2021 Corn Yield Forecasts as of July 14

2021 Corn Yield Forecasts as of July 14

Simulations of 2021 end-of-season corn yield potential and real-time crop stage were performed on July 14 for 40 locations across the U.S. Corn Belt using the UNL Hybrid-Maize crop model in collaboration with faculty and extension educators from 10 universities. This article summarizes the simulated crop stages and yield forecasts; the data can be found in Table 1. Details on the UNL Hybrid-Maize crop model and the underpinning methodology to simulate phenology and forecast end-of-season yields, as well as on interpretation and uses of yield forecasts, are described in a previous article.

A summary of weather conditions during the last 60 days (from May 14 to July 13) is shown in Figure 1. The season started with warm conditions throughout the north and northwestern fringes of the Corn Belt, showing temperatures above normal in ND, MN, IA, MI, and northern NE and near-normal temperature in the rest of the region. Most of the northwestern region (MN, ND, IA, and eastern NE) presented below normal rainfall. Remaining sites showed near normal rainfall records, except for MO and a few scattered locations in IL and IN with rainfall above normal.

Graph of Daily solar radiation, maximum and minimum air temperature, total rainfall, and total reference grass-based evapotranspiration (ET) for the time period between May 14 and July 13, 2021
Figure 1. Daily solar radiation, maximum and minimum air temperature (Tmax and Tmin), total rainfall, and total reference grass-based evapotranspiration (ET) for the time period between May 14 and July 13, 2021. Vertical bars indicate the range for these variables based on 20-plus years of weather records. The horizontal thick line indicates the long-term average and the red dots indicate the 2021 values for the same period.

Table 1. Data from simulations of 2021 end-of-season corn yield potential and real-time crop stage performed on July 14
LocationWater regimeLong-term average yield (bu/ac) §Range of Yp forecasts as of Jul 14 (bu/ac)¶ 25thRange of Yp forecasts as of Jul 14 (bu/ac)¶ 75thProbability (%) of 2021 yield to be: Below (relative to the long-term Yp)†Probability (%) of 2021 yield to be: Near (relative to the long-term Yp)†Probability (%) of 2021 yield to be: Above (relative to the long-term Yp)†Simulated current crop stage*
NE Alliance Irrigated 193 188 222 3% 59% 38% V14
Beatrice Dryland 162 107 168 68% 13% 19% R1, Silking
Irrigated 230 216 247 6% 81% 13% R1, Silking
Clay Center Dryland 160 64 149 72% 15% 13% V16
Irrigated 245 235 257 13% 72% 15% V18
Concord Dryland 177 88 142 79% 10% 10% V16
Irrigated 249 232 265 18% 72% 10% V18
Elgin Irrigated 252 229 263 15% 76% 9% V16
Holdrege Dryland 115 84 131 36% 30% 33% V16
Irrigated 242 225 261 12% 73% 15% V16
McCook Dryland 88 68 117 31% 23% 46% V18
Irrigated 225 211 235 18% 72% 10% V18
Mead Dryland 183 118 190 59% 28% 13% V18
Irrigated 235 217 247 21% 64% 15% R1, Silking
North Platte Dryland 91 43 99 56% 21% 23% V14
Irrigated 234 223 260 13% 51% 36% V16
O'Neill Irrigated 227 205 239 25% 61% 14% V16
IA Ames Dryland 231 176 203 82% 18% 0% R1, Silking
Crawfordsville Dryland 230 224 246 10% 71% 19% R1, Silking
Lewis Dryland 209 197 239 26% 39% 35% V18
Nashua Dryland 229 188 206 75% 25% 0% V18
Sutherland Dryland 211 187 218 28% 62% 9% V16
IL Bondville Dryland 235 225 266 17% 48% 34% V18
Freeport Dryland 213 143 195 65% 35% 0% V16
Olney Dryland 189 192 233 6% 35% 1058 R1, Silking
Peoria Dryland 210 212 240 4% 61% 36% V18
Springfield Dryland 178 210 237 0% 14% 86% R1, Silking
IN Butlerville Dryland 225 198 238 33% 61% 186 V16
Columbia City Dryland 224 212 241 17% 67% 17% V16
Davis Dryland 231 222 242 0% 100% 0% V14
West Lafayette Dryland 238 228 261 0% 72% 28% V18
KS Garden City Irrigated 219 200 228 14% 80% 6% V18
Hutchinson Dryland 100 68 113 45% 29% 26% R2, Blister
Manhattan Dryland 135 104 165 47% 17% 36% R1, Silking
Scandia Dryland 132 19 81 91% 6% 3% V16
Irrigated 225 209 248 11% 63% 26% V18
Silverlake Dryland 140 138 174 3% 40% 57% R1, Silking
Irrigated 210 186 224 29% 54% 17% R1, Silking
MI Ceresco Dryland 177 168 231 10% 40% 50% V14
MN Eldred Dryland 115 12 47 100% 0% 0% V12
Lamberton Dryland 215 158 195 71% 29% 0% V16
Waseca Dryland 219 202 234 22% 56% 22% V16
MO Brunswick Dryland 181 188 218 5% 52% 43% V18
Monroe City Dryland 172 192 233 0% 25% 75% V18
St Joseph Dryland 165 186 220 14% 5% 81% V18
ND Dazey Dryland 113 2 78 92% 4% 4% V12
OH Custar Dryland 208 198 227 17% 61% 22% V16
South Charleston Dryland 216 191 228 32% 48% 19% V16
Wooster Dryland 210 210 239 6% 58% 36% V14

