Effects of supplemental irrigation time and nitrogen rates on yield and agronomic characteristics of dryland wheat (Triticum aestivum L.) Kohdasht variety

This study carried out to investigate the effect of supplemental irrigation and nitrogen application times on seed yield and agronomic characteristics of dryland wheat (Triticum aestivum L.) Kohdasht variety in Gachsaran dryland agricultural research station. For this purpose, the irrigation times in main plots (Rainfed, Planting, Flowering, Planting Flowering with rates of 50mm) and different nitrogen rates (0, 30, 60, 90 and 120 kg.h-1) in sub plots were studied based on RCBD split plot design for three consecutive years, during 2009-12 seasons. According to the results, the relationship between the amount of applied nitrogen and seed yield following the quadratic regression equation and average requirement of nitrogen for Kohdasht variety wheat was determined 80 kg.h-1 to achieve 95 percent of maximum seed yield. This value change of nitrogen, could explain 86 percent of variation in grain yield (R2=0.86). Also among supplemental irrigation treatments, the amount of 50 mm irrigation at wheat flowering stage compared to rainfed (non-irrigated), increased grain yield by 43 percent. Finally, according to the findings of this study, it is necessarily recommended to apply 80 kg.h-1 nitrogen in combination with supplemental irrigation at wheat flowering stage, to improve and increase yield.