PHOSPHORUS IN VIRGIN PEAT SOILS Armi Kaila Department of Agricultural Chemistry, University of Helsinki Received March 12. 1956. Our present information of phosphorus in peat soils is scarce. Finnish peat lands are considered to be poor in phosphorus, a view corroborated by the fact that when cultivated they generally respond to phosphate fertilizers. This perhaps is the reason why only very little attention has been paid to the native peat phos- phorus. In connection with some Finnish investigations the total phosphorus content of virgin peat soils has been determined (12), but almost nothing is known of the forms in which this peat phosphorus occurs. Also in other countries the composition of phosphorus in peat soils has only in a low degree interested soil scientists. This probably can be partly attributed to the difficulties connected with the analyses of peat samples. In the present paper results are reported of an attempt to elucidate the phos- phorus composition of some virgin peat soils in Finland. The main object was to study the organic phosphorus content of these soils and the factors on which it depends. Also some data upon the solubility of inorganic phosphorus are examined. Material and methods The material of this investigation consisted of 217 samples of various kinds of peat collected mostly from Northern Finland, although also other parts of the country were represented. Samples were taken both from the surface and the deeper layers. https://www.c-info.fi/en/info/?token=0hsc2Lw8KKGIv7Nu.IMqkPdymlx96Y8vikSUu4Q.IPz8zf2eBXQX11WG6SI9t6MWha41ZqQ9-fy2eR-EMpN4WtEJrGpPLrS-keh29BijMBbFPlrblEHJ34VVqEnBsSEhNhqbLPMEp-TfLFG6irF3GYUKfnbO7HVQ2_8_ENqJZv9eMnx7yUazm27nwCqZJJythj36LXsX PHOSPHORUS IN VIRGIN PEAT SOILS 143 The peat type and the degree of humification were determined by direct examination of the fresh samples in the field. All the other analyses were performed using samples which were air-dried and ground in a Wiley mill. The soil pH was estimated in water suspension (1:4, vol.) using a Beckman pH-meter with glass electrode. The volume weight was determined with an apparatus developed by Mr. Jaakko Kivekäs M.S. in this laboratory (8). The Kjeldahl procedure was modified to allow the common determination of nitrogen and the colorimetric estimation of total phosphorus from the aliquotes of the same digest. For that purpose sodium selenite and sodium sulphate were substituted for copper sulphate and potassium sulphate, respectively. All the phosphorus analyses were performed by the molybdenum blue method modified by the author (7). When the solutions obtained from the Kjeldahl digestion were analysed, it was sometimes found that about half an hour after the reduction the blue solution began to turn turbid. Therefore, care was taken to measure the colour intensity of these solutions within 25 minutes after the reduction. The cause of this phenomenon was not examined in more detail. Perhaps it may be attributed to the effect of selenite although this was present only in a very low concentration. A similar phenomenon was found to occur also when digests of plant ma:erial were analysed. Organic phosphorus content was determined by the acid-alkali extraction method developed for the analyses of peat soils and also an ignition method was used (11). The data reported are average values of the results of both these methods. In addition to the information of the solubility of inorganic phosphorus obtained in connection with the analyses of organic phosphorus, also phosphorus soluble in 0.5 N acetic acid was estimated. These extractions were performed in a ratio of 1 to 20, and the time of extraction was one hour. The peat samples and some of their characteristics are listed in Table 1 as groups of various kinds of peat and in the order of the increasing degree of humifi- cation. The title »Bog type» means peat land vegetation type. The letter R = räme or pine bog, N = neva or wet treeless oligotrophic bog, K = korpi or spruce-broad- leaved tree swamp, and L = letto or rich treeless fen. The column titled »Bo» repre- sents the degree of land quality, estimated on the basis of the surface vegetation. The grading from 1 to 10, common in Finnish soil survey, is used, the classes from 5 to 10 being tillable. The 32 samples of Sphagnum peat (Sp) represent treeless oligotrophic bogs or pine bogs with a low degree of land quality. The origin of the 34 samples of Carex- Sphagnum peat (CSp) is not markedly better, but the average sampling depth of a large part of the CSp group was greater. Among the 62 samples of Sphagnum-Carex peat (SCp) a large number was collected from tillable peat lands, but also the poor land quality is represented. All the 12 samples of eutrophic Sphagnum-Carex peat (EuSCp) are from rich treeless fens, and also the peat lands from which the 36 samples of Bryales-Carex peat (BCp) originates are of a high quality, mostly fens. The 41 samples of Carex peat (Cp) were taken from various kinds of peat lands; peat lands with a poor surface vegetation were represented by samples from the deeper layers. In connection with this work no attention was paid to the content of ligneous residues in some of these samples. It may be mentioned that samples Al-A3 and 105 can be determined as LS-peat, samples 35, 69—71 as LCS-peat, samples K23 as LSC-peat, and samples 23, 30 32, 38, 111, 137, K27 and K3O as LC-peat. 144 A.RMI KAILA Table I. Peat samples Bog Depth Volume SamP le type Bo dm H P H weight Ash % N % I 23 45678 9 Sphagnum peat 65 N I—2 o—2 1 3.7 0.05 1.4 0.82 144 R 1 o—2 1 5.1 0.07 1.5 0.89 K 31 N 1 o—2 1 4.2 0.08 5.9 2.44 K 32 N 1 4—6 1 4.4 0.08 3.9 1.47 K 21 N 2 o—2 1 4.3 0.09 8.0 0.86 K 34 N 2 o—2 1 4.2 0.09 5.0 1.03 A 4 R 1 3—5 1 4.7 0.10 1.0 0.64 K 37 N 1 o—2 1 4.5 0.11 4.9 1.45 K 6 R 2 I—2 1 4.5 0.11 4.2 1.19 A 27 N 2 o—2 1 4.5 0.12 5.2 0.73 36 R 2 o—2 1 4.0 0.12 11.2 1.24 A 58 N 1 I—3 1 3.8 0.13 4.2 0.47 A 37 N 2 o—2 1 4.4 0.28 10.8 1.09 A 31 N 2 o—2 1 3.9 0.29 5.7 1.89 K 22 R 1 2—4 2 5.0 0.14 2.8 1.15 K 7 R 2 2—3 2 4.6 0.17 4.5 1.49 V 6a N 1 I—3 2 4.9 0.22 10.6 1.82 66 N I—2 2—5 2 3.6 0.09 1.5 0.95 A 5 R 1 5—7 3 4.9 0.23 2.1 1.17 V 6b N 1 5—7 3 5.1 0.26 7.4 2.24 AIR 1 2—3 3 3.7 0.29 4.4 1.72 A 32 N 1 3—5 3 4.0 0.34 4.0 2.16 A 6 R 1 12—14 4 4.7 0.21 2.9 1.19 V la N 3 I—3 4 4.3 0.31 7.6 1.92 V 15a N 1 I—3 4 4.5 0.33 8.1 3.34 67 N I—2 5—9 4 3.8 0.21 2.9 2.07 105 R 2 2—4 4 4.4 0.20 2.2 1.42 V Ib N 3 5—7 5 4.3 0.33 8.5 2.15 A 2 R 1 3—4 5 3.8 0.49 4.3 1.75 68 N I—2 9—ll 6 4.2 0.32 2.4 1.49 V 15b N 1 5—7 6 4.4 0.41 4.9 1.96 A 3 R 1 7—lo 7 4.4 0.38 6.3 1.85 Carex-Sphagnutn peat V 24a N 2 I—3 1 4.5 0.10 7.9 1.03 100 N 2 o—2 1 5.1 0.11 7.7 1.71 V 23a N 2 I—3 1 45 0.11 9.5 1.26 V 16a N 3 I—3 2 4.4 0.12 6.9 0.96 69 R 2 o—3 2 4.2 0.09 3.4 1.22 V 2a N 3 I—3 2 43 0.15 5.5 1.06 K 38 N 1 2—4 2 4.6 0.23 5.0 2.23 101 N 2 3—5 3 5.2 0.14 6.5 2.30 107 N 3 I—3 3 4.4 0.16 5.0 3.26 1 23 4 5 6 7 S g V 24b N 2 5—7 3 4.8 0.17 7.5 3.14v 23b N 2 5—7 3 4.9 0.19 7.8 2.97 28 N 3 4—6 3 4.2 0.23 2.7 2.98 37 N 2 o—3 3 4.7 0.33 9.9 2.99 A 52 N 2 I—3 3 3.8 0.33 7.8 2.01 K 39 N 1 4—6 4 4.6 0.25 4.3 2.12 V 21a N 3 I—3 4 5.0 0.30 4.9 2.02 V 21b N 3 5—7 4 5.2 0.28 9.8 2.86 A 28 N 2 5—7 4 4.3 0.30 3.5 1.11 70 R 2 3—5 4 4.4 0.25 9.7 2.11 V 16b N 3 5—7 4 4.5 0.29 6.0 2.27 V 22b N 3 5—7 4 5.1 0.28 4.3 1.87 V 2b N 3 5—7 4 4.2 0.31 4.6 2.03 34 N 3 o—3 4 4.5 0.34 12.4 2.74 V 22a N 3 I—3 4 4.7 0.37 13.4 2.45 35 R 3 o—3 4 4.5 0.38 9.4 2.47 K 8 R 2 3—4 5 4.6 0.39 5.5 2.41 K 33 R 1 6—B 5 4.5 0.25 5.8 2.61 102 N 2 7—lo 5 5.3 0.31 4.9 2.60 2 9 N 3 15—20 5 5.1 0.33 4.4 2.74 A 29 N 2 B—lo 5 4.1 0.35 4.0 1.70 106 N 7 2—4 6 4.7 0.26 22.4 2.32 71 R 2 7—lo 6 4.3 0.36 6.2 2.71 K 42 R 2 2—4 7 3.9 0.39 