Input of Organic Carbon to Soil with Post-Harvest Crop Residues.

Post-harvest crop residues are the main carbon source for arable lands. The aim of this research was to determine the amount and portion in the phytomass of post-harvest crop residues of major crops and carbon, which is input to soil with them. For this purpose, samples of winter and spring wheat, barley, oats, and soybean were taken in five farms of Kursk, Ryazan, and Samara oblasts and in the Chuvash Republic in 2019–2021. The ratio between plant fractions—roots, stubble, stems, leaves, chaff, and grain—was calculated. Post-harvest residues (roots and stubble) of cereal and leguminous crops account for 1/4–1/5 of the dry phytomass: the stubble portion is 1/6–1/10 of the mass and the share of roots does not exceed 10%. The portion of productive part (grains and chaff) is 1/2–1/3, and that of by-products (stems and leaves) is 1/3 for cereals and 1/2 for soybean. The amount of carbon input to the plow layer with root residues decreases in the sequence: winter wheat (569 kg C/ha) > spring wheat (508 kg C/ha) > barley (503 kg C/ha) > oats (488 kg C/ha) > soybean (204 kg C/ha). The stubble of field crops is an additional carbon source for the soil, the amount of which is directly proportional to the plant height: 419 kg C/ha for spring wheat, 405 kg C/ha for winter wheat, 281 kg C/ha for oats, 232 kg C/ha for soybean, and 135 kg C/ha for barley. Regression equations of the dependence of the amount of stubble and root residues on grain yield were calculated for winter wheat. [ABSTRACT FROM AUTHOR]