ON THE CHEMICAL COMPOSITION OF PEATS OF TOMSK OBLAST

G. N. BLINKOV, A. F. BOROVKOVA

On the territory of Tomsk Oblast there are exceptionally large reserves of peat. These peats are still almost unused and poorly studied, which prompted our department to investigate them. Peats are studied by the department in various directions. In the present work, studies on peat chemistry are briefly summarized.

For the rational use of peat it is necessary to know its quality, which depends above all on the nature of the bog in which it was formed. Peats and the bogs in which they occur are varied. They are usually subdivided into two main types: raised and lowland. Raised peats are formed predominantly from white mosses (sphagnum) and are characterized by sharp acidity, strongly expressed disinfecting properties, and unusually high moisture capacity and gas-absorbing capacity, but they contain little nitrogen and ash. Peats of lowland bogs are formed from various grasses and woody species and are distinguished by weak acidity and a high content of nitrogen and ash, but possess the other properties indicated above to a lesser degree. From the characterization given it follows that raised peats are most suitable for livestock bedding, and lowland peats for fertilization. This conclusion is also confirmed by practice.

However, peats differ substantially in a whole series of features even within a type, which is also useful to take into account. In our opinion, the most important indicator of peat quality is its chemical characteristic; therefore we devote much attention to chemical analyses of peats in connection with their use as fertilizer.

For our analyses we take peat samples layer by layer at different depths: 0–5, 5–30, 30–55, 55–100, 100–150, 150–200 cm, etc., down to the bottom of the peat bog. To a depth of 1.0–1.5 m the samples are taken by means of a sharp spade, and deeper by means of a special auger.

The department studies peats from various districts of Tomsk Oblast, but predominantly lowland peats from Tomsk District. Special attention is paid to the Tagan peat bog, one of the most extensive and promising. Since 1964 this peat bog has already been developed by a mechanized brigade created by the oblast executive committee on the initiative of the department. The extracted peat is used as fertilizer mainly by the Takhtamyshevo State Farm, on whose territory the Tagan bog is located.

Peats were analyzed for the content of various groups of substances, total nitrogen, and the principal ash elements. For group analy-

a set of methods was used according to the scheme developed by A. R. Kizelev [9], with modifications borrowed from Waxman [5], N. N. Ivanov [7], M. M. Kononova [10], and other authors. In this procedure, bitumens were extracted by the Soxhlet method using gasoline and alcohol-benzene; sugars were determined by Bertrand’s method; total nitrogen by Kjeldahl’s method; phosphorus by a volumetric method in the modification of A. A. Shmuk [5]; potassium by spectral analysis; and ash, together with the iron, calcium, magnesium, and silicon contained in it, by the usual methods described in biochemical manuals [6], [7]. At the same time, the pH of the peats was determined by the electrometric method.

The results obtained have been partly summarized in the works of Prof. G. N. Blinkov and his collaborators [2], [3], [4]. Certain mean data from duplicate determinations for the group analysis are given in Tables 1 and 2, and for the analysis of nitrogen and ash elements—in Table 3.

Table 1

Percentage content of various groups of substances in the dry matter of lowland peats of a high degree of decomposition, and the pH of these peats

Note. The analyses were carried out by Associate Professor L. P. Romanova.

Judging from the data in Table 1, the peats studied have an almost neutral reaction (their salt pH = 6.0–6.2) and a moderate amount of ash (9–11%), which is characteristic of typical lowland peats. Among the organic substances contained in the peats, lignin occupies first place (40–50%); after it, in decreasing order, come: crude protein (17–20%), bitumens (9.6–11%), and, finally, substances soluble in water (3.5–6.3%). The peats of the Porosinsko-Petrovskoe and Taganskoe bogs contain much hemicellulose (11–12%); cellulose is absent in all the peats.

Table 2 shows that in a lowland peat deposit, with increasing depth, the content of lignin and bitumens increases, while the content of other organic substances decreases, i.e., crude protein, hemicellulose, and substances soluble in water. Cellulose appears in the form of traces

only in the upper horizons down to a depth of 50 cm (the last layer should not be included in the calculation, since it contains very much ash). The indicated pattern is also observed for upland peat; nitrogenous substances are an exception, their content increasing with depth. Cellulose is abundant in the sphagnum peatland in the upper layer (33%), but as depth increases it decreases sharply.

Table 2

Percentage content of various groups of substances in the dry mass of upland and lowland peats at different depths of occurrence and the pH of these peats

Note. The analyses were carried out by graduate student V. S. Kozlov.

From the comparisons presented it is evident that, from group analysis, one may judge not only the chemical composition of peat, but also the intensity of mineralization of various organic substances. In particular, cellulose, which in peat-forming plants occupies first place among the other substances (for example, in sphagnum mosses, according to Waksman [5], it exceeds 60%), decomposes relatively rapidly.

Our data for most groups of substances are generally similar to the data of Waksman [5], obtained on the basis of analysis of American peats. However, the peats of our country, in comparison with American ones, differ sharply in their high content of bitumens, which was first noted by G. L. Stadnikov [14], [16] and subsequently emphasized by Waksman.

