2012 Corn Yield Potential Forecast Based on Aug. 13 Hybrid-Maize Simulation

2012 Corn Yield Potential Forecast Based on Aug. 13 Hybrid-Maize Simulation

August 15, 2012

Yield projections improve slightly at some sites; some Nebraska irrigated sites near average.

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.

The 2012 corn growing season has been unusually hot and dry. 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 13 and historical long-term weather data thereafter. (Data  from each of the past 30 years was used.) 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 13 until the corn crop reaches maturity.

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 versus the long-term average gives the size of the expected yield difference. While the 25th percentile projection is most likely if weather conditions are harsher than normal from August 13 until crop maturity, the 75th percentile scenario is more likely if weather is more favorable than is typical 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 that it will be at or below the 25th percentile value.

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. Details about the Hybrid-Maize model and our simulation forecast methods can be found in a previous CropWatch article.

As the season progresses, the range of yield outcomes shrinks and the 25th and 75th percentile values converge toward the median value. Indeed, August 13 projections give a much narrower range than our projections two weeks earlier based on July 30 simulations. The good news is that projected yield potential since July 30 has stabilized or even increased slightly at 7 of 12 sites as weather has improved, especially during the most recent week. The bad news is that projections of final yield potential are below the long-term average at all but two sites.

Dryland Corn

Even in hot, dry years like 2012, parts of the Corn Belt escape untouched and catch adequate rainfall. This appears to be the case in the northern tier of the Corn Belt (e.g. Brookings, South Dakota) and near the Great Lakes (e.g. Dekalb, Illinois) (Figure 1) where projected dryland yield potential is within 2% of the long-term average. In contrast, there is moderate yield loss of 26-33% for dryland corn in south central Nebraska (Clay Center), central and northeast Iowa (Gilbert and Nashua), and west central Illinois (Monmouth). Severe yield loss of 40-65% is projected for dryland corn in eastern and northeastern Nebraska (Mead, Concord), northwest Iowa (Sutherland), and south central Illinois (Bondville).

Irrigated Corn

In contrast to large loss of yield potential in these dryland systems, drought years like 2012 highlight the value of irrigated agriculture and the stability it provides to our food system. Although hotter than average temperatures have shortened the grain filling period at all irrigated sites, which reduces yield potential somewhat, projected decreases are modest at about 5% in south central Nebraska (Clay Center, Holdrege), and 10% in east and northeast Nebraska (O’Neill, Concord, Mead). High grain prices are likely to offset the impact such losses will have on profits from irrigated corn.

Model Reliability

Given the severity of reductions in yield potential at some locations, and the apparent lack of negative impact at others, the question arises as to how reliable these projections are? In areas with relatively little heat or water stress, past experience indicates that predictions of yield potential using Hybrid-Maize are robust. In contrast, we would expect predictions of yield loss to be underestimated by Hybrid-Maize in areas where there was high temperature stress during the critical two to three day period of pollination, or where there were large 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.


The bottom line is that 2012 will be a difficult year in terms of U.S. corn production. Although irrigated yields will be somewhat lower than long-term averages, dryland corn yield potential in much of the Corn Belt will be moderately (25-33% below normal) to severely reduced (40-65% below normal). Where both prolonged drought and high temperature stress at pollination occurred, yields could be reduced by 65% or more. The final outcome will be determined by weather conditions until maturity. Fortunately, predicted weather patterns indicate a trend toward more normal temperatures and rainfall in many places.

While 2012 will certainly be a significant drought year, episodic droughts of this magnitude have occurred at regular intervals in the U.S. Corn Belt over the past 100 years of recorded weather data. Nebraska is fortunate that about 70% of total corn production comes from irrigated systems, and that improved agronomic management practices such as conservation tillage and more stress-tolerant hybrids can significantly reduce dryland corn yield losses under moderate drought. But there is little that can be done to mitigate the impact of severe, prolonged drought especially when coupled with high temperature stress at critical growth periods.

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

Table 1.  2012 In-season yield potential forecasts as of August 13  using UNL Hybrid-Maize Model

Location, State Water Regime Soil type¶ & Initial Water PP (ac-1) RM¶ (days) Planting Date Long-term
Yp (bu/ac)
 2012 Forecasted Yp (bu/ac)
 75th*  Median 25th**

Holdrege, NE Irrigated Silt loam  32.4k 113  April 27  248  
 239  232 223
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  
Concord, NE Irrigated
Silt loam
100% ASW
104 May 3 235  
O’Neill, NE Irrigated Sandy loam
100% ASW
 32.4k 106  May 3 225  
 212 203 199

Brookings, SD Rainfed Silt clay loam
100% ASW
 30.0k 98  May 4 120  
 127 118 111

Sutherland, IA Rainfed Silt clay loam
100% ASW
 31.4k 99  May 1 168  
 110 99 88
Gilbert, IA Rainfed Loam
100% ASW
 32.4k  110  April 26 200  
 157 144 141
Nashua, IA Rainfed Loam
100% ASW
 32.4k 99  May 1 198  
 152 147 141

Monmouth, IL Rainfed Silt loam
100% ASW
 32.4k 112  April 27 212  
 161 143 128
DeKalb, IL Rainfed Silt clay loam
100% ASW
 32.4k 111  May 1 201  
 227 204 185
Bondville, IL Rainfed Silt clay loam
100% ASW
 32.4k 114  April 20 197  
 110 105 88

  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.