Simulations of 2024 end-of-season corn yield potential and real-time crop stage were performed on July 23 for 43 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 viewed 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 23 to July 22) is shown in Figure 1. The season began with near-average temperatures in the central Corn Belt, while daytime temperatures were below normal in the northwestern fringe of the region (ND and MN). Total rainfall was near the historical average at most sites. However, consistent with drought monitor reports, rainfall was below average in western NE and parts of KS and OH, and above average in southern MN, northern IA and eastern NE.

§ Long-term (last 20-plus years) potential yield at each location and surrounding area. 
¶ Range of forecasted 2024 potential yields based on average planting date in 2024, 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 2024 yield below (10%) than the long-term potential yield at each location; or 5% at each irrigated location, respectively.

Simulated Corn Stage Across 43 Locations

Corn has reached the silking stage at all sites except for the northwestern fringe of the region (ND and northern MN), where it is still in vegetative phases (Figure 2). Additionally, most sites in the southern part of the Corn Belt have reached the milk stage (central and southern IL, southern NE, and western and southern IN and OH) or even the dough stage (KS and MO).

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 early in the season, there is a relatively high probability of near-average yields for most irrigated sites, with above-average yields more likely in western NE. Weather conditions during the grain filling will ultimately determine if most irrigated sites achieve near-average yields.

Variation in 2024 Forecasted Rainfed Corn Yield

Forecasted yield potential is variable across rainfed sites (Figures 3 and 4). Overall, at this point of the season, the probability of near-average yields is relatively high in the northern, central, and eastern fringe of the Corn Belt (ND, MN, IA, IL, IN, MI and OH). Indeed, there is a high probability of near-average yields (>75%) in eight sites, which is consistent with USDA NASS crop reports.

Conversely, the probability of above-average yields increases towards the west and southwest of the Corn Belt (southwestern IA, southern and eastern NE, eastern KS, and MO). Finally, the western fringe of the region (western NE and southern KS) exhibits a high probability of below-average yields. Whether these trends persist will depend on precipitation and temperature patterns during the rest of July and early August.

Conclusions

Corn has reached reproductive stages throughout most of the region. While it is still early to make strong inferences about end-of-season yields for irrigated corn, there is a relatively high probability of near-average yields for most sites, but this could change depending on temperatures during the next weeks.

For rainfed corn, the scenario is diverse across regions, with near-average yields likely in the northern, central and eastern regions of the Corn Belt. However, above-average yields are expected in southern and eastern NE, eastern KS and MO, whereas limited rainfall is leading to below-average yields in western NE and southern KS.

Temperature and rainfall through the end of July and early August will be crucial in determining whether these projections persist.

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 yield potential 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.