EXTRACTABLE CALCIUM. MAGNESIUM, POTASSIUM AND
SODIUM IN DIEFFERENT PEAT TYPES

Jaakko Kivekäs and Armi Kaila

University of Helsinki, Department of Agricultural Chemistry
Received September 11, 1956

According to the common view peat types in which remains of Carex or Bryales
dominate are of a better quality than those mainly composed of Sphagnum species.
Thus within the Finnish classification in which the moss peats are divided into
Sphagnum peat (Sp) and Carex-Sphagnum peat (CSp), and the fen peats into Sphag-
num Carex peat (SCp), eutrophic Sphagnum-Carex peat (EuSCp), Carex peat (Cp)
and Bryales-Carex peat (BCp), the quality of the peat is supposed to improve in
this order. This, however, is not always the case when results of peat analyses are
examined a marked variation within a certain peat group both in the nutrient
content and other characteristics may be established (c.f. Kivinen 1933, Kaila
et ai. 1954, Kaila 1956 b). The differences between the mean values are often
significant, but the individual data of one group are almost always overlapping the
corresponding range of the other groups.

It was not likely to obtain markedly differing results when the cation content
of various peat types was chosen as the object of the present study. In most of the
papers dealing with the nutrient content ofpeat only the total amounts are reported.
Yet, the authors found it desirable to get more information of the plant-available
calcium, magnesium, and potassium in samples of virgin peat soils.

The problem of the availability of these nutrients to plants was conventionally
solved. Considering the fact that the samples were air-dried and ground the results
obtained by any method are likely to yield only an approximate estimate of the
plant-available amounts under the natural conditions. Therefore, instead of the
usual determination of exchangeable cations by washing with barium acetate the
analytically more convenient extraction with ammonium chloride was employed.

Material and methods

The material of the present study was partly the same as in a previous work
(Kaila 1956 b). It consisted of 208 samples of virgin peat soils collected mostly
from Northern Finland. The samples originated both from the surface and the
deeper layers.

The peat type and the degree of humification were estimated by direct exami-
nation of the fresh samples in the field. All the other analyses were performed

https://www.c-info.fi/en/info/?token=gi4SwceyVyJRPI-i.ywlpTlzxTN_qsgNf0TTqoQ.ut-JkZJIQnT0JjWxgMyAVDl7MNtqNWgjipcCley8R86wwHEBb_eQ6GTyfPZWckhHqpJgLVECP0_LewYXjm8tKGh44kaSztIH2pSBp-zUYt0a6mgj1Yg93_8K7j1ma-MLEsda03yBHCDmCVOEgPKAgzXv8JsCR5QtVNsGBj1hLK8H1FPsV9RRGqQd6oostM5d


42

using samples which were air-dried and ground in a Wiley mill. The soil pH was
determined in water suspension (1: 4) by a Beckman pH-meter with glass electrode.
The volume weight was measured with an apparatus developed in this laboratory
(cf. Kaila 1956).

The determination of the extractable cations was performed shaking 5 g samples
of peat in 100 ml of 1 N ammonium chloride for two hours. The suspension was
filtrated through paper without washing. Calcium, potassium and sodium in the
filtrate were determined using a flame photometer by Lange. Magnesium content
of the filtrate was calculated as the difference between the total calcium and mag-
nesium content estimated by the versenate titration (Cheng and Bray 1951) and
the calcium content obtained in the flamephotometric way.

Origin and quality of the samples

The results are reported in Table 1. The title »Bog type» means peat land
vegetation type. The letter R = »räme» or pine bog, N = »neva» or treeless oligo-
trophic bog, K = »korpi» or spruce-broadleaved tree swamp, and L = »letto» or
rich treeless fen. The column titled »Bo» represents the degree of land quality,
estimated on the basis of the surface vegetation. The grading from 1 to 10, com-
mon in Finnish soil survey, is used. The classes from 5 to 10 are generally considered
tillable.

There are 32 samples of Sp from treeless oligotrophic bogs or pine bogs with
a low degree of land quality. The origin of the 31 samples of CSp is not markedly
better. A large part of the 59 SCp-samples were collected from tillable peat lands,
but among them are also samples particularly from the deeper layers of peat lands
with a poor surface vegetation. Only 7 samples of EuSCp were available, all of
them from rich treeless fens as well as all the 33 samples of BCp. The origin of
the 46 samples of Cp is variable: several of them represent deeper layers of peat
lands with a poor surface vegetation.

Owing to the fact that a large part of the moss peat samples originates from
layers of a lower depth than those of the fen peats tend to do, also the degree of
humification in the former samples appears to be lower than that in the latter ones.
This may be illustrated by the mean values of the sampling depth and the degree
of humification computed for the different peat groups. These were the following:
{as a measure of variation the confidence limits at 95 % level are given):

Correlation coefficient
Depth dm H between depth and H

32 Sp samples 3.3 ± 1.12.7 ± 0.7 0.695***
31 CSp » 4.4 ± 1.23.6 ± 0.6 0.391*
59 SCp * 5.0 ± 2.84.0 ± 1.6 0.548***

7 EuSCp * 8.9 ± 3.84.7 ± 1.60.772
46 Cp » 9.0 ± 1.85.2 ± 0.5 0.473**
33 BCp » 7.8 ± 2.53.8 ± 0.60.163



43

Table 1. Calicium, magnesium, potassium and sodium extracted by 1 N ammonium chloride from
virgin peat samples.

