Effectiveness of cyclic irrigation on yield, yield components and water productivity.

The efficiency of cyclic irrigation (CI) (using river water (RW) and drainage water (DW)) was investigated and compared with normal irrigation (NI) (using only RW). A 24 × 30 m research area was selected and divided into three plots – A (maize), B (soybean) and C (sunflower). Plot A was designed to produce DW for the irrigation of plots B and C. In plot B, a split-plot design was applied with randomised complete blocks with two treatments: irrigation type and rate of urea fertiliser application. The experimental design of plot C was similar to that of plot B except for the rate of fertiliser application. Analysis of variance (Anova) results for soybean revealed that the interaction between irrigation type and urea level had significant effects on growth yield and biological water productivity (WP) (P < 0.01) and fresh leaf weight (P < 0.05). The Anova results for sunflower showed that the interaction between irrigation type and urea level had significant effects on 100-seed weight, seed yield and seed WP (P < 0.05). The highest increase in WP for sunflower was for forage WP (0.768 kg/m3 for NI and 2.603 kg/m3 for CI). The WP of RW for total forage, total seed and total biological yields for CI compared with NI increased by 76.67%, 72.95% and 75.45%, respectively. The lowest increase in WP was for sunflower seed yield (0.276 kg/m3 for NI and 0.821 kg/m3 for CI). Overall, the data showed that, compared with NI, CI led to water savings of 45.59% and increased WP. [ABSTRACT FROM AUTHOR]