How to decompose plant residues efficiently?

CONTROLLED DECOMPOSITION OF PLANT RESIDUES IS A MUST

Rehabilitation of soil fertility in today’s agriculture is impossible without efficient management of the organic matter of plant residues that remain in the field after harvest. Within the conditions of environmental problems associated with excessive greenhouse gas emissions into the environment, it is important that carbon accumulated in organic matter on the surface of the field is not subjected to rapid mineralization with CO2 emission, but fixed in the soil in the form of organic substrates (process of sequestration).

And on the top of that, the systematic cultivation of plants with the same biological requirements, same chemical and biochemical composition, development of particular diseases and pests pose a threat to the soil, which is also a living organism. There is such a phenomenon as soil exhaustion – an accumulation of toxic substances, pathogens, imbalance of agrophysical properties in soil, resulting in a decrease in productivity of crops. The application of mineral fertilizers only and the use of chemical plant protection products do not eliminate, but accelerate the manifestation of soil exhaustion. Most of the phytoncides (including the toxic ones that can suppress subsequent crops) are concentrated in the aerial parts of plants, so it is necessary to populate the beneficial microflora inhibiting the soil pathogens to improve the soil condition.

It is well known that the decomposition of organic residues is accomplished through a complex of microorganisms, some of which feed only on water-soluble substances, the other ones decompose starch, fiber, hemicellulose and other complex carbohydrates, and a certain amount of them destroys lignin. In other words, the destruction of organic matter is a multi-stage process with its regularities and principles: the products generated in the process of intermediate decomposition are a substrate for the vital activity of the subsequent.

WHY IT IS NOT ENOUGH TO INCORPORATE CROP RESIDUES INTO THE SOIL?

Uncontrolled incorporation of crop secondary products (straw, stalks of corn, sunflowers, soybeans), apart from the positive effect, can create a number of challenges for farmers. First of all, this includes straw, that has the longest period of decomposition in the soil - from six months to a year and a half. The increase in period of decomposition of organic matter:

• increases nitrogen deficiency in the soil (microorganisms use its soil reserves for destruction),
• slows down the intensity of decomposition and the availability of nutrients accumulated in organic matter to plants,
• increases the accumulation of toxic substances, pathogens, etc., in the soil due to poorly decomposed organic matter.

HOW TO ACHIEVE A RATIONAL APPROACH TO THE DECOMPOSITION?

The issues described above can be solved by applying microorganisms directly to the organic matter, that is, by treating it with destructors. A destructor has to be a must-have element of technology!

One of the most common destructors in Ukraine is Ecostern, which consists of fungi and bacteria accelerating the decomposition of crop residues, antagonists of pathogenic microorganisms, living cells of Bacillus subtilis, Azotobacter, Enterobacter, Enterococcus bacteria and fungi Trichoderma lignorum, Trichoderma viride, total viable count is 2,5×109 CFU/cm3.

Let’s take a look at the key aspects of Ecostern's effectiveness.

1 - Biocontrol of soil pathogens

In the formulation of Ecostern the role for control of phytopathogens belongs to Bacillus subtilis and fungi of the Trichoderma genus. Because of their ability to produce a number of metabolites (including proteins, polypeptides, cyclic lipopeptides, non-peptide compounds), these microorganisms are a powerful tool for controlling approximately 20 types of phytopathogens.

Their effect on phytopathogens is evaluated from fungistatic (inhibition of development) to fungicidal (destruction). It has been proved that strains of Bacillus subtilis and Trichoderma strongly resist pathogens of mold, root rot and other diseases, the pathogens of which are concentrated in the soil.

In case of application of Ecostern on the surface of plant residues, this controlling is carried out in an integrated manner, i.e. at the level of organic matter where the agronomically valuable microflora gets inhabited, and after incorporation of this organic matter pathogenic species of microorganisms concentrated in the soil are suppressed.

