Effect of Plant Biomass on Gray Forest Soil’s Nitrogen Rate and Field Crop Productivity

Abstract

The plant biomass (postharvest and crop residues, green manure crops, etc.) actively used in Siberian agriculture partly contributes to the replenishment of mineral nutrients needed to sustain field crop yields and to maintain soil fertility. A comparative assessment of kinetic parameters for mineralization of manure, green manure crops (sweet clover, oilseed rape, and winter rye), and straw on the gray forest soil of the fallow arable land and their impact on productivity of fodder crops through their effects and aftereffects was performed. The observations for mineralization of nitrogenous substances in organic fertilizers showed that manure and biomass of high-protein crops (oilseed rape and sweet clover) have the greatest ability to mineralize nitrogen, while the crops with higher contents of carbon (winter rye and straw) have a lower capability to do it. Nitrate nitrogen as the preferred nitrogen source of plant nutrition is the dominant form of nitrogen according to the 3-year observations for the rates of mobile forms of mineral nitrogen in the gray forest soils during the land fallow process and beneath the crops. The results of the aggregate accounts for the crop yields for a year of crop-biomass effects and for 2 years of its aftereffects allowed us to ascertain almost the same impact of all the types of the organic biomass on the overall crop yield under the crop-rotation conditions. The only exception was the wheat-straw biomass, since the cycle of its decomposition in soil was not completed for 1 year of fallowing and three seasons beneath the crops.