Abstract
Available irrigation water is the main limiting factor for crop production in Saudi Arabia. Nowadays increasing human population is resulting in ever increasing water demands, which cannot be accommodated by continually developing large-scale water desalination projects. In such cases irrigation techniques adapted to conserve crop water use are a must in order to face water shortages under local conditions. Drip irrigation potentially provides the opportunity for more efficient water use and thus the objectives of this study were to investigate the effects of subsurface drip irrigation on safflower crop growth, oil yield and water use efficiency. Subsurface trickle irrigation was applied at 0, 0.15, 0.25, 0.35 and 0.45 m depths in amount calculated using tensiometer readings.
Leaf area index (LAI) was influenced more by the season than by the depth of emitters. Mean LAI during seed filling reached 3.1 and was 8% greater in 0.25m depth than in surface trickle irrigation. There were higher seed and oil yields in the 0.25 and 0.35m treatments than in others. For 0, 0.15 and 0.45 treatments the yields were significantly the same. The water use efficiency (WUE) was calculated as the ratio between oil yield and total water received by the crop. The WUE of safflower was 22% high under 0.25 treatment (2.67 kg/ha/mm) than under 0 treatment (2.19 kg/ha/mm). Emitter depths of trickle irrigation did not significantly influence the depth or distribution of safflower roots.