This article summarizes the simulated crop stages and yield forecasts performed on Aug. 23 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 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.

Over the past three weeks, weather remained near the historical average except for a combination of high rainfall and low solar radiation in MO and parts of IL and IN. Overall, nighttime temperature matched historical records throughout the entire Corn Belt. A summary of weather conditions during the last three weeks is shown in Figure 1.

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 Aug. 2 and Aug. 22, 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.

Table 1. Data from simulations of 2023 end-of-season corn yield potential and real-time crop stage performed on Aug. 23.

	Location	Water regime	Long-term average yield (bu/ac) §	Range of Yp forecasts as of Aug 23 (bu/ac)¶ 25th	Range of Yp forecasts as of Aug 23 (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	190	217	12%	50%	38%	R4, Dough
	Beatrice	Dryland	160	188	200	0%	0%	100%	R5, Dent
		Irrigated	229	218	229	0%	100%	0%	R5, Dent
	Clay Center	Dryland	155	84	107	95%	5%	0%	R4, Dough
		Irrigated	245	226	241	15%	85%	0%	R4, Dough
	Concord	Dryland	173	132	158	68%	32%	0%	R4, Dough
		Irrigated	248	242	264	2%	85%	12%	R4, Dough
	Elgin	Irrigated	252	237	258	9%	80%	11%	R4, Dough
	Holdrege	Dryland	112	107	130	0%	66%	34%	R5, Dent
		Irrigated	242	231	254	11%	74%	14%	R4, Dough
	McCook	Dryland	86	99	107	0%	0%	100%	R5, Dent
		Irrigated	224	205	221	10%	90%	0%	R5, Dent
	Mead	Dryland	181	202	214	0%	17%	83%	R5, Dent
		Irrigated	234	228	242	0%	98%	2%	R5, Dent
	North Platte	Dryland	90	121	137	0%	0%	100%	R4, Dough
		Irrigated	234	228	264	7%	59%	34%	R4, Dough
	O'Neill	Irrigated	226	230	260	3%	53%	45%	R4, Dough
IA	Ames	Dryland	228	215	228	6%	91%	3%	R5, Dent
	Crawfordsville	Dryland	227	165	178	100%	0%	0%	R4, Dough
	Lewis	Dryland	205	201	210	0%	100%	0%	R5, Dent
	Nashua	Dryland	228	170	188	97%	3%	0%	R4, Dough
	Sutherland	Dryland	208	191	218	12%	85%	3%	R4, Dough
IL	Bondville	Dryland	235	237	252	0%	81%	19%	R4, Dough
	Freeport	Dryland	213	199	228	12%	73%	15%	R4, Dough
	Olney	Dryland	191	212	217	0%	21%	79%	R5, Dent
	Peoria	Dryland	211	238	253	0%	10%	90%	R4, Dough
	Springfield	Dryland	182	223	233	0%	0%	100%	R5, Dent
IN	Butlerville	Dryland	224	221	231	0%	90%	10%	R4, Dough
	Columbia City	Dryland	224	251	270	0%	20%	80%	R4, Dough
	Davis	Dryland	230	247	260	0%	55%	45%	R4, Dough
	West Lafayette	Dryland	236	239	253	0%	85%	15%	R4, Dough
KS	Garden City	Irrigated	217	194	205	27%	73%	0%	R5, Dent
	Hutchinson	Dryland	99	Black layer on Aug. 10. Final yield: 97 bu/ac					Matured
	Manhattan	Dryland	137	Black layer on Aug. 16. Final yield: 160 bu/ac					Matured
	Scandia	Dryland	129	96	97	100%	0%	0%	R5, Dent
		Irrigated	226	202	210	41%	59%	0%	R5, Dent
	Silverlake	Dryland	141	Black layer on Aug. 18. Final yield: 164 bu/ac					Matured
		Irrigated	209	210	215	0%	100%	0%	R5, Dent
MI	Ceresco	Dryland	180	182	215	5%	32%	64%	R3, Milk
MN	Eldred	Dryland	114	80	106	59%	41%	0%	R4, Dough
	Lamberton	Dryland	212	187	202	42%	58%	0%	R4, Dough
	Waseca	Dryland	219	199	213	23%	77%	0%	R4, Dough
MO	Brunswick	Dryland	181	94	97	100%	0%	0%	R5, Dent
	Monroe City	Dryland	175	134	138	100%	0%	0%	R5, Dent
	St. Joseph	Dryland	169	205	210	0%	0%	100%	R5, Dent
ND	Dazey	Dryland	108	84	120	39%	36%	25%	R4, Dough
OH	Custar	Dryland	208	219	239	3%	45%	53%	R3, Milk
	South Charleston	Dryland	216	220	248	3%	55%	42%	R4, Dough
	Wooster	Dryland	210	194	229	16%	66%	18%	R2, Blister

