Effects of irrigation cuting off at different growth stages and nitrogen fertilizer levels on pinto bean (Phaseolus vulgaris L.) yield

Drought stress due to water scarcity is one of the most important factors reducing bean yield. To investigate the effect of irrigation cuting off and nitrogen fertilizer on the yield of pinto bean, a split-plot design was used in a randomized complete block design with four replications in the research farm of Agricultural and Natural Resources Campus of University of Tehran, Karaj, in 2018. The experimental treatments were irrigation at four levels: full irrigation (control), irrigation cut off at vegetative stage (V4), irrigation cut off at flowering stage (R1) and irrigation cut off in grain filling stage (R5) in main plots and nitrogen fertilizer application at three levels: without fertilizer, 70 kg and 140 kg of nitrogen per hectare in sub plots. Results showed that irrigation treatments significantly reduced plant height, pod / plant number, grain / pod, 100-seed weight, grain yield and harvest index. Nitrogen fertilizer application had significant effect on all traits except number of pods per pod. The average reduction in pinto bean yield was 12% at vegetative growth stage (V4), 17% at flowering stage (R1) and 49% at irrigation stage (R5). The highest increase in bean yield was 17%, observed in 70 kg N ha-1 and 9% obtained from 140 kg N ha1 compared to no fertilizer application. Therefore, it is recommended that 70 kg N ha-1 can reduce damages to pinto bean seed yield caused by irrigation cuting off in Karaj & similar regions climate conditions.