Late sowing and nitrogen application to optimize canopy structure and grain yield of bread wheat in a fluctuating climate

Adjustment of sowing date and nitrogen (N) use help alleviate farmland contradiction under fluctuating climate in Jianghuai region of China. In this study, two wheat varieties were used to study the interactive effect between two sowing dates and two basal to topdressing ratios of N fertilizer, each treatment of eight combinations arranged in Randomized Complete Block Design (RCBD) with three replications was conducted in two consecutive growth seasons of bread wheat. As results of two years of investigation, wheat plants with an excessively delayed sowing date showed a significant reduction in flag leaf angle, flag leaf area, main stem spike length and photosynthesis rate, yet a increased basic seedling number and transpiration rate, which corresponded to a notable loss in thousand kernel weight and grain yield. An increase in the proportion of topdressed N led to an increase in flag leaf angle and leaf area index, and a lower spike number per unit and thousand kernel weight, to indicate a loss of grain yield. These findings suggest that excessively delayed sowing date and high N topdressing ratios severely affected the canopy structure and thousand kernel weight of bread wheat, and subsequently reduced grain yield. Based on membership function analysis, a sowing date of 25 October coupled with the N topdressing ratio of 7:3 (the basal to topdressing ratios of N fertilizer) was the ideal combination to optimize the wheat industry in Jianghuai region of China.