Salinity effects on four sunflower hybrids

Sunflower (Helianthus annuus L.) is becoming an increasingly important source of edible vegetable oil throughout the world because of its high polyunsaturated fatty acid content and no cholesterol. The increasing demand for this oil may promote increased hectarage of sunflower in the western USA, where some soils are saline or have the potential to become so, Since there is little information concerning the response of sunflower grown under saline conditions, a 2-yr field plot study was conducted, Six salinity treatments were imposed on a Holtville silty clay (clayey over loamy, montmorillonitic [calcareous], hyperthermic Typic Torrifluvent) by irrigating with Colorado River water artificially salinized with NaCl and CaCl2 (1:1 by weight), Electrical conductivities of the irrigation waters both years were 1.4 (control), 2.0, 3.4, 4.4, 6.0, and 8.0 dS m(-1). Seed yield and oil content of the seed were measured. Relative seed yield of four hybrids was unaffected by soil salinity up to 48 dS m(-1) (electrical conductivity of the saturation extract, EC(e)). Each unit increase in salinity above 48 dS m(-1) reduced yield by 5.0%. These results indicate that sunflower is appropriately classified as moderately tolerant to salinity. Yield reduction was attributed primarily to a reduction in seeds per head. Oil concentration in the seed was relatively unaffected by increased soil salinity up to 10.2 dS m(-1). Sunflower appears to be well adapted for growth under moderately saline soil conditions.