BIOTECHNOLOGY - V. H. Gerasymenko - 2006

Part II. Special Biotechnologies

Chapter 23. BIOTECHNOLOGY FOR ORGANIC WASTE UTILIZATION THROUGH VERMICULTURE

23.11. VERMICOMPOST, ITS COMPOSITION AND APPLICATION

The biotechnological process of vermicompost production is based on the ability of earthworms to consume organic residues, transform them within their digestive tract, and excrete them as coprolites (excrement).

Humic substances are formed during the Digestion of organic waste in the gut of earthworms. They differ in chemical composition from humus formed in soil solely through microflora activity. This is because the earthworm gut facilitates the polymerization of organic decomposition products, forming humic acid molecules that create complex compounds with mineral components, which persist for a long time as stable formations. Unlike other soil-dwelling organisms, only earthworms possess the specific capability for soil amelioration and Structuring. The soil processed by earthworms—amounting to their own body weight per day—is transformed into granules known as coprolites. The concentration of humic substances in earthworm coprolites is 4 to 8 times higher than in manure biomass. Coprolites are dense, odorless, dark brown, non-caking pellets. They form The basis of the substance known as vermicompost, while their granular (crumbly) form gives it a friable texture, which is crucial for soil structuring.

Vermicompost, or worm castings, is an organic fertilizer produced by The breakdown of organic matter by heterotrophic organisms. Its foundation consists of earthworm coprolites. In addition, microflora and microfauna belonging to the biocenosis of the compost windrow take part in its formation.

The COMPOSITION AND PROPERTIES of vermicompost depend on the initial substrate composition and the composting (vermiculturing) technology used. Vermicompost accumulates a large amount of macro- and microelements, growth regulators, Vitamins, Antibiotics, Amino Acids, and beneficial microflora. It is hydrophilic, highly Water-resistant, and boasts high water-holding capacity, mechanical strength, and a complete absence of weed seeds. Vermicompost can retain up to 70% water and is 15–20 times more effective than any standard organic fertilizer.

On average, vermicompost has the following composition (%): dry organic matter — 40–60%; humus — 10–12; N — 0.9–3.0; P — 1.3–2.5; K — 1.2–2.5; Ca — 4.5–8; Mg — 0.5–2.3; Fe — 0.5–2.5%; (mg/kg): Cu — 3.5–5.1; Mn — 60–80; Zn — 28–35; and a pH of 6.8–7.2.

Nutrients in vermicompost are present in an organic form readily accessible to plants. It features a granular Structure resistant to water erosion and dissolves slowly in water, ensuring a prolonged release effect.

Vermicompost derives particular value from the presence of humic acids, the content of which ranges from 5.6 to 17.6% of dry matter. For instance, in Italy, vermicompost prices are determined by its humic acid content. These acids comprise C, O, H, N, P, S, Si, Al, and others, which are constituents of humus. Humus determines soil fertility and consists of three main groups of compounds:

1) substances originating from initial organic residues (Proteins, CARBOHYDRATES, Lignin, etc.);

2) intermediate products of organic residue breakdown — amino acids, monosugars, etc.;

3) humic substances, which account for up to 85–90% of the mass of humus and determine its properties.

Over the past 20–25 years, a decline in soil humus content has been observed. A significant portion of arable land has lost 15 to 40% of this substance (Horodniy M. M. et al., 1996). The widespread use of mineral fertilizers, pesticides, and chemical soil amelioration, alongside initial yield increases, has led to numerous problems: loss of humus, soil degradation into an inert mass incapable of absorbing and retaining moisture, and increased susceptibility to water and wind erosion. Soil oversaturation with various chemicals sterilizes it, destroying the biological entities that form a complex ecological system.

Research results have demonstrated that the positive impact of vermicompost on crop yields is due to its content of essential plant nutrients in a well-balanced, readily assimilable, and mobile form. It has an optimal soil pH (6.8–7.2) and contains a vast bacterial flora capable of restoring dead soils. One gram of vermicompost contains up to 2 trillion colonies, compared to 150–350 million in manure, which is traditionally considered the best natural organic fertilizer.

Vermicompost contains a high amount of BIOLOGICALLY ACTIVE SUBSTANCES (1 m³ of vermicompost is equivalent to 70,000 m² of soil).

Earthworms ingest large quantities of plant residues, microorganisms, Fungi, and Algae along with soil, digest them, and excrete large amounts of intestinal microflora within their coprolites. This microflora possesses antibiotic properties that prevent The Development of pathogenic microflora and putrefactive processes.

After worm Separation, vermicompost has a moisture content of 70–82%. If used on the same farm, it can be applied without additional technological Processing.

For commercial distribution, vermicompost is dried to a moisture content of 50–60% and sieved through screens with various mesh diameters. In Western countries, humus is divided into 3 fractions according to particle (granule) size: the finest — granules up to 0.1 mm; fine — 0.3–0.7 mm; and coarse — over 0.7 mm.

The finest fraction, or humic flour, dissolves immediately upon application to the soil and is rapidly assimilated by plants. It is used for plant "Treatment" and quick remedial effects. The fine fraction is applied to fertilize garden, greenhouse, and conservatory crops (vegetables, flowers). The third fraction is used in general crop production and horticulture. In Ukraine, vermicompost is also sorted into three fractions, but they are significantly larger: the finest fraction comprises granules up to 1 mm, the fine fraction up to 2 mm, and the coarse fraction up to 3 mm.

Vermicompost is packaged in polyethylene bags or sacks, which maintain moisture levels around 50%.

In Italy, liquid fertilizer containing 10% dry matter is produced from vermicompost in the form of a paste-like mass.

The optimal application rates are 3–3.5 tonnes of pure vermicompost or 4–5 tonnes of unrefined vermicompost (containing substrate residues) per hectare. However, these are approximate guidelines, as it is impossible to "over-fertilize" soil with vermicompost. The exact dose is determined based on economic feasibility. The maximum recommended dose is 4 t/ha. In terms of nutrient value, 1 tonne of vermicompost is equivalent to 60–70 tonnes of manure.

As foreign experience shows, vermicompost "rejuvenates" soils. Even depleted, cold, and "dead" soils are revitalized following systematic Applications of vermicompost over a 4-year period at a rate of 3 t/ha.

The technology of processing manure and other organic wastes using earthworms makes it possible to revitalize the soil through The Use of vermicompost, increasing its fertility and resistance to water and wind erosion. Furthermore, this is practically the only method for reclaiming soils that have been 'sterilized' and 'poisoned' by chemical agents.

There is an international standard for vermicompost, according to which vermicompost must have (%): moisture content 30-40; organic matter — 20-30; water-soluble salts — 0.5; residual nitrogen — 1; P — 1.5; K — 1; Mg — 1; Ca — 4; pH — 6.5-7.5.