Biomass of humus formation in the national model of carbon budget management in soils of agroecosystems

Biomass of humus formation is an important part in a national carbon budget management model. The purpose of the study was to determine the acceptability of replacing the method of determining the biomass of humus formation, represented by the mass of matter in the method of CINAO to the approach of substance fractionation (crop, root and crop residues, by-products) used in the method of RosNIIzemproekt. The masses of humus-forming matter obtained by different methods were compared, as well as the humus balances (HB) calculated for them. Standard methods of regression and correlation analysis were used, as well as the method of pair difference between conjugate sequences. The quality of regression models was assessed using the Cheddock scale. The study confirmed the acceptability of substituting the humus formation biomass determination in the CINAO method for the approach adopted in the method of RosNIIzemproekt. Based on calculations of humus formation biomass, it was revealed that all calculated HBs consistently increased with increasing winter wheat yield. It is shown that the maximum HB values (13.6 c/ha) were obtained for high straw cutting according to the CINAO methodology. Reduced yield (25 c/ha or average area-weighted by the region 23.9 c/ha) forms a negative HB in grain production technologies that collect straw as a by-product. In technologies that include straw in the humus-forming biomass, the yield value below which the HB becomes negative decreases to a yield of 20 c/ha or 18.3 c/ha, respectively. The noted values of yields act as criteria for the feasibility of initiation of soil-climatic projects on arable soils. Obviously, the goal of humus (carbon) accumulation in arable soils will not be achieved under crops that demonstrate negative HB. Yields below which it is inappropriate to initiate a soil-climatic project are proposed to be called: “Soil-climatic project initiation threshold (SCPIT)”.