Bog Depth WeiBht Ca US K Na
No Bo , H pH oftype dm '

volume '

p.p.m.

Samples of Sp

65 N 2 o—2 1 3.7 0.05 1800 1500 930 400
144 R 1 o—2 1 5.1 0.07 950 1900 550 120

K 31 N 1 o—2 1 4.2 0.08 4100 1100 190 120
K 32 N 1 4—6 1 4.4 0.08 4700 900 100 300
K 21 N 2 o—2 1 4.3 0.09 6200 700 200 30
K 34 N 2 o—2 1 4.2 0.09 3400 900 200 20
A 4 R 1 3—5 1 4.7 0.10 2800 1200 200 100

K 37 N 1 o—2 1 4.5 0.11 4900 1400 600 20
K 6 R 2 I—2 1 4.5 0.11 7000 400 1000 400
A 27 N 2 o—2 1 4.5 0.12 2000 1400 40 40

36 R 2 o—2 1 4.0 0.12 2000 1800 500 40
A 58 N 1 I—3 1 3.8 0.13 1580 900 200 50
A 37 N 2 o—2 1 4.4 0.28 3200 1400 700 40
A 31 R 2 o—2 1 3.9 0.29 2100 1700 250 10
K 22 R 1 2—4 2 5.0 0.14 10600 4000 400 30
K 7 R 2 2—3 2 4.6 0.17 6800 400 800 400
V 6a N 1 I—3 2 4.9 0.22 4300 1600 200 230

66 N 2 2—5 3 3.6 0.09 2300 1200 200 150
A 5 R 1 5—7 3 4.9 0.23 3500 1600 100 100
V 6b N 1 5—7 3 5.1 0.26 4600 2100 100 160
A 1 R 1 2—3 3 3.7 0.29 3200 800 100 20
A 32 R 1 3—5 3 4.0 0.34 1500 900 50 10
A 6 R 1 12—14 4 4.7 0.21 7100 3600 100 100
Via N 3 I—3 4 4.3 0.31 1700 900 200 50
V 15 a N 1 I—3 4 4.5 0.33 2200 950 140 90

105 R 2 o—2 4 4.4 0.20 5800 330 150 120
V 1 b N 3 5—7 4 4.3 0.33 1500 800 100 50

67 N 2 5—9 5 3,8 0.21 1700 800 130 . 110
A 2 R 1 3—4 5 3.8 0.49 3600 1100 100 20
V 15 b N 1 5—7 6 4.4 0.41 3600 850 50 80

68 N 2 9—ll 7 4.2 0.32 1800 900 90 40
A 3 R 1 7—lo 7 4.4 0.38 5600 1700 50 30

Samples of CSp
V 24 a N 2 I—3 1 4.5 0.10 2400 1200 100 190
V 23 a N 2 I—3 1 4.5 0.11 1700 1400 100 120
V 16 a N 3 I—3 1 4.4 0.12 3800 2000 410 280

69 R 2 o—2 2 4.2 0.09 2300 2200 2600 240
V 2a N 3 I—3 2 4.3 0.15 2400 1200 450 60
K 38 N 1 2—4 2 4.6 0.23 43C0 750 360 40

107 N 3 o—2 3 4.4 0.16 2000 2900 160 120
V 24 b N 2 5—7 3 4.8 0.17 800 1000 50 90
V 23 b N 2 5—7 3 4.9 0.19 1500 600 30 10



44

1 2 34567 8 9 10 11

28 N 3 4—6 3 4.20.23 2100 750 40 20
37 N 2 o—2 3 4.70.33 2800 1400 300 600

A 52 N 2 I—3 3 3.80.33 1530 430 210 100
K 39 N 1 4—6 3 4.60.25 3500 540 130 10
V 21 a N 3 I—3 3 5.00.30 3900 1800 80 120
V 21 b N 3 5—7 3 5.20.28 3400 1600 50 120
A 28 N 2 5—7 4 4.30.30 1600 1100 10 30

70 R 2 3—5 4 4.40.25 1730 1500 640 1340
V 16 b N 3 5—7 4 4.50.29 2300 1200 100 100
V 22 b N 3 5—7 4 5.10.28 3500 1600 60 100
V 2b N 3 5—7 4 4.20.31 1950 860 290 50

34 N 3 o—2 4 4.50.34 1300 1200 300 50
V 22 a N 3 5—7 4 4.70.37 3100 1600 260 160

35 R 3 o—2 4 4.50.38 2600 1300 300 70
K 8 R 2 3—4 5 4.60.39 3900 190 270 100
K 33 R 1 6—B 5 4.50.25 4400 900 60 20

29 N 3 15—20 5 5.10.33 4400 1000 30 30
A 29 N 2 B—lo 5 4.10.35 1800 1200 20 10

106 N 7 o—2 6 4.70.26 5600 2000 320 430
71 R 2 7—lo 6 4.30.36 1180 1180 180 410

K 42 R 2 2—4 6 3.90.39 3000 260 1350 220
A 46 R 2 4—6 7 4.10.49 2200 600 80 50

Samples of SCp
K 28 N 1 o—3 1 4.50.20 4500 1000 50 90
V 3a N 3 I—3 1 4.40.14 2900 2000 200 50
A 19 N 2 o—2 2 5.00.25 6000 1700 410 170
A 12 N 3 3—5 2 4.80.25 4600 1800 80 50
A 13 N 3 B—lo 2 4.80.20 3800 1900 170 50
A 23 N 2 I—3 2 4.70.38 4400 1400 280 50
V 19 a N 5 I—3 2 4.70.21 4600 2200 370 230
V 5a N 4 I—3 3 4.60.24 4000 1000 60 40
K 12 N 4 o—l 3 4.4 0,27 5100 1300 160 130
A 53 N 2 I—3 3 4.20.42 1100 300 70 50

