Phenotypic Traits, Grain Yield and Yield Components of Maize Cultivars Under Combinations of Management Practices in Semi-arid Conditions of Iran

In semi-arid regions, selecting cultivars and planning management practices are critical issues for improving yields and reducing risks of maize cultivation in the short summer cropping season. This study aimed to assess the responses of grain yield (GY) and important phenotypic characteristics of maize cultivars from different maturity groups under various irrigation regimes, planting dates, and nitrogen rates, in a 2-year experiment. According to the clusters identified in the loading plot, stover yield, radiation use efficiency (RUE), height, leaf greenness index, stem weight, and ear size during flowering (VT/R1) were strongly correlated with GY, yield components and harvest index. Based on analysis of variance, more irrigation or N, or their interaction often increased GY, rows ear(-1), grains row(-1) and hundred-grain weight. Late planting decreased GY of KSC704 (late maturity cultivar). KSC260 (early maturity cultivar) had greater flexibility in planting time, required less days for maturity, and had less water consumption. The findings highlight the physiological basis of the relationship between the different phenotypic characteristics and how they affect GY and its components. They were in line with the established theories that higher RUE, biomass and sink activity (e.g. grain weight and numbers, and larger ear size) are associated with better genetic gains to produce high GY. Although the results were not consistent between years, findings suggested the good performance of recently released early maturity cultivars for use during the summer growing season.