The influence of field crop rotations on the accumulation of crop-root residues in the arable layer of sod-podzolic soil

The aim of the research is to take a comparative assessment of the amount of plowed down plant residues in various field crop rotations in the conditions of the Republic of Mari El. The study was carried out in 2013-2018 on a stationary site in a two-factor experiment. Factor A ‒ types of crop rotations and shift of crops: 1. Grain and grass crop rotation (oats + clover, clover of the 1st year of use (y.u.) for green mass, winter rye, vetch and oat mixture for grain, spring wheat, barley. 2. I fruit-changing crop rotation (vetch and oat mix for green fodder, winter rye, barley, potato, vetch and oat mixture for grain, spring wheat). 3. II fruit-changing crop rotation (vetch and oat mixture for grain, spring wheat, potato with manure (80 t/ha), barley + clover, clover of the 1st year of use for green mass, winter rye). 4. III fruit-changing crop rotation (barley + clover, clover of the 1st year of use for green mass, clover of the 2nd year of use for green mass, winter rye, potato, oats). Factor B ‒ mineral fertilizers: 1. Without fertilizers. 2. N60P60K60. In the control grain and grass crop rotation with a oneyear use of clover, 3.02±0.06 t/ha of crop-root residues were received per year on the average. In the I fruit-changing crop rotation, due to the replacement of clover with potato, residues formed 2.14±0.04 t/ha, which was significantly less than the control variant (LSD05 in factor А ‒ 0.21). In the II fruit-changing crop rotation, the accumulation of crop-root residues amounted to 2.91±0.07 t/ha. Compared to the control, it was within the limits of experimental error. The largest number of crop-root residues was accumulated in the III fruit-changing crop rotation (3.37±0.07 t/ha). The use of mineral fertilizers significantly increased the bulk of crop-root residues in all crop rotations by 0.16 t/ha per year on the average (LSD05 in factor B ‒ 0.15). Carbon to nitrogen ratio (C:N) in the crop-root residues of clover and potato was 18…20, in the vetch-oat mixture it was 25…31, in spring grain crops it was 39…41, and in winter rye it was 53.