Optimizing irrigation and nitrogen fertilization of Iranian sesame cultivars for grain yield and oil quality

Abstract

The impacts of water deficit stress, nitrogen (N) application rate and cultivar and their combination on sesame seed quality have not been previously studied. Hence, field experiments were conducted in a semi-arid area of Iran during the 2016 and 2017 growing seasons. The experiments were carried out in a randomized complete block design arranged in split factorial with three replications. Water deficit and full irrigation regimes were allocated to the main plots and factorial arrangement of sesame cultivars (Naz, Oltan and Dashtestan) and N rates (0, 60 and 120 kg N ha−1) were randomized to the sub-plots. The results indicated that an increase in N rate (0–120 kg N ha−1) could enhance sesame grain yield by 62 %, 112 % and 70 % under full irrigation conditions and by 32 %, 55 % and 67 % under water deficit irrigation conditions in Naz, Oltan and Dashtestan cultivars, respectively. Water deficit irrigation caused a considerable reduction in sesame seed oil content. This study obtained the highest unsaturated fatty acids when the Dashtestan cultivar was fully irrigated and treated with 120 kg N ha−1. The lowest amount of saturated fatty acid was achieved when full irrigation accompanied with 60 kg N ha−1 in Naz cultivar. The results demonstrated that water deficit irrigation reduces linoleic, oleic and stearic fatty acids and increases palmitic and linolenic fatty acids. Also, N application caused a significant increase in oleic and stearic fatty acids and significantly reduced linoleic and palmitic fatty acids. Overall, although plants’ genetic background is the most critical factor determining the oil content and fatty acid composition, environmental factors including water and N availability significantly affect fatty acid composition in sesame cultivars.