Iowa Crop Variety Yield Testing: A History and Annotated Bibliography

Variety testing by U.S. agricultural universities, often in cooperation with experiment stations, and professional crop associations is recognized as an independent, unbiased validation of the viability of commercial crop varieties. In Iowa, variety testing has also been conducted by many private agricultural companies and individual farmers. Records for crop variety evaluations within the state can be traced back to 1871, well before the creation of the Iowa Agricultural Experiment Station in 1888. The Iowa Corn Yield Test (ICYT) is undeniably the most famous of the Iowa variety yield trials; however, corn (Zea mays L.) varieties were being tested long before that program was initiated. Furthermore, Iowa researchers have been conducting variety yield tests on many other field crops. Knowledge of how Iowa variety tests have been organized and published could be helpful to researchers looking for similar, long-term evaluations from other states and around the world. Variety tests from the past also have the potential to help guide new research efforts and may provide an important untapped resource for unique varietal data. As crop scientists and agronomists look to find new sources for biofuels, bio-products, and other industrial uses for various crops, data from historical varieties could be useful. The objective for this review is to provide an historic account with sections on varietal testing in Iowa. It is presented in chronological order followed by sections devoted to specific crops. A Supplemental Information file containing a detailed annotated bibliography is also provided

Lengthening of maize maturity time is not a widespread climate change adaptation strategy in the US Midwest

Increasing temperatures in the US Midwest are projected to reduce maize yields because warmer temperatures hasten reproductive development and, as a result, shorten the grain fill period. However, there is widespread expectation that farmers will mitigate projected yield losses by planting longer season hybrids that lengthen the grain fill period. Here, we ask: (a) how current hybrid maturity length relates to thermal availability of the local climate, and (b) if farmers are shifting to longer season hybrids in response to a warming climate. To address these questions, we used county‐level Pioneer brand hybrid sales (Corteva Agriscience) across 17 years and 650 counties in 10 Midwest states (IA, IL, IN, MI, MN, MO, ND, OH, SD, and WI). Northern counties were shown to select hybrid maturities with growing degree day (GDD°C) requirements more closely related to the environmentally available GDD compared to central and southern counties. This measure, termed “thermal overlap,” ranged from complete 106% in northern counties to a mere 63% in southern counties. The relationship between thermal overlap and latitude was fit using split‐line regression and a breakpoint of 42.8°N was identified. Over the 17‐years, hybrid maturities shortened across the majority of the Midwest with only a minority of counties lengthening in select northern and southern areas. The annual change in maturity ranged from −5.4 to 4.1 GDD year−1 with a median of −0.9 GDD year−1. The shortening of hybrid maturity contrasts with widespread expectations of hybrid maturity aligning with magnitude of warming. Factors other than thermal availability appear to more strongly impact farmer decision‐making such as the benefit of shorter maturity hybrids on grain drying costs, direct delivery to ethanol biorefineries, field operability, labor constraints, and crop genetics availability. Prediction of hybrid choice under future climate scenarios must include climatic factors, physiological‐genetic attributes, socio‐economic, and operational constraints

The international competitiveness of the U.S. corn-ethanol industry: A comparison with sugar-ethanol processing in Brazil

An indicator of competitive position, the cost difference between ethanol import from Brazil with sugar processing and domestic production with corn in the United States under ideal conditions without tariffs in the ethanol market, is developed conceptually. An ex ante version of the indicator that is based on historical prices and today's technology is calculated for the last 30 years and subjected to time series analysis. Results suggest that there are no trends, but there are cyclical periods of advantage for both industries. Further, long-term averages suggest that profits would be similar in both countries under ideal trade conditions. However, the corn wet-milling industry may have slightly higher profits than other processes and locations. Finally, the U.S. dry-milling industry could improve its competitive position using modified corn varieties with high starch content, and using corn residues for biomass generation of electrical and heat energy. [EconLit Classifications: F140, L650, Q420]. © 2006 Wiley Periodicals, Inc. Agribusiness 22: 109-134, 2006.