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).

Figure 1. Daily solar radiation, maximum and minimum air temperature (Tmax and Tmin), total rainfall, and total reference grass-based evapotranspiration (ET) for the time period between May 13 and July 12, 2023. Vertical bars indicate the range for these variables based on 20-plus years of weather records. The horizontal thick line indicates the long-term average and the red dots indicate the 2023 values for the same period.

Table 1. Data from simulations of 2023 end-of-season corn yield potential and real-time crop stage performed on July 12.

	Location	Water regime	Long-term average yield (bu/ac) §	Range of Yp forecasts as of Jul 19 (bu/ac)¶ 25th	Range of Yp forecasts as of Jul 12 (bu/ac)¶ 75th	Probability (%) of 2023 yield to be: Below (relative to the long-term Yp)†	Probability (%) of 2023 yield to be: Near (relative to the long-term Yp)†	Probability (%) of 2023 yield to be: Above (relative to the long-term Yp)†	Simulated current crop stage*
NE	Alliance	Irrigated	193	176	216	21%	44%	35%	V8
	Beatrice	Dryland	160	120	171	48%	27%	24%	R1, Silking
		Irrigated	229	209	239	24%	70%	6%	R1, Silking
	Clay Center	Dryland	155	67	158	61%	15%	24%	V16
		Irrigated	245	226	250	15%	76%	10%	V16
	Concord	Dryland	173	155	226	27%	17%	56%	V16
		Irrigated	248	234	266	15%	71%	15%	V16
	Elgin	Irrigated	252	235	265	11%	74%	14%	V16
	Holdrege	Dryland	112	84	134	37%	23%	40%	V14
		Irrigated	242	217	249	26%	60%	14%	V14
	McCook	Dryland	86	70	116	29%	7%	63%	V14
		Irrigated	224	199	231	27%	61%	12%	V14
	Mead	Dryland	181	129	188	51%	32%	17%	V18
		Irrigated	234	213	242	20%	66%	15%	V18
	North Platte	Dryland	90	110	134	2%	20%	78%	V12
		Irrigated	234	212	255	22%	54%	24%	V12
	O'Neill	Irrigated	226	209	249	16%	58%	26%	V12
IA	Ames	Dryland	228	198	236	43%	40%	17%	V16
	Crawfordsville	Dryland	227	179	213	58%	39%	3%	V18
	Lewis	Dryland	205	154	207	44%	44%	12%	R1, Silking
	Nashua	Dryland	228	197	224	41%	56%	3%	V14
	Sutherland	Dryland	208	193	225	21%	62%	18%	V14
IL	Bondville	Dryland	235	222	259	13%	58%	29%	V16
	Freeport	Dryland	213	164	225	42%	42%	15%	V14
	Olney	Dryland	191	190	225	18%	27%	55%	R1, Silking
	Peoria	Dryland	211	214	251	3%	57%	40%	V16
	Springfield	Dryland	182	162	212	30%	35%	35%	V18
IN	Butlerville	Dryland	224	209	237	10%	70%	20%	V14
	Columbia City	Dryland	224	217	251	0%	60%	40%	V12
	Davis	Dryland	230	237	262	0%	50%	50%	V12
	West Lafayette	Dryland	236	222	242	10%	80%	10%	V14
KS	Garden City	Irrigated	217	204	236	19%	62%	19%	V14
	Hutchinson	Dryland	99	83	119	36%	12%	52%	R2, Blister
	Manhattan	Dryland	137	134	169	16%	37%	47%	R1, Silking
	Scandia	Dryland	129	71	119	73%	14%	14%	R1, Silking
		Irrigated	226	202	244	27%	51%	22%	R1, Silking
	Silverlake	Dryland	141	111	167	41%	24%	35%	R1, Silking
		Irrigated	209	191	229	19%	57%	24%	R1, Silking
MI	Ceresco	Dryland	180	167	222	14%	32%	55%	V8
MN	Eldred	Dryland	114	51	108	67%	19%	15%	V10
	Lamberton	Dryland	212	197	226	19%	65%	15%	V16
	Waseca	Dryland	219	196	230	28%	63%	9%	V16
MO	Brunswick	Dryland	181	97	131	91%	9%	0%	R1, Silking
	Monroe City	Dryland	175	99	171	55%	45%	0%	V18
	St. Joseph	Dryland	169	139	187	35%	39%	26%	R1, Silking
ND	Dazey	Dryland	108	108	168	21%	11%	68%	V10
OH	Custar	Dryland	208	214	238	3%	47%	50%	V10
	South Charleston	Dryland	216	192	246	27%	45%	27%	V12
	Wooster	Dryland	210	192	225	24%	58%	18%	V8

§Long-term (last 20+ years) potential yield at each location and surrounding area.
¶ Range of forecasted 2023 potential yields based on average planting date in 2023, 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 2023 yield below (10%) than the long-term potential yield at each location.

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.

Figure 2. Simulated developmental stage for irrigated and rainfed corn at each location. Vn: vegetative stage (nth leaf); R1: silking; R2: blister. Separate maps are shown for irrigated corn (top) and rainfed corn (bottom).

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.

Figure 3. Vertical lines indicate the range of forecasted 2023 corn yield potential by July 12 based on average planting date in 2023 at each location. Horizontal lines indicate the 25th and 75th percentiles of the yield distribution (associated with respective adverse and favorable weather scenarios during the rest of the season). The blue squares indicate the long-term (2005-2022) average yield potential at each location. Separate charts are shown for irrigated corn (top) and rainfed corn (bottom).

Figure 4. Probability of the 2023 yield potential to be below (10%, green color) the long-term (2005-2022) average yield potential at each location. Separate maps are shown for irrigated corn (top) and rainfed corn (bottom). The larger a color section is within the pie chart, the higher the probability that end-of-season corn yield will be in that category.

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.