Productivity of grain sorghum at application of post-emergence herbicides

During the four-year field experiments, the influence of post-emergence herbicides such as Pik, Prima and Grantox on the phytosanitary state of grain sorghum crops and the formation the grain productivity of plants was established. It was found that the applied chemicals did not affect the main stages of ontogenesis by sorghum plants. The use of the active ingredient of Prima and Grantox led to a decrease the linear growth of plants. The height of sorghum plants with increasing the application dose of Prima decreased from 101.7 to 98.5 cm. When increasing the dose of Grantox, the toxic effect of the active ingredient on sorghum plants increased, as a result their height decreased significantly from 103.1 to 98.1 cm. With regard to the Pik herbicide, with increasing of application doze, the plant height increased from 105.5 to 107.9 cm. Due to the use of the application dose of 20 g/ha, the highest grain yield of sorghum was obtained (4.04 t/ha). It is only 0.22 t/ha less compared to the variants where weeds were removed manually. These results indicate a significant effect of the Pik herbicide on weeds and weak phytotoxicity against sorghum plants. When using the Prima herbicide, it was observed activation of tillering with a slight decrease in the number of panicles. All studied herbicides were characterized by high efficiency against dicotyledonous weeds: Grantox – 78.0–86.2 %, Prima – 75.4–83.1 %, Pik – 80.6–89.3 %. Despite the different phytotoxic effect on plants, grain productivity of grain sorghum increased due to the application of post-emergence herbicides compared to plots with natural weed infestation: Prima – by 0.66–0.92 t/ha, Grantox – by 0.60–0.97 t/ha, Pik – by 1.02–1.40 t/ha . Based on the research, it was found that the application of Pik herbicide in dose of 15–20 g/ha at the 4–5 leaf stage of sorghum was safest for plants and the most effective for the control of dicotyledonous weeds. Key words: grain sorghum, growth and development, weeds, herbicide, yield.