Effect of Deficit Irrigation and Humic Acid on Yield and Water Use Efficiency in Common Bean

Water scarcity is one of the most important environmental factors limiting crop production. Consumption of natural fertilizers can make optimal use of water in irrigation. The aim of this study was to investigate the effect of deficit irrigation and humic acid on yield and water use efficiency in common bean. The experiment was conducted in split plots based on randomized complete block design, with three replications in Guilan province, in 2016. The main factor was irrigation at three levels (rainfed, 50%, and 100% water requirement) and the sub factor included humic acid spraying at four levels (0, 2, 4, and 6 L.ha-1). In irrigation treatments, highest average seed yield (2610 kg.ha-1) was obtained in full irrigation conditions (100% water requirement). In the humic acid spraying applications, maximum seed yield was observed at 6 L.ha-1 with average of 2661 kg.ha-1. In interaction of irrigation and humic acid, the highest seed yield was obtained in full irrigation and 6 L ha-1 humic acid with an average of 3547 kg.ha-1. The highest seed yield (3030 kg.ha-1) was obtained in 50% water requirement and 6 L.ha-1 humic acid. The highest seed yield in rainfed conditions was obtained at 4 and 6 L.ha-1 of humic acid, with an average of 1461 and 1406 kg.ha-1, respectively. In different irrigation treatments, the highest water use efficiency was obtained with the mean of 1.78 kg.m-3 in rainfed treatment. The humic acid treatments had a positive effect on water use efficiency in comparison with the non-humic acid treatments, but there was no significant difference between treatments 2, 4, and 6 L.ha-1. Altogether, the results of this study indicate the beneficial effects of humic acid on water deficit stress in common bean cultivation in the study area.