THE EFFECT OF WEATHER CONDITIONS AND MINERAL NUTRITION ON SOYBEAN PRODUCTIVITY
The research goal was to determine the degree of the effect of weather conditions and mineral nutrition on soybean productivity in crop rotation under long-term fertilization. The research was conducted in a long-term experiment started in 1962-1964 designed for studying the effect of different systems of fertilizers in five-course soybean-cereal crop rotation on soil fertility and crop productivity. The soybean variety Lydiya planted in the 2nd and the 4th courses of crop rotation was studied. The research results over the period of 2008-2012 are presented. It was found that under adverse moisture conditions and low air temperature in the critical period of legume-rhizobium symbiosis formation, the application of nitrogen-phosphorus fertilizers, even at the current increased level of soil fertility, contributed to the formation of greater crop productivity by 0.30-0.47 t ha of seed units than in the control. Soil nitrogen utilization coefficient in the variants without nitrogen fertilization was 109-115%; with N <sub>30 </sub>application it decreased to 92-86%, and with N <sub>60</sub> - to 73%. During the growing seasons which were relatively favorable in terms of hydrothermal regime the utilization of nitrogen-phosphorus fertilizers was accompanied not only by the formation of relatively high productivity (2.17-2.64 t ha of seed units), but also by significant soil nitrogen uptake by soybean. The nitrogen utilization coefficient ranged within 193-176% in the variants without fertilizers, and reached 176-171% with N <sub>30</sub>P <sub>60 </sub>application. The phosphorus utilization coefficient did not depend on the weather conditions and ranged from 21 to 7% ensuring a constant positive phosphorus balance in the soil.