Oil Content and Saturated Fatty Acids in Sunflower as a Function of Planting Date, Nitrogen Rate, and Hybrid

The fatty acids (FA) composition of sunflower (Helianthus annuus L.) determines its uses and health effects on humans, while oil content determines the price paid to producers. The hypothesis of this study was that agronomic factors (genotype, planting date, and N rate) will affect total saturated fatty acid (TSFA) concentration and oil content of sunflower. Additionally, Mississippi-grown sunflower will have a different FA composition than the original seeds produced in more northern latitudes and used for planting. A field experiment was performed in four locations in Mississippi (Newton, Starkville, and two locations in Verona) to assess the effect of planting date (20 April, 20 May, and 20 June), N application rate (0, 67, 134, and 202 kg N ha⁻¹) and genotype (hybrid, DKF3875, DKF2990, DKF3510, and DKF3901) on sunflower seed oil content and composition. The TSFA and oil content were significantly affected by planting date, hybrid, and N rate. Overall, later planting dates increased TSFA relative to the first planting, and in most instances TSFA concentrations in sunflower from the third planting was higher than in seeds from the second. Generally, the first planting date provided the highest oil content of the four hybrids, the second planting reduced oil content, while the third was not different from the second. Our results suggest that an earlier planting date may reduce the TSFA and increase oil content of sunflower in Mississippi. Regarding individual FA, overall, palmitic (16:0) and stearic acid (18:0) concentrations in sunflower seed grown in Mississippi from the first planting were reduced relative to the respective concentrations in the original seed. Later planting tended to increase these two acids relative to the first planting and relative to the original seed. The three minor saturated fatty acids (SFA), arachidic (20:0), behenic (22:0), and lignoceric acid (24:0) followed a similar pattern. This study demonstrated that agricultural factors such as planting date, hybrid, and N rate may significantly modify FA composition and oil content of sunflower grown in Mississippi, suggesting that these could be used as management tools for decreased TSFA and increased oil content.