Soil Toxicity Depending on the Mass and Chemical Composition of Plant Residues

An important role in determining the level of soil fertility is played by such a biological indicator as toxicity, caused by the accumulation of substances that have a certain effect on cultivated plants. Studies to determine the level and dynamics of soil toxicity were conducted in the Voronezh Region on typical chernozem under sunflower crops grown in the crop rotation link: clean fallow - winter wheat - barley - sunflower. The studied factor was the methods of increasing soil fertility. It was established that the incorporation of the predecessor's straw (barley) into the soil leads to the formation of a higher (by 2.3 abs.%) reserve of toxins in the soil already by the beginning of the active vegetation of sunflower and is accompanied by its further growth during the vegetation. The green mass of the green manure helps to reduce the content of toxic substances in the soil not only by the phase of full shoots of the oilseed crop, but also by the phase of its full maturity. In this case, the reduction in soil toxicity varies from 2 to 2.6 times depending on the combination of green manure with other techniques. The intensity of accumulation or reduction of the content of colines in the soil was determined by the mass and chemical composition of plant residues (r = -0.705 for the mass of plant residues in the soil; r = 0.427 for the C:N ratio in them). The reduction in soil toxicity to the level of stimulation of growth processes with a content of at least 5.5 t/ha of plant residues in the soil with a C:N ratio in them no wider than 52:1 is confirmed by the constructed 3D model of dependence. Higher soil toxicity rates are characteristic of dry vegetation periods.