Yield response of bean genotypes to irrigation stress and nitrogen fertilizer levels

Legume crops as human and animal feed are high in protein and have a positive effect on the yield of other crops when grown in rotation with cereals or as cover crops. However, drought can reduce pulse grain yield by 10 to 100 percent. It has been observed that drought stress has different effects on the yield of various genotypes of lentils; additionally, drought stress reduces grain yield in various cultivars of pinto beans and other genotypes of beans. According to reports, nitrogen can effectively mitigate the damaging effects of drought stress on maize. It has also been reported that the application of fertilizer treatments to various chickpea cultivars increases yield. The creation of stress-resistant plant cultivars has always been regarded as an effective method for mitigating the negative effects of stress. Consequently, the purpose of this study was to examine the impact of irrigation stress and varying nitrogen fertilizer levels on yield and yield components of bean genotypes. In 2020, two separate experiments (normal irrigation and low irrigation) were conducted on the research field of the school of Agriculture and Natural Resources at the University of Tehran in order to evaluate the effect of low irrigation stress and different levels of nitrogen fertilizer on bean plant yield and yield components. The experiment was designed with a factorial layout based on a completely randomized block with three replications. The experimental treatments included two levels of irrigation (normal irrigation and 50% normal), five levels of bean genotype (Pak, Dorsa, Goli, Sadri, D81083), and three levels of nitrogen fertilizer (no nitrogen fertilizer, 50% nitrogen fertilizer, and 100% nitrogen fertilizer). SAS 9.4 and Excel 2016 were utilized for data analysis, combined analysis of variance of both experiments, comparison of means, and graphing. Also, Minitab was utilized to examine the homogeneity of error variance. Prior to the combined analysis of variance, the homogeneity of variance of the experiments was examined, and it was determined that the homogeneity of variance of error in none of the experiments (at the one percent level) was rejected. The results of a combined analysis of variance indicated that irrigation stress and bean genotypes had a significant effect on all investigated traits. In addition, the application of different nitrogen fertilizer levels had a significant effect on all traits except harvest index and number of grains per pod. The dual interaction of treatments and the triple interaction of irrigation, nitrogen, and genotype on the number of seeds per pod. A comparison of the means of different levels of irrigation revealed that the values of all yield traits and yield components of beans decreased when low irrigation stress was applied. Significant reduction in grain yield, biological yield, and harvest index percentage under drought stress conditions were 30.5, 23 and 12 percent, respectively, when compared to the fully irrigated treatment, demonstrating the significance of drought stress effects on bean crop yield. The findings of this study indicate that drought stress and nitrogen fertilizer have a significant effect on yield and yield components for all bean genotypes. In such a way that a 30% reduction in grain yield is observed with low irrigation stress. Nevertheless, application of nitrogen fertilizer caused relative resistance of bean genotypes to low irrigation stress, so that using 100% nitrogen fertilizer treatment, the highest grain yield was obtained for white beans (4481 kg / ha), pinto beans Sadri (4373 kg / ha), and red bean (3936 kg / ha), among the five genotypes. In general, the findings of this study indicated that the destructive effects of low irrigation stress or drought on bean grain yield could be mitigated to some extent by selecting suitable bean genotypes and applying appropriate nitrogen fertilizer levels.