Peat
Peat.
Peat — organic fertilizer, consisting of plant residues at various degrees of decomposition.
The area of peatlands in Russia is over 80 million ha; total peat reserves on an air-dry matter basis are 160 billion t, which equals more than 1/2–2/3 of world reserves.
Peat reserves in Russia are distributed as follows: about 70% is located in the West Siberian region, 13% in the Northwest, 6% in the Urals, and 3–4% each in the Far Eastern, Central, and East Siberian regions. 50.6% of deposits are represented by raised-bog peat, 31.1% by fen peat, and the rest by transitional peat.
Peat types are not equivalent in quality, so the methods of using it as a fertilizer also differ. All peat bogs and extracted peats are divided into raised-bog, fen, and transitional. Depending on the degree of peat decomposition, determined by the content of humified substances, peats are distinguished as:
- slightly decomposed — degree of decomposition 5–25%;
- moderately decomposed — 25–40%;
- highly decomposed — more than 40%.
Types of peat
Peat type is determined by the bog’s position in the relief and by the composition of vegetation.
The raised-bog type forms on elevated relief elements from white sphagnum mosses with small amounts of cottongrass, marsh rosemary, bog blueberry, cranberry, and other plants undemanding in elements of plant nutrition. Sphagnum raised-bog peat is the poorest in nutrients, very acidic, poorly humified (up to 20%), low in ash, has the highest moisture- and gas-absorption capacity, and contains up to 40% hemicelluloses and cellulose. It is the best bedding material for animals and a component of composts.
The fen type forms under the influence of groundwater with a high content of mineral substances in relief depressions with sedges, reeds, reedgrasses, horsetails, green hypnum mosses, alder, willow, birch, and other moisture-loving plants more demanding for nutrients.
Fen peat consists of remains of herbaceous and woody vegetation, contains more nutrients, is less acidic, has a high ash content, contains up to 50% humic substances, has a high absorption capacity, and is enriched with lime and phosphorus. When drained, it is suitable for cultivating vegetables, fodder, and other crops; it can be used as an organic fertilizer in open and protected ground, for making pots, and as a component of composts.
The transitional type is intermediate between raised-bog and fen types. Moreover, the lower layers of transitional peats are usually closer to fen, and the upper layers to raised-bog.
The variety of peat is determined by poorly decomposed remains of peat-forming plants, whose content is more than 20% by mass of dry matter.
Composition and properties of peats
For agrochemical assessment of peat quality, the following are important: botanical composition, degree of decomposition, ash content, nutrient content, acidity, moisture capacity, and absorption capacity (CEC). Ash content, acidity, degree of humification, and nutrient supply depend on botanical composition.
Degree of decomposition is an indicator for the agronomic use of peat. Slightly decomposed peat is used mainly for animal bedding; moderately decomposed peat, after extraction and airing, is used as fertilizer, for preparing composts, or for cultivating crops after hydromelioration of peatlands.
Ash content of peats can be normal, i.e., up to 12%, or high — more than 12%. High-ash peats are, as a rule, fen peats (20–30%), obtained when they contain deposits of sand, clay, increased amounts of lime (peat-tufa), or vivianite. Increased ash content due to calcium and phosphorus (vivianite) increases the value of peat. Peat-tufas and vivianite peat without composting are applied as a direct fertilizer, and also for liming of acidic soils and phosphate fertilization.
Table. Agrochemical indicators, % on an absolutely dry mass basis, of different peat types.
| Peat type | Ash | pH | Organic matter | N | P2O5 | K2O | CaO | pH of salt extract | Hh | T | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| H2O | KCl | mg-eq/100 g dry mass | |||||||||
| Fen | 8-15 | 5,5-7,0 | 4,8-5,8 | 85-92 | 2,5-3,5 (2,3-3,3) | 0,2-0,6 (0,12-0,5) | 0,15-0,20 (< 0,15) | 2,0-6,0 | 4,7-5,5 | 70-80 | 160-250 |
| Transitional | 5-8 | 4,0-6,0 | 3,5-4,8 | 90-95 | 1,2-2,5 (1,0-2,3) | 0,10-0,25 (0,1-0,2) | < 0,15 (0,1) | 0,2-0,4 | 3,5-4,7 | — | — |
| Raised-bog | < 5 | 3,0-4,5 | 2,6-3,2 | 95-98 | 0,7-1,5 (0,8-1,2) | < 0,15 (0,06-0,12) | < 0,10 | < 0,4 | 2,8-3,5 | 120-180 | 100-200 |
Nitrogen contained in peat is in organic compounds that are poorly assimilated by plants. Therefore, using peat in pure form is ineffective. The costs of extracting and applying peat in pure form often do not pay off with increased yield.
