Pashinska K. Influence of doses and terms of fertilizer application on yield and quality of grain of grain sorghum in the Forest-Steppe of Ukraine

Scientific novelty of the obtained results. For the first time in the conditions of sufficient moisture of the Forest-Steppe of Ukraine the efficiency of the alternative organic-mineral fertilization of grain sorghum has been established. It is proved that the application of winter wheat straw and the optimal dose of mineral fertilizers provides stable yields and high grain quality. In conditions of insufficient moisture, the application of nitrogen fertilizers in the spring was determined to be effective, the optimal dose and methods of fertilizer application were established. It was improved the system of grain sorghum fertilization in the conditions of sufficient moisture through the combined use of straw and mineral fertilizers, insufficient moisture – by optimizing the doses and methods of nitrogen fertilizers. It was further developed the issues of efficiency of organic-mineral fertilization in achieving high yield and grain quality of sorghum grain in conditions of sufficient moisture; nitrogen nutrition – in conditions of insufficient moisture. The practical significance of the obtained results. Based on the results of temporary field research, agrochemical principles of effective use of organic and mineral fertilizers for grain sorghum in conditions of sufficient moisture, nitrogenfertilizers for growing grain sorghum in conditions of insufficient moisture in the forest-steppe of Ukraine have been formed. According to field experiments and their production testing, a system of efficient use of straw, mineral fertilizers and nitrogen for grain sorghum has been developed, which provides grain yield over 8 t/ha with a profit from fertilizer over 7000 UAH/ha. The main results of research. It was found that under conditions of sufficient moisture (HTK=1.3) the highest reserves of mineral nitrogen in 0-40 cm layer of leached chernozem in the phase of 3-5 leaves of grain sorghum were formed at doses of fertilizers N120R120K120: nitrate – 108 kg/ha, ammonium – 70 kg/ha with an advantage to the control without fertilizers – by 42 and 9 kg/ha, respectively. The addition of 4 t/ha of straw reduced the mineral nitrogen reserves in the soil by 13-17 kg/ha. At the end of the growing season, the reserves of nitrate nitrogen in the soil decreased to the initial in 6.4-7.7 times, ammonium nitrogen – by 31-33%. It was investigated that in conditions of insufficient moisture (HTK=0.9) the use of nitrogen fertilizers in pre-sowing cultivation of grain sorghum increased the mineral nitrogen fund mainly in the upper 0-30 cm layer of weakly saline chernozem. The highest content of mineral nitrogen in the layer of 0-30 cm was formed at doses of nitrogen fertilizers 150 kg/ha: nitrate – 25.2 mg/kg, ammonium – 13.5 mg/kg of soil with reserves of mineral nitrogen in the layer 0-90 cm – 244 kg/ha with an advantage to the control without fertilizers by 79 kg/ha. At the end of the growing season, the reserves of mineral nitrogen in the soil decreased in 1.8 times, which is a consequence of its transformation and use by plants. According to the results of field research, it was found that the content of mobile phosphorus in the arable 0-30 cm layer of chernozems depended on the dose of phosphorus fertilizers. The highest content of mobile phosphorus in leached chernozem was observed in the phase of 3-5 leaves for application of N120P120K120 – 139 mg/kg with exceeding the control without fertilizers by 12 mg/kg of soil; weakly saline chernozem – for dose of fertilizers N90R90K90 – 55.5 mg/kg in excess of control without fertilizers by 10.3 mg/kg of soil. During the growing season, the content of mobile phosphorus in leached chernozem decreased to the initial – by 10-13%, weakly saline chernozem – by 18-19%. It was studied that the content of mobile potassium in chernozem soils depended on the application of potassium fertilizers and straw of winter wheat. The highest content of mobile potassium in the 0-30 cm layer of leached chernozem in the phase of 3-5 leaves was observed for the application of 4 t/ha of straw + N120P120K120 – 111 mg/kg; weakly saline chernozem – for doses of fertilizers N90R90K90 – 182 mg/kg of soil. During the growing season, the content of mobile potassium in leached chernozem decreased to the original – by 26-28%, weakly saline chernozem – by 16-19%.