2012 Corn Yield Potential Forecast Based on Aug. 27 Hybrid-Maize Simulation - August 30, 2012

2012 Corn Yield Potential Forecast Based on Aug. 27 Hybrid-Maize Simulation - August 30, 2012

August 30, 2012

Irrigated corn yield potential is predicted to be 2-8% below long-term average, while dryland yield potential in much of the Corn Belt will be moderately to severely reduced, falling 22-67% below normal.


Map of sites used for yield forecasts

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). Link to a larger version of Figure 1.

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 up to August 27, and historical long-term weather data to complete the season using data from each of the past 30 years. This approach gives a “real-time,” in-season estimate of expected yield potential (the median value shown in Table 1), and the most probable range (25th to 75th percentiles) depending on weather conditions from August 27 until the corn crop reaches maturity (see Applying the Hybrid-Maize Predictions, below).

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. (Also see Applying ...  for how to interpret simulations shown in Table 1.)

August 27 projections give a narrower range than our projections based on August 13 simulations, and, at some locations the crop reached blacklayer during the past week (Mead, Concord, O’Neill, and Nashua, Iowa). Projected yield potential since August 13 has not changed by more than 7% across all locations, except for the two locations in west central Illinois (Monmouth) and south central Illinois (Bondville) where predicted dryland yield has increased by 30% due to good rains and cooler weather. It should be noted, however, that if unusually hot, dry weather occurred during pollination at these Illinois locations, such a large yield improvement would not be expected due to reduced seed set. Still, projections of final yield potential are below the long-term average at all sites, under both irrigated and dryland conditions (Table 1).


Applying the Hybrid-Maize Predictions

By comparing this range of possible simulated end-of-season yield potential against the long-term average (Long-term Yp, fourth column from right in Table 1), it is possible to estimate the likelihood for below-average (25th percentile), average (median), or above-average (75th percentile) yields. Comparing estimated 2012 yield potential with the long-term average gives the size of the expected yield difference.

The 25th percentile projection reflects what would most likely occur if weather conditions are harsher than normal from August 27 until crop maturity, while the 75th percentile projection shows what would be more likely if weather is more favorable than is typical for this period at a given site. There is roughly a 50% probability that final yield potential will fall between the 25th and 75th percentile levels, a 75% chance that yield will be at or below the 75th percentile, and a 25% probability they will be at or below the 25th percentile value. As the season progresses, the range of yield outcomes shrinks and the 25th and 75th percentile values converge toward the median value. At some sites the model predicts the crop was mature as of August 27.

How reliable are these projections? In areas where there has been relatively little heat or water stress, past experience indicates that predictions of yield potential using Hybrid-Maize are robust. In contrast, we would expect Hybrid-Maize yield loss predictions to be underestimated in areas where there was high temperature stress during the critical two- to three-day pollination period, or where there were water deficits that severely reduced development of the leaf canopy before tasseling. Both 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.

Earlier Hybrid-Maize Predictions

There is a modest yield loss (5-8%) for locations in South Dakota (Brookings) and west central and north central Illinois (Monmouth and DeKalb) while a moderate yield loss of 22-28% is predicted for dryland corn in central and northeast Iowa (Gilbert and Nashua). Severe yield loss of 32-67% is projected for dryland corn in south central, eastern, and northeastern Nebraska (Clay Center, Mead, and Concord), northwest Iowa (Sutherland), and south central Illinois (Bondville) (Table 1). In contrast to large loss of yield potential in these dryland systems, the projected losses in yield potential at all irrigated sites are modest at about 2-3% in south central Nebraska (Clay Center, Holdrege), and 7-8% in east and northeast Nebraska (O’Neill, Concord, and Mead) (Table 1). Projected irrigated yield potential since August 13 has increased by about 3% due to cooler weather during the past two weeks.

The bottom line is that 2012 irrigated yields will be moderately lower than the long-term averages (2-8% below normal), while dryland corn yield potential in much of the Corn Belt will be moderately to severely reduced (22-67% below normal). It is important to keep in mind that yields can be even lower at places where both prolonged drought and high temperature stress at pollination have occurred. Also, greater field-scale variability is being observed this year in irrigated fields due to the inability of some irrigation systems to keep up with crop water use demand, problems with pivot irrigation nozzles and uneven watering, and additional stresses from insects and diseases. Such problems can contribute to reduced yields at irrigated sites of more than the 2-8% simulated by the model.

Patricio Grassini, Research Associate Professor, Agronomy and Horticulture Department
Jenny Rees, UNL Extension Educator
Haishun Yang, Associate Professor, Agronomy and Horticulture Department
Kenneth G Cassman, Professor, Agronomy and Horticulture Department


Table 1.  2012 In-season yield potential forecasts as of August 17  using UNL Hybrid-Maize Model

Location, State Water Regime Soil Type &
Initial Water
Planting Date Long-term
2012 Forecasted Yp (bu/ac)
 75th*  Median 25th**

Holdrege, NE Irrigated Silt loam 32.4k 113  April 27  248    
246 243
Clay Center, NE Irrigated
Silt clay loam
100% ASW
113 April 23
April 23
Mead, NE Irrigated
Silt clay loam
100% ASW
113  April 30  240    
—  224
Concord, NE Irrigated
Silt loam
100% ASW
104 May 3 235    
—   218
O’Neill, NE Irrigated Sandy loam
100% ASW
32.4k 106  May 3 225    
—   207 —  

Brookings, SD Rainfed Silt clay loam
100% ASW
30.0k 98  May 4 120    
116  110 105

Sutherland, IA Rainfed Silt clay loam
100% ASW
31.4k 99  May 1 168    
104 102
Gilbert, IA Rainfed Loam
100% ASW
32.4k  110  April 26 200    
153  145 141
Nashua, IA Rainfed Loam
100% ASW
32.4k 99  May 1 198    
—   155 —  

Monmouth, IL Rainfed Silt loam
100% ASW
32.4k 112  April 27 212    
193  189 183
DeKalb, IL Rainfed Silt clay loam
100% ASW
32.4k 111  May 1 201    
208  190 177
Bondville, IL Rainfed Silt clay loam
100% ASW
32.4k 114  April 20 197    
135  134 131

  Simulations based on dominant soil series, average planting date, and plant population (PP) and relative maturity (RM) of most widespread hybrid at each location (Grassini et al., 2009).
Average (20+ years) simulated yield potential (Yp).
* 75th and ** 25th percentile yields, which represent favorable and unfavorable weather scenarios for the rest of the season, respectively.


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A field of corn.