Effects of water deficit stress and potassium on yield and water use efficiency of potato by line source sprinkler irrigation

In order to study the effect of water deficit and potassium fertilizer on the yield and water use efficiency (economic and biologic) a split block experiment based on RCBD was conducted with three replications using line-source sprinkler irrigation in Khorasan Razavi Agricultural and Natural Resources Research Center. Potassium levels including 0, 90, 180, and 270 kg K2O ha-1 were considered as main plots. Water deficit levels including 0.75m (control), 3.75m (very light), 6.75m (light), 9.75m (severe deficit), and 12.75m (very severe deficit) from the line source were considered as sub plots. These factors were investigated in a special line-source statistical design with three replications (in right and left of line-source), so that the right or left direction of the line source was assigned as the sub-sub plots. Results showed increased tuber yield and biological yield of potato through application of potassium, whereas increasing the distance from the line source decreased these traits. Under very severe stress conditions (12.75m from the line source), the tuber yield was 80% and 62.67% lower than the control at the first and second year of the study, respectively. The highest economical water use efficiency (EWUE), biological water use efficiency (BWUE) and tuber yield resulted from 270 kg K2O ha-1. Interaction effects of potassium and water amounts on yield, EWUE and BWUE were significant in the second year. The greatest yield was obtained from 270 kg K2O ha-1 and control treatment (sufficient water) and the highest BWUE was observed using 270 kg K2O ha-1 and severe deficit.