Maize grain is an important source of human and animal feed, and its quality can be affected by management practices and climatic conditions. This study aimed to evaluate the concentration and composition of starch, protein and oil in grain of maize cultivars in response to different planting dates (20 June and 21 July), irrigation (12-day and 6-day intervals) and nitrogen rates (0 and 184 kg N ha−1). The first two principal components (PCs) accounted for 84.5% of the total variation. High N fertilization increased protein (by 6.0 and 10.9 g kg−1) and total nonessential amino acids (by 3.4 and 2.4 g kg−1) during 2018 and 2019, respectively. With the high irrigation rate, the high N rate increased oil, total unsaturated fatty acids, and starch and amylopectin, whereas with the low irrigation rate, there was no effect of the N rate. With earlier planting, total saturated fatty acids were higher. The findings highlight the complicated relationship between the different factors and how they affect quality characteristics of maize grain. There was a large impact of year, which to a great extent cannot be controlled, even in this environment where water supply was controlled and rainfall did not affect the results.

In order to study the effect of drought stress on morphophysiologic characteristics, yield and yield components of 8 new hybrids of corn (Zea maize L.) and KSC704 commercial hybrid as control resistant to drought and warm (which were bred and screened in Khozestan province condition), an experiment was conducted in a Randomized Complete Block Design (RCBD) with three replications under drought stress and normal irrigation at Khorasan-Razavi Agriculture Research Center, Mashhad, Iran on June 10, 2011. The results of analyze variance showed that under normal irrigation and drought condition, there was a significant difference (p<0.01) between the hybrids. Mean comparison of hybrids revealed that in normal irrigation H6 and in drought stress H8 hybrid had the maximum grain yield (12.85 and 6.75 ton/ha, respectively). Based on the grain yields of studied hybrids, stress tolerance index (STI), stress susceptibility index (SSI), tolerance index (TOI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM) and golden mean (GM) were estimated. Results showed that among drought tolerance indices, MP, GMP, STI and HM were the best indices for corn and KSC704 hybrid and H4 had the highest tolerance to drought in Mashhad weather condition.

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