Safflower yields and water use efficiency as affected by irrigation at different soil moisture depletion levels and plant population density under arid conditions

A field experiment was carried out over two years to investigate the effects of an irrigation regime and its interaction with plant density on yield, yield components and water use efficiency (WUE) of safflower Giza 1 cv. The experiment was laid out in randomized complete block design with split plot arrangement with three replications. There were three available soil moisture depletion levels (ASMD) under this study (I-1:50% of ASMD, I-2:65% of ASMD and I-3:80% of ASMD), which were kept in main plots and three plant population densities (D-1: 10, D-2: 20 and D-3: 40 plants m(-2)), which were randomized in sub-plots. Significant interaction effects between irrigation regime and plant population density were detected for seed and oil yields, 1000-seed weight and seed weight plant(-1) as well as WUE. The highest seed and oil yields were found for D2I1. Meanwhile, the highest WUE was found for D2I1 or D2I2. Based on these results, the combination of an irrigation rate of 50% of ASMD at a density of 20 plants m(-2) when irrigation water supplies are sufficient or a rate of 65% of ASMD at the same plant density when irrigation water are limited, are recommended for planting safflower under similar soil and climatic conditions.