Vermicompost
Vermicompost, or biohumus, vermiculture, is a product of processing manure or organic waste by earthworms. It contains macro- and microelements, plant growth regulators (auxin, gibberellin), enzymes (phosphatases, catalases), and has biological activity.
During the formation of vermicompost, the number of pathogenic microorganisms (Salmonella) and viruses decreases. Worms feed on all organic substances that consist of 20-25% cellulose, for example, straw, cardboard, paper, and sawdust. Abroad, vermiculture is considered an element of environmentally friendly agricultural production; it receives state support in the form of preferential financing and exemption of vermifarms from a number of taxes.
The method of vermicultivation helps solve the problems of accumulation and processing of livestock waste:
- composting of liquid manure (Germany, Italy);
- processing of domestic and industrial waste into fertilizer, for example, municipal garbage and sewage sludge (USA, Italy, Netherlands);
- processing of industrial waste into compost (Japan);
- processing of fat waste (France, Toulouse).
In vermiculture, the manure worm Euseniasoetieda is used, the so-called red hybrid California worm, bred in the late 1940s in the USA. It is distinguished by a high growth rate, fertility, and longevity.
In the worm's digestive tract, organic residues undergo profound changes: they decompose into simple compounds, are enriched with calcium, magnesium, nitrates, and phosphorus; humic acids are formed; many mineral compounds are converted into a plant-available form. Under the action of calcite secreted in the esophagus, acids contained in the substrate are neutralized. Organic residues and soil that have passed through the worms' intestines are excreted as excrement, which constitutes vermicompost (biohumus). In one day, an adult worm passes through its intestine an amount of food equal to its own body weight. About 40% of this amount is spent on vital activity and 60% is released in the form of coprolites. Biohumus is characterized by high water stability and forms soil components that determine its structure.
The red California worm processes almost all types of organic waste: manure, poultry manure, waste from fruit and vegetable depots, processing and pulp-and-paper mills, brewing waste, meat-processing plant waste, sewage treatment plant sludge, and household garbage.
Table. Chemical composition of biohumus, % (Sheudzhen et al., 2004).
| Indicator | Content | Indicator | Content |
|---|---|---|---|
| Humus | 25-30 | Magnesium | 0.6-1.5 |
| Nitrogen | 1.5-3.0 | Iron | 0.6-1.3 |
| Phosphorus | 1.8-4.0 | Copper | 0.03-0.04 |
| Potassium | 1.5-3.0 | Manganese | 0.06-0.09 |
| Calcium | 4.5-7.0 | Zinc | 0.08-0.09 |
To obtain high-quality compost, the substrate must undergo a fermentation process, as a result of which the temperature increases, leading to the death of seeds of weeds and pathogenic microflora.
In various countries of the world, regulatory requirements for the composition of vermicompost (biohumus) have been developed. Worm excrement in biohumus must account for at least 70% of dry matter. No significant differences in the requirements for biohumus composition are noted either in Russia or in other countries.
Table. Requirements for biohumus composition.
| Indicators | Russia (price list 708201) | FRG (GOST) | Poland (GOST) | ATP “Goretskoye” (experiments) |
|---|---|---|---|---|
| Organic matter content, % | 40-45 | 40-45 | 40-60 | 43-60 |
| C/N ratio | 15 | 15 | — | 15 |
| Available nitrogen content, % | not less than 1.5 | not less than 1.5 | 1.5-3.0 | 1.8-2.0 |
| P2O5 content, % | 1.2 | 1.2 | 1.8-4.0 | 1.8-3.0 |
| K2O content, % | 0.5 | 0.5 | 1.5-3.0 | 0.75 |
| Humus, % | not less than 15.0 | — | — | 20.0 |
| Moisture, % | 50.0 | 40-60 | 40-60 | 50-60 |
| pH | 6.5-7.5 | 6.5-7.5 | 6.8-7.2 | 7.0-7.1 |
Due to its high content of nutrients, agronomically beneficial groups of microorganisms, and biologically active substances, vermicompost has a positive effect on the growth and development of plants and soil biota. If 1 g of manure contains 150-350 million colonies of bacteria, then vermicompost contains 100-200 billion. Biohumus is characterized by a neutral reaction of the medium; pH is usually in the range 6.8-7.2.
Average doses of vermicompost for application to soil are 3-5 t/ha.
The yield of cereal crops in the first year after biohumus application increases by 0.6-1.0 t/ha, and of potato tubers by 5-6 t/ha. Biohumus can be used in open-field and protected-ground vegetable growing.
In many indicators, biohumus surpasses composts, has better physical properties — higher water-holding capacity, contains more plant-available nutrients, primarily nitrogen, which is explained by the greater abundance of nitrogen-fixing bacteria in worm coprolites. Humic acids give biohumus special value; their content ranges from 5.6 to 17.6% on a dry matter basis.
In foreign countries, biohumus is used mainly as a nutrient substrate for growing vegetable and ornamental plant seedlings. Due to the high production cost, its use for field crops is limited.
According to their responsiveness to biohumus, several groups of plants are distinguished:
- Vegetable crops, tuber crops, and root crops are characterized by high responsiveness — yield increases are 35-40%;
- Cereal crops respond well — increase up to 25%;
- Grain legumes respond satisfactorily — increase up to 15%;
- Oilseed crops show little response.
References
- Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. by Mineev V. G. Moscow: Publishing House of the D. N. Pryanishnikov VNIIA.