59 N 5 o—2 3 3.60.23 1600 2100 610 250
A 47 R 2 2—4 3 4.60.23 2400 1200 120 160
V 3 b N 3 5—7 3 4.30.25 2400 1200 60 50
V 30 N 5 2—3 3 5.10.26 3800 1200 130 40
A 11 N 3 o—2 3 4.90.26 2400 1100 180 30
A 16 N 2 6—B 3 4.50.30 1800 1300 20 30
V 5b N 4 5—7 3 4,9 0.30 4500 1100 60 50
A 35 N 6 o—4 3 5.50.31 13200 4700 260 30
V 10 b N 3 5—7 3 4.90.24 1800 1600 180 150
V 9 b N 3 5—7 3 4.90.24 1800 1200 90 170
V 13 a N 4 I—3 3 4.40.25 1800 1200 200 190
K 18 N 4 o—2 3 5.50.27 3300 700 60 20
V 9a N 3 I—3 3 4,9 0.27 1900 1200 140 150
V 10 a N 3 I—3 3 4.70.27 1700 1200 250 190
V 14 a N 4 I—3 4 4.50.29 1500 1300 190 60
V 20 a N 5 I—3 4 4.60.33 3000 1600 250 100



45

1 2 3 456 7 8 9 10 11

K 24 R 1 6—B 4 5.10.35 6600 1300 110 20
A 49 N 5 I—3 4 4.30.34 2700 500 350 290
V 11 b N 3 5—7 4 4.80.24 1600 1700 60 120
V 8a N 4 I—3 4 4.70.25 1400 1000 230 70
V 26 N 5 2—3 4 5.00.26 4800 1800 110 40
Vila N 3 I—3 4 4.70.28 1700 1000 180 150

33 N 6 o—20—2 4 4.70.30 2700 1500 490 60
A 20 N 2 4—6 4 4.20.30 2900 1400 110 50
V 12 a N 4 I—3 4 4.40.30 1600 1100 190 150
V 17 a N 4 I—3 4 4.80.30 3400 1400 130 200
V 17 b N 4 5—7 4 4.90.30 3100 1600 50 90
V 18 a N 4 I—3 4 4.80.32 3000 1000 200 120
V 18 b N 4 5—7 4 4.90.31 3300 1600 70 70
A 15 N 2 2—4 4 4.3 0 34 2100 1100 130 30
V 8b N 4 5—7 4 4.90.25 1700 1400 60 170
V 7 a N 6 I—3 5 4.70.29 1200 1000 240 70
A 33 N 2 B—lo 5 4.10.30 1300 700 350 0

60 N 5 3—9 5 3.50.32 1700 2100 250 190
K 35 R 3 4—6 5 4.90.34 3400 900 180 20
V 31 N 5 4—6 5 5.10.35 6000 1000 70 100
V 27 N 5 4—6 5 5.20.37 5600 1900 50 90
K 23 R 1 4—6 5 5.00.32 7900 2200 190 20
K 59 N 4 o—s 5 5.30.34 3000 400 90 60
V 19 b N 5 5—7 5 5.10.39 4100 1700 70 200
V 32 N 5 B—lo 6 5.20.37 9700 1900 80 60
V 28 N 5 B—lo 6 5.30.40 6400 2300 40 60
V 14 b N 4 5—7 6 4.50.40 2400 1000 50 290
V 13 b N 4 5—7 6 4.50.40 2000 1400 80 100
V 12 b N 4 5—7 6 4.40.40 2000 1400 70 60
V 20 b N 5 5—7 6 5.50.42 5200 2100 60 120

61 N 5 10—13 7 4.20.40 1900 1800 120 360
V 7b N 6 5—7 7 5.00.40 730 1200 110 150

76 R 1 60 9 4.80.71 4400 3100 60 130

Samples of EuSCp
62 L 8 o—2 3 4.40.18 3400 3500 1600 430
40 L 8 o—2 3 5.60.25 14000 5060 690 1930

K 5 L 8 4—6 3 5.40.27 14000 2950 420 310
63 L 8 6—B 5 4.70.32 9550 2340 170 210
117 L 8 17—20 6 5.20.41 13100 4500 80 250
118 L 8 20—23 6 5.40.47 12400 4000 30 200
64 L 8 B—lo 7 4.30.38 5200 2370 120 160

Samples of Cp

K 29 N 4 5—7 2 4.60.20 3700 820 360 360
A 41 N 3 3—5 3 4.80.25 2400 1200 50 60
A 43 N 3 2—6 3 4.50.24 3000 1300 80 130
A 40 N 3 o—2 3 4.70.30 3550 1360 280 50
A 38 N 2 3—5 3 4.50.29 2100 860 190 30
A 8 K 5 o—2 3 4.70.32 3970 820 10 20



