Composts

Composting

Composting — a biothermal process of mineralization and humification of one or more organic components, sometimes with additions of mineral fertilizers and soil amendments that reduce nutrient losses, accelerate decomposition of organic mass, and increase nutrient availability to plants.

During composting of organic waste, thermal disinfection occurs; the temperature rises to 60 °C, which kills eggs and larvae of flies and helminths, pathogenic non-spore-forming microorganisms, and suppresses seeds of weeds.

In organic composts, one of the components may act as an absorbent of moisture, ammonia, and carbon dioxide, while without composting it may decompose poorly, for example, peat, sawdust, household waste, soddy soil, straw. Some components may be enriched with microflora, for example, manure, liquid manure, feces, poultry manure, and contain large amounts of decomposing nitrogenous and non-nitrogenous organic compounds.

The readiness of composts is assessed by the degree of their decomposition and the uniformity of the mass.

Peat-manure composts

Peat-manure composts are prepared near livestock buildings, in manure storage facilities, or in field stacks. The ratio of manure to peat depends on the quality of the components and the availability of these materials on the farm. In winter, this ratio is usually 1:1; in summer, up to 1:3. Any peats with moisture content up to 60% are suitable for composting.

Layer composting is used at any time of year. To do this, peat is leveled in a layer up to 50 cm on prepared sites 4–5 m wide and of arbitrary length. Then it is covered with a layer of manure, which is again covered with peat. Layers of peat and manure alternate until the stack height reaches 2 m. The thickness of the layers depends on the ratio of the components. The stack is finished on top with a layer of peat.

Focal composting is preferably used in winter. For this, manure is placed on a prepared 50–60 cm layer of peat as a continuous or interrupted layer 70–80 cm thick and 1.0–1.5 m narrower than the underlying peat. If manure is insufficient, it is placed in an interrupted layer (heaps), covered on all sides with a 50–70 cm layer of peat. In winter, a stack of focal compost is laid in 1–2 days, preferably during thaws; then the temperature inside does not fall below 25–30 °C.

In layer and focal composting, to improve the quality of peat with manure, 1.5–3.0% (15–30 kg/t) of phosphate rock is added to the mixture. This produces peat-manure-phosphate composts, which in effectiveness at a manure content of 30–50% are not inferior to good manure. The layers of peat and manure are interspersed with phosphate rock.

When composting manure and peat together with phosphate rock, potassium fertilizers are added at the rate of 5–6 kg of fertilizers per 1 t of peat. Depending on acidity, lime fertilizers are additionally added; in this case, phosphate rock is added to the manure, and potassium and lime fertilizers to the peat. The effectiveness of such compost at equivalent doses is higher than that of manure.

Peat-slurry composts

With effluents, liquid and semi-liquid manure, peat is composted in the same way as with liquid manure.

Peat-slurry composts are prepared with any peat, except calcareous peat with a calcium content of more than 5%, in winter in manure storages or next to livestock buildings, in summer in field stacks and on drained peatlands. Per 1 ton of aired peat, depending on moisture, 1–3 t of liquid manure and 1.5–2.0% of the compost mass of phosphate rock are added. Peat is laid in two adjacent ridges with a trough-shaped depression between them, into which liquid manure is poured.

After the peat absorbs the liquid, the mass is raked into stacks, covered with peat, and when the temperature reaches 60 °C, it is compacted. Depending on the properties of the components and ambient temperature, the mass is kept for 1–4 months. It is used as the main fertilizer for crops in the same doses as bedding manure. Peat-slurry-phosphate composts are not inferior in effectiveness to good manure.

Peat-feces composts

Peat-feces composts are obtained by composting fecal masses with peat or straw, municipal waste, and other slowly decomposing materials. A fast-acting organic fertilizer. Fecal mass contains on average 0.5–0.8% N, 0.2–0.4% P₂O₅, and 0.3–0.4% K₂O. 70–80% of nitrogen is in the form of ammonium compounds and urea; phosphorus and potassium are in forms assimilable by plants. Dried fecal masses (poudrettes) contain 2% N, 4% P₂O₅, and 2% K₂O. To reduce nitrogen losses during drying of fecal masses, 8–10% by mass of dry peat powder is added to them. Poudrettes are applied under ornamental and bast crops at a dose of 2–3 t/ha. In effectiveness they are not inferior to equivalent doses of mineral fertilizers.

