THE INFLUENCE OF MINERAL FERTILIZERS ON GRAIN YIELD CAPACITY OF OAT
In 1972-2017 the influence of increasing doses of complete mineral fertilizer (0, 30, 60, 90, 120, and 150 kg of acting ingredient/ha) on the yield capacity of different oat varieties was studied in six-field grain-fallow-grass crop rotation at long-term station of Federal Agrarian Scientific Center of North-East. The experiment was conducted on sod-podzolic, middle loamy soil formed from eluvium of Perm clay. Argochemical parameters of plough layer at the beginning of experiment were the following: рНKCl. - 4.8, content of Р<sub>2</sub>О<sub>5</sub> - 46 mg/kg, К<sub>2</sub>О - 160 mg/kg of soil, humus - 1.5%. Mineral fertilizers such as ammonium nitrate, double superphosphate, and potassium chloride were applied to the pre-plant cultivation. The yield capacity of all studied oat varieties increased up to N<sub>60</sub>P<sub>60</sub>К<sub>60</sub>, N<sub>90</sub>P<sub>90</sub>К<sub>90</sub> with increase in mineral fertilizer doses. Higher doses of NPK did not improve the yield capacity of oat. On average over the nine years, the maximum yield of chaffy oat varieties (3.27 t/ha) was obtained at application of complete mineral fertilizers of 60 kg of acting ingredient/ha; the yield capacity of control variant was 1.55 t/ha. On average over the nine years, the recoupment of 1 kg of acting ingredient of applied fertilizers by chaffy oat grain was equal to 3.9-9.6 kg. The highest recoupment was observed in variant with a minimal dose of N<sub>30</sub>P<sub>30</sub>К<sub>30</sub>. Each increase in fertilizer dose led to decrease in recoupment by oat grain. Among all chaffy oat varieties cultivated in study, the maximum yield capacity (4.08 t/ha) was achieved in 2003-2005 by the quality-valuable Argamak variety (selected in Flenskaya selective station) with N<sub>120</sub>P<sub>120</sub>К<sub>120</sub> fertilizer dose. On average over the six years, the maximum yield capacity of naked oat varieties (3.17 t/ha) was obtained when complete mineral fertilizer was applied in a dose of N<sub>120</sub>P<sub>120</sub>К<sub>120</sub>. The yield capacity of oat was mainly determined by application of nitric and phosphoric fertilizers.