Amir Aynehband, Sara Asadi and Afrasyab Rahnama
A field experiment was conducted to study the effect of different competition patterns on nitrogen balance in wheat agroecosystem. Experimental design was split–plot based on randomized complete block with four replications. The main plots consisted of different nitrogen rates (i.e. 0, 50, 100 and 150 kg N ha-1) and sub-plots consisted of the four different competitiveness patterns including: no competition, intraspecific competition, interspecific competition and intra- and interspecific competition. Our results showed that wheat grain yield had no significant increase when N application rates exceeded 50 kg ha-1 (in spite of improved with increasing N rates). All nitrogen use efficiencies diminished as N fertilizer rates increased (except N reliance index), with significant difference among competition types. In addition, NPE and APE were lowest in the intra- and interspecific competition treatment than others. The differences between each intra and interspecific competition treatments were not significant for NPE, APE and NAE. We suggested that greatly increased suppression of weeds through increased crop density for reducing the use of herbicide can play an important role in a change in both crop yield (reduced) and crop N use efficiencies.
