other fashion, A rough estimate of the quantity of selenium transmitted
to the edible part of the plant in the first year (spring wheat and barley 1978, potato
1978—79) demonstrates that grain and potatoes are fairly alike in this regard:

wheat barley potato

Se- Sc increase Se- Se increase Sc- Sc increaseSc content

of fertilizer uptake %of quantity uptake %of quantity uptake %of quantity
g/ha given g/ha given g/ha giveng/ha given g/ha given

0.00 0.24 - 0.22 - 0.03 -

0.01 0.28 0.08 0.66 0.88 0.10 0.07
0.05 0.92 0.27 2.32 0.84 0.65 0.13
0.10 1.81 0.36 5.70 1.10 1.14 0.11

The above figures demonstrate that a maximum of slightly over one per cent of
the selenium given was transmitted to the edible part of the plant. There is a slight
indication that a greater proportion of selenium is transmitted to the crop when the
amount given is large than when it is small. The largest Se quantities increased the
Se intake of the harvest by a factor of B—3B when compared to the zero level.

Both grain and potato showed a slight residual effect in the second year. This
finding agrees with the findings of earlier Finnish studies (SYVÄLAHTI and KORK-
MAN 1978). The study will be followed for a few more years in this respect.

A comparative study of the efficiency of selenite and selenate in practical fertili-
zing will be made in Finland in the near future (YLÄRANTA personal
communication). It is hoped that this forthcoming study will enable the efficiency of
selenium fertilizers to be improved.



503

Summary

Selenium fertilizer experiments were made in 1978 and 1979 at the Kemira Oy
experimental farm. Sodium selenite, Na 2Se0 3 5H 2 0, was employed as the selenium
source. Barley was subjected to spraying tests, and fertilizers were transmitted
through the soil for barley, spring wheat and potatoes. Two types of selenium fertili-
zer were prepared at the Kemira research factory for the fertilizer trials. The fertili-
zers contained 0.00, 0.01, 0.05 and 0.10 % of selenium.

When 0.1, 0.5 and 1.0 kg Se/ha was sprayed, selenium content figures were
obtained which were clearly excess of the content which is often used as an objecti-
ve, 50—100 ,u g Sc/kg of the absorbent parts of the plant. More field tests will have
to be carried out to ascertain the right quantities to be used and the best spraying ti-
me before spraying may be used in order to boost the selenium content of crops.

The extents to which selenium fertilizers raised the selenium content of grain
when the fertilizer was transmitted through the soil were as follows: 50 g Se/ha
boosted the Se content by more than 50 /.i g/kg; 250 g Se/ha by approximately
400 ,« g/kg; and 500 g Se/ha by more than 900 ,u g/kg. Selenium was distributed
in spring wheat in such a fashion that the content of the husk was the highest and
the content of the kernel the lowest. However, the Se content of the husk was a me-
re mean 32 % higher than that of the kernel.

The selenium content of potatoes rose to 100 fi g Se/kg dry matter when the
soil was enriched with 500 g Se in the form of Na 2SeO } per hectare. The selenium
content of potatoes was found to be very low when no added selenium was given.
The selenium content of potatoes did not fall when the potatoes were boiled.

The present series of experiments was unable to increase selenium uptake of
crops by liming. It should, however, be borne in mind that the pH value of the test
plots was high for Finnish conditions —it stood at 6.0—6.2 whereas the mean pH
value of Finnish arable soil is 5.6.

References

CARY, E.E. & ALLAWAY, W.H. 1973. Selenium content of field crops grown on selenite-treated soils. Ag-
ron. J. 65. 922-92 5.

DAVIES, E.B. & WATKINSON, J.H. 1966. Uptake of native and applied selenium by pasture species. I.
Uptake of Se by browntop, ryegrass, cooksfoot and white clover from Atiamuri sand. N.Z.J. Agric. Res.
9: 317-327.

GEERING, H R., CARY, E.E., JONES, L.H.P. & ALLAWAY, W.H. 1968. Solubility and redox criteria
for the possible forms of selenium in soils. Soil Sei. Soc. Amer. Proc. 32: 35—40.

GISSEL-NIELSEN, G. 1971. Selenium content of some fertilizers and their influence on uptake ofselenium in
plants. ]. Agr. Food Chem. 19. 564—566.

