Effect of the interaction of water and nitrogen on sunflower under drip irrigation in an arid region

Sunflower has become an important crop for oil production in many arid regions across the globe. However, with water as a scarce resource, efficient water and nutrient management systems need to be identified. The goal of this project was to determine the interaction between water and nitrogen (N) for sunflower grown in an arid environment. Experiments were conducted during 2010 and 2011 in an arid region in Iran that included two sunflower hybrids, four levels of surface drip irrigation, ranging from severe deficit irrigation to over irrigation, and three levels of N fertilizer, i.e. 0, 47, and 93 kg N ha−1. The treatments were arranged in a strip-plot design with complete randomized blocks with three replications. Irrigations were based on daily monitoring of soil moisture in the experimental plots. For both hybrids, irrigation and the interaction of water and N had a significant effect (P < 0.01) on total biomass, seed yield, oil yield, and N Use Efficiency (NUE). Maximum sunflower seed and oil production (4031 and 1635 kg ha−1, respectively) occurred in over irrigation and 93 kg N ha−1. The lowest soil N uptake was 31 kg ha−1 for deficit irrigation, while the highest was 99.5 kg ha−1 for over irrigation. The highest seed NUE was 26.7 kg kg−1 and oil NUE was 12.2 kg kg−1 for over irrigation with no N input. Increasing the amount of N fertilizer was not a suitable strategy under severe deficit irrigation. Overall, the optimal levels of N depended on the sunflower hybrid type and varied for different levels of irrigation. Adjusting N fertilizer rates to meet crop requirements based on the amount of water applied and the type of hybrid not only prevented a negative environmental impact, but also increased yield and conserved agricultural inputs for sunflower grown in an arid region.