Aftereffect of Fertilizers Applied in a Crop Rotation System with Sugar Beet on the Fertility of Leached Chernozem Soils and the Yield and Quality of Grain Crops in the Central Black Earth Region

This paper examines the aftereffect of fertilizers applied for a long time to sugar beet cultivated in a nine-field grain–black-fallow–row crop rotation system in the forest–steppe unstable moistening zone of the Central Black Earth Region on the fertility of leached chernozem soils under grain crops and their yield and quality. The experiment launched in 1936 includes the following fertilizer systems (per rotation): N₉₀P₉₀K₉₀ + manure (25 t/ha), N₁₈₀P₁₈₀K₁₈₀ + manure (25 t/ha), N₂₇₀P₂₇₀K₂₇₀ + manure (25 t/ha), N₃₀₀P₃₀₀K₃₀₀ + manure (50 t/ha), N₃₈₀P₃₈₀K₃₈₀, and a variant without fertilizers (control). Mineral fertilizers are applied to sugar beet twice per rotation; manure is applied to the black fallow field once per rotation. The most significant changes in agrochemical characteristics of the leached chernozem soil (0–40-cm layer) caused by the effects of mineral fertilizers and manure were noted under winter wheat (the P₂O₅ content increased by 21.3–77.2%, the total mineral nitrogen content (N-NO₃ + N-NH₄) by 8.1–133.2%, and pHKCₗ by 0.07–0.37), while the least significant changes were under oats (the P₂O₅ content increased by 16.3–44.4%). Soil saturation with fertilizers increases the oat productivity to the greatest extent (by 12.2–65.5% in comparison with the control); the effect on barley and winter wheat in the black fallow link is somewhat less (13.0–59.1% and 7.37–57.6%, respectively); and the effect on winter wheat in the clover link is the least significant (29.9–47.8%). The aftereffect of fertilizers increases the protein content by 0.5–1.0% in oat grains and by 0.6–1.8% in barley grains in comparison with the control. A significant positive correlation between the amount of applied fertilizer elements and the yield capacity of barley, oats, and winter wheat was registered in both crop rotation links (r = 0.67–0.95). The following fertilization systems ensure the highest productivity of the grain–black-fallow–row crop rotation system in combination with a satisfactory quality of wheat, barley, and oat grains: (1) N₁₃₅P₁₃₅K₁₃₅ applied to sugar beet twice per rotation + manure applied to the black fallow field (25 t/ha) and (2) N₁₉₀P₁₉₀K₁₉₀ applied to sugar beet twice per rotation (without manure). The additional yield reaches 14.4–16.8 kg of grain per 1 kg of NPK.