Influence of the solid fraction of pig manure on the structural state of quasi-gleyic agrochernozem

The aim of the work was to study the effect of the solid fraction of pig manure on the structural-aggregate composition and water resistance of the structural aggregates of quasi-gleyic, abraded, medium-arable, low-humus, light loamy agro-chernozem. The studies were carried out in field experiments on the experimental field of the Omsk State Agrarian University in 2016-2019. The structural state of the soil was studied in the control and in the variants with a solid manure fraction of 20 and 60 t/ha. The arable layer of agrochernozem was characterized, in general, by a good structure in terms of the ratio of aggregates of different sizes and a high degree of aggregation. However, a high content in the soil of the fraction of aggregates larger than 10 mm (20.2-53.6%) was noted. The number of agronomically valuable aggregates with a size of 0.25-10 mm was 31.6-57.7%; the coefficient of structure was 0.77-1.36. The introduction of manure into the soil had no effect on the structural and aggregate composition. There was no relationship between the dose of manure and the number of agronomically valuable aggregates. Structural aggregates of the soil of the control variant had a weighted average diameter of 5.0-9.6 mm, agronomically valuable fraction - 3.3-3.6 mm. Under the action and aftereffect of manure, these indicators changed slightly. An inverse relationship was established between the weighted average diameter of aggregates and the content of agronomically valuable fraction: r = -0.88 ± 0.13. An unfavorable property of the structure of the arable soil layer was their weak water resistance, due to the low content of humus, light granulometric composition, and susceptibility to water erosion processes. As a result of the use of pig manure, the water resistance of air-dry aggregates 3-5 mm in size increased by 67% per year of fertilizer action, and by 48-150% in the years of aftereffect relative to control. The relationship between the number of water-resistant aggregates and the dose of manure was characterized by a correlation coefficient: r = 0.57 ± 0.16.