Optimizing sulfur for improving salt tolerance of sunflower (Helianthus annuus L.)

Soil salinization limit crop yield and deteriorate product quality in arid and semi-arid agroecological regions. Under such conditions regulation of mineral nutrients may help to sustain crop productivity. Therefore, a pot experiment was carried out to identify optimal sulfur level and source for enhancing salt adaptability of sunflower (Helianthus annuus L.). A uniform salinity level of 100 mM NaCl was developed in each pot and then six S treatments viz. S 0, control; S 1, 20 mg sulfur kg -1 soil; S 2, 40 mg sulfur kg -1 soil; S 3, 60 mg sulfur kg -1 soil; S 4, 80 mg sulfur kg -1 soil and S 5, 100 mg sulfur kg -1 soil were applied by using elemental S and K 2 SO 4 as sulfur source. Supplementation of sulfur caused reduction in tissue Na + accumulation and electrolyte leakage while increase in tissue K + and Ca 2+ with a subsequent increase in relative water content and photosynthetic rate of sunflower. Increasing sulfur levels in the form of K 2 SO 4 depicted linear increase in plant growth and yield attributes up to 80 mg sulfur kg -1 soil beyond which there was decline in these growth characteristics suggesting that sulfur as K 2 SO 4 at 80 mg sulfur kg -1 soil might be optimum in mitigating NaCl toxicity in sunflower.