Interaction effects of deficit irrigation and row spacing on sunflower (Helianthus annuus L.) growth, seed yield and oil yield

Productivity of sunflower is strongly regulated by the availability of water. In order to study the influence of deficit irrigation (I-1:100% FC, I-2 and I-3:75 and 50% FC during stem elongation period, respectively; I-4 and I-5:75 and 50% FC at flowering stages) and two row spacings (45 - 50 and 75 cm) on growth, yield and oil yield of sunflower, an experiment was conducted using a split plot design with three replications in the 2007 - 2008. Results indicated that Maximum (374.67 gm(-2)) and minimum (198.5 gm(-2)) grain yield was obtained from I-1 and I-3 treatments. Compared to I-1, grain yield was reduced significantly under deficit irrigation treatments (I-2, I-3 and I-5). Interaction effects of row spacing and deficit irrigation indicated that the highest seed yield (458.0 gm(-2)) and oil percentage (31.66%) was obtained from I-1 and 75 cm row spacing. Reduction of grain yield due to deficit irrigation (I-4) was not significant (374.6 vs. 340.1 gm(-2)), compared to full irrigation. Therefore, we confirm that irrigation levels significantly affected seed yield and oil percentage. Our results indicated that deficit irrigation, during the critical growth period should be avoided.