Hybrid-Maize is a corn simulation model that estimates corn yield potential under irrigated or dryland conditions, based on weather, planting date, hybrid maturity and soil type, assuming optimal crop management. By comparing simulated end-of-season yield potential against the long-term average, it is possible to estimate the expected yield difference.

The question arises: how reliable are these projections? In areas where there has been relatively little heat or water stress, experience indicates that predictions of yield potential using Hybrid-Maize are robust. In contrast, we would expect Hybrid-Maize to underestimate predictions of yield loss in areas where there was high temperature stress during the critical two- to three-day period of pollination, or where there were severe water deficits that reduced development of the leaf canopy before tasseling, These phenomena are not well accounted for in the current version of the model although we plan to release an improved version of Hybrid-Maize later this year that addresses these deficiencies.

Likewise, for irrigated systems that had trouble keeping up with meeting crop water demand, or where there were uneven plant stands or lodging, the model does not “see” these constraints because it assumes no limitations other than temperature and solar radiation for irrigated production, and temperature, solar radiation, and rainfall for dryland production.

 

Figure 1. Locations used by the Hybrid-Maize model for in-season yield forecasting with actual weather and dominant management practices and soil series at each site (indicated by starts).  Green areas indicate where corn is planted.  Weather data used is from the High Plains Regional Climate Center and the Water and Atmospheric Resources Monitoring Program through the Illinois Climate Network (Illinois State Water Survey, Prairie Research Institute, and the University of Illinois at Urbana-Champaign).

To evaluate the impact on potential production at 12 sites across the Corn Belt (Figure 1), we used the Hybrid-Maize model to estimate end-of-season yield potential based on actual weather data during the 2012 crop season. Simulations were run for dryland corn in Iowa, Illinois and South Dakota, and for both irrigated and dryland corn in Nebraska. Simulations were based on the typical planting date, hybrid relative maturity, plant population and soil properties at each location. Underpinning data used in these simulations are provided in Table 1.