§Long-term (last 20-plus 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 entered the dough stage across a majority of sites, except for three sites in the eastern fringe of the region. At this point, corn has reached kernel dent stage in central to southern regions of the Corn Belt, and has even reached black layer at three sites in KS (Figure 2). Current corn stage is similar to that reported by mid-August last year.

Figure 2. Simulated developmental stage for irrigated and rainfed corn at each location. R2: blister; R3: milk; R4: dough; R5: dent; physiological maturity: Matured. Separate maps are shown for irrigated corn (top) and rainfed corn (bottom).

Irrigated Corn: Near or Below-average Yields are Expected

The forecasted range of irrigated corn yield potential for each location, along with the probabilities for yields above, near or below average, are shown in Figures 3 and 4. Most irrigated sites (eight out of 13) show a high probability (>75%, that is, three out of four chances) of near-average yield potential. Near-average yield is also likely in the rest of the sites. At this point, the forecasted scenario for irrigated maize in the current season appears more favorable than that of 2022.

Rainfed Corn: Yield Potential is Highly Variable Across Rainfed Sites

Forecasted yield potential is highly variable across the 35 rainfed sites (Figures 3 and 4). Consistent with our previous forecast, two distinct regions have a high probability of experiencing below-average yields. The first region includes portions of ND, MO and eastern IA, while the second covers the northeastern and south-central areas of NE, along with north-central KS. Compared with our previous forecast, the environmental conditions during the past three weeks have increased the probability of above-average yield potential in the eastern states (most of IL, IN and OH). Overall, 11 sites distributed across IL, IN, NE, KS and northwestern MO have a high probability (>75%, that is, three out of four chances) of above-average yields (Figures 3 and 4). Additionally, seven sites, primarily situated in western IA and the eastern part of the Corn Belt (IN and IL), exhibit a high probability of achieving near-average yields.

Spanning from west to east and in comparison with the 2022 forecast, the forecasted scenario for rainfed maize appears to be more favorable in the western region (NE, ND, northern MN, and most of IA and KS), more pessimistic in central areas (MO, northeastern IA, south of MN, and western IL), and largely similar in the eastern fringe of the Corn Belt (IL, IN, MI and OH).

Figure 3. Vertical lines indicate the range of forecasted 2023 corn yield potential by Aug. 23 based on average 2023 planting date 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 and the red dots represent the forecasted 2023 corn yield potential at sites that have already reached maturity. 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 has already reached the dough stage across the majority of the Corn Belt, while dent stage (or even black-layer) has been attained in the southern fringe of the region. When compared to our previous forecasts, most sites in the eastern part of the Corn Belt have increased the likelihood of achieving near or above-average yields. Temperature and rainfall during the rest of August will likely determine the trend for the eastern fringe of the Corn Belt. Moreover, above-average yields are also expected at a few spots in NE, KS and northwestern MO.

In contrast, two regions, one in south-central NE and north-central KS, and the other in MO, eastern and northern IA exhibit a high probability of below-average yields.

Overall, the regional average yield this season is expected to be near the historical average (

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. We will follow up with the final forecasted yield and analysis of the 2023 crop season in September.