The effectiveness of cyclic irrigation (by normal and drainage water) in yield, yield components, and water productivity of maize, soybean, and sunflower

This study evaluated the efficiency of normal and drainage water for cyclic irrigation at a research farm at Shahid Chamran University of Ahvaz from 2019 to 2020. To this end, a 24×30 m farm (was selected and divided into 3 plots (A, B, and C). Corn, soybean, and sunflower were cultivated in plots A, B, and C, respectively, and drainage water was used for irrigation of the next plots (B and C). In plot B, a split-plot design was applied with randomized complete blocks with two treatments: irrigation type (Karun River water and drainage water) and urea fertilizer (100%, 75%, and 50% application) (with three replicates). The experiment design in plot C was similar to that of plot B except for 75% urea fertilizer. ANOVA results for soybean revealed that the interaction between irrigation type and urea levels had significant effects on growth yield and biological water productivity (P<0.01) and fresh leaf weight (P<0.05). ANOVA results for sunflower showed that the interaction between irrigation type and urea levels had significant effects on 100-seed weight, seed yield, and seed water productivity (P<0.05). The highest increase in productivity of the cyclic irrigation system for plot C was related to forage water productivity which increased from 0.768 to 2.603 kg.m−3. The water productivity of Karun River water in the total forage yield, total seed, and total biological yield for the cyclic irrigation system compared to conventional irrigation increased by 76.67%, 72.95%, and 75.45%, respectively. The lowest increase in water productivity from 0.276 to 0.821 (kg.m−3) was related to sunflower seed yield which was 2.97 times higher than conventional irrigation in the cyclic irrigation system. Overall, the data showed that compared to normal irrigation, cyclic irrigation with drainage water saved water and increased water productivity by 45.59% and 100%, respectively.