N and S Effects on Sweet Basil Yields, Oil Content, and Composition.

This study evaluated the effect of N (0, 60, 120, and 180 kg N ha^-1) and S (0, 20, 40, and 80 kg S ha^-1) rates on biomass production, oil content, and oil composition for sweet basil (Ocimum basilicum L. ‘German’)  at three locations in Mississippi (Stoneville, Poplarville, and Verona).  Location, N rate, and their interaction were significant on basil dry herbage yields.  The herbage yield means were 4,967 kg×ha^-1, 2,907 kg×ha^-1, and 2,122 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.  Based on quadratic regression analysis, essential oil yields were maximized at N application rates of approximately 50 to 60 kg N ha^-1, whereas maximum response to S fertilization appeared to be beyond 80 kg S ha^-1 based on a linear response.   Location and N application rates had 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.