wheat yield response to the competition stress and different levels of nitrogen

optimum management of intra- and interspecific competitions are key subject in most agroecosystems. the objective of this experiment was the study effect of intra- and interspecific competitions and n rates on yield and yield components of wheat which was carried out in agricultural faculty of shahid chamran university of ahvaz during 2011-2012. the experimental design was split–plot based on rbcd with 3 replications. the main plots including 4 n rates (i.e. 0, 50, 100 and 150 kg n ha-1) and sub-plots including 4 different competition pattern: (i.e. without competition, intraspecific competition, interspecific competition and intra- and interspecific competition). our results showed that both nitrogen and competition pattern had significant effect on quantity and quality of wheat yield. the highest grain yield was obtained in no competition and application of 100 or 150 kg n ha-1 (i.e. n100d1w0 and n150d1w0). grain yield reduced by increasing in competition intensity. the lowest grain yield was obtained in n0 treatments. in addition, the highest protein percent was obtained in the highest nitrogen application rate, but it is reduced by increase in competition intensity. moreover, in lower n levels, interspecific competition had the highest negative effect on wheat crop yield. but, at the highest n level, intraspecific competition had the same effect on wheat crop yield.