46

12 3 45 6779 10 11

A 24 N 2 5—6 3 5.0 0.34 3700 1700 20 10
K 25 N 6 I—3 3 4.60.21 3400 850 30 10
K 26 N 6 5—7 3 4.20.20 3500 1400 30 10
K 14 N 4 5—7 3 5.10.26 3400 1100 10 20
K 13 N 4 I—3 3 4.90.28 3900 1100 20 20

38 K 7 o—2 4 4.90.36 6800 2680 560 490
K 27 K 6 11—14 4 4.40.23 2900 1400 30 10

109 N 6 o—2 4 4.60.24 1300 660 660 280
111 K 6 o—2 4 4.70.26 2700 1200 50 120
103 N 4 o—2 4 4.80.28 3200 1350 300 320

A 44 N 3 6—B 4 4.30.27 3300 1350 100 120
A 42 N 3 B—lo 4 4.90.23 2700 1200 100 110

110 N 6 o—2 4 4.60.24 2800 1200 50 100
47 N 6 4—6 5 5.20.32 12200 1700 210 510
48 N 6 7—lo 5 5.40.36 12100 1900 170 190

A 17 N 2 B—lo 5 4.10.31 2000 1050 210 40
K 36 N 2 4—6 5 4,9 0.34 3700 1100 60 10
K 41 R 4 2—6 5 4.20.28 3900 1130 1400 430
K 30 R 4 2—5 5 4.80.34 3600 510 80 30

49 N 6 12—15 6 5.60.38 12900 2600 200 160
50 N 6 17—20 6 5.50.39 14300 3000 170 540

104 N 6 o—2 6 4.60.29 2300 1500 270 80
K 20 N 4 6—B 6 5.40.30 3800 1300 20 10

131 L 8 27—30 6 5.00.35 7600 3100 60 390
A 25 N 2 B—9 6 5.10.37 4100 1700 20 10

138 L 8 20—23 6 5.50.43 20000 3300 130 200
K 4 N 6 3—6 6 5.20.35 13500 2900 410 150

51 N 6 22—25 7 5.60.50 14800 3200 210 850
52 N 6 32—35 7 5.80.47 19800 4100 120 850
53 N 6 37—40 7 5.6 0,48 22400 4100 180 1160
54 N 6 42—45 7 5.30.44 15200 5200 150 1010

A 21 N 2 B—lo 7 5.80.37 9000 4600 90 30
137 L 8 17—20 7 5.60.39 19400 3400 60 250

A 50 N 3 3—5 7 4.60.31 2100 510 100 100
31 K 6 3—6 7 4.90.39 13400 2900 130 690

K 19 N 4 3—5 8 5.40.46 3400 710 20 10
30 K 6 o—3 8 4.60.54 13200 3600 250 520
32 K 6 o—s 8 4.7 0,69 7700 7600 500 140

A 45 N 3 12—14 8 4.90.52 2900 1150 80 50
K 60 N 4 .10—14 8 4.90.53 3550 1180 50 40

Samples of BCp
K 9 L 7 o—2 1 4.90.16 5200 900 300 200
K 1 L 7 o—2 1 5.50.14 10500 1100 300 400
K 10 L 7 2—4 2 5.20.24 3700 400 100 100

74 L 7 o—2 2 6.20.20 13300 3000 70 140
122 L 8 14—17 2 4.90.22 8100 3500 50 200
139 L 8 o—2 2 3.90.48 4400 2200 300 200
39 L 7 o—2 3 4.70.23 4300 1500 200 100

119 L 8 4—7 3 5.10.30 5900 2700 50 100



47

1 2 34567 89 10 11

120 L 8 7—lo 3 5.00.25 7900 3000 50 300
121 L 8 10—13 3 4.80.21 9000 3400 50 200
129 L 8 20—23 3 4.80.27 10000 3400 50 200
143 L 7 o—2 3 4.10.21 3200 2000 70 210
113 L 8 4—7 3 5.60.28 13500 4300 50 200
126 1 L 8 10—13 3 4.90.25 7600 3300 50 100
127 L 8 14—17 3 4.90.24 8700 3400 50 200
128 L 8 17—20 3 4.80.25 8800 3400 50 200

K 2 L 7 3—5 3 5.20.28 8600 1100 300 300
73 L 8 o—2 3 8.00.44 23500 4000 80 210

125 L 8 4—7 4 4.90.30 7300 4100 70 150
123 L 8 17—20 4 4.90.24 8600 3000 50 300
114 L 8 7—lo 4 5.40.29 13000 4100 100 200
141 L 7 o—2 4 5.60.45 14000 5100 200 270
75 L 7 o—2 4 5.40.24 10200 3500 30 120

130 L 8 24—27 5 5.00.36 8200 3400 50 200
142 L 8 o—2 5 4.80.53 11700 4000 360 220
115 L 8 10—13 5 5.40.37 12700 4100 50 200
135 L 8 10—13 6 5.80.44 13800 4000 100 200
116 L 8 14—17 6 5.30.39 12000 4100 50 200
140 K 10 o—2 6 5.10.58 14700 2200 200 300
134 L 8 4—lo 6 5.70.43 11500 3400 100 200
136 L 8 14—17 7 5.70.42 15000 4500 100 200

K 3 L 7 7—9 7 5.30.34 6800 700 200 100
K 11 L 7 5—7 7 5.00.37 4000 700 10 200

In this material distinct differences exist between the peat groups both in the
degree of humification and in the sampling depth. It is worth noticing that in the
BCp-group the average degree of humification is markedly lower than on the basis
of the average sampling depth it could be supposed to be. In all the other peat
groups the degree of humification tends to grow with the depth, although the total
correlation coefficient between these quantities does not always appear to be very
high.