12.4 2.37 A 46 R 2 4—6 7 4.1 0.49 6.6 2.13 Sphagnum-Carex peat K 28 N 1 o—2 1 4.5 0.20 6.5 1.74v 3a N 3 I—3 1 4.4 0.14 6.7 1.07 A 19 N 2 I—3 2 5.0 0.25 12.3 1.86 A 13 N 3 B—lo 2 4.8 0.20 6.5 1.71 A 12 N 3 3—5 2 4.8 0.25 4.0 1.75 A 23 N 2 I—3 2 4.7 0.38 8.0 2.68 v 19a N 5 I—3 2 4.7 0.21 8.1 1.74 v 5a N 4 I—3 2 4.6 0.24 16.3 2.03 K 12 N 4 o—l 3 4.4 0.27 9.8 3.40 A 53 N 2 I—3 3 4.2 0.42 11.0 1.96 59 N 5 o—2 3 3.6 0.23 24.4 1.65 A 47 R 2 2—4 3 4.6 0.23 9.6 1.90v 3b N 3 5—7 3 4.3 0.25 5.1 1.19 A H N 3 o—2 3 4.9 0.26 16.7 2.28 A I 6 N 2 6—B 3 4.5 0.30 3.7 2.08v 5b N 4 5—7 3 4.9 0.30 8.5 2.42 A 35 N 6 o—4 3 5.5 0.31 9.3 2.43 v 10a N 3 I—3 3 4.7 0.27 18.4 2.61 v 10b N 3 5—7 3 4.9 0.24 8.1 2.37 v 9a N 3 I—3 3 4.9 0.27 18.9 2.75 v 13a N 4 I—3 3 4.4 0.25 9.7 2.88 K 18 N 4 o—2 3 5.5 0.27 15.4 4.51 145PHOSPHORUS IN VIRGIN PEAT SOILS 1 2 3 4567 8 9 V 9b N 3 5—7 3 4.9 0.24 11.5 2.54 V 14a N 4 I—3 4 4.5 0.29 9.2 3.21 V 20a N 5 I—3 4 4.6 0.33 7.8 1.61 K 24 R 1 6—B 4 5.1 0.35 2.2 2.51 A 49 N 5 I—3 4 4.3 0.34 6.2 2.49 86 N 6 o—2 4 4.4 0.21 4.7 2.40 89 N 6 o—2 4 4.5 0.22 9.4 2.35 V 11a N 3 I—3 4 4.7 0.28 22.0 2.19 V 11b N 3 5—7 4 4.8 0.24 14.4 2.78 V 8a N 4 I—3 4 4.7 0.25 15.8 2.40 57 N 6 o—3 4 4.8 0.25 15.5 2.57 33 N 6 o—3 4 4.7 0.30 5.1 3.24 A 20 N 2 4—6 4 4.2 0.30 5.8 2.07 V 12a N 4 I—3 4 4.4 0.30 10.8 3.27 V 17a N 4 I—3 4 4.8 0.30 10.1 2.32 V 17b N 4 5—7 4 4.9 0.30 5.8 2.24 V 18a N 4 I—3 4 4.8 0.32 7.4 2.27 V 18b N 4 5—7 4 4.9 0.31 5.7 2.22 A 15 N 2 2—4 4 4.3 0.34 6.5 2.02 55 N 6 o—3 4 5.2 0.44 25.5 2.50 V 8b N 4 5—7 4 4.9 0.24 6.1 2.39 V 7a N 6 I—3 5 4.7 0.29 10.2 3.34 A 33 N 2 B—lo 5 4.1 0.30 3.1 2.01 60 N 5 3—9 5 3.5 0.32 3.5 2.59 K 90 N 6 3—5 6 4.8 0.30 3.3 2.62 K 35 R 3 4—6 5 4.9 0.34 6.1 2.54 87 N 6 3—5 5 4.5 0.29 2.6 2.40 K 23 R 1 4—6 5 5.0 0.32 2.0 2.37 V 19b N 5 5—7 5 5.1 0.39 7.4 1.92 K 59 N 4 o—s 6 5.3 0.45 9.6 5.07 58 N 6 3—7 6 4.9 0.25 6.9 2.76 V 14b N 4 5—7 6 4.5 0.40 5.3 2.48 V 13b N 4 5—7 6 4.5 0.40 5.4 2.45 V 12b N 4 5—7 6 4.4 0.40 4.1 2.46 V 20b N 5 5—7 6 5.5 0.42 6.9 1.83 56 N 6 o—3 6 5.1 0.43 32.6 3.24 88 N 6 7—lo 6 5.2 0.30 4.0 2.41 61 N 5 10—13 7 4.2 0.40 13.2 2.58 V 7b N 6 5—7 7 5.0 0.40 9.1 2.51 76 R 1 60—62 9 4.8 0.71 11.2 1.92 Eutrophic Sphagnum-Carex peat 91 L 8 o—2 2 5.8 0.18 9.1 2.32 62 L 8 o—2 3 4.4 0.18 18.4 1.96 40 L 8 o—3 3 5.6 0.25 9.8 2.21 95 L 8 3—5 3 5.8 0.36 7.7 2.15 K 5 L 8 3—5 4 5.4 0.27 5.3 2.54 92 L 8 3—5 4 5.9 0.36 8.2 2.49 63 L 8 3—7 5 4.7 0.32 4.9 2.30 146 ARMI KAILA 1 2 3 4 567 89 96 L 8 7—lo 5 5.8 0.51 14.2 2.33 93 L 8 7—lo 6 5.8 0.41 8.9 2.66 117 L 8 17—20 6 5.2 0.41 7.5 2.36 64 L 8 B—lo 7 4.3 0.38 5.1 2.16 118 L 8 20—23 7 5.4 0.47 19.2 2.48 Bryales-Carex peat K 9 L 7 o—2 1 4.9 0.16 9.9 1.96 K 1 L 7 o—2 1 5.5 0.14 9.0 2.53 K 10 L 7 2—3 2 5.2 0.24 15.6 2.98 74 L 7 o—3 2 6.2 0.20 5.7 3.13 122 L 8 14—17 2 4.9 0.22 8.2 2.55 139- L 8 o—2 2 3.9 0.48 7.5 2.29 39 L 7 o—2 2 4.7 0.23 4.2 3.16 119 L 8 4—7 3 5.1 0.30 17.1 3.17 120 L 8 7—lo 3 5.0 0.25 6.0 2.22 121 L 8 10—13 3 4.8 0.21 6.8 2.58 129 L 8 20—23 3 4.8 0.27 5.9 1.96 143 L 7 I—3 3 4.1 0.21 3.7 2.09 113 L 8 4-7 3 5.6 0.28 6.7 2.37 126 L 8 10—13 3 4.9 0.25 3.7 1.95 127 I. 8 14—17 3 4.9 0.24 4.8 1.97 128 L 8 17—20 3 4.8 0.25 4.7 1.95 K 2 L 7 3—5 3 5.2 0.28 7.5 2.76 9" I- 7 o—2 3 3.9 0.26 4.3 2.02 73 L 8 o—2 3 8.0 0.44 15.1 2.56 125 I 8 4—7 4 4.9 0.30 4 4 2.56 123 L 8 17—20 4 4.9 0.24 4.4 2.36 114 I- 8 7—lo 4 5.4 0.29 7.5 2.37 141 L 7 2—4 4 5.6 0.45 5.1 2.53 75 L 7 o—2 4 5.4 0.24 7.1 3.10 130 L 8 24—27 5 5.0 0.36 5.1 2.36 98 L 7 3—5 5 4.4 0.34 3.3 1.98 142 I. 8 2—4 5 4.8 0.53 6.6 3.19 115 L 8 10—13 5 5.4 0.37 6.5 2.05 135 I. 8 10—13 6 5.8 0.44 9.8 3.16 116 L 8 14—17 6 5.3 0.39 7.0 2.14 140 K 10 2—4 6 5.1 0.58 8.9 3.29 99 L 7 7—lo 6 4.9 0.45 4.6 2.27 134 L 8 4—lo 6 5.7 0.43 15.3 2.86 136 L 8 14—17 7 5.7 0.42 11.8 2.79 K 11 L 7 5—7 7 5.0 0.37 10.6 3.62 K 3 L 7 7—9 7 5.3 0.34 4.4 2.76 Carex-y>eat K 29 N 4 5—7 2 4.6 0.20 5.1 1.99 A 40 N 3 o—2 3 4.7 0.30 5.5 3.08 A 41 N 3 3—5 3 4.8 0.25 5.1 2.54 A 8 K 5 o—3 3 4 7 0.32 5.0 2.73 A 38 X 2 3—5 3 4.5 0.29 10.0 2.94 147PHOSPHORUS IN VIRGIN PEAT SOILS 1 2 3 4 567 89 A 24 N 2 5—6 3 5.0 0.34 5.5 2.50 A 43 N 3 2—5 3 4.5 0.24 5.1 2.23 38 K 7 o—2 4 4.9 0.36 6.7 3.16 K 13 N 4 I—3 4 4.9 0.28 5.1 3.47 K 14 N 4 5—7 4 5.1 0.26 4.9 2.68 K 25 N 6 I—3 4 4.6 0.21 4.5 2.33 K 26 N 6 5—7 4 4.2 0.20 3 1 2.40 103 N 4 2—4 4 4.8 0.28 7.7 2.95 109 N 6 I—3 4 4.6 0.24 24.8 2.16 111 K I—3 4 4.7 0.26 3.0 2.62 K 27 N 6 11—14 4 4.4 0.23 5.3 2.04 A 44 N 3 6—B 4 4.3 0.27 6.9 1.70 A 42 N 3 B—lo 4 4.9 0.23 4.2 2.55 110 N 6 2—4 5 4.6 0.24 3.6 2.56 K 36 N 2 4—6 5 4.9 0.34 6.1 2 54 A 17 N 2 B—lo 5 4.1 0.31 5.5 2.23 K 30 R 4 2—5 5 4.8 0.38 4.9 2.73 K 41 R 4 2—6 5 4.2 0.28 3.5 3.61 23 K 6 5.0 0.34 24.2 2.46 26 L 9 2—4 6 6.1 0.34 14.2 2.32 K 20 N 4 6—B 6 5.4 0.30 4.8 2.88 104 N 6 2—4 6 4.6 0.29 7.6 3.11 131 L 8 27—30 6 5.0 0.35 8.2 3.04 138 L 8 20—23 6 5.5 0.43 11.3 2.75 A 25 N 2 B—9 6 5.1 0.37 8.7 2.48 K 4 N 6 3—6 7 5.2 0.35 6.6 2.74 A 21 N 2 B—lo 7 5.8 0.37 7.2 2.05 137 L 8 17—20 7 5.6 0.39 12.9 2.64 K 19 N 4 3—5 7 5.4 0.46 8.1 3.52 A 50 N 3 3—5 7 4.6 0.31 5.3 2.05 31 K 6 3—6 8 4.9 0.39 7.8 2.18 30 K 6 o—3 8 4.6 0.54 9.1 2.40 32 K 6 o—s 8 4.7 0.69 23.6 2.30 A 9 K 5 o—3 8 4.6 0.58 6.9 2.84 A 45 N 3 12—14 8 4.9 0.52 20.6 2.33 K 60 N 4 10—14 8 4.9 0.53 7.(1 2.56 It may be of interest to examine the possible differences in the characteristics of the different kinds of peat on the basis of the data in Table 1. Therefore, the mean values of the degree of humification, pH, volume weight, ash content, and nitrogen content are calculated for the peat groups. As a measure of the distribution the confidence limits at the 95 per cent level are given. These data are collected in Table 2. In the present material the group of Sp appears, on the average, to be of a lower degree of humification than the other groups, except that of the SCp. The Cp-group seems to represent a higher degree of humification than the other ones. Partly, this is connected with the sampling depth of the various kinds of peat: 148 ARMI KAILA PHOSPHORUS IN VIRGIN PEAT SOILS 149 Table 2. Mean values of the degree of humification, pH, volume weight, ash content, and nitrogen content for the different peat groups (with 95 % confidence limits) Kind Number T7. , Volume of , of H P H weight Ash % N % peat samples Sp 32 2.6 ±0.6 4.3 ±0.2 0.21 ±0.04 5.0±1.0 1.50 ±0.22 CSp 34 3.7 ±0.6 4.5 ±O.l 0.26±0.04 7.2±1.3 2.20±0.22 SCp 62 3.1 ±0.4 4.7 ±O.l 0.31 ±0.02 9.5±1.5 2.43±0.17 EuSCp 12 4.6 ±l.l 5.4 ±0.3 0.34±0.07 9.9±3.2 2.33±0.13 BCp 36 4.1 ±0.6 5.2 ±0.2 0.32±0.04 7.5±1.2 2.60±0.16 Cp 41 5.2 ±0.6 4.9 ±O.l 0.34±0.07 8.2±1.6 2.55±0.14 the ,Sp-samples originate, on the average, from a less deep layer than all the other groups. Yet, the BCp-group with a lower average degree of humification than the Cp-group represents markedly deeper layers than the latter one. The total correla- tion coefficient between the sampling depth and the degree of humification was calculated and a highly significant, but not very close correlation, was found, the coefficient being r = 0.414***. The average pH values of the different groups are in accordance with the corresponding data reported by Kivinen (12). Only the BCp samples in his material tend to be somewhat less acid than the present samples, the difference of the means is even highly significant. In the present material the Sp samples, as a group, have a lower pH than all the other kinds of peat, the BCp and EuSCp samples are less acid than the other groups, but no significant difference can be found between the CSp and SCp groups on one hand and between the SCp and Cp groups on the other hand. In the volume weights the low degree of humification of the Sp samples appears. The volume weights of all the groups in which the Carex-residues dominates are equal and higher than those of the Sp and CSp samples. The ash content of the BCp group is rather low, yet significantly higher than that of the Sp group, which again appears to be the poorest kind of peat. Owing to the large variation in the ash content no significant difference can be found between the average values of the other kinds of peat. These means are also of the same order as those reported by Kivinen (12) for various peat groups, the only exception again being the BCp samples. As to the Kjeldahl nitrogen content of the peat groups, the results agree well with the corresponding results by Kivinen (12). In the present material the nitrogen contents of the Cp, BCp and SCp groups do not significantly differ from each other, the nitrogen percentage in the CSp-group is lower than in these but higher than in the poor Sp-group and equal to that in the EuSCp samples. The low number of the EuSCp samples makes their group less representable than the larger ones. Generally the EuSCp seems to be like the SCp and differs from the latter only in its lower acidity. 