Photosynthetic productivity of sorghum (Sorghum bicolor L. (Moenh) in the conditions of the Right-Bank Forest-Steppe of Ukraine

Sorghum (Sorghum bicolor L. (Moenh) is a technical, food, and fodder crop and can be used for various purposes, given its value, the acreage should be substantially expanded in Ukraine, and the elements of cultivation technology should be thoroughly examined. The purpose of the study was to determine the effect of the growth regulator on the photosynthetic productivity of sorghum in the conditions of the Right-Bank Forest-Steppe of Ukraine. The following methods were used in the study: field, measuring and weighing, mathematical, and statistical. The study was conducted in conditions of unstable moisture in the Right-Bank Forest-Steppe of Ukraine in 2016-2019. Based on the results of the study, it was determined that the use of a plant growth regulator affected photosynthetic productivity, namely, the leaf surface area, photosynthetic potential and net photosynthesis productivity. The indicators for the content of chlorophylls changed. Thus, the assimilation area of leaves reached a maximum with seed treatment and spraying of crops and amounted to 8.56 thousand m2 /ha during the tillering period, during the period of stem elongation – 29.6 thousand m2 /ha, during flowering and full ripeness – 40.32 and 4.97 thousand m2 /ha. Net photosynthetic productivity in the control was the lowest – 4.67 g/m2 , the use of a growth regulator on seeds and crops contributed to its increase by 0.27 and 0.79 g/m2 . With the treatment of seeds and crops, the net photosynthetic productivity was the highest and amounted to 6.12 g/m2 . The sum of chlorophylls a+b had the highest rates during the tasselling period and, depending on the experiment options, ranged from 4.36 to 5.35. The yield of grain and biomass also varied depending on the use of the preparation, and was the highest in the version with seed treatment and spraying of crops (7.1 and 35.9 t/ha). The close relationship between photosynthetic productivity and the yield of sorghum is also determined. The study can contribute to the widespread use of growth regulators in sorghum crops, ensure the full development of plants, and increase grain yields and biomass