The amount of accumulated GDD for developing seeds of the oilseed hybrids to reach 40% moisture, regardless of seed position, was 44–47 °C d less than that required to reach 35% (Fig. 5A and B; based on linear equations). Based on the equations derived from the relationship of accumulated GDD to DOY at the Minnesota and North Dakota sites (Fig. 6), 40% seed moisture occurred at least 3–4 d earlier than 35% moisture. Although this is not a large amount of time, it does allow a larger window of opportunity to apply desiccant under ideal weather conditions, which can translate into earlier harvest, making a significant difference in some years for avoiding crop-loss resulting from severe weather and/or bird predation.
Even more striking were differences in accumulated GDD between 35% moisture and that of 50%, which we found to coincide with PM for the confectionary hybrid (i.e., 2215). Across field sites and seed position, the number of GDD to reach 50% seed moisture ranged from 120 to 137 °C d less than that required to reach 35% moisture (Fig. 6C and D). This translated into a 9–12 d difference (Fig. 6), indicating that the confectionary hybrid could be desiccated nearly 2 weeks earlier than presently recommended (i.e., 35% seed moisture), without sacrificing yield because of not reaching PM. In addition to the importance of early desiccation and harvest for reducing yield loss, the earlier a desiccant is applied in sunflower growing areas of Minnesota and North Dakota, the greater the chance of taking advantage of warmer, drier weather that can further aid in hastening drydown of the treated crop.