GRAIN YIELD AND BIOMETRIC INDICATORS OF MAIZE HYBRIDS OF DIFFERENT FAO GROUPS UNDER CONSTANT CROPPING AND PROTECTION SYSTEMS AGAINST SEGETAL VEGETATION

Abstract

The purpose of the research is to establish morphometric indicators of maize hybrids of different FAO groups and their relationship with grain yield under different systems of protection against segetal vegetation in constant five-year crops. Field experiments were conducted at the Institute of Climate-Oriented Agriculture of the National Academy of Sciences of Ukraine in the agroecological zone of the Southern Steppe of Ukraine. Field studies were conducted at the Institute of Climate-Oriented Agriculture of the National Academy of Sciences of Ukraine in the agroecological zone of the Southern Steppe of Ukraine (2021–2025, 46°38′24″ N lat. 32°36′52″ E long.). The studies used innovative hybrids of Ukrainian selection (FAO 190-430), which are included in the State Register of Plant Varieties Suitable for Distribution in Ukraine. The studies were conducted under drip surface irrigation with a pre-irrigation soil moisture level in the 0–50 cm layer of 75% RH. To protect plants from segetals, the herbicides Frontier® Optima and Meister® Power were used. In the fifth year of continuous crops without the use of herbicides, the plant height, on average across hybrids, decreased from 256.0 to 220.0 cm. The lateripening hybrids Tronka and Arabat (FAO 380 and 430) responded most to weeding. Their plant height decreased by 40 and 52 cm, respectively, in the fifth year of continuous crops, indicating a corresponding negative impact of segetal plants. The early-ripening hybrids Stepovy and Khotyn responded less to weeding due to the shorter duration of the growing season, which reduced the period of regeneration of soil segetal reserves. The smallest difference in plant height of maize hybrids in the first and fifth year of permanent crops was observed when using the combined action of soil and insurance herbicides, which allows optimizing the growth processes of maize hybrids with such a system of protection against segetal plants. The grain yield of the studied hybrids over a five-year period of permanent crops and various systems of protection against segetals is positively correlated with plant height. The highest correlation coefficients were recorded in hybrids with an extended vegetation period and higher potential yield – Tronka and Arabat (r = 0.87 and 0.89, respectively), which indicates the possibility of preliminary forecasting of grain yield of hybrids by the parameters of plant height and the location of the productive ear. A dual system of protection of maize hybrids from segetals with the use of soil and insurance herbicides in constant crops ensures the preservation of the initial optimal biometric parameters of the genotype and their positive relationship with grain yield.