§Long-term (last 20+ years) potential yield at each location and surrounding area.
¶ Range of forecasted 2021 potential yields based on average planting date in 2021, indicating the potential yields in the 25th and 75th percentile of the potential yield distribution (associated with respective adverse and favorable weather scenarios during the rest of the season).
† Probability of obtaining a 2021 yield below (<-10%), near (±10%), and above (>10%) than the long-term potential yield at each location.

Simulated Corn Stage Across 40 Locations

Corn has reached silking in Kansas, southeastern Nebraska, and southern Iowa and Illinois. In the rest of the region, corn is still in vegetative phases but it is expected to reach silking soon, especially in NE, IA, IL, IN and MO (Figure 2). Most locations are similar to or slightly behind last year’s corn development by July 14.

Figure 2. Simulated developmental stage for irrigated and rainfed corn at each location. Vn: vegetative stage (nth leaf); R1: silking; R2: blister. Separate maps are shown for irrigated corn (top) and rainfed corn (bottom).

Irrigated Corn: High Probability of Near-average Yields

The range of forecasted irrigated corn yield potential for each location, as well as the probabilities for yields above, near, or below average are shown in Figures 3 and 4. Although it is still too early in the season, there is a relatively high probability of near-average yields for all sites. There is a high probability of near-average yield (>75%, that is, a chance of three out of four) at three sites in southcentral NE and one site in western KS. Weather conditions during the rest of the growing season will determine if most irrigated sites will have near-average yield potential.

Variable 2021 Forecasted Corn Yield Across Rainfed Locations

Forecasted yield potential is highly variable across rainfed sites (Figures 3 and 4). Overall, at this point of the season, probability of near-average yield is relatively high towards the eastern fringe of the Corn Belt (southeastern IA, IL, IN and OH). In contrast, below-average yields probability increases towards the western and northern fringes of the region due to a combination of low precipitation and high temperature. Along these lines, there is a high probability of below-average yield (>75%) at five sites distributed across ND, MN, IA, eastern NE, and northern KS. This projection may change depending on precipitation and temperature during the rest of July and August. Similarly, yields can be higher than predicted here in fields with water table as the latter can help buffer against rain-free periods. Finally, there are three sites in the southern fringe of the region (St. Joseph, MO, Monroe City, MO, and Springfield, IL) where there is a high probability (>75%) of above-average yield due to higher rainfall.

Figure 3. Vertical lines indicate the range of forecasted 2021 corn yield potential by July 13 based on average planting date in 2021 at each location. Horizontal lines indicate the 25th and 75th percentiles of the yield distribution (associated with respective adverse and favorable weather scenarios during the rest of the season). The blue squares indicate the long-term (2005-2020) average yield potential at each location. Separate charts are shown for irrigated corn (top) and rainfed corn (bottom).
Figure 4. Probability of the 2021 yield potential to be below (<10%, red color), near (± 10%, yellow color), and above (>10%, green color) the long-term (2005-2020) average yield potential at each location. Separate maps are shown for irrigated corn (top) and rainfed corn (bottom). The larger a color section is within the pie chart, the higher the probability that end-of-season corn yield will be in that category.

Conclusions

The probability for a “record yield year” for the whole country seems low considering that the probability for above average yield is small (<25%) in 66% of the rainfed sites and 75% of the irrigated sites. Although it is still too early to make strong inferences about end-of-season yields for irrigated corn, there is a relatively high probability for near-average yields for a majority of sites, but this can change depending upon temperature during the next four weeks.

For rainfed corn, the scenario is diverse across regions, with higher probability of below-average yields in the north and western fringe of the region due to the limited rainfall over the past two months. Temperature and rainfall during the rest of July and early August will likely define the trend for all sites across the region. These forecasts do not take into consideration problems with stand emergence, hail/flooding damage, replanting situations, disease, or nitrate leaching. In fields negatively affected by these constraints, actual yields will be lower than estimates provided here.

It is important to keep in mind that yield forecasts are not field specific and, instead, represent an estimate of average on-farm yield for a given location and surrounding area in absence of the yield-reducing factors mentioned here. Likewise, crop stages and forecasted yields will deviate from the ones reported here in fields with planting dates or hybrid maturities that differ markedly from those used as the basis for the forecasts. We will follow up with further forecasts in early August.