Effect of Increased Nitrogen Application Rates and Environment on Protein, Oil, Fatty Acids, and Minerals in Sesame (Sesamum indicum) Seed Grown under Mississippi Delta Conditions

Information on the effect of nitrogen fertilizer rates and environment on sesame seed composition and nutrition is scarce. The objective of this research was to investigate the effects of nitrogen fertilizer application rates on sesame seed yield, protein, oil, fatty acids, and mineral nutrition. A two-year (2014, 2015) field experiment was conducted. Nitrogen fertilizer (urea ammonium nitrate) solution (UAN, 32% N) was applied by side dressing to four sesame varieties (S-34, S-35, S-38, S-39) at rates of 44.7, 67.2, 89.6 and 112.0 kg·ha-1. Rate of 44.7 kg·ha-1 was used as control since this rate is traditionally recommended in the region. Increasing nitrogen application rates resulted in higher protein and oleic acid contents in two varieties in 2014, and in all varieties in 2015. Increased protein and oleic acid were accompanied by lower total oil and linoleic acid. Increased nitrogen application also resulted in higher seed N, S, B, Cu, Fe, and Zn in 2014 in S-34 and S-35, but either a decline or no clear change was observed in seed levels of these nutrients in S-38 and S-39. In 2015, increased nitrogen application resulted in significantly higher seed N in all varieties, and higher S, B, Cu, Fe, and Zn in some varieties. A significant positive correlation was observed between nitrogen application rate and yield, and with seed levels of protein, oleic, acid, N, B, Cu, Fe, and Zn. A significant negative correlation was observed between nitrogen application rate and seed oil and linoleic acid. Thus, increased nitrogen fertilizer application resulted in higher seed protein, oleic acid, and some mineral nutrients, but lower oil and linoleic acid. However, this effect depended on variety and environmental conditions. Because higher protein and oleic acid are desirable traits for sesame seed nutritional value and oil stability, regional breeders should select sesame varieties for efficient fertilizer response.