Productivity, Oil Content, and Oil Composition of Sweet Basil as a Function of Nitrogen and Sulfur Fertilization

Nitrogen (N) and sulfur (S) were believed to be important nutrient management tools for the production of sweet basil (Ocimum basilicum L. 'German') with desirable oil content and composition and acceptable herbage yields. A multilocation research study was initiated to evaluate the effect of N (0, 60, 120, and 180 kg·ha-1 N) and S (0, 20, 40, and 80 kg·ha-1 S) rates on biomass production, oil content, and oil composition for sweet basil. The three locations in Mississippi (Stoneville, Poplarville, and Verona) were selected based on soil type, geographic, and climatic variation. Location, N rate, and their interaction were significant on basil dry herbage yields. The herbage yield means were 4967 kg·ha-1, 2907 kg·ha-1, and 2122 kg·ha-1 for Poplarville, Verona, and Stoneville, respectively. Oil content was significantly affected by location with means of 0.69%, 0.80%, and 0.64% for Stoneville, Poplarville, and Verona, respectively. Location, N, and S had significant effects on oil yields with means of 14.7, 38.7, and 18.5 kg·ha-1 for Stoneville, Poplarville, and Verona, respectively. The significant quadratic response of essential oil yields to N fertilization rates showed oil yields were maximized for fertilization between 50 and 60 kg·ha-1 N. In contrast, the response to S fertilization appeared to continue to increase beyond the maximum fertilization rate evaluated of 80 kg·ha-1 S. Location and N application rates had a significant effect on the yields of the major basil oil constituents (-)-linalool, eugenol, (-)-bornyl acetate, and eucalyptol, whereas S had a significant effect on eucalyptol yield only. Eucalyptol concentration was positively correlated to the concentration of (-)-bornyl acetate. This is the first study to quantify (in real concentration) the response of the major sweet basil oil constituents (-)-linalool, eugenol, (-)-bornyl acetate, and eucalyptol as a function of N and S application rates. Also, it is the first study to demonstrate a strong response of basil oil yield to S. The results from this study demonstrated that N and S applications can be used as management tools with respect to sweet basil production, oil content, and oil composition.