Nutrient content decreases from fen to raised-bog peat. Peats contain most nitrogen, and most of it is in organic form and becomes available to plants only after mineralization, which hardly occurs in acidic media; however, it can be accelerated after neutralization and when composting with manure, slurry, poultry manure, and feces.
Phosphorus content in peats is low, with 2/3 soluble in weak acids and available to plants.
Potassium is the least abundant in peats, and only half of the total content is available to plants; among trace elements, copper is the least abundant. Therefore, when cultivating crops on drained peatlands, they are fertilized with potassium and copper fertilizers.
Peat acidity is an indicator of its type and methods of use. At acidity below 5.5, fen decomposed peat is unsuitable for use as fertilizer without preliminary composting with lime, phosphate rock, ash, manure, or slurry. All peats are capable, when composted with phosphate rock, of converting phosphorus into plant-available forms.
Raw peat contains 80–90% water. With one ton of such peat, 100–200 kg of dry organic matter is applied. Raw peat does not allow high-quality uniform application across a field. Too dry peat is also impractical to use, since it has a high absorption capacity. Peat with a moisture content of 35–40% absorbs moisture from the soil layer, which leads to soil drying and causes moisture deficiency. In a dry arable layer, the rate of peat decomposition is very slow.
Absorption capacity is important when peats are used as bedding material for poultry and animals, owing to absorption of moisture and gases, in particular ammonia. The maximum moisture capacity of raised-bog peats is 1000–1800% on a dry mass basis, and gradually decreases toward fen peats, remaining at 500–1000%. The absorption capacity of all peat types is higher than that of thick chernozem. This is also important for storing significant amounts of industrial liquid ammonia and locally prepared peat-ammonia fertilizers (PAF) in peat when storage facilities are absent.
Use of peat and peatlands
Peat is used:
- for bedding for animals and poultry;
- as a component of composts;
- for making peat-manure pots and cubes;
- as a mulching material;
- as a substrate for cultivating crops in protected ground;
- as an organic fertilizer.
For bedding, primarily raised-bog sphagnum peat is used with a degree of decomposition up to 25%, ash content up to 10–15%, moisture content 50%, and content of wood particles up to 6 cm in size up to 10%. Hypnum, sedge, and reed peat types are rarely used for these purposes and only in a slightly decomposed state (up to 20%).
As a direct fertilizer, fen peats rich in lime or phosphorus are used, mainly on light soils, with pH above 5.5, ash content more than 10%, including CaO more than 4%, and degree of decomposition more than 40–50%. Doses of pure peat of 50–100 t/ha can be reduced when it is applied together with liquid manure (5–10 t/ha), semi-liquid manure, feces, or poultry manure. Doses of peat-tufas are determined by CaO content; vivianite peats by P2O5 content.
As a mulching material, surface-aerated fen and transitional peats are used in a layer up to 5 cm in the interrows of berry, fruit, and vegetable plantings. Mulching improves the water, air, thermal, and nutrient regimes in the upper soil layer, suppresses the growth and development of weeds, and prevents soil crust formation.
The use of peatlands after drainage for cultivating agricultural crops is possible with and without removal of the upper peat layer; however, in the latter case, the thickness of the peat layer must be at least 50 cm.
Peat soils need liming.
Since peatlands are poor in phosphorus, potassium, and copper, mineral fertilizers are applied when cultivating crops. On newly developed peatlands, nitrogen fertilizers are also effective; on developed ones, after 8–10 years, they often lose effectiveness. Since peatlands are poor in microflora, on newly developed ones, to accelerate decomposition of organic matter, it is advisable to apply small doses of fertilizers rich in microflora, for example, feces, poultry manure, manure, liquid manure, and bacterial preparations. Doses of macro- and micronutrient fertilizers are set taking into account crop requirements and the planned yield.
Use of peat for composting
Peat in pure form as an organic fertilizer is ineffective. It is used to prepare peat-manure, lime-bacterial, peat-phosphate, and peat-phosphate-lime composts.
To increase the availability of peat nitrogen to plants, it is composted with biologically active components or used as bedding for livestock.
Composts are laid in round heaps with a base diameter of 3–4 m, top diameter 1–2 m, and height up to 1.5 m, or in stacks 1.5–2 m wide, 1 m high, and length depending on the amount of material. Loose materials are compacted and covered with soil, straw, or peat to prevent drying.
In all composts, any peat is the most valuable component; however, peat with a higher degree of decomposition (more than 20%), ash content up to 25%, and content of wood inclusions up to 10% is better, and for use with lime, ash, and phosphate rock — with pH less than 5 and ash content less than 10%. Lime must be thoroughly mixed into the organic mass.
For making seedling cubes and pots, compost, humus, poultry manure, silt, sod soil, mineral fertilizers, lime, or ash are added to peat. For these purposes, fen and transitional peats with a neutral or slightly acidic reaction, degree of decomposition 30–40%, and ash content up to 15% are better suited.