In any case there are reasons to pay attention to this difference in the quality
of the samples of the different peat groups when the results of this study are exami-
ned. It was found in connection with a previous work (Kaila and Kivekäs 1956)
that in peat soil profiles generally a large part of extractable potassium is accumu-
lated in the surface layers. The magnesium content, on the other hand, tended to
be higher in the deeper layers.

Extractable cations in the peat samples

In Table 1 the amounts of cations extracted by 1 N ammonium chloride solution
are reported as parts per million of the dry matter. According to the authors’
opinion it is not justified to suppose that the results obtained by the present method



48

would correspond to the exchangeable cations. Therefore, the results have not
been reported as milliequivalents per 100 g.

In order to get a better survey of the data in Table 1, the means for the cation
contents in the different peat groups were computed. Also the cation content
expressed on the volume basis was calculated. This quantity does not, of course,
correspond to the real amounts of these nutrients as kg/ha in the natural peat
layers of a depth of 20 cm. Yet, it may be supposed to give a relative estimate of
the amounts of these extractable cations.

First the means of the calcium content in the different peat types are examined.
In addition to the means with their confidence limits at 95 per cent level also the
minimum and maximum values are reported.

Ca p.p.m. Ca kg/ha
mean min. max. mean min. max.

Sp (32) 3 690 ± 720 950 10 600 1 460 ± 360 130 4 260
CSp (31) 2 680 ± 850 800 5 600 1 460 ± 330 270 3 040
SCp (59) 3 410 ± 590 730 13 200 2 160 ± 270 590 8 190
EuSCp (7) 10 240 ± 4 090 3 400 14 000 6 890 ± 2 670 1 230 11 660
Cp (46) 7 070 ± 1 780 1 300 22 400 5 530 ± 1 090 630 21 510
BCp (33) 9 720 ± 1 510 3 700 23 500 6 510 ± 1 670 1 660 20 680

According to these means there appears to be a distinct difference between the
groups of Sp, CSp, and SCp and the groups of EuSCp, Cp and BCp. Thus in this
material the SC-peat, generally counted among the fen peats, resembles more the
moss peats known to be poor in calcium. In the material studied by Kivinen
(1933) the average content of total calcium in the different peat types was of the
same order as in this paper the respective data for calcium extracted by 1 N ammo-
nium chloride. The mean values reported by Kivinen for calcium dissolved by
1 % citric acid were generally somewhat lower than our data, and the Cp group
was surprisingly poor in calcium.

The mean quantities of magnesium extracted by the present method were the
following;

Mg p.p.m. Mg kg/ha
mean min. max. mean min. max.

Sp (32) 1 310 ± 250 330 4 000 530 ± 150 90 1 290
CSp (31) 1 240 ± 200 190 2 900 610 ± 120 200 1 190
SCp (59) 1 460 ± 190 300 4 700 920 ± 160 250 4 400
EuSCp (7) 3 540 ± 1 180 2 340 5 060 2 480 ± 1 010 1 500 3 760
Cp (46) 2 010 ± 440 510 7 600 1 600 ± 520 320 10 490
BCp (33) 2 950 ± 460 400 5100 1 960 ± 590 190 4 590

The variation in the magnesium content is marked as it also was in the calcium
content. In regard to the magnesium content the SCp group belongs to the moss
peats, although less distinctly than in regard to the calcium content.

Now, of course, arises the question whether the difference in the sampling
depth plays any part in these results. The SCp samples were, on the average, col-



49

lected from layers which were far less deep than were the layers from which the Cp,
EuSCp and BCp samples originated. In the mean degree of humification, on the
other hand, the differences between SCp samples and samples of the BCp and
EuSCp groups are insignificant. The correlation coefficients between the cation
contents and the degree of humification or of the sampling depth are the following:

Cap.p.m. Mg p.p.m.

Depth H Depth H
Sp (32) 0.113 0.0200.375 0.078
CSp (31) 0.3300.149 0.269 0.279
SCp (59) 0.0480.052 0.357** 0.114
EuSCp (7) 0.281 0.1650.026 0.409
Cp (46) 0.568*** 0.393** 0.528*** 0.652***
BCp (33) 0.0120.275 0.3200.216
AU (208) 0.398*** 0.198* 0.433*** 0.219*

These total correlation coefficients do not reveal any connection between the
calcium or magnesium content and the depth or the degree of humification, except
in the Cp-group. The fact that the samples of Cp, BCp and EuSCp groups generally
originated from deeper layers and contained higher amounts of these extractable
cations is probably the reason for the significant correlations between the depth
and the calcium and magnesium contents in all the material. As to the connection
between the cation contents and the degree of humification only a low correlation
can be demonstrated. Consequently, the differences found in the mean contents of
calcium and magnesium in the various peat types probably do not arise only from
the differences in the sampling depth.

The amounts of potassium extracted by 1 N ammonium chloride from these
samples were far lower than those of calcium and magnesium. In connection with
some other work it was found that almost all of the potassium in this kind of peat
samples was extracted by the present method. This is in accordance with what
is known of the occurence of potassium in peat soils.

