Effect of humic acid on grain yield and yield components in chickpea under different irrigation levels

In order to investigate the effect of soil application of humic acid on grain yield and yield components in chickpea (Cicer arietinum L.), an experiment was conducted as factorial based on randomized complete block design with three replications in 2016 and 2017. Factors were irrigation at two levels of full irrigation and drought stress (20% of full irrigation from flowering to harvesting) and humic acid at four levels of 0, 2.5, 5 and 7.5 mg per pot. The results showed that drought stress reduced dry weight of leaf, number of grains and pods, total dry weight and grain yield. Application of humic acid in two years increased the value of all studied traits under full irrigation. In the first year, application of 2.5 and 5 mg humic acid increased 1000-grain weight, and total and leaf dry weight under drought stress conditions, respectively. In the second year, with higher consumption of humic acid, grain yield, total dry weight and harvest index increased significantly under drought stress conditions. Application of 7.5 mg humic acid in the second year, produced the highest proline under optimum irrigation (393.10 mg kg-1 DW) and drought stress (507.90 mg kg-1 DW) conditions.