150 ARMI KAILA Table 3. Phosphorus in the peat samples Organic P Inorganic P,ppm Total P n / r ~, n soluble in Sample PP m %of N/ P ppm kg/ha tot.P org. 0.5 N 0.2 N matter HAc H^SOj 1 234567 8 9 Sphagnum peat 65 400 40 250 63 0.02 33 60 60 144 220 30 130 59 0.01 68 28 40 K 31 480 80 320 67 0.03 76 46 70 K 32 390 60 30C 77 0.03 49 24 50 K 21 430 80 300 70 0.03 29 37 50 K 34 730 130 550 75 0.06 19 5 60 A 4 190 40 140 74 0.01 46 7 10 K 37 840 180 590 70 0.06 25 55 90 K 6 970 210 660 68 0.07 18 21 140 A 27 380 90 290 76 0.03 25 8 40 36 730 170 540 74 0.06 23 15 80 A 58 340 90 210 62 0.02 21 37 50 A 37 530 300 360 68 0.04 30 5 50 A 31 850 490 620 73 0.07 30 29 50 K 22 580 90 400 69 0.04 29 57 50 K 7 1180 400 890 76 0.09 17 14 160 V 6a 560 250 380 68 0.04 48 6 30 66 470 80 320 68 0.03 30 30 20 A 5 360 170 270 75 0.03 43 5 0 V 6b 490 250 350 72 0.04 64 5 20 A 1 570 330 430 76 0.04 40 14 30 A 32 760 520 590 78 0.06 37 9 30 A 6 370 160 290 79 0.03 41 4 10 V la 880 540 640 73 0.07 30 11 20 V 15a 690 460 460 67 0.05 37 7 30 67 680 280 500 73 0.05 41 16 20 105 370 150 260 70 0.03 55 22 20 V lb 830 550 650 78 0.07 33 9 20 A 2 620 610 520 84 0.05 34 15 30 68 630 400 540 86 0.06 28 4 0 V 15b 490 400 370 75 0.04 53 3 20 A 3 710 540 560 79 0.06 33 1 10 Carex-Sphagnum peat V 24a 360 70 280 78 0.03 37 4 20 100 460 100 260 57 0.03 66 20 V 23a 410 90 310 76 0.03 41 4 20 V 16a 520 120 350 67 0.04 27 14 50 69 770 140 510 66 0.05 24 73 240 V 2a 670 200 500 75 0.05 21 g 30 K 38 760 350 550 72 0.06 41 50 60 101 510 140 380 75 0.04 60 10 PHOSPHORUS IN VIRGIN PEAT SOILS 151 1 23456 7 8 9 107 790 250 530 67 0.06 62 9 30 V 24b 410 140 330 80 0.04 95 5 10 V 23b 420 160 360 86 0.04 82 5 10 28 590 270 430 73 0.04 69 1 30 37 880 580 700 80 0.08 43 9 40 A 52 700 460 490 70 0.05 41 1 30 K 39 840 420 700 83 0.07 30 14 20 V 21a 610 370 470 77 0.05 43 4 30 V 21b 540 300 430 80 0.05 67 7 10 A 28 440 260 330 75 0.03 34 4 20 70 1310 650 1110 85 0.12 19 20 70 V 16b 770 450 610 79 0.06 37 6 20 V 22b 530 300 430 81 0.05 43 8 10 V 2b 1060 660 810 76 0.08 25 12 50 34 1480 1000 1120 76 0.13 24 1 60 V 22a 870 640 640 74 0.07 38 12 50 35 1280 970 1030 80 0.11 24 1 40 K 8 1810 1410 1570 87 0.17 15 5 70 K 33 770 380 660 86 0.07 40 10 20 102 650 400 550 85 0.06 47 10 29 570 370 410 72 0.04 67 0 10 A 29 550 390 460 84 0.05 37 3 20 106 620 320 420 68 0.05 55 28 60 71 1510 1090 1340 89 0.14 20 5 10 K 42 1290 1010 1110 86 0.13 21 9 30 A 46 1550 1520 1380 89 0.15 15 3 30 Sphagnum-Carex peat K 28 930 370 680 73 0,07 26 7 70 V 3a 550 150 430 78 0.05 25 9 20 A 19 540 270 400 74 0.05 47 19 20 A 13 480 190 440 92 0.05 39 10 A 12 500 250 420 84 0.04 42 3 10 A 23 1260 960 860 68 0.09 31 7 60 V 19a 860 360 600 70 0.07 29 7 50 V 5a 530 260 340 64 0.04 60 5 30 K 12 1270 690 1000 79 0.11 34 4 50 A 53 520 440 400 77 0.05 49 1 20 59 1070 490 780 73 0.10 21 8 150 A 47 1210 560 1010 83 0.11 19 4 20 V 3b 540 270 420 78 0.04 28 6 20 A 11 560 290 440 79 0.05 52 7 20 A 16 440 260 420 95 0.04 50 4 10 V 5b 550 330 420 76 0.05 58 3 10 A 35 710 440 580 82 0.06 42 4 20 V 10a 880 480 680 77 0.08 38 6 30 V 10b 690 330 550 80 0.06 43 4 20 V 9a 890 480 670 75 0.08 41 5 30 V 13a 670 340 450 67 0.05 64 8 30 152 ARMI KAILA 1 234567 8 9 K 18 570 310 440 77 0.05 103 5 50 V 9b 690 330 550 80 0.06 46 4 20 V 14a 680 390 470 69 0.05 69 7 20 V 20a 1150 760 880 76 0.09 18 50 K 24 450 310 360 80 0.04 70 8 10 A 49 1230 840 860 70 0.09 29 2 60 86 830 350 560 67 0.06 43 30 89 1280 560 840 66 0.09 28 100 V 11a 870 490 640 74 0.08 34 6 30 V 11b 700 340 550 79 0.06 51 4 10 V 8a 880 440 660 75 0.08 36 7 50 57 1110 550 900 81 0.11 29 2 20 33 1110 670 850 77 0.09 38 20 100 A 20 750 450 650 87 0.07 32 13 10 V 12a 700 420 510 73 0.06 64 8 30 V 17a 900 540 680 75 0.08 34 6 20 V 17b 810 490 640 79 0.07 35 2 20 V 18a 890 570 680 76 0.07 33 6 30 V 18b 810 500 670 83 0.07 33 3 10 A 15 680 460 550 81 0.06 37 6 10 55 640 560 510 80 0.07 49 1 10 V 8b 660 320 530 80 0.06 45 3 10 V 7a 950 550 720 76 0.08 46 4 50 A 33 630 380 500 79 0.05 40 20 90 730 440 560 77 0.06 47 10 60 1100 710 890 81 0.09 29 7 20 K 35 1180 800 900 77 0.10 28 4 50 87 570 330 450 79 0.05 53 10 K 23 610 390 470 77 0.05 50 25 40 V 19b 750 590 600 80 0.06 32 3 10 K 59 460 410 380 83 0.04 133 2 10 58 1000 500 830 83 0.09 33 2 0 V 14b 570 450 390 69 0.04 64 3 10 V 13b 540 430 390 72 0.04 63 3 10 V 12b 530 420 410 77 0.04 60 3 10 V 20b 1080 910 920 85 0.10 20 3 10 56 1030 890 830 80 0.12 39 1 90 88 840 500 690 82 0.07 35 10 61 1290 1030 990 77 0.11 23 2 30 V 7b 1010 810 880 87 0.10 29 3 20 76 560 800 410 78 0.05 47 9 30 Eutrophic Sphagnum-Carex peat 91 1470 530 1230 84 0.14 19 80 62 1500 540 1110 74 0.14 18 15 100 40 860 430 670 78 0.07 33 57 80 95 810 580 650 80 0.07 33 20 K 5 550 300 470 85 0.05 54 18 40 92 820 590 690 84 0.07 36 20 PHOSPHORUS IN VIRGIN PEAT SOILS 153 1234'5 6 7 8' 9 63 750 480 600 80 0.06 38 7 10 96 2050 2090 1910 93 0.22 12 30 93 770 630 650 84 0.07 41 20 117 670 550 590 88 0.06 40 20 64 500 380 4CO 80 0.04 54 2 0 118 1040 980 920 88 0.11 27 60 Bryales-Carex peat K 9 580 190 400 69 0.04 49 12 70 K 1 340 100 200 59 0.02 126 ' 21 50 K 10 530 250 430 81 0.05 69 5 50 74 520 210 380 73 0.04 82 22 20 122 300 130 230 77 0.02 110 10 139 1190 1140 890 75 0.10 26 17 140 39 500 230 370 74 0.04 86 12 30 119 350 210 270 77 0.03 117 20 120 270 140 240 89 0.03 93 10 121 260 110 200 77 0.02 130 20 129 320 170 240 75 0.03 81 10 143 570 240 440 77 0.05 48 25 30 113 530 300 430 81 0.05 55 20 126 270 130 210 78 0.02 93 10 127 290 140 250 86 0.03 79 10 128 330 160 250 75 0.03 78 10 K 2 660 380 530 80 0.06 52 4 40 97 750 390 500 67 0.05 40 40 73 650 570 510 79 0.06 50 8 30 125 370 220 300 81 0.03 85 10 123 310 150 280 90 0.03 84 10 114 530 310 470 88 0.05 50 20 141 690 620 540 78 0.06 47 50 75 620 300 450 72 0.05 69 5 50 130 410 300 320 78 0.03 74 10 98 610 410 500 82 0.05 40 10 142 450 480 330 73 0.03 98 29 40 115 450 330 390 87 0.04 53 10 135 1120 990 970 87 0,11 33 20 116 540 420 460 85 0.05 47 10 140 860 1000 730 85 0.08 45 30 99 680 610 530 78 0.06 43 10 134 1130 970 980 86 0,11 29 20 136 900 760 780 87 0.09 36 20 K 11 610 450 490 81 0.05 74 3 20 K 3 520 350 420 81 0,04 66 4 30 Carex-peat K 29 850 340 630 74 0.07 32 5 50 A 40 810 490 650 80 0.07 47 4 20 A 41 470 230 370 79 0.04 69 3 10 154 ARMI KAILA 1 234567 8 9 A 8 570 370 510 90 0.05 54 2 0 A 38 550 320 400 73 0.04 73 7 20 A 24 850 580 720 85 0.08 35 3 10 A 43 1180 570 1010 86 0.11 22 2 10 38 1410 1020 1060 75 0.11 30 9 140 K 13 1060 590 880 83 0.09 39 4 20 K 14 890 460 730 82 0.08 37 2 20 K 25 1140 480 930 82 0.10 25 4 20 K 26 1210 