Weather conditions over the last three weeks were far from average (Fig. 1). Across our Forecasting and Assessment of Cropping sysTemS (FACTS) locations, precipitation was 48% below average, while heat stress (defined as maximum temperature above 86oF), growth degree days (GDD), and radiation were 53%, 25%, and 19% above the long-term average. However, our northeast Iowa was the exception; it received 7 inches of rain from June 5 to June 25, while all the other sites have received less than 1 inch of rain (Fig. 1).
Figure 1. 2016 weather deviations from climatic average for the period June 5 to June 25, 2016.
Will this unusual weather impact end-of-season crop yields? Are crops sensitive during vegetative phases? Can Iowa soils offset the lack of June rain? The answers depend on the current stage of the crop and soil moisture conditions. To explore the impact of high temperature and moisture stress from June 5 to 25 on corn and soybean yields we used a mechanistic model (APSIM) and 20 combinations of sites, crop and management treatments that are currently monitored in the FACTS project.