Simulations of 2023 end-of-season corn yield potential and real-time crop stage were performed on Aug. 2 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 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.

A summary of weather conditions during the last three weeks is shown in Figure 1. Over the past three weeks, average air temperature has remained near average values in most of the Corn Belt. However, sites located in ND, MN, and most of IA showed night temperatures below historical average while two sites in MO have experienced above-average day-time temperatures. Rainfall was well below normal in MO, MN, ND, northern and eastern IA, and some spots in OH, IL and NE. Rainfall was near normal records in the remaining locations.

Simulated Corn Stage Across 40 Locations

Corn has reached the kernel milk stage, except for the northern and eastern fringes of the region. Corn in the southern fringe (KS, MO and southern IL) is ahead of the rest of the locations, having already reached the dough and even the dent stage (Figure 2). The current corn stage is similar to that reported by early August last year, except at ND, MO and southern IA, where crop development has been faster.

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. Six out of 13 sites in eastern NE and KS exhibit a high probability (>75%, that is, a chance of three out of four) of near-average yield potential. Near-average yield is also likely in the rest of the sites, depending upon the temperature during the rest of August. At this point, the forecasted scenario for irrigated maize in the current season seems better than 2022.

Variable 2023 Forecasted Corn Yield Across Rainfed Locations

Forecasted yield potential is highly variable across the 35 rainfed sites (Figures 3 and 4). Two regions have a high probability of below-average yields: one includes portions of MN and MO and eastern IA, and other includes south-central NE and north-central KS. Conversely, there is a high probability of above-average or near-average yield (>75%) in western IA, the eastern fringe of the region and a few spots in NE.

Compared with our previous forecast, below-average rainfall in eastern IA and most of northern MO during the past three weeks increased the probability of below-average yields in that area, reducing the forecasted yield for the 2023 season. A few scattered sites in the eastern states (IL, IN and OH) have reduced the probability of above-average yields due to below-average rainfall and above-average daytime temperatures in the last three weeks. In contrast, due to cooler weather in southeastern NE, the associated yield forecasts have been improved relative to mid-July, now showing a high probability of near- and even above-average yields.

Compared with the 2022 forecast, the forecasted scenario for rainfed maize seems more favorable in NE (except for south-central sites) and western IA, while in MO, eastern IA and MN, and western IL the scenario looks more pessimistic. In the remaining area, the scenario looks similar to the 2022 season.

Conclusions

There is a high probability of near-average yields for most of the irrigated sites, while for rainfed corn the scenario is diverse across regions. Most sites in the eastern part of the Corn Belt have a high probability of near-average yields, while above-average yield is expected at MI and a few spots in NE. In contrast, two regions, one in south-central NE and north-central KS, and the other in MO, eastern and northern IA, and MN exhibit a high probability of below-average yields. Temperature and rainfall during August will 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.