480 920 76 0.09 26 2 20 103 1550 870 1150 74 0.12 26 7 110 109 580 280 320 55 0.04 68 6 90 111 1480 770 1270 86 0.13 21 3 20 K 27 1240 570 1080 87 0.11 19 2 20 A 44 1020 550 880 86 0.09 19 2 10 A 42 500 230 400 80 0.04 64 5 10 110 890 430 740 83 0.08 35 2 20 K 36 1070 730 940 88 0.10 27 1 10 A 17 550 340 500 91 0.05 45 10 K 30 1120 760 830 74 0.09 33 1 20 K 41 670 380 500 75 0.05 72 6 30 23 1350 1030 1020 76 0.14 24 6 100 26 1340 910 1080 81 0.13 22 39 90 K 20 870 520 620 71 0.06 46 1 30 104 710 410 520 73 0.05 60 5 50 131 450 320 350 78 0.04 87 20 138 660 570 580 88 0.06 48 20 A 25 910 670 800 88 0.09 31 2 20 K 4 630 440 520 82 0.06 53 4 30 A 21 660 490 590 89 0.06 35 5 10 137 530 410 460 87 0.05 57 20 K 19 750 690 540 72 0.06 65 2 30 A 50 890 550 760 86 0.08 37 3 10 31 750 580 650 87 0.07 34 1 10 30 950 1030 820 86 0.09 29 2 20 32 1250 1720 1070 86 0.14 22 1 20 A 9 830 960 680 82 0.07 42 3 20 A 45 2350 2440 1950 83 0.25 12 1 180 K 60 1230 1300 1090 89 0.12 22 2 30 According to this survey the present material appears to be satisfactorily typi- cal for a study of Finnish peat soils. Only the BCp-group seems to be in some respects of a poorer quality than is generally suggested. Total phosphorus The total P content of the peat samples expressed both as ppm and as kg/ha in a 20 cm-layer is reported in Table 3. Quantities ranging from 190 to 2350 ppm PHOSPHORUS IN VIRGIN PEAT SOILS 155 or from 30 to 2440 kg/ha can be found. In order to obtain an idea of the differences between the various kinds of peat the corresponding mean values are computed. The minimum and maximum values are also given and the distribution is charac- terized by the confidence limits at the 95 per cent level. Total P ppm Total P kg/ha mean min. max. mean min. max 32 Sp samples 580 ±BO 190 1180 260 ±7O 30 610 34 CSp » 800 ± 120 360 1810 470 ± 170 70 1520 62 SCp » 800 ±6O 440 1290 490 ±5O 150 1030 12 EuSCp » 980 ± 290 500 2050 670 ± 300 230 2090 36 BCp » 560 ±9O 260 1190 390 ±9O 100 1140 41 Cp » 950 ± 120 450 2350 660 ± 130 230 2440 The most striking result is the low average value for the total P content of the BCp-group expressed on the weight basis. It is equal to that of the Sp-group and significantly lower than the mean phosphorus content of Cp, SCp, and CSp samples. Owing to the higher volume weight of the BCp samples their P content expressed as kg/ha tends to be somewhat higher than the corresponding value for the Sp-group. Even then the BCp seems to be poorer in phosphorus than the Cp, but the difference between the BC-group and the CSp and SCp groups is less signi- ficant. Attention must, however, be paid to the fact that the figures calculated on the basis of the volume weight determined in this work on air-dry and ground samples do not correspond to the real conditions in nature. The Cp and EuSCp groups tend to show the highest average content of total phosphorus. The difference between the total phosphorus in the Cp-group and the SCp-group is statistically significant. The variation in the CSp and EuSCp groups violates the demonstration of a significant difference between the P content of these kinds of peat and of that of the Cp-group. The poverty of the Sp and BCp in total P is indisputable. These data are well in accordance with the results reported by Kivinen (12) of his own analyses and of the analyses performed by some other peat scientists in Finland. Only the poor BCp-group of this material forms an exception. The average phosphorus content of the 21 BCp samples analysed by Kivinen is about 700 ppm. Vahtera (19) in his thesis reports even higher phosphorus contents for the BCp; his average value of 24 samples is about 1400 ppm, as far as it is possible to estimate it on the basis of the distribution tables given. This quantity cannot, however, be typical for Finnish BCp. It is probable that the analyses performed by Vahtera are not reliable, since also the average phosphorus content which can be calculated for his 97 Sp samples seems to be higher than 1300 ppm, and one fifth of his 58 Cp samples contain more than 3000 ppm of total P. The total P content of the present samples appears to be in no correlation with the land quality determined on the basis of the surface vegetation. The cor- ARMI KAILA156 relation coefficient for all the samples is r = 0.070. This; probably, arises from the fact that the sampling depth of the material varied considerably and the peat quality of the deeper layers does not an}/ more exert a distinct effect upon the nutrition of the surface vegetation. If only the surface samples are chosen and the correlation coefficient between their total P content and the degree of land quality is calculated, a low but significant correlation coefficient, r = 0.361*** can be obtained. An even closer correlation is found if the BCp samples which all origi- nate from peat lands of a high quality but which contain rather low amounts of total phosphorus, are excluded. This correlation coefficient is r = o.4Bl***. In a previous paper (9) the dependence of the total P content of peat samples on the sampling depth was studied. It was found that even within the same profile the P content could vary quite irregularly, but often some tendency appeared to exist: in the peat lands of better quality the surface samples were higher in phos- phorus than the deeper ones, and in the peat lands of lower quality an increase in the P content with the depth was detected. In order to study whether the total phosphorus content of peat is connected with some of its other characteristics the total correlation coefficients between the total P and the total N, or the ash content, or the degree of humification were calculated. The following data were obtained: Correlation coefficients between total P content and H N % Ash % 32 Sp samples 0.135 0.406* 0.382* 34 CSp » 0.573*** 0.2220.243 62 SCp » 0.1080.049 0.109 12 EuSCp » 0.318 0.640* 0.700* 36 BCp » 0.377* 0.1480.298 41 Cp » —0.019 0.308 0.346* Ali the 217 » 0.317*** 0.206* 0.289** Although statistically even highly significant correlation coefficients between the total P content and the other characteristics of all the material could be found, these figures are, almost without exception, so low that no marked dependence between these quantities can be expected to exist. In addition to this, the coeffi- cients calculated for the various peat groups do not encourage to imagine that the total P content of a peat would be connected with the total N or ash contents, generally not even with the degree of humification. The present material corroborates the opinion that the Finnish virgin peat soils are mostly rather poor in phosphorus. Some exceptions were detected: in 26 of all the 217 samples a P content higher than 1200 ppm was found, but only in two of the samples the P content exceeded 2000 ppm. On the other hand, in 40 samples less than 500 ppm of total P occurred. Yet, the total amount of phosphorus is not PHOSPHORUS IN VIRGIN PEAT SOILS 157 enough to characterize the phosphorus conditions in a soil: the forms in which the phosphorus occurs can be more important, at least when the plant nutrition is in question. Organic phosphorus There is in the literature very little information of the organic phosphorus con- tent of peat soils. In 1899Nannes (14) isolated from peat an organic preparate with a high P content thus proving that phosphorus in peat soils occurs, at least partly in organic form. This had been suggested already by Eggertz and Nilson (4) although the method which they employed for the determination of organic P was unreliable. Since then only some scattered data concerning the occurence of organic P in peat lands