Introduction: Drought is one of the major limiting factors in crop production worldwide. The drought stress effects on growth yield and yield components of corn depend on the time of stress happening, development stage, plant genotype, cultivars, plant cultivation method, soil quality and changes in environmental conditions during growth season. Much difference in response of corn cultivars to drought stress has been reported; but there is a little information regarding drought stress effect on yield and yield component of different cultivars at late planting condition. So, this study was set up to determine the effects of drought stress on yield and yield component of different corn cultivars at late planting condition.
Materials and Methods: This experiment was carried out as a split plot design based on randomized complete block design with three replications in 2014-2015. The main factor was drought stress time (omitted irrigation at 4-6 leaves stage, omitted irrigation at pollination stage and grain filling stage) and cultivars were considered as the sub plot (Simon, B.C., Maxima and KSC704). In final season of growth 5 plants were selected randomly and evaluated in terms of plant height, ear number, row number per kernel and seed per kernel. Also, economic yield and biological yield were determined after considering marginal effect.
Results: Analysis of variance showed that plant height, seed per kernel, seed 1000 weight, biological yield and economic yield was affected by drought stress. The cultivar effect on plant height, ear number, row number per kernel and seed number per row, biological yield and economic yield was significant. All traits respond to stress time × cultivar interaction except plant height. Drought stress at seed filling had the highest plant height (196 cm); whereas plant height significantly was decreased (10.42%) by drought stress at vegetative stage. Simon had the highest height (206 cm) and Maxima had the least height (175 cm) in cultivars. KSC704 cultivar had the highest ear number per plant (1.05), row number per kernel (47.33), seed 1000 weigh (194 g), economic yield (12.83 t/ha) and biological yield (67.99 t/ha) in drought stress at vegetative or seed filling stage. Simon cultivar s showed more sensitivity to drought stress at seed filling stage in terms of economic yield with minimum production (4.90 t/ha); whereas B.C. cultivar had the minimum economic yield from drought stress at vegetative time (6.12 t/ha).
Conclusion: Overall, the results showed different cultivars response to water stress time is different in late planting; while drought stress les to increased yield in Maxima and B.C. cultivars, Simon and KSC704 cultivars yield were decreased in delayed planting. Simon showed the maximum sensitivity to drought stress especially when drought stress happened in seed filing stage. KSC 704 cultivar was more stable in the late planting date in cultivars. Therefore, apparently drought stress at vegetative stag in late planting date had more negative effect than other stage and remobilization might be a little effective in decreasing the effect of drought stress.
Keywords: Corn cultivars, Drought stress, Planting date, Yield reduction