Planting Date Effects on Quantity and Quality of High-Oleic Soybean.

High-oleic soybean varieties must produce competitive grain yields while maintaining superior oil quality across growing conditions and management decisions. Oil extracted from these varieties improves oxidative stability, thus eliminating the trans fats produced during hydrogenation. Planting date can alter the growing environment to which soybean is exposed during the growing season and therefore can greatly influence grain yield and seed composition. Field experiments were conducted near West Lafayette, Indiana to investigate the planting date effects on grain yield and oil quality of high-oleic and standard soybean cultivars.  Two high-oleic and two standard varieties were planted five times between the first week of May to the first week of July in 2014 and in 2015. These treatments were replicated 4 times and were arranged in a strip plot design. Weekly growth stages, canopy closure, and crop reflectance was collected throughout the growing season. Grain subsamples were collected at harvest and analyzed by capillary gas chromatography to determine the fatty acid profile of soybean oil. Grain yield decreased as planting date was delayed for all varieties in both years. The standard varieties yielded more than high-oleic varieties when averaged across planting dates in 2014 (~280 kg/ha), yet no differences were observed in 2015. The high-oleic varieties were higher in oleic composition than standard varieties across planting dates and years (~70% vs. ~25%). In 2014, the oleic composition decreased as planting was delayed for the high-oleic varieties. Whereas, the oleic composition increased in the standard varieties. Percentage oleic acid was stable across the planting series for both high-oleic and standard varieties in 2015. The final planting date of the high-oleic varieties had a slight decrease in oleic acid (~2%). The inconsistency of grain yield and oleic acid production to planting date requires further evaluation of varieties and environmental conditions that influence soybean fatty acid composition.