In the Low Stress environments, yields were reduced by less than 20% when planting was as late as mid-June. Yields were not statistically different for any planting date before May 20 (starting from early April). Maximum yield in these non-irrigated environments was 176 bu/acre. The yield responses were similar for hybrids of all maturities.
In the Early Stress environments, yields actually increased as planting was delayed until late June. This response was similar for all hybrid maturities. These environments had favorable temperatures and rainfall throughout July and early August. Maximum yield in these environments was 145 bu/acre.
In the High Stress environments (hot, dry summer conditions), yields dropped by about 1% per day of planting delay, depending on hybrid maturity. The shorter-season hybrids had the best yields if they were planted before late May (max. yield = 150 bu/acre), but all hybrids had yield reductions of more than 50% when planting was delayed until early to mid-June.
In many ways, the current growing season is shaping up like the “Early Stress” scenario above, with cool conditions early in the season. Will this cool spring be followed by favorable temperatures and rainfall, or by hot and dry conditions during the rest of the growing season?
While long-term weather predictions are highly unreliable, the National Weather Service Climate Prediction Center (http://www.cpc.ncep.noaa.gov/) three-month outlook indicates a 40% likelihood of above-normal precipitation and near-normal temperatures for most of the state.