PHOTOSYNTHETIC INDICATORS OF CORN HYBRIDS DEPENDING ON SOWING DATES AND PLANT PROTECTION SYSTEMS UNDER IRRIGATION CONDITIONS

Abstract

The purpose – to investigate the influence of sowing dates and plant protection on the photosynthetic performance of corn hybrid crops under irrigation conditions. Research methods and materials. Field experiments were conducted during 2017–2019 at the experimental field of the Institute of Irrigated Agriculture of the National Academy of Sciences. The methodological basis of this research is: empirical (field experiments and observations; measurement of indicators of the research object; comparison of the impact of elements of agricultural technologies), theoretical (proposing a hypothesis and forming conclusions based on the results of research; statistical; mathematical. The results. The maximum value (at the level of 52.9 thousand m2/ha) of the assimilation surface area was reached by growing the Tronka corn hybrid in the first sowing period – April 25 and by observing chemical plant protection. A decrease in the photosynthetic rate by 1.4 times (up to 38.2 thousand m2/ha) was manifested during the cultivation of the Skadovsky hybrid, which was sown on May 15 (the third sowing period) and biological plant protection was observed. The sowing of both researched hybrids in the first season provided the largest assimilation surface area of corn crops. The first term (25.04) was the best, during which the leaf area increased to 48.6 thousand m2/ha, during the second (05.05) and third (15.05) terms it decreased by 5.9 and 13.6%. Sowing dates had an impact on the "net productivity of photosynthesis" indicator. Thus, the maximum level of this indicator was during the first sowing period – April 25, when it was equal, on average, by a factor of 7.5 g/m2 per day. During the second sowing period (May 5) there was a decrease by 8.7% (to 6.9 g/m2 per day), and during the third period (May 15), even more significantly – by 22.9% (to 6.1 g/m2 per day). The photosynthetic potential of crops varied widely – from a minimum value of 1.67 million m2/ha × days – in the Skadovsky hybrid during the third sowing period (May 15) and without plant protection to 2.27 million m2/ha × days – in the variant with hybrid Tronka, which was sown in the first period (April 25) and chemical protection of plants against harmful organisms was observed. Therefore, the difference between these opposite indicators was 36.5%. Maximum photosynthetic productivity was ensured by chemical protection of plants. In this option, the photosynthetic potential of crops had the highest average factorial value – 2.09 million m2/ha × days, which was 16.4% more than the control, and 5.9% more than the option with biological protection, respectively. Conclusions. Sowing Skadovskyi and Tronka hybrids in the first season provided the largest assimilation surface area of corn crops. On average, according to factor B, the Skadovskyi hybrid had a leaf area of 46.5 thousand m2/ha during sowing on April 25 (the first season), which was 5.6 and 16.9% more than in the second and third seasons of sowing, respectively. An identical result was obtained in relation to the Tronk hybrid. The first term (April 25) was the best, during which the leaf area increased to 48.6 thousand m2/ha. During the second (05.05) and third (15.05) terms, it decreased by 5.9 and 13.6%. The net productivity of photosynthesis in the Tronka hybrid was 7.3 g/m2 on average in the first half of the growing season, which was 7.4% higher than that of the Skadovsky hybrid, which was 6.8 g/m2. With the use of the biological protection system, the net productivity of photosynthesis increased by 15.2%, and with chemical protection – by 20.3%. The photosynthetic potential of crops varied widely – from 1.67 million m2/ha × days – in the Skadovsky hybrid for sowing on May 15 and without plant protection to 2.27 million m2/ha × days – for the Tronka hybrid for sowing on April 25 and adherence to chemical protection. A one-vector significant influence of sowing dates and plant protection agents on photosynthetic indicators of innovative hybrids of different FAO groups under irrigation conditions was established.