are reported. Schmoeger (16) found in a peat sample 600 ppm of organic P, and amount which corresponded to 57 per cent of the total P content of the soil. Dickman and Deturk (2) obtained the same percentage for their peat soil which contained 1040 ppm of organic P. Dmitrenko (3) reported that in some meadow-bogs the organic P content varied from 920 to 1700 ppm. In a Swedish raised bog the organic P content estimated by an ignition method was in the 90— 100 cm layer 65 ppm and in the 140—150 cm layer 130 ppm corresponding to the relative amounts of 71 and 84 per cent of the total P contents, respectively (13). In a previous publication the author studied the organic P content of 37 cultivated peat soils (5). The data varied from 170 to 1670 ppm and the relative amount of organic P of total P dissolved ranged from 30 to 80 per cent. Also some virgin peat samples were analysed, but the method of fractionation employed for these latter estimations probably yielded too high results. It was emphasized in a previous paper (11) that the determination of total organic P in samples of virgin peat soils often requires a more drastic treatment than that which is needed when mineral soils or old cultivated peat soils are in question. In the same paper analyses for organic P were reported. In 32 samples of virgin peat soils the amount of organic P varied from 180 to 1180 ppm, and in the 8 samples of cultivated peat soils the corresponding limits were 600 and 1260 ppm. In the present paper the organic P content of the samples was determined as an average of the results of an extraction method, particularly developed for the analyses of virgin peat samples, and an ignition method. The former method tends to yield too low estimations of the amount of organic P. The latter one, on the other hand, tends to give too high values. Hence, it can be supposed that the average of the results obtained by the respective methods is fairly reliable. In these 217 peat samples (Table 3) the amount of phosphorus which occurs in organic form ranges from 130ppm to 1950 ppm with an average value of 600 40. The organic P content expressed as a percentage of the total P content ranges from 55 % to 95 % with an average of 78 ± 1 %. The organic P content of the various peat groups was the following (the con- fidence limits of the means are given at the 95 per cent level): 158 ARMI KAILA Org. P. ppm Org. P % of tot. P mean min. max. mean min. max. 32 Sp samples 430 ±6O 130 890 73 i 2.2 59 —B6 34 CSp » 630 ± 120 280 1570 77 ± 3.0 57 89 62 SCp » 620 ± 50 340 1010 77 ± 1.6 64 95 12 EuSCp » 820 ± 280 400— 1910 83 ± 3.3 74 —93 36 BCp » 440 ± 70 200 980 79 ± 2.4 59 90 41 Cp » 770 ± 100 320 1950 81 ± 2.2 55 91 The relation between the organic P content of the various peat groups appears to be similar to that which exists between the results obtained for the total P content of the samples. This arises from the fact that the correlation between the total and organic phosphorus contents of these peat samples is very close, the total corre- lation coefficient for the material being markedly higher than 0.9. The average contents of organic P are not very high when expressed as parts per millions but the corresponding relative amounts indicate that in all the peat groups the largest part of P occurs in organic form. A more detailed picture of the distribution of the organic P content within the various peat groups is presented in the Tables 4 and 5. The data in Table 4 indicate that only 22 of the samples contain more than 1000 ppm of organic P. All the samples of Sp and BCp lie below this limit. To these groups also belong the three samples in which the organic P content is lower than 200 ppm. As to the proportion of organic P of total P, the distribution of the samples of the various peat groups in the different classes appears to be more equal (Table 5). There seems, however, to be a tendency to lower percentages in the Sp samples and to higher percentages in the Cp samples as compared with those of the other peat groups. This may be connected with the fact that a large part of the Sp samples originates from the less humified surface layers and most of the Cp samples from Table 4. Distribution of samples of various peat groups in classes of organic phosphorus content. Org. P ppm Sp CSp SCp EuSCp BCp Cp Total <2OO 2 1 3 210—400 14 8 5 15 3 45 410—600 11 13 27 3 15 11 80 610—800 4 5 15 5 2 9 40 810—1000 1 1 13 1 3 8 27 1010—1200 4 2 1 8 15 1210—1400 2 1 1 4 1410—1600 1 1 1610—1800 _______ 1810—2000 _ 1 1 2 PHOSPHORUS IN VIRGIN PEAT SOILS 159 Table 5. Organic phosphorus as a percentage of total phosphorus in various peat groups. Org. P % Sp CSp SCp EuSCp BCp Cp Total 51—55 _____ 1 1 56—60 1 1 _ 1 3 61—65 2 1 3 66—70 10 5 8 2 25 71—75 9 7 9 1 7 9 42 76—80 8 10 29 -4 10 6 67 81—85 1 5 11 4 8 9 38 86—90 1 6 2 2 8 15 34 91—95 2 1 1 4 deeper layers of peat lands. The author has found (9) that generally, at least within the same profile, the proportion of phosphorus occurring in organic form increases with the depth. Tables 1 and 3 reveals that all the samples in which the percentage of organic P of total P is 65 % or lower were collected from the surface layers not deeper than 3 dm. On the other hand, all the samples in which more than 91 per cent of total P occurs in organic form arises from deeper layers between 6 and 10 dm. This, of course, cannot mean that the proportion of organic P would depend only on the depth or on the age of the peat. In order to study the different factors which control the occurence of peat phosphorus in organic form, the present material was submitted to further statistical examination. First the absolute amounts of organic P were studied. It has already been mentioned that this quantity closely depends on the total P content of peat. In addition to this, it can be supposed that the degree of humification could exert some effect upon the accumulation of organic P. Also the relations of N content and organic P content may be noteworthy. The total linear correlation coefficients between the amount of organic P and the total P content, or the degree of humi- fication, or N content were for the various peat groups and for the total material the following: Correlation coefficients between organic P ppm and total P ppm H N % 32 Sp samples 0.968*** 0.010 0.420* 34 CSp » o.9BB*** 0.559*** 0.243 62 SCp » 0.955*** 0.1570.052 12 EuSCp » 0.938*** 0.200 —O.lll 36 BCp » 0.977*** 0.441** 0.307 41 Cp » o.9Bl*** 0.147 0.084 Ml the 217 » 0.934*** 0.336*** 0.184 ARMI KAILA160 When compared with the close correlation of organic P and total P contents the conftection of the former with the degree of humification appears to be weak and the dependence of the former on the N content is insignificant. Even the effect of the degree of humification on the organic P content of these samples is indirect and arises from the connections between the total P content and the degree of humification: after the elimination of the effect of the two other factors the partial correlation coefficients between the organic P content (1) and the total P content (2) or the degree of humification (3) or the N content (4) were. r l2 . 34 = 0.927*** r l3 . 24 = 0.136 r r . 