For sanitary, agronomic, and environmental reasons, fecal masses are better used in the form of composts. To prepare them, 0.5 t of feces is added to 1 t of lowland peat with 70% moisture; 2 t to 1 t of highland peat; at peat moisture up to 50%, up to 3.5 t of feces. For disinfection and reduction of nutrient losses, composting should proceed at a temperature of 56–60 °C with subsequent compaction. The method of preparing compost is similar to preparing compost with liquid manure.

In the second year after laying, peat-feces composts can be applied under any crops except vegetables, at doses of 10–25 t/ha.

In effectiveness they often exceed manure at equivalent nutrient doses by 30–50%.

Peat-mineral composts

Peat-mineral composts may contain lime, ash, phosphate rock, liquid ammonia, and other mineral additives.

Peat-lime and peat-ash composts are prepared with acidic peat (pH_salt less than 5), sprinkling 15–20-centimeter layers with them when laying the stack. The lime dose is calculated from 0.8 of the hydrolytic acidity (H_g) of peat, that is, at peat moisture of 60–70%, on average 1–3% of the compost mass. The best form of lime fertilizer in this case is dolomite flour. Composts are kept for 4–5 months before application. They are poor in potassium and phosphorus.

To enrich with calcium, phosphorus, and potassium, composts with ash are prepared; additional neutralization of exchangeable acidity occurs. The stack is prepared in the same way as with lime, adding 2.5–5.0% ash (25–50 kg/t) per 1 ton of aired peat.

Peat-phosphate composts, with good mixing of components, after just a month of storage convert 30–60% of P₂O₅ of phosphate rock into a form assimilable by plants, with a simultaneous decrease in peat acidity.

For preparing these composts, acidic peat is used that does not contain mobile forms of aluminum. Per 1 ton at moisture 65–70%, 10–30 kg of phosphate rock is added and kept for 2–3 months.

Peat-lime and peat-phosphate composts are used in the same doses as manure. Their effectiveness increases when combined with nitrogen-potassium mineral fertilizers.

Peat-ammonia (TAU) and peat-mineral-ammonia (TMAU) fertilizers (composts) are prepared by saturating peat with liquid ammonia or its aqueous solution with the addition of phosphorus and potassium mineral fertilizers. Peats with ash content up to 25%, moisture 55–65%, and degree of decomposition for lowland 15–20%, for highland 20–25% are suitable. The composition of TMAU per 1 ton of dry peat includes 30–35 kg of phosphate rock or its mixture with superphosphate in a 1:1 ratio, 10–12 kg of potassium chloride or another potassium fertilizer, 30–35 L of 25% ammonia solution or an equivalent NH₃ dose of liquid ammonia. In TMAU based on lowland peat, the amount of mineral components is reduced by 30–50%.

Composts prepared on peatlands

Preparation of composts on drained peatlands near fertilized fields reduces cost and increases their effectiveness.

The technology for preparing composts on peatlands consists in combining their treatment and loosening with the application of organic and mineral components, for example, manure, liquid manure, fecal masses, lime, phosphate rock, followed by raking and compaction of mixtures into stacks.

When calculating amounts of components and compost, take into account that with a mass of 1 m³ of 400 kg and a depth of the raked layer of 20 cm, 800 t of peat are obtained per hectare of peatland per season.

Peat-plant composts

Peat-plant composts are obtained by growing legumes or green manure crops on peatlands, followed by plowing in and preparing stacks from the resulting mixtures of peat and plants.

The plant mass of green manure in the flowering phase is dug in, chopped, and plowed in to a depth of 15 cm. After 2–3 weeks, the peatland is disked, the peat-green manure mass is raked into stacks 1.5–2.0 m high and kept for 1–2 months. Peat-plant composts are applied under crops in the same doses as bedding manure. In effectiveness at equivalent doses, they are not inferior to half-rotted manure of dense storage.

Composts from household waste

Due to environmental protection requirements and the growing amount of household waste, industrial methods of biothermal disinfection of waste and preparation of composts based on them are becoming widespread. Factory-prepared composts contain on average, in % of dry mass: 40–52% organic substances, 1–1.3% N, 0.7–0.8% P₂O₅, 0.4–0.6% K₂O, 3% crushed glass less than 15 mm in size, 4% foreign inclusions. Moisture content of composts is 30–40%, pH_salt 6.0–7.8.

In their effect on yield, composts from household waste are not inferior to manure at equivalent doses. Application requires agrochemical monitoring for hazardous impurities.

List of sources

1. Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Edited by B. A. Yagodin. Moscow: Kolos.