Determination of optimum irrigation and effect of deficit irrigation strategies on yield and disease rate of peanut irrigated with drip system in Eastern Mediterranean

This study aimed at examining the effects of different irrigation regimes (amount and frequency) on yield, water use, water productivity (WP), irrigation water productivity (IWP) and disease rate of drip irrigated peanut (Arachis hypogaea) during the 2014 and 2015 seasons in the Eastern Mediterranean region of Turkey. The treatments consisted of combinations of 3 irrigation frequencies (IF) (IF1: 25 mm; IF2: 50 mm; IF3: 75 mm of cumulative pan evaporation (CPE)), and 7 irrigation water levels (WL1 = 0.50, WL2 = 0.75, WL3 = 1.00 and WL4 = 1.25). WL1, WL2, WL3 and WL4 treatments received 50, 75, 100 and 125 of CPE. In addition, partial root drying (PRD) treatments WL5 = PRD50, WL6 = PRD75 and WL7 = PRD100 treatments were considered. They received 50, 75 and 100% of WL3 treatment from alternate laterals, respectively These 21 treatment combinations were arranged and analysed in a split-plot design with 4 replications. The main plots and subplots were established to irrigation frequencies (IF1, IF2 and IF3) and levels (WL1, WL2, WL3, WL4, WL5, WL6 and WL7). Both IF and WL were observed to have significantly influenced peanut yields at 1% level. In each of the experimental years, the largest and the smallest average peanut yields were acquired from the IF2WL4 and IF3WL1 treatments, respectively. Results indicated that peanut crops under PRD produced higher than those under deficit irrigation upon usage of the same volume of water amount. Significant linear relationships between irrigation - yield and evapotranspiration - yield were obtained during different irrigation frequencies in each season. The yield response factor (ky) was 0.58-0.65 in IF1, 0.65-0.70 in IF2 and 0.90-0.91 in IF3 plots in both years. Water stress raised the disease emergence in peanut markedly in the experimental years. The WP and IWP of PRD peanut were significantly greater than full irrigation and deficit irrigation (DI) treatments in both growing seasons, which demonstrated that limiting water did not reduce WP values. We conclude that DI treatments resulted in importantly lower WP (p <= 0.05) than PRD treatments in both years in spite of applying the same volume of water.