July 10, 2012

Early this year, USDA-NASS released statistics on irrigated and dryland corn and soybean yields in Nebraska for the 2011 crop season. According to the data, the state average yields for corn and soybeans were 180 and 61 bu/ac under irrigation, and 132 and 47 bu/ac under rainfed conditions (Figures 1-2). While irrigated corn yield was the lowest since 2002, the 2011 irrigated soybean season had a “record-yield”  (Figure 3). Overall, 2011 was a good year for rainfed corn and soybeans, although not as good as 2009 (Figure 3).

Analysis of 2011 Corn Yield

The average yield for irrigated corn in 2011, at 180 bu/ac, was 6 bushels below the 2010 irrigated corn average and 6 bushels below the seven-year (2004-2010) average (Figure 1). These results were consistent with in-season Hybrid-Maize simulations of 2011 irrigated corn yield potential for Clay Center and Mead. The UNL corn model Hybrid Maize had predicted below-average end-of-season yields for both sites. These lower predictions were due to high day and especially nighttime temperatures during the pollination and early grain-filling periods in July and early August.

See the CropWatch articles reporting on the 2011 Hybrid-Maize models and harvest yields:

• Projected Corn Yields Drop Below Average in Aug. 1 Model
• End of Season Yields — What did Hybrid-Maize Predict?

Wet and cold weather conditions early in the season may have contributed to the lower yields of irrigated corn due to delayed planting, potential nitrogen deficiency due to nitrate leaching, and excess moisture favoring damping off pathogens resulting in reduced plant stands. Highest county-level average irrigated corn yields, in the range of 190 to 205 bu/ac, were reported for counties located in northeast and south central Nebraska (Figure 1).

Contrary to irrigated corn, 2011 was a relatively good year for rainfed corn, averaging 132 bu/ac, 6 bushels below the 2010 Nebraska average but still 6 bushels higher than the seven-year Nebraska average (2004-2010) (Figure 1). This was consistent with in-season simulation of 2011 rainfed yield potential using the Hybrid-Maize model for Clay Center, Concord, and Mead. The model had indicated sufficient rainfall during the grain-filling period to sustain above-average rainfed corn yields. Highest county-level average rainfed corn yields, in the range of 150-170 bu/ac, were reported for counties in the northeastern corner of the state (Figure 1).

Overall, yields for both irrigated and rainfed corn continue to trend upward (Figure 3).

Analysis of 2011 Soybean Yield

The average yield of irrigated soybean in Nebraska in 2011, at 61 bu/ac, was one bushel above the 2010 irrigated soybean state average and three bushels over the seven-year average (2004-2010) (Figure 2). Highest county-level average irrigated soybean yields, in the range of 66 to 70 bu/ac, were reported for counties in south central Nebraska (Figure 2).

A possible explanation for the better performance of soybean, as compared to corn, is that the pod and seed-filling period of soybean took place in August under relatively cooler conditions, while pollination and kernel set in corn occurred during hotter July conditions. It was also a good year for rainfed soybean, averaging 47 bu/ac, one bushel above the 2010 state average for rainfed soybean and four bushels above the seven-year average (2004-2010). The highest county-level average rainfed soybean yields, in the range of 48 to 58 bu/ac, were reported for counties in south central and east central Nebraska.

Overall, yields for both irrigated and rainfed soybean continue to trend upward (Figure 3).

Summary

Overall, the Hybrid-Maize model did a good job of predicting and helping to explain 2011 yields, showing how weather conditions impacted yields. In-season Hybrid-Maize simulations will be run for 2012 across the entire U.S. Corn Belt and shared in CropWatch articles in the coming months. See the first of these reports in this week’s CropWatch, Forecasted Corn Yields Based on Hybrid-Maize Model Simulations.

Patricio Grassini, Research Associate Professor, UNL Agronomy and Horticulture
Jenny Rees, UNL Extension Educator