Deficit Sprinkler Irrigation of Sunflower and Safflower 1

Increasing competition for water supplies and rising costs of applying water make efficient irrigation increasingly important. Yield and water use of sunflower ( Helianthus annuus L.) and safflower ( Carthanus tinctorius L.) were evaluated on silt loam soil. Deficit irrigation treatments using the line source method were initiated near the time of canopy closure and continued until maturity. Moisture stress on sunflower and safflower caused shortened plant height, early blooming, early maturity, and decreased seed yield. In 1980 sunflower yields ranged from 2.41 to 4.50 Mg ha −1 for 2.5 to 35.0 cm irrigation. In 1981 sunflower yields ranged from 1.56 to 3.37 Mg ha −1 for 2.5 to 45.0 cm irrigation. Safflower yields in 1981 ranged from 1.84 to 5.15 Mg ha −1 for the same irrigation rates. In 1981, sunflower and safflower received the same total amount of water to produce maximum seed yield. Increased irrigation water results in increased yield for both sunflower and safflower; however, yield per unit applied water decreases with increased irrigation rates so that at some point, the expected increase in yield would not cover the cost of additional water application. Increased irrigation increased oil concentration of sunflower except for cv. 894 in 1980. Oil concentration of safflower did not respond to increased irrigation rates. It was concluded that limiting irrigation on sunflower and safflower to ≤ 30 cm permits utilization of residual soil water on silt loam soil with consequent savings in irrigation water supplies and costs of application. Soil moisture is then recharged by winter rainfall.