Stadnikov also clarified the concept of “bitumens.” To this group of substances he assigns natural mixtures of hydrocarbons or their oxygen-containing derivatives, soluble in organic solvents and carbon disulfide. Peat bitumens consist mainly of waxes and resins, which are present in approximately equal proportions [8].

From Table 3 it is evident that our lowland peats are rich in such a most important element for plant nutrition as nitrogen: nitrogen accounts for 2–3% of the weight of the dry mass of peat, which is 1.5 times higher than its content in straw manure.

Our data correspond to the literature [3].

The greatest amount of nitrogen is found in the upper layers of peatlands, and with increasing depth it regularly decreases, regardless of

Table 3

Content of nitrogen, ash, and the principal ash elements in lowland peats of Tomsk Oblast
(in % of dry weight)

End of Table 3

Note: The analyses were carried out by postgraduate student V. S. Kozlov.

ash content. We explain the noted regularity by the fact that in the upper horizons of peat bogs, owing to better conditions of aeration and warming, nitrogen fixation by Azotobacter—which, according to our data, is present in large quantities in the peat bogs studied—undoubtedly proceeds more intensively.

Because of its high nitrogen content, peat is considered above all as a nitrogenous fertilizer. In the words of Academician D. N. Pryanishnikov [1], peat is a kind of “nitrogen ore.” It should be emphasized, however, that in peat nitrogen is contained mainly as part of organic compounds unavailable to plants, and is released from them in the form of ammonia assimilable by plants in the process of ammonification, which proceeds extremely slowly in pure peat. The mineralization not only of nitrogenous substances but also of other peat substances is appreciably accelerated when it is composted.

In terms of phosphorus content, the peat bogs presented in Table 3 should be classified as vivianite-bearing. In the different layers of the peat bogs the content of phosphoric acid varies sharply: its minimum amount is 1%, while the maximum exceeds: in the Porosinsko-Petrovskoe peat bog—3%, in the Vershininskoe—4%, in the Rozhnevskoe—6%, in the Taganskoe—9%, and in the Ipatovskoe it is 10.75%.

In the underlying layer of the Taganskoe peat bog, vivianite often occurs; according to our data it contains more than 23% phosphoric acid. According to the investigations of N. A. Polyanskii [11], the phosphorus of vivianite is assimilated by plants approximately as well as the phosphorus of superphosphate; this conclusion is also confirmed by the still unpublished data of G. N. Blinkov and V. S. Kozlov. Thus, the peats of the listed bogs can serve as a source not only of nitrogen but also of phosphorus.

The ash of our peat bogs contains a considerable amount of calcium carbonate, especially in the bottom and underlying layers of the Rozhnevskoe and Ipatovskoe bogs. Evidently the latter can also serve as material for liming. The ash also contains much iron, magnesium, and silicon, but little of such a valuable element for plants as potassium: the amount of potassium oxide is 0.08–0.93%. It should be noted that our potassium data are within the normal range: according to the literature [13], \(K_2O\) in lowland peats of the northern zone, calculated on their dry weight, is 0.03–0.2%, and in peats of the Russian forest-steppe [12]—from 0.16 to 1.16%.

Table 4 gives information on the content of nitrogen, phosphorus, and ash in the peats of new sections of lowland bogs of Tomsk District, already presented in Table 3, and in the peats of three other bogs, of which the Shegaro-Iksinskoe bog belongs to the transitional type, while the other two are lowland.

Table 4 confirms the regularities noted above concerning the high nitrogen content in lowland peat bogs and the fact that, with increasing depth, the nitrogen content in peat bogs regularly decreases. In the upper horizon (5–25 cm) the amount of nitrogen differs among different peat bogs: it ranges from 2.05 to 3.41%; the minimum is in the Rozhnevskoe and the maximum in the Kolarovskoe peat bogs.

As a rule, peats with a moderate ash content are richest in nitrogen and, conversely, high-ash peat bogs are poorer in nitrogen. This proposition is confirmed by the data from the just-mentioned Rozhnevskoe and Kolarovskoe peat bogs. However, there are exceptions to this rule; an example is the peat from the section of the Vasyugan bog analyzed by us: in the upper layer (0–30 cm) of this section there is 3.18% nitrogen at an ash content of 32%, and in the next layer 2.73 nitrogen at an ash content of about 46%.

Table 4

Content of nitrogen, phosphorus, and ash in peats from various districts of Tomsk Oblast

Note. Samples from all bogs, except the last, were analyzed by assistant A. F. Borovkova with the participation of assistant V. M. Bykov and laboratory assistant V. V. Troitskii; for the Shegaro-Iksinskoe bog—by graduate student M. F. Razumnikov.

The transitional Shegaro-Iksinskii peat bog is also rather rich in nitrogen, and with depth the content of this element also decreases: in the 0–20 cm layer, nitrogen on a dry-weight basis is 2.91%, while at a depth of 70–115 cm it is only 2.23%.

