Photosynthetic activity of sugar sorghum under weed infestation of sowings as affected by the components of cultivation technology in Ukraine

Abstract

To reveal the peculiarities of the photosynthetic activity and formation of sugar sorghum agrophytocenosis productivity with different row spacing and plant density, application of plant growth stimulator Vympel 2 and the intensity of weed infestation of sowings in the Forest-Steppe of Ukraine. Methods. The study investigated hybrids ‘Dovista’ and ‘Huliver’ with a row spacing of 45 and 70 cm and plant density of 150,000, 200,000 and 250,000 plants/ha. Growth stimulator Vympel 2 (0.5 L/t) was used in pre-sowing seed treatment. The same growth stimulator was used as a foliar application in the tillering stage at the application rate of 0.5 L/ha. Results. The summative content of chlorophylls a and b in the leaves of ‘Dovista’ at the stage of tasseling with using growth stimulator was 9.3 mg/kg of dry matter and in ‘Hulliver’ 9.5 mg/kg of dry matter. The increase in the content of chlorophylls compared to the control treatments was 0.30 and 0.60 %, respectively. A plant density of 250,000 plants/ha and a row spacing of 45 cm contributed to the optimal photo responsibility of sugar sorghum agrophytocenosis and the minimum intensity of weed infestation. The latter made up 13.3 plants/m2, with a formation of vegetative mass of 112.0 g/m2 and dry mass of 37.4 g/m2 in ‘Dovista’ and 13.4 plants/m2 119.0 g/m2 and 39.5 g/m2 in ‘Huliver’, respectively. Seed treatment with Vympel 2 and its use for foliar dressing was effective for the phytocenotic restriction of weed growth and development. The study has shown that ‘Dovista’ hybrid has significant productivity potential due to a longer vegetation period. With varying row spacing and plant density, ‘Dovista’ yield exceeded ‘Huliver’ by 3.6 t/ha on the average of the experiment. Seed treatment with Vympel 2 (0.5 L/t) + foliar dressing in the tillering stage (0.5 L/ha) at a row spacing of 45 cm and increased plant density from 150,000 to 250,000 plants/ha ensured a yield increase from 7.3 to 13.0 t/ha. Similar treatments at a row spacing of 70 cm ensured yield values higher by 6.7–12.6 t/ha than in control treatments. Conclusions. Hybrid ‘Dovista’ ensured the highest yield of green biomass at a plant density of 250,000 plants per hectare and seed treatment with growth stimulator Vympel 2 (0.5 L/t) + foliar dressing in the tillering stage (0.5 L/ha) amounting to 98.8 t/ha, which was 5.3 t/ha higher than ‘Huliver’ with row spacing of 45 cm. The maximum FAR efficiency was obtained by growing sorghum sugar plants with a plant density of 250,000 plants per hectare, row spacing of 45 cm, and application of growth stimulator Vympel 2. It made up 5.2 % in ‘Dovista’ and 4.7 % in ‘Huliver’. It was found that using growth stimulator Vympel 2 together with a row spacing of 45 cm and plant density of 250,000 plants per hectare appeared the most effective limiting factor of the reoccurring weed infestation of the sowings. The highest energy yield, 457.35 GJ/ha in ‘Dovista’ and 467.82 GJ/ha in ‘Huliver’ was obtained at the row spacing of 45 cm with the increased plant density of 250,000 plants per hectare and seed treatment with growth stimulator Vympel 2 (0.5 L/t) + foliar dressing in the tillering stage (0.5 L/ha).