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Latest 2012 #Corn Yield Predictions

2012 Corn Yield Potential Forecast Based on Aug. 27 Hybrid-Maize Simulation:  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. Predictions are assuming no stress during pollination and fully irrigated fields with no equipment, disease, or insect problems.
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 stars).  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. 

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. 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) depending on weather conditions from August 27 until the corn crop reaches maturity.

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).

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.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.

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

Earlier Hybrid-Maize Predictions

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)

Holdrege, NE Irrigated Silt loam 32.4k 113  April 27  248
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

Brookings, SD Rainfed Silt clay loam

100% ASW

30.0k 98  May 4 120

Sutherland, IA Rainfed Silt clay loam

100% ASW

31.4k 99  May 1 168
Gilbert, IA Rainfed Loam

100% ASW

32.4k  110  April 26 200
Nashua, IA Rainfed Loam

100% ASW

32.4k 99  May 1 198

Monmouth, IL Rainfed Silt loam

100% ASW

32.4k 112  April 27 212
DeKalb, IL Rainfed Silt clay loam

100% ASW

32.4k 111  May 1 201
Bondville, IL Rainfed Silt clay loam

100% ASW

32.4k 114  April 20 197

  Simulations based on dominant soil series, average planting date, and plant population (PP) & relative maturity (RM) of most widespread hybrid at each location (Grassini et al., 2009). 

 Average (20+ years) simulated yield potential (Yp). 

2012 Last Irrigation Scheduling

While farmers may be tired of irrigating right now, I think all who have irrigation are thankful for it in such a dry year.  Honestly, thankfully with our irrigation we have some of the best looking crops in the Corn Belt right now.  Even so, with corn that hasn’t been replanted nearing dent or stages of starch fill, you may be wondering how to schedule for your last irrigation.

For those of you in our Nebraska Ag Water Management Network using watermark sensors, the goal is to use them to determine when the soil profile reaches 60% depletion (for silty-clay soils in our area aim for an average of 160 kpa of all your sensors).  You may be thinking, “An average of 90kpa was hard enough!” but as Daryl Andersen from the Little Blue Natural Resources District points out, you’re only taking an additional 0.30 inches out of each foot.  So if you’re averaging 90kpa on your three sensors, you have depleted 2.34 inches in the top three feet so you still have 0.96 inches left (see the Soil Moisture Depletion Chart).  If you add the fourth foot (using a similar number from the third foot), it would bring the water available to the plant up to 1.28”. 

At beginning dent corn you need 24 days or 5 inches of water to finish the crop to maturity.  If you subtract 1.28 from 5 you will need 3.72” to finish out the crop.  Corn at ½ milk line needs 13 days or 2.25” to finish the crop to maturity-so subtracting it from 1.28 would be only 0.97”.  

Soybeans at the beginning of seed enlargement (R5) need 6.5”.  Soybeans in R6 or full seed which needs 3.5 inches yet for maturity.  Subtracting off the 1.28” in the four foot profile would lead to 2.22”.  The UNL NebGuide Predicting the Last Irrigation of the Season provides good information on how determine your last irrigation in addition to showing charts on how much water the crop still needs at various growth stages.  

Several people I’ve talked to who have been irrigating using watermark sensors aren’t replenishing the second foot, so you may have a few rounds yet to go  on corn and beans.  For a quick way to know where you’re at, think about irrigating this way as explained by Daryl Andersen at the Little Blue Natural Resources District:

One way to look at this is by the numbers of days left.  At 1/4 starch, there are about 19 days before maturity so you can let your sensors average 130kpa on the first week and 150kpa on the next week.  If these targets are met during the week, you would put on about 1 inch of water.  By going to these numbers, it might give you a higher probability for rain in the next couple of weeks.  I’m hoping for many answered prayers that we will see rain in August!

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