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The effect of the combined use of humic preparations and pesticides in various dosages on the quantitative composition of carbohydrates in agronomically valuable soil aggregates was studied. Biologically active humic substances indirectly, through plants and microorganisms, intensify the release of sugars, which play an essential role in the initial stages of the soil aggregates formation. Pesticides have a depressing effect on the soil microflora development, which, in turn, is one of the factors of the agronomically valuable soil structure formation. The introduction of humic preparations reduces the toxic effect of pesticides and reduces seasonal deterioration in the structural state of the soil. It has been shown that the distribution of aggregates according to variants, both in the case of dry sieving and in the case of wet sieving, correlates with the dynamics of the carbohydrate content in soil particles. This tendency is especially perceptible in the variants where pesticides were introduced into the soil together with the humic preparation. The correlation between the distribution of soil aggregates and carbohydrates according to Chaddock’s scale is salient (r = 0.532). The introduction of humic preparations makes it possible to reduce the loss of the agronomically valuable structure even in aftereffect.

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The article presents the results of a 3-year experiment to study the soil structure with the combined use of insecticides and a humic preparation. Crops were peas (Pisum sativum) and chickpeas (Cicer arietinum). The experiment was carried out in 2019–2021 at the experimental fields of the Federal Rostov Agrarian Scientific Center, located in the Rostov region in the south of the European part of Russia (47°21′ N, 39°52′ E). Soil was Calcic Chernozem Loamic. The studies were carried out both without fertilization and with the use of mineral fertilizers (N40P40K40). Sowings of leguminous crops were treated with a mixture of insecticides and a humic preparation in the phase of bean formation. The humic preparation BIO-Don10 was obtained according to the authors’ technology by alkaline extraction from vermicompost—a product of manure processing by compost worms of the Eisenia foetida species. The preparation contains salts of humic acids and fulvic acids in the amount of 1.9 g/L; the concentration in the mixture with the insecticide was 0.002%. An increase in the structure and water resistance coefficients was observed. A decrease in the block fraction and an increase in the total number of agronomically valuable aggregates were substantiated. It was found that in the cultivation of legumes, the application of mineral fertilizers had a negative effect on the structure of the soil, while, when using pesticides, the structure was preserved better by the end of the growing season. The revealed patterns can be associated with the activity of microorganisms participating in the hydrolysis of organic compounds that stabilize soil aggregates.

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The purpose is to study the influence of individual and joint application of humic preparation Lignohumate and microbiological fertilizer Baikal-EM on the structural state and enzymatic activity of ordinary chernozem. Materials and methods. Soil samples were investigated by the method of dry sieving to calculate the structural coefficient, by the method of wet sieving to determine the number of water-stable aggregates; the analysis of the dynamics of soil humus was carried out; the dynamics of catalase and invertase activity has been studied. Results. The dynamics of humus during the study period has a similar picture in all variants, however, the end of the growing season in 2011 demonstrated a statistically significant increase in the amount of humus by 0.25 % when a humic preparation and a concentrate of microorganisms are simultaneously applied into soil, in the same variant in the same period, an increase in catalase activity was noted up to 29 ml О₂/(g · min) compared to 20 ml О₂/(g · min) in the control. The application of microorganisms also revealed a correlation between humus and invertase activity: option 4 showed an increase in this indicator to a statistically significant 18 mg glucose/(g · 24 h) in the absence of a significant difference in dynamics in other options. The structural characteristics of soil showed the greatest response to treatment with Lignohumate and Baikal-EM, their application led to the increase in the structure coefficient up to 2.75 compared to 1.6–1.7 in the control variant and with the application of Lignohumate on the leaf. The content of water-stable aggregates in the control variant and with foliar treatment throughout the entire experiment was in the range of 70–75 %, while soil treatment with preparations led to the increase in water resistance of the structure to 90 %. Conclusions. Chernozem turned out to have response to the Lignohumate, application especially in combination with Baikal-EM, directly into soil, which is associated with the stimulation of its own soil microflora by the applied concentrate of microorganisms.