Simulations of 2024 end-of-season corn yield potential and real-time crop stage were performed on Aug. 5 for 43 locations across the U.S. Corn Belt using the UNL Hybrid-Maize crop model in collaboration with faculty and extension educators from ten universities. This article summarizes the simulated crop stages and yield forecasts; the data can be seen 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.

Warm weather prevailed over the past two weeks, except for MO, IN and IL where temperatures remained near average. In turn, most sites in MO, NE and KS exhibited below-normal rainfall, while a few sites in IL, OH and MN received rainfall amounts that exceeded the historical average. The remaining locations across the Corn Belt showed near-normal records. A summary of weather conditions during the past two weeks is shown in Figure 1.

Simulated Corn Stage Across 43 Locations

Corn has reached the dent stage in the southern fringe of the Corn Belt (KS, MO and southern IL). In the rest of the region, corn has reached dough stage, except for a few sites in the northern region (ND, MI and northern MN) where corn is still in milk or even blister stage. In general, corn development is ahead relative to the 2023 crop season, except for ND, MN and IA where development is similar to last year (Figure 2).

Irrigated Corn: Near to Below-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. In general, there is a relatively low probability of above-average yields. Temperature during the rest of August will determine whether yields will be near or below average. Conversely, the scenario is highly uncertain in western and northeastern NE, where there is still a relatively high probability of near or above-average yields. Overall, the scenario for irrigated corn in NE and KS is more optimistic compared to last season's forecast.

Variable 2024 Forecasted Corn Yield Across Rainfed Locations

Forecasted yield potential is highly variable across the 39 rainfed sites (Figures 3 and 4). There is a high probability of near-average yield (>75%) at 11 sites across MN, IA, IL, IN and OH. Conversely, five sites distributed across NE, KS, MO and IL have a high probability (>75%) of above-average yields. The probability of below-average yield is relatively high (>75%) only in western NE and KS.

Compared with our previous forecast, below-average rainfall in most parts of NE and KS during the past two weeks increased the probability of below-average yields in that area, reducing the forecasted yield for the 2024 season. In contrast, the scenario improved for sites located in southern IN, IL and OH because of the above average rainfall during the last two weeks. In the remaining area, the scenario looks similar compared with our previous forecasts.

When compared with the 2023 season results, the current season's scenario is more optimistic in ND, MN, IA and MO. In contrast, the forecasted results are more pessimistic in KS and OH than last season, while NE, IL and IN are expected to have fairly similar yields overall.

Conclusions

Probability of above-average yields for most of the irrigated sites is low, with temperature during the rest of August determining if final yield will be near or below average. For rainfed corn, yields are expected to be near or above-average, except for sites in western NE and KS where there is a high probability of below-average yields. Temperature and rainfall during 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 late August.