Fertilization of Annual Grasses on Gray Forest Soils of the Vladimir Opole

In a long-term stationary experiment, the effect of fertilizers on the yield of annual grasses (vetch and pea mixtures) and the nitrifying activity of gray forest soils were studied. For 8 years, both without the use of fertilizers and with them, the yield of herbs changed by 1.72–1.88 times. It was found that the use of nitrogen of mineral fertilizers provided 88.3% of the total variation in their yield, the aftereffect of manure – 8.1, the aftereffect of РК fertilizers – 1.8%. For 7 out of 8 years, a high degree of correlation between the yield of grasses and the reserves of N-NO₃ in the 0–40 cm layer of soil in the phase of grass germination was revealed. At the same time, the minimum reserves of N-NO₃ were formed at a hydrothermal coefficient for the growing season equal to 1.21. The use of fertilizers, increased moisture content and temperatures during the growing season of grasses led to an increase in the nitrification activity of gray forest soil. It is proposed to evaluate the participation of mobile forms of nitrogen in plant nutrition in relation to the content of N-NO₃ in the soil to the content of N-NH₄ in the water extract (1 : 1). The values of this parameter in the phases of germination and harvesting of grasses confirmed the determining role of N-NO₃ reserves in the nutrition of annual grasses. The difference coefficients of the use of nitrogen Naa in doses N60 and N75, which ranged from 40 to 49%, were calculated. An algorithm for calculating the size of the accumulation of N-NO₃ during the growing season of grasses is proposed. In nitrogen-fertilized variants, a good coincidence of the utilization coefficients of accumulating N-NO₃ reserves with the difference ones has been established.