Svyrydova L. Forming the crop productivity of grain sorghum hybrids depending on the rates and method of sowing in the Eastern Forest steppe of Ukraine

The thesis is devoted to solving the important scientific problem concerning developing and improving agricultural practices (method and rates of sowing) of optimizing the parameters of plants growth and development, forming the productivity of modern grain sorghum hybrids in the conditions of the Eastern Forest Steppe of Ukraine. The comparative analysis of phenology stages duration, field’s sprouting, preserving the crops density, the main biometric indices, forming the structure indices, the crop productivity and quality of grain under different methods and rates of sowing. During the years of research the highest photosynthetic potential of crops according to the hybrids and methods of sowing on the average (3474,9 thousand m2. 24 hours/ha) was about the rate of sowing seeds 240 000 items/hectare. Net productivity of photosynthesis on the average during the vegetation suffered greater changes under the rates of seeds sowing influence. Thus under its influence the net productivity of photosynthesis changed within 2,48 –3,73 gr/m2, under the influence of sowing method – within 3,02-3,23 gr/m2, and under the hybrid influence – within 3,00-3,17 gr/m2. The maximum index of net productivity of photosynthesis on the average was 4,26 gr/m2, on sown areas of Dash E hybrid with interrows of 45 cm and sowing rates of 240 000 items/hectare. The part of influence of investigated factors in the variability of indices of biological productivity , crop productivity and sorghum hybrid grain quality was determined. The level of ties and correlation sets of ties between grain yield and its structural indices were defined. The ties level of rates of seeds sowing with the quantity of plants and sorghum panicles on the unit of area was the closest in the sowings of grain hybrid sorghum Sprint W. The close and direct ties in the sowings of all investigated sorghum hybrids existed between grain crop productivity and the index of leaf surface at the phase of plants tubing and maturing. It was defined that it is necessary to have the differentiated approach as to the rates of seeds sowing taking into account the weather conditions and sowing method. A wide row method of sowing with the width of interrows of 45 cm under the rate of sowing 200 000 items/ha prevailed. The highest crop productivity (6,33 t/ha) among all hybrids of the studied group was observed in the sorghum hybrid Dash E.