The mean content of potassium in the different peat types of this material
was the following (the means expressed with the confidence limits at 95 per cent
level);

K p.p.m. K kg/ha
mena min. max. mean min. max.

Sp (32) 260 ± 100 40 1000 90 ± 30 10 390
CSp (31) 300 ± 180 10 2 600 140 ± 70 5 1050
SCp (59) 160 ± 30 40 610 90 ±l5 10 300
EuSCp (7) 440 ± 500 30 1 600 210 ± 180 30 580
Cp (46) 180 ± 70 10 1 400 130 ±55 5 790
BCp (33) 110 ± 30 30 300 80 ± 30 10 380

The variation in the potassium content is high in all the peat groups. Generally
it appears to be even higher than the corresponding variation in the calcium and



50

magnesium content. Although no significant difference can be noticed between the
mean values for the peat groups, a slight tendency to higher potassium content
may be observed in the moss peats or groups of Sp and CSp as compared with the
groups of BCp, Cp, and SCp. Some high numbers in the EuSCp group heighten the
mean of these few samples. Probably the conclusion which can be drawn on the
basis of these data is that there are no distinct difference in the content of extractable
potassium in the peat types.

The amounts of sodium extracted by the present method also varies markedly
within all the groups. The values are of the same order as those of potassium, and
mostly far lower than the calcium and magnesium contents. The mean values and
the variation limits for sodium are the following:

Na p.p.m. Na kg/ha
mean min. max. mean min. max.

Sp (32) 100 ±3O 10 400 30 ± 10 5 135
CSp (31) 170 ± 90 10 1 340 90 ± 50 5 670
SCp (59) 110 ± 30 0 360 80 ± 30 0 405
EuSCp (7) 490 ± 600 160 1 930 280 ± 280 120 970
Cp (46) 230 ± 90 10 1 160 180 ± 90 5 1 115
BC (33) 200 ± 20 100 300 130 ± 25 5 350

The Sp and SCp groups are fairly low in extractable sodium. Also the CSp-
samples contain less sodium than the EuSCp, Cp, and BCp groups, particularly as
expressed on the volume basis. It looks as if the relations between the sodium
content of these peat groups would be more like those of calcium content than
those of potassium.

The connection between the depth or the degree of humification and the
amounts of extractable potassium or sodium in the different peat groups were
calculated and the following total correlation coefficients were obtained:

K Na
Depth H Depth H

Sp (32) 0.566*** 0.484** 0.254 0.217
CSp (31) 0.331 0.074 0.115 0.087
SCp (59) 0.205 0.207 0.047 0.191
EuSCp (7) 0.709 0.728 0.538 0.574
Cp (46) 0.211 0.029 0.696*** 0.406**
BCp (33) 0.222 0.074 0.205 0.051
All (208) 0.211* 0.187* 0.249** 0.144

It was found in a previous paper (Kaila & Kivekäs 1956) that the content of
extractable potassium in peat soil profiles tends to be higher in the surface layers
than in the deeper ones. In this material a significant correlation between the
sampling depth and the potassium values exist only in the Sp-samples. The very
slight connection for all the material does not tell whether the differences in the
sampling depth have any effect on the amounts of potassium in the samples of the
different peat groups. The same holds true with the connection between potassium
•content and the degree of humification.



51

The latter characteristic is not at all correlated with the content of extractable
sodium in these samples, except in the Cp-group. In this group also a high corre-
lation with depth can be noted, the reason of which is not clear.

Extractable cations and acidity of the samples

It is a common knowledge that the composition of the cation system in the
soil is the factor on which the acidity of the soil mostly depends. The authors
found it desirable to study the relation of the content of these extractable cations
and the soil reaction.

In this material the pH-values measured in a water suspension of air-dried
samples were, on the average, the following for the various peat groups:

Sp: pH 4.3 ± 0.2
EuSCp: pH 5.0 ± 0.5

CSp: pH 4.5 ± 0.1
Cp: pH 4.9 ±O.l

SCp: pH 4.7 ± 0.1
BCp: pH 5.2 ± 0.2

These are typical means for the pH-values of the different peats and they
are well in accordance with the data reported by Kivinen (1933). Only the pH
in the Sp group is slightly higher and in the BCp group somewhat lower than the
corresponding results reported by Kivinen.

The correlation was calculated for the pH values and the cation contents of
the peat groups and the following coefficients were obtained:

Correlation coefficients between pH and

Ca p.p.m. Mg p.p.m. K p.p.m. Na p.p.m.

Sp (32) 0.475** 0.469** 0.048 0.062
CSp (31) 0.407* 0.284 0.388* 0.067
SCp (59) 0.542*** 0.172 0.374** 0.207
EuSCp (7) 0.927** 0.758* 0.374 0.472
Cp (46) o.7oB*** 0.458** 0.167 0.401*
BCp (33) 0.833*** 0.275 0.210 0.172
All (208) 0,692*** 0.470*** 0.245** 0.199*

As could be expected the correlation between the pH-values and the content
of calcium is fairly high in most of the peat types. The positive correlation between
pH and magnesium content is less distinct for all the samples and for several of the
peat groups no correlation between these quantities exists. The potassium content,
on the other hand, tends to show a slight tendency to decrease with decreasing
acidity. No correlation, worth of notice occurs between the acidity and the sodium
content of these samples, except in the Cp group.

