Optimizing sulphur application in sunflower (Helianthus annuus) under irrigated semi-arid tropical conditions

A field experiment comprising varying levels of sulphur (0, 20 and 40 kg S/ha) applied through different sources (ammonium sulphate, single super phosphate, gypsum and elemental sulphur) was conducted on loamy sand soil at Ludhiana, Punjab during spring seasons of 2008 and 2009 to identify the optimum dose and better source of sulphur for higher sunflower productivity. Significant improvement in seed yield of sunflower was observed with each incremental dose of sulphur up to 40 kg S/ha with 6.9–9.0% yield superiority over control. The application of graded doses of sulphur at the rates of 20 and 40 kg S/ha through gypsum increased the seed yield over control by 8.6 and 10.7%, respectively, whereas the corresponding increases were 8.5 and 10.4% for ammonium sulphate, 5.4 and 7.3% for single super phosphate and 4.9 and 7.5% for elemental sulphur at the respective levels of sulphur nutrition. Highest seed yield (2.66 t/ha), oil content (42.9%), net returns ( 46.3 × 10³/ha) and B:C ratio (4.08) was recorded with application of 40 kg S/ha applied through gypsum. Positive and highly significant correlation was observed between seed yield and head diameter (r=0.977**), dry matter accumulation (r=0.935), seed weight (r=0.810**). Oil content in the seed recorded a positive and highly significant relationship with uptake of N (r=0.984**), P (r=0.993**) and S (r=0.978**), signifying the importance of balanced nutrition in improving the oil content. Almost similar seed yield can be obtained with economic optimum dose of sulphur, indicating the saving of S ranging from 0.4 to 6.6 kg/ha depending upon the source.