There is much phosphoric acid in the samples under discussion only for the Rozhnevskii peat bog, whereas in all the other peat bogs there is less of it than in the previous amounts (Table 3). The content of phosphoric acid varies, depending on the peat bog, within the following limits (not counting the very lowest layers, where ash predominates): in the Rozhnevskii—from 1.38 to 5.18%; in the Taganskii from 0.40 to 0.60%; in the Porosinsko-Petrovskii—from 0.31 to 0.73%; in the Kolarovskii—from 0.26 to 1.55%; in the Vasjugan—from 0.19 to 0.50%; and in the Shegaro-Iksinskii from 0.20 to 0.30%.

According to numerous data from earlier analyses by our department [3], [4], the content of phosphoric acid in Tagan peat ranges from 1 to 9%, and in Porosinsko-Petrovskii peat—from 1 to 4%. It follows from this that in the named bogs peat with a high content of phosphoric acid predominates, which is characteristic of the vivianite group of peats.

Conclusions

1. In lowland peats, among the organic substances lignin sharply predominates; after it, in descending order, come nitrogenous substances; in peats of an intermediate degree of decomposition—hemicelluloses; and in peats of a high degree of decomposition—bitumens; the last place is occupied by substances soluble in water. Cellulose is detected in the form of traces only in the upper layers of weakly decomposed peats. With increasing depth in the peat bog, the content of lignin and bitumens increases.

2. The indicated regularities are, in general, also applicable to a raised peat bog, but for it, in addition, a large amount of cellulose in the upper horizon is characteristic, which sharply decreases with depth; it is also characteristic that the content of nitrogenous substances increases with depth.

3. Nitrogen in the upper layer of peat bogs (5–30 cm) of the lowland type ranges, calculated on dry matter, from 2 to 3.4%; with depth its content regularly decreases, independently of the ash content.

4. The content of phosphoric acid in lowland peats varies from 0.2 to 10%. The richest in phosphorus are vivianite peats, which are often encountered (or even predominate) in a number of bogs of the Tomsk region: in the Taganskii, Rozhnevskii, Porosinsko-Petrovskii, Ipatovskii, and Vershininskii.

5. In the underlying layer of the Taganskii peat bog there often occurs vivianite, in which the phosphoric acid content exceeds 23%. Vegetation experiments have established that this vivianite, in its nutritive value, is not inferior to good superphosphate.

6. The peats of the listed bogs have a weakly acidic or even neutral reaction, which is associated with the presence in their composition of a considerable amount of calcium carbonate. Especially rich in calcium are the bottom and underlying layers of the Rozhnevskii and Ipatovskii peat bogs, which may serve as material for liming soils.

7. The potassium content in our lowland peats ranges from 0.08 to 0.93%, which, in accordance with the literature data, is within the normal range.

References

1. D. N. Pryanishnikov. Selected Works, vol. 1, Agrochemistry, Selkhozgiz, 1952.

2. G. N. Blinkov, L. P. Romanova, A. F. Borovkova. Peat and its use in agriculture under Siberian conditions. Scientific Notes of the Tomsk Pedagogical Institute, vol. XXI, issue II, p. 3, Tomsk, 1964.

3. G. N. Blinkov, V. S. Kozlov. Chemical composition of lowland peats of the Tagan and Petrovka bogs. Proceedings of the Tomsk Branch of the All-Union Botanical Society, vol. V, p. 99, Krasnoyarsk, 1964.

4. G. N. Blinkov, V. S. Kozlov. On the chemical composition of peats of Tomsk District. In: Problems of Chemization of Agriculture of Tomsk Oblast, p. 88, Notes of the Siberian Book Publishing House, Tomsk Branch, Tomsk, 1965.

5. S. A. Waksman. Humus. Selkhozgiz, Moscow, 1937.

6. A. I. Ermakov, V. V. Arasimovich, M. I. Smirnova-Ikonnikova, I. K. Murri. Methods of Biochemical Research on Plants. Selkhozgiz, Moscow–Leningrad, 1952.

7. N. N. Ivanov. Methods of Plant Physiology and Biochemistry. Selkhozgiz, Moscow–Leningrad, 1946.

8. L. I. Kashtanov. Chemistry of Peat. Gostekhizdat, Moscow–Leningrad, 1932.

9. A. R. Kizel. A Practical Manual of Plant Biochemistry. Biomedgiz, Moscow–Leningrad, 1934.

10. M. M. Kononova. The Problem of Soil Humus and the Present Tasks of Its Study. Publishing House of the Academy of Sciences of the USSR, Moscow, 1951.

11. N. A. Polyansky. Valuable Local Fertilizers. Publishing House of the Ministry of Agriculture of the RSFSR, Moscow, 1960.

12. N. I. Pyavchenko. Peatlands of the Russian Forest-Steppe. Publishing House of the Academy of Sciences of the USSR, Moscow, 1958.

13. Handbook on Peat. Selkhozgiz, Moscow, 1960.

14. G. L. Stadnikov. Chemistry of Peat. Gostekhizdat, Moscow–Leningrad, 1932.

15. A. A. Shmuk. Chemistry of Tobacco and Makhorka. Pishchepromizdat, Moscow, 1938.

16. Stadnikov G. Neuere Torfchemie. Dresden, 1930.