23 = 0.072 Consequently, of the characteristics of the peat samples examined here, only the total content of P appears to regulate the absolute amount of organic P. There may exist other factors which exert their effect on the accumulation of organic P in peat soils, but it seems probable that the generally rather low total P content is the minimum factor which impedes the effect of those other characteristics to become observable. It can be supposed that the proportion of phosphorus occurring in organic form depends on the degree of humification and on the depth, on the acidity of peat and possibly also on the total P content of the samples. This material revealed the following correlation coefficients between the percentage of organic P of the total P and these other characteristics: Correlation coefficients between the percentage of organic P of total P and H Depth pH total P 32 Sp samples 0.567*** 0.636*** —O.lOB 0.309 34 CSp » 0.586*** 0.362 —0.016 0.326 62 SCp » 0.180 0.220 0.310* —0.075 12 EuSCp » 0.204 0.627 0.267 0.076 36 BCp » 0.576*** 0.297 0.090 0.134 41 Cp » 0.290 0.243 0.073 0.038 All the 217 » 0.504*** 0.334*** 0.234* 0.222* The low correlation between the percentage of organic P and the total P content of all the material disappears when the effect of the degree of humification is eli- minated: the partial correlation coefficient is r = 0.076. The elimination of the degree of humification does not, on the other hand, change the correlation between the organic P percentage and the acidity: the partial correlation coefficient is r = 0.228*. The elimination of the degree of humification also leads to the dis- appearance of the significant correlation between the proportion of organic P and the depth: the partial correlation coefficient is r = 0.159, but the elimination of the effect of depth only slightly lowers the correlation between the organic P per- centage and the degree of humification: the partial correlation coefficient is r = 0.427***. In a previous paper (9) in wTiich the distribution of P in various peat profiles was studied, the observation was made that the proportion of organic P was rather PHOSPHORUS IN VIRGIN PEAT SOILS 161 closely correlated both with the degree of humification and with the depth. Since both these characteristics were also closely correlated with each other the elimination of the effect of either one of them led to equally high partial correlation coefficients. Hence, it could not be concluded which of these factors was the primary one to regulate the accumulation of organic P in peat. The present results tend to suggest that the degree of humification probably plays the more important role in this connection. Yet, the examination of the respective correlation coefficients for the various peat groups shows that the degree of humification cannot be the main factor. It is of interest to notice that the rather low correlation coefficient between the proportion of organic P and the pH value is positive. Generally, it has been supposed that the effect of the reaction would be the contrary, at least in mineral soils and in cultivated peat soils (5, 18). If this positive correlation found for the present material really would be of any significance it could be explained on the basis of the supposition that the biological turning over of inorganic P compounds into organic forms occurs more intensively under the less acid conditions. When mineral soils are in question, the fact is emphasized that under acid conditions the mineralization of organic P is slower than is the case in less acid soils. In virgin peat soils, however, the biological absorption may be the dominating process. Theoretically it indeed seems that in most of these peat samples no net mine- ralization of organic phosphorus can be expected to be observed, because of their extremely low organic P content. The amount of organic P expressed as a per- centage of organic dry matter is in the larger part of the samples markedly lower than the general limit of mineralization of organic P or about 0.2 per cent (5). Even if allowance is made to the fact that the carbon compounds of peat are not easily available for microorganisms and, hence, the limit value must be lower in peat than in materials containing more available sources of energy and carbon, it seems improbable that this limit could be markedly lower than about 0.1 per cent organic P of the organic material. In the present peat samples the organic phosphorus content of organic dry matter presented in Table 3 gives the following average and limit values for various peat groups (the means are reported with the corresponding confidence limits at the 95 per cent level): Organic P as a percentage of organic dry matter mean min. max. 32 Sp samples 0.04 + 0.007 0.01 0.09 34 CSp » 0.07 ± 0.013 0.03 0.17 62 SCp » 0.07 ± 0.005 0.04 0.12 12 EuSCp » 0.09 ± 0.03 0.04 0.22 36 BCp » 0.05 ± 0.008 0.02 0.11 41 Cp » 0.08 ± 0.013 0.04 0.25 All the 217 » 0.07 + 0.004 0.01 0.25 162 ARMI KAILA As it can be observed from the maximum value in the Sp-group there are no samples containing 0.1 per cent of organic P. Table 3 reveals that in the group of CSp seven samples exceed this limit, in the SCp-group their number is five, in the group of EuSCp four, in the BCp-group two and in the group of Cp it is ten. The mean values for all the groups, except for the EuSCp-group, are significantly lower than 0.1 per cent. It can be supposed that the percentage of organic P of the organic dry matter increases with the degree of humification. On the basis of this material a positive correlation coefficient was obtained between these variables; r = 0.382***, which indicates a significant but not very close connection. As to the different peat groups the corresponding correlation coefficients varied markedly being the following: Sp; r = 0,344 SCp: r = 0.159 EuSCp: r = 0.243 BCp: r = 0.378* Cp: r = 0.298CSp: r = 0.621*** These coefficients do not significantly differ from the figures obtained for the dependence between the degree of humification and the organic P content of the dry matter. This, of course, could be expected because of the low ash content of most of the samples. In view of the marked variation in the total P content of the samples and the close dependence of the organic P content on it no answer to the question »does the organic P in organic dry matter increase or decrease by advancing humification» can be given by this material. The close relation of P and N contents of soil organic matter has sometimes been emphasized (1, 15, 17, 18). According to a previous paper (5) this connection seems to be rather distinct in mineral soils, but in peat soils the ratio of N to organic P markedly varied: in 70 mineral soils N/org. P ranged from 5 to 16, in 30 cultivated peat soils the limits were 8 and 74. In the present material a low correlation between the N and organic P contents of the samples were found (cf. p. 159). Therefore, no constant number for the ratio of N/org.P can be expected in this material. The data reported in Table 3 reveal that the ratio of N/org.P ranges from 12 to 133. The mean value is 45 ± 3. If the ratio in mineral soils is supposed to be, on the average, 10, a figure often used as a typical mean value, the ratio in peat soils appears to be approximately five times higher. This again emphasizes the fact that peat soils are relatively richer in nitrogen and poorer in phosphorus than the mineral soils. In the various peat groups the means of N/org.P (with the confidence limits at 95 % level) and the minimum and maximum values are the following: N/org. I mean mm. max. 32 Sp samples 38 ±6 17 —76 34 CSp » 41 ± 6 15 95 62 SCp » 43 ± 4 18 133 12 EuSCp » 34 ±ll 12 —54 36 BCp » 68 ± 6 26'—130 41 CP » 40 + 6 12 87 PHOSPHORUS IN VIRGIN PEAT SOILS 163 The BCp-group has the highest mean value of the ratio N/org.P, obviously owing to its low organic P content. No difference exists between the other peat groups. It was found that the degree of humification appears to be in no correlation with the ratio of N/org.P. Easily soluble inorganic phosphorus Before the results of