The need of treating plant residues with Ecostern is related to the fact that the horizontal and vertical movement of the microorganisms is rather slow due to the adsorption of them by soil particles and the porous structure of the soil. In addition, soil cultivation may result in different conditions - aerobic and anaerobic processes are capable of affecting the activity of a particular group of microbes, and, accordingly, the intensity of the destruction of organic matter. Therefore, the application of Ecostern promotes the active settlement of organic matter with microbiota and its rapid incorporation into decomposition processes.

2 – Improvement of nutrition and increasing availability of nutrients

As the French microbiologist of the XIXth century Louis Pasteur said, “The role of the infinitely small in nature is infinitely large.” Thanks to the research of the last decades, this idea has been completely confirmed! This also is applied to the participation of microorganisms in the recirculation of food compounds. It was established that microbes, taking an active part in natural processes, involve approximately 70 elements of Mendeleev's periodic table in a large geological cycle of the matter. Microbes, as participants of a small biological cycle, provide the flow of nutrients through the transformation of organic matter. Thus, according to multiple data, 25-35 kg of nitrogen, 14-20 kg/ha of phosphorus, 50-85 kg of potassium, 15-17 kg of calcium are concentrated in biomass of 6-8 t of straw. There is a certain amount of micronutrient elements in this amount of plant residues in addition to macronutrients: boron at the average of 30 g/ha, 20 g of copper, 180 g of manganese, 2-3 g of molybdenum, 200-300 g of zinc, that should return to the soil as far as possible. Thus, the use of Ecostern helps to accelerate this process. The 6-year studies of the Company BTU-CENTER, both their own and in partnership with independent scientific and manufacturing enterprises, showed that depending on the soil moisture level the degree of straw destruction increased from 21 to 48% during the first month after its application.

Laboratory tests indicate that the treatment of corn stalks with Ecostern increased the carbon content of volatile organic compounds by 9.7% and had a positive tendency to increase humus content. It has been established that the content of mobile phosphorus in the soil, where the straw treated with biodestructor was incorporated, increased by 33%, and the exchangeable potassium  - by 3% as compared to control without biological preparation.

The ratio between carbon and nitrogen (C:N) is an important indicator for effective decomposition, the optimum of which is 20-30:1, whereas for example for straw of cereal crops it increases to 70-90:1. Due to such an extensive ratio in the decomposition process, a decrease in nitrates and ammonium in the soil takes place, i.e. microbiological processes are shifting towards nitrogen immobilization. That is why when applying Ecostern for soils with significant nitrogen deficiency, it is necessary to apply up to 5-15 kg of primary nutrients of nitrogen fertilizers per 1 ton of straw. However, Azotobacter, which is included in the destructor, will gradually accumulate nitrogen, thereby narrowing its ratio to carbon. When the destruction of the organic matter is completed, the die-away of microbial population accompanied by release of additional nitrogen occurs.

3 - Increase in crop yields

One of the main criteria for the efficiency of an agricultural activity is its impact on crop yield. The agrarians' saying “The silo will show the efficiency of the preparation” required not only the systematic performance of experimental but also production tests to study the efficiency of Ecostern for all soil and climatic zones of Ukraine. The data obtained over the past 10 years and confirmed by the relevant certificates of implementation certify that the use of 1.5-2.0 l/ha of this biological product provided a statistically significant increase in the yield of winter wheat at average of 0.35 t/ha, sunflower – approximately 0.15 t/ha, soybeans - 0.2-0.3 t/ha, corn - 0.28-0.45 t/ha. Such or even better effect is guaranteed to be achieved in case of compliance with the conditions of application (this is crucial!), including treatment in the morning or evening, or in cloudy weather at the rate of water discharge of 150 l/ha or more.

Thus, a destructor is a must-have element of the technology! Biodestructor Ecostern is a solution for efficient and controlled decomposition of plant residues. It provides a biocontrol of soil pathogens, a decrease of the soil toxicity level, an increase in availability of nutrients, an improvement of soil structure and an increased crop yield.