There is in these peat groups no significant correlation between the depth or
the degree of humification and the pH-value. Therefore, it is unnecessary to calcu-
late the partial correlation coefficients by eliminating the effect of the sampling
depth and the degree of humification between the pH and the cation contents.



52

Extractable cations in the surface layers and the peat land quality
In the present material a large part of the samples originated from fairly deep

layers. So far as the cultivation of peat soils is in question, generally only the
surface layers are of importance. Therefore, also an examination of this part of
the material is desirable.

The samples down to a depth of 3 dm contain, on the average the following
quantities of calcium and magnesium;

Ca p.p.m. Mg p.p.m.
Sp (18) 3 510 ± 970 1 120 ± 280
CSp (12) 2 690 ± 730 1 590 ± 400
SCp (26) 2 930 ± 590 1 260 ± 202
EuSCp (2) 8 700
Cp (11) 4 380 ± 2 230 1 490 ± 620
BCp (11) 10 500 ± 4 370 2 680 ± 910

These mean values of the calcium content are equal to those calculated for
the whole material, except in regard to the Cp group. These samples are markedly
lower in calcium than the average of all the samples indicates. As to the magnesium
content no significant difference appears to exist between the surface samples and
the whole material.

The potassium content, on the other hand seems to be somewhat higher in the
surface samples than in the deeper layers. The extractable sodium occurs in equal
amounts in the surface peat and in the older deposits. The following mean values
for potassium and sodium content in the surface samples demonstrate this.

K p.p.m. Na p.p.m.
Sp (18) 385 ± 150 120 ± 65
CSp (12) 445 ± 435 190 ± 90
SCp (26) 220 ±6O 115 ±35
EuSCp (2) 1 145 1 120
Cp (11) 225 ± 155 185 ± 125
BCp (11) 190 ± 75 215 ± 55

The peat land quality estimated on the basis of the surface vegetation, mainly
depends on the nutrient content and other conditions in the surface layers of peat.
Therefore, when the contents of extractable cations and the degrees of land quality
were studied, there was no cause to examine the whole material. The samples from
layers not deeper than 3 dm were chosen to the object of this testing. The statistical
treatment yielded the following results:

Correlation coefficient between Bo and
Ca p.p.m. Mg p.p.m. K p.p.m. Na p.p.m.

Sp (18) 0.034 0.218 0.170 0.064
CSp (12) 0.788** 0.341 0.147 0.374
SCp (26) 0.183 0.222 0.370 0.569**
EuSCp (2)
Cp (11) 0.225 0.342 0.240 0.383
BCp (11) 0.206 0.055 0.167 0.269
All (80) 0.551*** 0.369** 0.025 0.149



53

It could be expected to find a fairly close connection between the calcium
content and the land quality. This however, was not the case within the different
peat types. For all the surface samples the correlation is significant, although not
very high. The same holds true with the extractable magnesium for which the
correlation is even lower. The scant supply of potassium in peat lands is not cor-
related with the land quality. The distribution of sodium in the surface samples
does not correspond to the land quality.

Connection between the amounts of extractable cations

It seems possible that there exists some dependence between the quantities of
these extractable cations in the peat samples. Indeed, a rather high correlation
could be found for the contents of calcium and magnesium, as the following cor-
relation coefficients indicate:

Total correlation coefficients between the contents of
Ca and Mg Ca and K Mg and K K and Na

Sp (32) 0.613*** 0.142 0.075 0.238
CSp (31) 0.317 0.103 0.537*** 0.329
SCp (59) 0.672*** 0.013 0.039 0.059
EuSCp (7) 0.834* 0.585 0 0.295
Cp (46) 0.679*** 0.109 0.201 0.247
BCp (33) 0.729*** 0.105 0.491 0.646***
All (208) 0.782*** 0.042 0.009 0.172

The data listed above show no connection between the contents of calcium
and potassium on the one hand, or between the amounts of extractable magnesium
and potassium, on the other hand. As to the potassium and sodium extracted by
ammonium chloride, no significant correlation between them is to be found, except
in the BCp group.

Discussion
This statistical study, the aim of which was to elucidate the nutrient conditions

in regard to calcium, magnesium and potassium in different kinds of peat, gave
results which emphasize the large variation of the nutrient content in every peat
group. The individual data for one group are always overlapping the range of the
other ones. Generally, even the means do not significantly differ from each other.

This large variation did not arise only from the fact that in the material ana-
lyzed the sampling depth varied from 1 to 60 dm. The extent of variation in the
different groups of surface samples was as large as that for the whole material.
No significant correlation was found to exist between the sampling depth and the
content of the different cations, except in a few cases. This also shows that this
variation must be attributed to some other reasons than the age of the deposit.

One factor which may be held liable for the variation in the contents of extract-
able cations in the different peat groups is the location of the sampling place in the
peat land. It has been observed (Kivinen 1933) that particularly in large peat
lands moistened by waters from outside the peat deposits on the edge of the area



adsorb a large part of the cations in the running water and only water fairly poor
in nutrients reaches the middle part of the peat bog. In the long run this, of course,
brings about changes in the composition of the surface vegetation and further in
the quality of peat. Meanwhile, this phenomenon may at least partly be held
responsible for the large variation in the nutrient content within the same peat
group.