inorganic P soluble in 0.5 N acetic acid or in 0.2 N sul- phuric acid, reported in Table 3, are examined, it must be pointed out that the analyses were performed on air-dry and ground samples. This may mean that the figures obtained differ from the amounts of inorganic P soluble from the samples under natural conditions. Particularly the changes occurring in the colloids of peat during the drying are claimed to cause considerable changes in the solubility of inorganic P. However, only a few data are given to prove this opinion, and usually they are results obtained when the drying is performed at higher tempera- tures. In clay soils even drying at room temperature could either increase or de- crease the amount of inorganic P soluble in 0.5 N acetic acid, but in a swamp peat sample analysed the difference in the quantities of P dissolved by this extractant from fresh and air-dried portions was almost insignificant (10). Therefore, for the present it can be supposed that these data obtained using the air-dried samples give at least an approximate idea of the easily soluble inorganic P in peat. The treatment with 0.2 N sulphuric acid is rather intensive and usually the amounts of P dissolved are markedly higher than the quantities extracted by 0.5 N acetic acid. It has been assumed that acetic acid would not dissolve P retented by iron and its compounds, and thus gives a fairly reliable idea of the easily available part of soil P (cf. 6). The kind of P compounds or complexes the 0.2 N sulphuric acid extracts from peat cannot, for the present, be estimated. Since the P extracted by the sulphuric acid obviously represents an indefinite part of the inorganic peat phosphorus no statistical examination of these data was performed. Generally, it can be said that in the Sp-group the inorganic P seems to be more easily soluble in 0.2 N sulphuric acid and particularly in 0.5 N acetic acid than in the other kinds of peat. This again can be connected with the fact that a large part of the Sp samples originated from the surface layers. It has been found (9) that in the same profile the solubility of inorganic P in diluted acid dropped drastically on going deeper. On the average the amounts of inorganic P soluble in 0.2 N sulphuric acid appears to correspond to about 15 30 per cent of the total inorganic P in the peat samples. The percentages are highest in the Sp-group. The other groups do not seem to differ markedly from each other in this respect. The 0.5 N acetic acid extracts on the average about 15 per cent of the total inorganic P in the Sp samples but only about 2 per cent of the inorganic P in the Cp-group. The other groups seem to stand between these extremes. ARMI KAILA164 Discussion Obviously the most distinct result of the present investigation is the discovery that the largest part of phosphorus in these virgin peat soils occurs in organic form. An average proportion of 78 d; 1 per cent of the total P content is detected. The accumulation of organic P in peat soils may, of course, arise from various factors. On the basis of the present knowledge, it seems to the author most probable that phosphorus is generally a minimum factor in the »metabolism» of a peat land. This means that the need of P by the surface vegetation and by the microorganisms which live in the different peat layers is higher than the available sources, at least in peat lands without any support from outward. In addition to the requirements of the living organisms also the chemical and physicochemical retention ability of unsatisfied inorganic and organic complexes must be taken into consideration. In a mineral soil or in an old cultivated peat soil the ratio of C : N : P in the organic matter is generally supposed to be approximately 100 : 10 : 1. In a virgin peat soil as those examined above this ratio may, on the average, be about 700 : 35 ; 1. This indicates that a peat soil of this kind is still far from the end product of humification, and also that the nitrogen supply in peat is far better than the possibilities to find enough of phosphorus for an intensive humification. The supposition that in a typical peat soil the greatest part of phosphorus is in the living material or in organic form in the residues of plants and microorganisms is corroborated by some of the results in the present paper. First, the proportion of organic P of total P is high and no correlation exists between these quantities: it means that even in peat soils with the highest total P content most of the phos- phorus occurs in organic form. Second, the extremely low content of organic P, on the average far less than 0.1 per cent of organic dry matter, indicates that the synthetic processes of microorganisms probably dominate, even if allowance is made to the fact that the conditions in peat lands and the low availability of the carbon compounds in peat and in the residues of peat land plants decrease the limit value of mineralization of organic phosphorus. The positive correlation between the proportion of organic P and the pH-values also tends to indicate the dominance of the biological synthesis in the phosphorus metabolism in a peat soil. Unpublished data obtained by the author also corroborate the supposition of the importance of the biological absorption in peat soils. It was found that in soils fertilized with mineral phosphates about one half of the phosphorus left in the soil could be accumulated as organic compounds. This, probably, was resulted both by the activity of plants and of microorganisms. The present paper reports results of a statistical study of phosphorus in virgin peat soils. As such it is only a basis for further investigation in which the problems discussed here have to be treated in more detail. Summary. In the present paper the total and organic P content of virgin peat soils is studied on the basis of 217 peat samples mostly collected from Northern Finland PHOSPHORUS IN VIRGIN PEAT SOILS 165 and consisting of 32 Sp, 34 CSp, 62 SCp, 12 EuSCp, 36 BCp, and 41 Cp samples. The material was found to be satisfactorily typical for a study of Finnish peat soils as to the pH, ash and N contents. Only the BCp samples were, in some respect, of a poorer quality than in general. The total P content of the 217 samples ranged from 190 to 2350 ppm or from 30 to 2440 kg/ha. In the Sp and BCp groups the mean P content was equal, 580 ± 80 ppm and 560 ± 90 ppm resp., and significantly lower than the corresponding value in all the other groups which was 950 ±l2O ppm in the Cp-group, 980 ± 290 in the EuSCp-group, 800 ± 60 in the SCp-group, and 800 ± 120 ppm in the CSp-group. A low but significant correlation was found to exist between the degree of land quality estimated on the basis of the surface vegetation and the P content of the surface samples: r = 0.361***. When the BCp samples were excluded an even closer correlation was detected: r = o.4Bl***. The correlation coefficient between the total P content and the degree of humification was r = 0.317***, that between the total P and the ash contents r = 0.289**, and that between the total P and N contents r = 0.206*. The organic P content of the 217 samples ranged from 130 to 1950 ppm with an average of 600 ± 40 ppm. The Sp and BCp groups showed significantly lower means, 430 ± 60 ppm and 440 ±7O ppm resp., than the other groups with averages of 630 ± 120 ppm in the CSp-group, 620 ± 50 ppm in the SCp-group, 770 ± 100 ppm in the Cp-group and 820 ± 280 in the EuSCp-group. The organic P content was very closely correlated with the total P content; the total correlation coefficient was r = 0.934***. The connection with the degree of humification was not distinct: