EFFECT OF IRRIGATION INTERVALS ON YIELD AND WATER-USE EFFICIENCY OF SUNFLOWER (HELIANTHUS-ANNUUS L) IN AL-AHSA, SAUDI-ARABIA

Effect of interval of irrigation on yield, yield components, and water use efficiency of sunflower (Helianthus annuus L.) was studied on a sandy-clay-loam soil under field conditions in 1986/87 and 1987/88 crop seasons. Mean values for different plant growth parameters were 1.72, 1.70, and 1.57 m (maximum plant height); 5.22, 4.82, and 4.12 tons ha-1 (dry matter); 3.11, 3.05, and 2.37 tons ha-1 (see yield); 10.09, 9.32, and 8.32 g (100-seed weight); and 0.89, 0.75, and 0.66 (seed/head weight ratio) for I-1 (40% depletion of available water), I-2 (60% depletion of available water), and I-3 (80% depletion of available water) treatments, respectively, for 1986/87 crop season. Mean values of different plant growth parameters were 1.85, 1.76, and 1.59 m (maximum plant height); 5.88, 5.15, and 4.38 tons ha-1 (dry matter); 3.48, 3.20, and 2.32 tons ha-1 (see yield); 10.38, 9.40, and 8.27 g (100 seed weight); and 0.91, 0.78, and 0.69 (seed/head weight ratio) for I-1 (40% depletion of available water), I-2 (60% depletion of available water), and I-3 (80% depletion of available water) treatments, respectively, for 1987-88 crop season. Mean values for water use efficiency were 5.19, 5.09, and 3.95 (kg seed ha-1 mm-1) for 1986/87 crop season and 5.79, 5.33, and 3.87 (kg seed ha-1 mm-1) for 1987/88 crop season corresponding to I-1 (40% depletion of available water), I-2 (60% depletion of available water), and I-3 (80% depletion of available water) treatments, respectively. The results obtained strongly suggest that an irrigation interval of 10 days, equivalent to 60% depletion of available water, is optimum for reasonable sunflower production in Al-Ahsa, Saudi Arabia.