Peat composts are used mainly in fodder crop rotations. In potato and vegetable crop rotations, they are alternated with manure.
Peat-manure composts
When peat is composted with manure, excessive peat acidity is eliminated, conditions for biological processes are created, peat decomposition is accelerated, and the amount of mobile, plant-available nitrogen increases. Microbiological processes proceed faster if during composting the temperature in the stack rises to 60–65°C; therefore, unlike manure, peat-manure compost stacks are not recommended to be compacted. Composting peat with manure also helps, owing to high absorption capacity, to preserve manure ammonia.
Peat-manure composts are prepared in field conditions, at the place of use, less often near livestock buildings or in manure storage facilities. For one weight part of manure in winter, 1 part of peat is taken; for spring-summer preparation, 1–2 parts. All peat types are suitable for preparing peat-manure composts, with moisture content not more than 60%.
It is recommended to add phosphate rock to peat-manure compost in an amount of 2–3% of the compost mass. If the compost is prepared for application under potatoes on light soils, potassium fertilizers are also added in an amount of 0.5% of the compost mass, provided good mixing and uniform subsequent spreading across the field.
Preparation of peat-manure composts is carried out in different ways.
The layered method can be used at any time of year. For this, peat is unloaded on a site and leveled with a bulldozer in a layer of 40–50 cm. Manure is brought onto the peat and leveled in a layer of 25–30 cm. Subsequent layered placement of peat and manure into stacks is carried out with loaders. The stack is completed with a peat layer 40–50 cm thick. The finished stack has a base width of 3–4 m, height 2 m, and any length. In winter, to avoid freezing of manure, the stack is laid within 1–2 days.
The focal method of preparation differs from the layered method in that manure is placed on a peat cushion in separate heaps at a distance of 1 m from one another, and the gaps between them are filled with peat. Placement is carried out with the same machines. The focal composting method provides greater heating of composts in winter.
The platform method consists in creating a peat cushion 25–30 cm thick, followed by applying and leveling manure. Then 2–3 passes of a heavy disc harrow are carried out to mix manure with peat; the mixture is gathered by a bulldozer into stacks for composting. This method is more suitable for preparing composts in spring-summer and autumn periods.
Properly prepared peat-manure composts are equivalent to manure in effect.
Peat-slurry and peat-feces composts
To preserve nutrients of liquid manure and feces, and also to increase the fertilizing effect of peat, peat-slurry and peat-feces composts are prepared. It is better to prepare them in spring and summer. For this, peat is laid in two continuous adjacent ridges so that a trough-shaped depression forms between them. The thickness of layers at the points of contact of the ridges should be 40–50 cm. The end walls are made manually or with a bulldozer. Slurry or feces are poured into this depression from a tank truck (ANZh-2) or a slurry spreader. The liquid must not overflow or leak through the side walls of the depression. After the slurry or feces are absorbed by the peat, the mass is gathered into stacks without compaction.
Per 1 t of peat, depending on type and moisture, 0.5–1 t of liquid manure or feces is taken. Feces, as a rule, contain 1.5 times more nitrogen than manure. It is desirable to add phosphate rock to peat-slurry composts in an amount of 1.5–2% of the compost mass. All peat types are used to prepare peat-slurry and peat-feces composts, except carbonate peat with a high amount of lime. They are often prepared in the field at the place of use. Peat-slurry composts during spring and summer preparation mature within 1–1.5 months.
Such composts are also prepared on drained peatlands, near sources of feces and the field to be fertilized.
For this, directly on the peat field, peat crumbs after drying are gathered into ridges by the layer-surface method, and feces are applied in a 1:1 ratio. If feces are insufficient, 3–5 t of fen peat are taken per 1 t; however, such compost is less concentrated, and its application doses are doubled. The compost is suitable for use after several months; it has a homogeneous appearance and crumbles easily.
During preparation of peat-feces compost, the temperature should rise to 55–60°C in order to destroy helminth eggs and pathogens under the action of high temperature. If the temperature in peat-feces compost does not rise to 55–60°C, it can be used under potatoes and vegetable crops only in the second year after laying.
Peat-feces and peat-slurry composts in effectiveness, as a rule, are not inferior to manure. They show the best effect on yield in combination with mineral fertilizers. Under cereal crops, 10–15 t/ha of peat-feces compost is applied as the main fertilizer; under potatoes, silage, and other fodder crops — 20–25 t/ha; under vegetables — 30–40 t/ha.
In the absence of peat, feces can be composted with soil. For this, feces and dry soil are laid layer by layer in a 1:1 ratio.
List of sources
- Mineev V. G., Sychev V. G., Gamzikov G. P., et al. (2017). Agrochemistry. Textbook. Edited by Mineev V. G. Moscow: Publishing House of VNIIA named after D. N. Pryanishnikov.
- Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Edited by B. A. Yagodin. Moscow: Kolos.
