Chenges in grain yield and yield components of winter barley in response to nitrogen supply and weed interference

Nutrients management, especially nitrogen, influences the weed-crop competition. Thus, to evaluate the effect of nitrogen and weed interference on yield and yield components of winter barley (Hordeum vulgare L. Var. Makoei), a field experiment was arranged as split-plot based on randomized complete block design with three replications at the Research Farm of the Faculty of Agriculture, University of Tabriz, Iran. The treatments included four levels of nitrogen (0, 40, 60 and 120 kg ha-1) and 10 weed interference periods in two sets (weed free and weed infested periods), that allocated to the main and subplots, respectively. Results indicated that increasing nitrogen supply increased spikes per area, grain and biological yields and decreased grain number per spike. Weed interference had significant effect on number of spike per m2, grain number per spike, and grain and biological yields. Increasing duration of weed interference led to significant decrease of spikes per m2, biological and grain yields of barley. Based on the results of this research, spike number per m2 was the most sensitive yield component of barley to nitrogen deficiency and weeds interference. Generally, by application of nitrogen up to 80 kg ha-1 and better weeds management by reducing duration of weed interference in barely, high performance in this crop can be obtained in similar conditions.