Influence density and sowing method of grain sorghum on the formation of assimilation surface and grain productivity of plants

In the course of conducted researches it was found that the leaf surface area of sorghum crops was directly proportional to the plant density. It was determined that the largest area of the assimilation apparatus forms in the panicle initiation stage. It was found that each increase in plant density by 20 thousand/ha leads to a decrease in the individual leaf surface area of the plant by 8.8–9.0 % (128–137 cm2) relative to the previous plant density. The row-width spacing was no influenced to this indicator. The largest grain weight per the panicle was formed at a plant density of 80 thousand pcs/ha. Crowdedness of crop (by 20 thousand/ha) led to a decrease in this indicator by 4.8–22.0 % compared to the previous one. An increase in agrocenosis density caused to decrease in grain weight and grain size of the panicle, but the 1000 grain weight was relatively stable. The optimal values of the 1000 grain weight in varieties and hybrids were obtained at plant density of 120–140 thousand/ha. The structure of the yield was significantly influenced by the genetic features of sorghum and the sowing density. The influence of the method of sowing was insignificant. On average, over the years of research, the highest yield of grain sorghum was in trials with a row spacing of 45 cm: Prime hybrid – 5.89 t/ha, Dniprovskyi 39 variety – 4.62 t/ha (plant density of 140 thousand/ha) and Vinets variety – 3.70 t/ha (160 thousand/ha). The grain yield of the Prime hybrid at growing with 70 cm row spacing was 5.70–5.71 t/ha at a plant density of 120–140 thousand/ha, respectively. The Dniprovskyi 39 variety had the same yield indicators (4.57 t/ha) at plant density of 120 and 140 thousand/ha. The grain yield of the Vinets variety at a plant density of 160 thousand/ha and a row spacing of 70 cm was 3.83 t/ha. Crowdedness of plants above the specified density caused a decrease in grain productivity. Key words: grain sorghum, plant density, leaf area, individual area of the assimilation apparatus, agrocenosis density, grain productivity.