the total correlation coefficient was r = 0.336***, but the partial correlation coefficient after the elimination of the effects of total P and N contents was only r = 0.136. No significant correlation existed between the organic P content and the N content, r = 0.184. The organic P content of the 217 samples expressed as a percentage of the total P content ranged from 55 to 95 per cent with an average of 78 ± 1 per cent. The proportion of organic P of total P was correlated with the degree of humi- fication, the total correlation coefficient was r = 0.504***, the partial correlation coefficient after the elimination of the effect of the sampling depth was r = 0.427***. No correlation with the sampling depth existed after the elimination of the effect of the degree of humification: the partial correlation coefficient was r = 0.159, whereas the total correlation coefficient was r = 0.334***. A low correlation existed between the percentage of organic P of total P and the pH value even after the elimination of the effect of the degree of humification, r = 0.228*, but the con- nection with the total P content appeared to be only indirect and arised from the effect of the degree of humification, the total correlation coefficient was r = 0.222*, the partial correlation coefficient r = 0.076. The amount of organic P expressed as a percentage of the organic dry matter ranged from 0.01 to 0.25 per cent with an average of 0.07 ± 0.004. The ratio of N/org.P ranged from 12 to 133 with an average of 45 ± 3. Owing to the low P content of the BCp-group its mean ratio was significantly higher than 166 ARMI KAILA that of the other groups. The degree of humification did not show any correlation with the ratio of N/org.P. The solubility of inorganic P in 0.5 N acetic acid and in 0.2 N sulphuric acid was highest in the Sp-group. On the average approximately from 15 to 30 per cent of total inorganic P was extracted by the latter solution. The acetic acid extracted only about 2 per cent of the inorganic P in the Cp-group but about 15 per cent in the Sp-group. The phosphorus conditions in virgin peat soils was discussed and it was attempt- ed to explain the results obtained on the basis of the supposition that phosphorus is a minimum factor in the metabolism of peat. REFERENCES (1) Auten. J. T. 1922. The organic phosphorus content of some lowa soils. Soil Sei. 13: 119—124. (2) Dickman, S. R. & DeTurk, E. E. 1938. A method for the determination of the organic phosphorus of soils. Ibid 45: 29—39. (3) Dmitrenko, P. A. 1948. (The phosphorus content in the organic portion of the soil.) Pochvovedenie 1948, p. 495—501. (Ref. Chem. Abs. 43: 4409). (4) Eggertz, C. G. & Nilson, L. F. 1889. Chemische Untersuchung von Moor- und Torfböden. K. landbr. akad. exp. fält. Medd. 7. (Ref. Biedermanns Centr.bl. 18: 664—668.) (5) Kaila, A. 1948. Viljelysmaan orgaanisesta fosforista. Summary: On the organic phosphorus in cultivated soils. Valt. maatal.koet. julk. 129. Helsinki. (6) —»— 1949. Maan fosforintarpeen määrittämisestä. Summary: On testing soils for phosphorus deficiency. Rep. State Agr. Res. 220. Helsinki. (7) »—• 1955. Studies on the colorimetric determination of phosphorus in soil extracts. Acta agr. fenn. 83: 25—47. (8) —»■— 1956 a. Determination of the degree of humification in peat samples. J. Sei. Soc. Agr. Finl. 28: 18 - 35. (9) —»— 1936 b. Phosphorus in various depths of some virgin peat soils. Ibid 28: 90—104. (10) —»— & Ryti, R. 1951. Observations on factors influencing the results of chemical soil tests Acta agr. scand. 1: 271—281 (11) —i)—- & Virtanen, O, 1955. Determination of organic phosphorus in samples of peat soils. J. Sei. Soc. Agr. Finl. 27: 104—115. (12) Kivinen, E. 1933. Suokasvien ja niiden kasvualustan kasvinravintoainesuhteista. Referat: Unter- suchungen über den Gehalt an Pflanzennährstoffen in Moorpflanzen und an ihren Stand_ orten. Acta agr. fenn. 27. (13) Mattson, S. & Koutler-Andersson, E. 1954. Geochemistry of a raised bog. Ann. Roy. Agr. Coll. Sweden 21; 321—366. (14) Nannes, G. 1899. Zur Frage über die Verbindungsformen der Phosphorsäure in der Moorerde J. F. Landw. 47: 45—48. (15) Salonen, M. 1941. Fosforin esiintymisestä Suomen maalajeissa. Acta agr. fenn. 48. (16) Schmoeger, M. 1897. Sind die im Moor vorhandenen durch starke Säuren nicht extrahierbaren Phosphor- und Schwefelverbindungen bereits in den Moorbildenden Pflanzen erhalten Landw. Jbuch. 26: 549—554. (17) Thompson, L. M. 1951. The mineralization of organic phosphorus, nitrogen and carbon in virgin and cultivated soils. la State Coll. J. Sei. 25; 369—370. (18) —» —■ & Black, C. A. 1950. The mineralization of organic phosphorus, nitrogen, and carbon in Clarion and Webster soils. Soil Sei. Soc. Amer. Proc. 14: 147—151. PHOSPHORUS IN VIRGIN PEAT SOILS 16 7 (19) Vahxera, E. 1955. Metsänkasvatusta varten ojitettujen soitten ravinnepitoisuuksista. (Referat: Über die Nährstoffgehalt der für Walderziehung entwässerten Moore.) Comm. inst, forest, fenn. 45.4. SELOSTUS LUONNONTILAISTEN TURVEMAITTEN FOSFORISTA Armi Kaila Yliopiston maanviljelyskemian laitos, Helsinki Tutkimuksessa on yritetty selvittää luonnontilaisten turvemaitten fosforin määrää ja koostu- musta. Tutkimusaineistona oli 217 turvenäytettä, jotka oli kerätty etupäässä maamme pohjoisosista ja jotka edustivat eri turvelajeja jä suotyyppejä. Näytteiden kokonaisfosforin pitoisuus vaihteli 190—2350 mg/kg ja 30—2440 kg/ha. Rahkatur- peitten ja ruskosammalsaraturpeitten ryhmät sisälsivät keskimäärin selvästi vähemmän fosforia kuin muut turvelajit. Pintanäytteiden ja soitten boniteetin välillä oli havaittavissa merkitsevä, joskin hei- kohko vuorosuhde, korrelaatiokerroin oli r 1 = 0.361***. Tilastollisesti merkitsevä korrelaatiokerroin saatiin myös kokonaisfosforin pitoisuuden sekä maatumisasteen välille, r = 0.317***, samoin kokonais- fosforin pitoisuuden ja tuhkapitoisuuden välille r = 0.289**. Kokonaisfosforin pitoisuuden ja Kjeldahl- typen pitoisuuden välillä oli myös havaittavissa merkitsevä riippuvuus, r = 0.206*. Näytteiden orgaanisen fosforin pitoisuus vaihteli 130—1950 mg/kg, keskiarvo oli 600 ± 40 mg/kg. Erot- eri turvelajien välillä olivat samanlaiset kuin kokonaisfosforin pitoisuuden kohdalla. Orgaanisen fosforin pitoisuuden ja kokonaisfosforin pitoisuuden riippuvuus oli erittäin voimakas; r = 0.934***. Orgaanisen fosforin suhteellinen määrä vaihteli 55—95 % kokonaisfosforista ja oli keskimäärin 78 ± 1 %. Tämä suure ei osoittautunut riippuvaksi kokonaisfosforin pitoisuudesta eikä näytteen otto- syvyydestä. Sen sijaan havaittiin verrattain voimakas korrelaatio orgaanisen fosforin suhteellisen määrän ja maatumisasteen välillä: osittaiskorrelaatiokerroin syvyyden vaikutuksen eliminoinnin jäl- keen oli r = 0.427***. Heikko, joskin tilastollisesti merkitsevä korrelaatio voitiin todeta myös orgaani- sen fosforin suhteellisen määrän ja pH:n välillä; maatumisasteen vaikutuksen eliminoinnin jälkeen saatu osittaiskorrelaatiokerroin oli r = 0.228*. Orgaanisen fosforin määrä ilmoitettuna prosentteina orgaanisesta kuiva-aineesta oli hyvin alhai- nen:00.00.251—0.25 %, keskimäärin 0.07 ± 0.004 %. Suhde N/org.P vaihteli 12—133 keskiarvon ollessa 45 ± 3. Ruskosammalsaraturveryhmän keski- määräinen N/org.P oli selvästi suurempi kuin muitten ryhmien. Maatumisasteella ei näyttänyt olevan vaikutusta suhteen arvoon. 0.2 n rikkihappo uutti noin 15—30 % turvenäytteiden epäorgaanisen fosforin kokonaismäärästä. 0.5 n etikkahappo uutti vain pari prosenttia saraturpeiden epäorgaanisesta fosforista, mutta noin 15 % rahkaturpeiden epäorgaanisesta fosforista. Saatujen tulosten perusteella oletettiin, että fosfori on eräs nimitekijöistä turvemaitten meta- bolismissa.