Simulations of 2023 end-of-season corn yield potential and real-time crop stage were performed on July 13 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 13 to July 12) is shown in Figure 1. The season started with warm weather in the central and northwestern regions of the Corn Belt, with temperatures above normal in ND, MN, IL, IA and NE. In south and east areas (KS, MO, IN and OH), temperature records were near the historical averages for most cases. In agreement with drought monitor reports, rainfall was below average across the whole region, except for the western fringe (ND, western NE and KS).

Simulated Corn Stage Across 40 Locations

Corn has not reached silking yet at most sites, except for the southern fringe of the region (Figure 2). Except for MN and ND, where corn development is ahead of last season, most locations are at a stage similar to 2022 at this time of the year.

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. Indeed, there is a high probability of near-average yield (>75%, that is, a chance of three out of four) in south and central NE. Weather conditions during the rest of the growing season will determine if most irrigated sites will yield near average.

Variation in 2023 Forecasted Rainfed Corn Yield

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 (IL, IN and OH) and southern MN. Conversely, the probability of below-average yields is relatively high in the central, western and southern regions, except for west NE and south KS, which is consistent with USDA NASS crop reports. Precipitation and temperature during the rest of July and early August will determine whether these trends persist or not. If rainfall increases, as has been the case over the past two weeks, we will expect forecasted yields to improve.

Conclusions

Corn is still in vegetative stages throughout most of the region. 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 most sites, but this can change depending upon temperature during the next four weeks.

For rainfed corn, the scenario is diverse across regions, with high probability of below-average yields in the south, central and western regions of the Corn Belt due to below-average rainfall. Temperature and rainfall during the rest of July and early August will be critical to understand if the current projections will 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 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.