GISSEL-NIELSEN, G. 1973. Uptake and distribution of added selenite and selenate by barley and red clover
as influenced by sulphur. J. Sci. Ed Agric. 24: 649—65 5.

GISSEL-NIELSEN, G. 1977. Control of selenium in plants. Rep. 370.
GRANT, A B. 1965. Pasture top-dressing with selenium. N.Z.J. Agric. Res. 8. 681—690.
KOIVISTOINEN. P. 1979. Ravinnon kivennäisainetutkimuksista. Kemia-Kerni 6: 694—699.
KÄÄNTEE, E. & KURKELA, P. 1980a. Comparative effects of barley feed and sodium selenite on selenium

levels in hen eggs and tissues. J. Scicnt. Agric. Soc. Eini. 52: 357—367.
KÄÄNTHH, E. & KURKELA, P. 1980b. The effects of trace clement supplements on blood levels of horses.

J. Sclent. Agric. Soc. Eini. 52: 468—476.



504

SAARI, E. & PAASO, A. 1980. Mineral element composition of Finnish foods. Analytical methods. Acta Agr.
Scand. Suppl. 22: 1 5—2 5.

SIPPOLA, J. 1979. Selenium content of soils and timothy (Phleum pratense L.) in Finland. Ann. Agric. Fenn.
18: 182-187.

SYVÄLAHTI, J. & KORKMAN, J. 1978. The effect of applied mineral elements on the mineral content and
yield of cereals and potato in Finland. Acta Agr. Scand. Suppl. 20: 80—89.

YLÄRANTA, T. 1980. Kasvien seleenistä. Maat. Tutkimuskeskus, Maantutk.lait. Tied. 11: 18—31.

Ms received September 30, 1980.

SELOSTUS

Seleenipitoisten lannoitteiden vaikutus ohran, kevätvehnän ja perunan seleenipi-
toisuuteen

Johan Korkman
Kemira Oy, 00101 Helsinki 10

Vuosina 1978 ja 1979 tehtiin Kemira Oy:n koetilalla scleenilannoituskokeita käyttäen selcenilähteenä nat-

riumselcniittiä, NaSeO,5H 2 O. Ruiskutuskokeita tehtiin ohralla, lannoituskokeita maan kautta ohralla, kevät-
vehnällä ja perunalla. Maahan annettavaa lannoitusta varten valmistettiin Kemiran koetehtaalla kahden lannoite-
lajin selcenipitoisia rinnakkaistuotteita, joissa oli 0,00, 0,01, 0,05 ja 0,10 % seleeniä.

Ruiskutettaessa 0,1, 0,5 ja 1,0 kg Sc/ha päästiin seleenipitoisuuksiin, jotka ovat selvästi korkeampia kuin ta-

voitteena usein pidetty 50—100 tU g Sc/kg kasvin kuiva-ainetta. Mikäli ruiskuttamalla pyritään korottamaan sa-

totuotteiden seleenipitoisuutta, tarvitaan vielä kenttäkoekokemuksia lisää oikean käyttömäärän ja ruiskutusajan-
kohdan määrittämiseksi.

Maahan annettaessa selccnilannoitus korotti viljojen pitoisuuksia siten, että 50 g Sc/ha korotti runsaalla 50
/*g/kg, 250 g Sc/ha noin 400 /ig/kg ja 500 gSe runsaalla 900 IX g/kg jyviä. Kevätvehnällä seleeni jakautui jy-
vän eri osiin siten, että kuoriosan pitoisuus oli korkein ja ydinosan pitoisuus alhaisin. Kuoren Se-pitoisuus oli kui-
tenkin keskimäärin vain 32 % korkeampi kuin ydinosan.

Perunan seleenipitoisuus nousi tasolle 100 fig Se/kg k.a. annettaessa maahan 500 gSe Na 2 SeO,:na hehtaa-
ria kohti. Ilman lisäseleeniä perunan Se-pitoisuudet olivat varsin alhaisia. Perunan seleenipitoisuudet eivät laske-
neet mukuloita keitettäessä.

Kalkituksella ei tässä koesarjassa pystytty lisäämään kasvien selecninsaantia. Tosin koemaiden pH :t olivat
6,0—6,2, mikä on melko korkea meikäläisissä oloissa; onhan maamme peltomaiden keskimääräinen pH 5,6.