Delayed Plantings Shift Reproductive Phases and Alter Oleic Production of Soybean.

High-oleic soybean varieties must produce competitive grain yields while maintaining superior oil quality across growing conditions and management decisions. Planting date directly influences the period in which soybeans develop pods and seeds to produce bushels of soybeans with the desired quality. 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 varieties. High-oleic and standard varieties were planted five times from late April to early July in 2014 and 2015. Treatments were replicated 4 times and were arranged in a split-plot design where the main plot was planting date and subplot was variety. Soybean growth stage was collected bi-weekly 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 with delayed planting for all varieties in all years. The standard varieties yielded ~326 kg ha^-1 greater than high-oleic varieties with planting delayed beyond early May in 2014. Grain yield decreased at a rate of ~34 kg ha^-1 day^-1 when planting was delayed beyond late May in 2015. No grain yield difference was observed between high-oleic and standard varieties in 2015. The high-oleic varieties were greater in oleic composition than standard varieties across all planting dates and years (~70% vs. ~25%). In 2014, the oleic composition decreased linearly (0.25% d^-1) as planting was delayed beyond late May for the high-oleic varieties. No difference in oleic acid was observed between early and late May planting dates during the 2014 season. Percentage oleic acid was stable across all planting dates except early July (~2% decrease) in 2015. Timely planting is a critical management decision that can optimize both grain yield and grain quality of high-oleic soybean.