Levels of nitrogen and iodosulfuron + mesosulfuron affecting the wheat competitive ability against weeds

The trial was a split plot experiment based on randomized complete block design (RCBD) with four replications in Abadeh, Fars, Iran, during 2010-2011 growing seasons. The treatments were consisted of three levels of nitrogen (200, 300, and 400 kg ha-1) and four herbicide application levels (53, 68, 83, and 97 g ha-1). Interaction effects of N fertilizer×herbicide levels on number spike per m2, number of kernels spike-1, 1000-seed weight, harvest index, seed yield, number of wild oat, number of common mallow and common mallow dry matter weight were significant. The maximum seed yield was related to 300 kg ha-1 N fertilizer with 97 g ha-1 herbicide treatment (3,526 kg ha-1) and the minimum seed yield was belonged to 200 kg ha-1 N fertilizer with 53 g ha-1 herbicide treatment (2,242 kg ha-1). Number of spikes m-2 was the most important trait contributing to the grain yield in wheat. In conclusion, weed control was essential for efficient use of N fertilizer by the crop. Therefore, integration of N fertilization and herbicide is recommended for the region to increase wheat grain yield.