Nitrogen Use Efficiency Assessment under Intra- and Inter-Specific Competitions Stress

Improving nitrogen use efficiency (NUE) is an important objective of the agroecosystem management. A field experiment was conducted to study the effect of different competition patterns on nitrogen balance in the wheat agroecosystem. Experimental design was split–plot based on randomized complete blocks with four replications. The main plots consisted of different nitrogen rates (i.e. 0, 50, 100, 150 kg N ha-1) and sub-plots consisted of four different competitiveness patterns including: no competition, intraspecific competition, interspecific competition and intra- and inter-specific competitions. Our results showed that NUE decreased with increasing N level, especially under higher N rates. N uptakeefficiency (NUPE), N harvest index (NHI), N remobilization efficiency (NRE), N harvest efficiency (NHE) and N fertilizer utilization efficiency (NFUE) were lowest in the intra- and inter-specific competition treatments than others. The differences between each intra-and inter-specific competition treatments were not significant for NUPE, N balance index (NBI), NHI, NRE and NHE. 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 and crop N use efficiency. This strategy increased NUE, N utilization efficiency and N reliance index (NRI). Moreover, higher intraspecific competition in most cases reduced NUPE, NBI and NHE but, had no significant effect on NHI, NRIand NFUE.