Attention must also be paid to the fact that even each of these six peat groups
may be composed of fairly different plant residues. The Sp group, for example,
can be developed from residues of poor Sphagnum fuscum vegetation or from
markedly richer residues of other Sphagnum species. Also the remains of Carex
differ from each besides this, the nutrient content of plants depends on the nutri-
tion conditions of the peat land and large variations even within the mineral com-
position of the same plant species may exist.

In any case, the results of this study emphasize that the determination of the
kind of peat does not give any probable estimate of the nutrient content of the
sample. An Sp sample may be richer in calcium, magnesium, and potassium than
a Cp or a BCp sample.

Summary

An attempt was made to elucidate the content of plant-available calcium,
potassium and magnesium in different kinds of virgin peat. The amounts of these
cations extracted by 1 N ammonium chloride solution were supposed to give an
estimate satisfactory for this purpose. Also the extractable sodium was determined.

The material consisted of 208 samples mainly collected from Northern Finland.
The variation in the content of extractable cations was high in all the peat

groups. The individual values of one group were overlapping the range of other
ones. The average calcium and magnesium contents of the Sp, CSp and SCp groups
were somewhat lower than those of Cp, BCp and EuSCp groups. The same seems
to be the case, with the content of extractable sodium whereas the moss peats tended
to be slightly less poor in potassium than the peats of better quality.

A more or less significant correlation existed in all the peat groups between the
calcium content and the pH-values. The correlation was markedly lower for pH
and extractable magnesium. A weak tendency to negative correlation could be
noticed between pH and extractable potassium.

The land quality and the calcium and magnesium content of all the surface
samples were correlated with each other, although not very strongly. Within the
different peat groups no correlation between these quantities could be found, except
in one case. The scant supply of potassium in the surface samples did not show any
connection with the land quality.

The reasons responsible to the large variation of the nutrient content within
a certain peat group were discussed. The fact was emphasized that on the basis of
the identification of the kind of peat nothing reliable is known of the nutrient con-
tent of the sample.

54



55

REFERENCES

(1) Cheng, K. L. & Bray, R. H. 1951. Determination of calcium and magnesium in soil and plant
material. Soil Sei. 72: 449—458.

(2) Kaila, A. 1956. Determination of the degree of humification in peat samples. J. Sei. Agric. Soc.
Finland 28: 18—35.

(3) —»— 1956 b. Phosphorus in virgin peat soils. Ibid. 28: 142—167
(4) —» — & Kivekäs, J. 1956. Extractable calcium, magnesium, potassium and sodium in dif-

ferent layers of peat soils. Ibid 28:
(5) Kivinen, E. 1933. Suokasvien ja niiden kasvualustan kasvinravintoainesuhteista. (Referat:

Untersuchungen über den Gehalt an Pflanzennährstoffen in Moorpflanzen und in ihren
Standorten.) Acta Agr. Fenn. 27. Helsinki.

SELOSTUS:

UUTTUVASTA KALSIUMISTA, MAGNESIUMISTA, KALIUMISTA JA
NATRIUMISTA ERI TURVELAJEISSA

Jaakko Kivekäs ja Armi Kaila

Yliopiston Maanviljelyskemian laitos, Helsinki

Tutkimuksessa tarkastellaan turvelajeittain ammoniumkloridilla uuttuvien kalsiumin, mag-
nesiumin, kaliumin ja natriumin määriä ja näiden riippuvuutta toisistaan.

Tutkimusaineistona oli 208 luonnontilaisilta, lähinnä pohjois-Suomen soilta otettua turvenäytettä.
Ilmakuivista, jauhetuista näytteistä määritettiin kahden tunnin huiskutuksen aikana 1-n ammonium-
kloridiliuokseen uuttaneiden em. kationien määrät; määritykset tapahtuivat Langen liekkifotometrilla
ja versenaattititrausta käyttäen.

Tutkittujen näytteiden perusteella on vaikea saada selviä eroja eri turpeiden em. kationien pitoi-
suuksissa. Selvän rajan vetäminen rahka- ja sarturpeiden välille on vaikeata. Kalsiumia ja magnesiu-
mia sisältävät S—t, CS—t ja myös SC—t keskimäärin vähemmän kuin muut turpeet. Myöskään ei
selviä eroja eri turvelajien keskimääräisissä kaliumin ja natriuminpitoisuuksissa voida havaita. Kaliu-
min ja natriumin määrät ovat huomattavasti pienempiä kuin kalsiumin tai magnesiumin määrät.

Tarkasteltaessa erikseen pintanäytteiden (0 —3 dm) kationipitoisuuksia havaitaan, että kalsiumin
ja magnesiumin määrät ovat samaa suuruusluokkaa kuin muissakin näytteissä. Kaliumia sensijaan
näyttäisi pintaturpeissa olevan keskimäärin runsaammin kuin syvemmältä otetuissa näytteissä.

Kalsiumin ja pH:n välillä voidaan eri turvelajeissa ja koko materiaalissa havaita melko selvä
positiivinen korrelaatio. Pintanäytteissä vallitsee, koko materiali huomioonottaen, melko selvä posi-
tiivinen korrelaatio kalsiumin ja boniteetin sekä magnesiumin ja boniteetin välillä. Eri turvelajeissa
ei näitä korrelaatioita sensijaan voida havaita.

Kalsiumin ja magnesiumin välillä voidaan havaita selvähkö positiivinen korrelaatio.