BIOTECHNOLOGY - V. H. Gerasymenko - 2006

Part II. Special Biotechnologies

Chapter 23. BIOTECHNOLOGY FOR ORGANIC WASTE DISPOSAL VIA 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, because the earthworm gut facilitates the polymerization of organic breakdown products, forming humic acid molecules. These molecules create complex compounds with mineral components that persist for a long time as stable formations. Unlike other soil-dwelling organisms, earthworms possess a unique capability for soil amelioration and Structuring. They convert processed soil—amounting daily to their own body weight—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 (lumpy) Structure gives it a friable appearance, which is crucial for soil structuring.

Vermicompost (or worm casting) is an organic fertilizer produced by The breakdown of organic matter by heterotrophic organisms. Its core consists of earthworm coprolites. Additionally, its formation involves the microflora and microfauna that make up the biocenosis of the compost pile.

The COMPOSITION AND PROPERTIES of vermicompost depend on the initial substrate composition and the composting (vermiculture) technology used. Vermicompost accumulates large amounts of macro- and microelements, growth regulators, Vitamins, Antibiotics, Amino Acids, and beneficial microflora. It is hydrophilic, highly Water-resistant, and moisture-capacitive, possesses high mechanical strength, and is free of weed seeds. Vermicompost can retain up to 70% water and is 15-20 times more effective than any conventional 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 mg/kg; Mn — 60-80; Zn — 28-35 mg/kg; and pH — 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.

The exceptional value of vermicompost stems from its high content of humic acids, ranging from 5.6 to 17.6% of dry matter. For instance, in Italy, the price of vermicompost is 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 derived from initial organic residues (Proteins, CARBOHYDRATES, Lignin, etc.);

2) intermediate products of organic residue transformation (amino acids, Monosaccharides, 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 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 has led—alongside initial yield increases—to numerous problems: loss of humus, soil destruction, and its conversion into an inert mass incapable of absorbing and retaining water, making it prone to water and wind erosion. Over-saturation with various chemicals sterilizes the soil, destroying the biological entities that form its complex ecological system.

Research results have demonstrated that the positive effect of vermicompost on crop yields is due to its well-balanced and easily assimilated mobile form of plant nutrients. It has an optimal soil pH (6.8-7.2) and contains an abundant bacterial flora capable of restoring degraded soils. One gram of vermicompost contains up to 2 trillion colonies, compared to 150-350 million in manure, which is traditionally regarded as the best natural organic fertilizer.

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

Earthworms consume large amounts of plant residues, microorganisms, Fungi, and Algae along with soil. They digest these Materials and excrete large quantities of intestinal microflora within their coprolites; this microflora possesses antibiotic properties that suppress pathogenic microflora and putrefactive processes.

After the worms are harvested, 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 hole diameters. In Western countries, humus is separated into 3 fractions by granule (particle) size: the finest fraction comprises granules up to 0.1 mm; the fine fraction, 0.3-0.7 mm; and the coarse fraction, over 0.7 mm.

The finest fraction, or humus flour, dissolves immediately upon soil application and is rapidly assimilated by plants; it is used for plant "therapy" and quick results. The fine fraction is utilized for fertilizing garden, greenhouse, and hotbed crops (vegetables, flowers). The third fraction is used in general crop production and horticulture. In Ukraine, vermicompost is also sorted into three fractions, though they are significantly larger: the finest fraction consists of 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, ensuring that moisture levels are maintained around 50%.

In Italy, liquid fertilizer is produced from vermicompost; it contains 10% dry matter and has a paste-like consistency.

The optimal application rates are 3-3.5 tons of pure vermicompost or 4-5 tons of unrefined vermicompost (containing residual substrate) per hectare. However, these are approximate guidelines, as it is impossible to "over-fertilize" soil with vermicompost. The dosage is determined based on economic viability, with a maximum recommended rate of 4 tons/ha. In terms of nutrient value, 1 ton of vermicompost is equivalent to 60-70 tons of manure.

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

The technology of processing manure and other organic wastes using earthworms makes it possible to use vermicompost to rehabilitate soil, increase its fertility, and enhance its resistance to water and wind erosion. Furthermore, this is virtually 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 contain (%): moisture 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.