INFLUENCE OF MINERAL NITROGEN ON THE EFFICIENCY OF SYMBIOTIC NITROGEN FIXATION AND YIELD OF LEGUMES IN THE FOREST-STEPPE OF UKRAINE
The results of the research on the influence of mineral nitrogen fertilizers and biologically active preparations on nitrogen fixation efficiency and biological yield of soybean and chickpea are discussed. The field trials were conducted on typical chernozems of the Ukrainian forest-steppe at the Research Station of the National University of Bio-Resources and Natural Resources Management of Ukraine. It has been found that under the soil and climatic conditions of the Ukrainian Right-Bank Forest-Steppe the application of nitrogen fertilizers at medium rates (up to 60 kg ha on primary nutrient basis) enhances nitrogenase activity of soybean and chickpea root nodules. In the trial variants with higher rates of nitrogen fertilizers there was no root nodules formation and no nitrogenase activity; the plants utilized mineral nitrogen from fertilizers. The application of moderate rates of mineral fertilizers (N <sub>30</sub>-N <sub>60</sub> against the background of P <sub>60</sub>K <sub>60</sub>) contributes to significant increase in yielding capacity of legumes.