Fertility of drained sod-podzolic soil in organic crop rotation

Goal. To study the influence of the biological fertilizer system on crop productivity in crop rotation and the balance of humus and nutrients in the soil. Methods. Field — stationary experiment, laboratory — determination of grain moisture and quality indicators of the soil according to generally accepted methods, analytical, theoretical generalization. Results. The research was conducted during 2021–2023 on drained sod-podzolic sandy soil with a low level of fertility in a short grain rotation: pea-oats —oats — vetch-oats — barley. It was established that the maximum indicators of the grain yield of pea-oats — 2.25 t/ha, oats — 1.88, vetch-oats — 1.68, barley — 1.61 t/ha were obtained with foliar feeding of crops with Biokompleks-BTU biological preparation and liquid bio-fertilizer Volynski humaty against the background of natural mineral fertilizers (P40K60 — phosphorite flour and potassium sulfate), straw and siderate, which was 25.8–43.5% compared to the control option (straw + siderate). It was determined that the synthesis of humus occurred mainly due to the by-products of grain and leguminous crops and root and post-harvest residues. As a result, 175–350 kg of humus accumulated in the soil every year, which provided a simple and extended reproduction of its fertility. Nitrogen, as the most limiting element in the Polissia zone, comes with oil radish siderate, by-products of grain and leguminous crops, and biologically fixed nitrogen from the atmosphere. Thanks to biological factors, the intensity of the nitrogen balance was 101–120%. Removal of phosphorus and potassium by crops was compensated by the supply of these elements with straw and siderate. Conclusions. In organic crop rotation, with 50% saturation with leguminous crops (pea and vetch) against the background of by-products and siderate and the application of foliar feeding of crops with preparations of biological origin, a deficit-free balance of humus and nutrients is achieved in sod-podzolic soil.