Effect of intercropping replacement ratios of maize (Zea mays L.) and bean (Phaseolus vulgaris L.) on yield and nitrogen use efficiency indices

To evaluate nitrogen use efficiency in intercropping replacement ratios of maize and bean, an experiment was conducted during two successive cropping years of 2014-2015 and 2015-2016 at Agricultural Research Station, Ferdowsi University of Mashhad, Mashhad, Iran. Experimental factors were arranged as split plots in randomized complete block design with three replications. The main plots consisted of sole culture of maize and bean, row intercropping with ratios of 50%:50%, 67%:33% (2 rows of maize: 1 row of bean) and 33%: 67% (1 row of maize: 2 rows of bean). Application and no-application of nitrogen (N) fertilizer (55 kg.ha-1) were assigned to sub plots. The results showed that different ratios of maize and bean intercroppings and application of nitrogen fertilizer had significant effects on grain yield and biomass as well as nitrogen use efficiency indices (such as uptake, utilization and productivity). Maximum grain yield and biomass of bean (3462.1 and 10124.5 kg.ha-1 respectively) and maize (5974.1 and 18321 kg.ha-1, respectively) were obtained from sole cropping of bean and maize. In both crops, N utilization efficiency was higher in all treatments when nitrogen productivity was calculated using grain yield. In nitrogen application treatment, the row intercropping ratio of 50:50 of bean and maize had higher nitrogen uptake efficiency for both crops. Also, the ratio of planting 1 maize: 1 bean (50% maize: 50% bean) had the highest total land equivalent ratio (1.10) using grain yield, nitrogen uptake efficiency (2.30) and nitrogen productivity efficiency (using grain yield (1.98) and biological yield (2.02)). Therefore, it can be concluded that the use of maize and bean row intercropping is an environmental friendly cfrop management pratctice to reduce nitrogen losses and improve its uptake efficiency, and to prevent the excessive use of chemical fertilizers and improve the productivity of these inputs in agroecosystems.