Expenditures of Fertilizers for an Increase in the Reserves of Nitrate Nitrogen in Soil under Crops in the Central Non-Black Soil Zone
Investigations were carried out in 2005 -2015 in long-term multifactor stationary and short-term field experiments on average cultivated sod-podzol soil with humus content 1.8-2.2%, characterized by a high content of mobile phosphorus, medium-of potassium and the reaction of the soil medium close to neutral (pH (KCl) = 5.8-6.5). We determined quantitative parameters of expenditures of nitrogen fertilizer to shift the reserves of N-NO3 in the root layer (0-60 cm) with respect to the early phases of development of winter and spring crops, grown in field crop rotations after different preceding crops. These data should be used to calculate doses of nitrogen fertilizers for preplant and additional application, taking into account the actual and desired level of nitrate nitrogen in soil. We identified the dependence of this indicator of the composition, biological features and the level of fertilization of preceding crop. The reduction of the fraction of legume component to the plowing of perennial grasses of 2-3 years of use during the substitution of pure legumes by cereal-legume mixtures resulted in the higher expenditures of nitrogen fertilizers for the increase in nitrogen reserve in the soil under winter wheat from 100130 kg/ha to 130-170 kg/ha. In the second year after plowing at the growing of spring crops the influence of the composition was neutralized. Cultivation of winter and spring crops after grain forecrop or in the seeded fallows provided a reduction in the cost level of nitrogen in comparison with the formation of herbs for winter wheat from 100-170 kg/ha to 120 kg/ha, for spring wheat, barley and oats-from 80170 kg/ha to 50-110 kg/ha, mainly due to the improvement of conditions for nitrification in the soil. Manure application led to a decrease in the cost of nitrogen fertilizer on the average by 30-40 kg/ha, in comparison with similar values, obtained without manure.