This is the last article in a series that summarizes the simulated crop stages and yield forecasts across the Corn Belt. To evaluate, in “real-time,” the impact of this season’s weather on corn yield and its spatial variability across the Corn Belt, simulations of 2023 real-time crop stage were performed for 40 locations across the U.S. Corn Belt using the UNL Hybrid-Maize crop model; 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 is described in a previous article.

Crop Stages and Weather Conditions During the Last Three Weeks

Corn has reached black layer stage at most of the sites, except for those located in western and eastern fringes of the region, including ND, western NE, IN and OH (Figure 2). During the late grain filling, temperature was above normal and rainfall below normal, except for the eastern region where temperature and rainfall were near average (IN and OH). Indeed, several sites across IN, IL, IA, MN and KS received very little or no rainfall during this period.

A summary of weather conditions during the past three weeks is shown in Figure 1.

Near but Below Average Yields in Irrigated Corn

Forecasted end-of-season irrigated yields are shown in Figure 3 and 4. About two thirds of the irrigated sites (eight out of 13) exhibited near-average yields. Compared with our previous forecast, forecasted yields are 7% lower because of higher temperatures during the last half of the grain filling. Although most irrigated sites present forecasted yields near historical records, expected yields are consistently lower than historical averages (average: 8% lower) and similar to the previous (2022) season.

Rainfed Corn: Yield Potential is Highly Variable Across Rainfed Sites

Lack of rainfall and high temperatures during the last portion of the seed filling led to a reduction of the projected end-of-season rainfed yields by nearly 5% compared to our previous forecast. Still, one-third (10 out of 36) of the sites are expected to achieve above-average yields. These sites are scattered across the region, including portions of western NE, northeast KS, southeastern NE, northwestern MO, IL, IN and OH (Figures 3 and 4).

Conversely, another third of the sites (13 out of 36) exhibit below-average yields. These sites are situated in the central and western areas of the Corn Belt (eastern IA, northwestern IL, northern MO, northeastern and south-central NE, north-central KS) and the northwestern region (north of IA, MN and ND).

The remaining sites showed a high probability of near-average yield and are located in the eastern part of the Corn Belt (eastern IL, IN and OH, and southern IA).

Overall, the 2023 yield scenario appears to be slightly more favorable than the previous year (2022) but is still 6% below the long-term average. Compared to the 2022 season, forecasted yield is higher for the current 2023 season for rainfed sites in NE, southwestern IA and southern KS. Conversely, 15% or more lower yield is forecasted for southern MN, northeastern IA, and MO compared with the previous year.

Conclusions

Aggregated at regional level, our forecasted yield potential this season is 7% below the historical average for both rainfed and irrigated corn. In line with USDA predictions, our forecast reduced expected yields compared to the August report and foresees similar average yield compared to that from last year.

Our forecast suggests a near average year for a majority of irrigated sites although 40% of them can expect yields to be below the historical average.

For rainfed corn, the scenario is diverse across regions. Most sites in the eastern part of the Corn Belt and a few scattered sites in central and western areas have a high probability of near-average rainfed yields. Above-average yield is expected at 10 locations scattered across the west and eastern areas of the Corn Belt. Conversely, 13 sites located in central, western and northwestern fringes of the Corn Belt exhibit a high probability of below-average rainfed yields.

Note that 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 those reported here in fields with planting dates or hybrid maturities that differ markedly from those used as the basis for these forecasts.