Locating varietal yield information may seem easy on the surface, but it is complicated by: different types of yield reports; many different types of tests/contests; similar terminology with different meanings; changing terminology over the years; published reports disseminated in a somewhat scattershot fashion throughout a number of experiment station or USDA publications; some experiment results are only available in unpublished theses/dissertations or the Iowa State University Library Archives; and, data from varietal tests done by private companies is proprietary and rarely distributed outside of the company. Research studies often pull bits and pieces of their data directly from agricultural experiment station variety trials without complete citations to the source of the data. This guide provides direct links and pointers for locating variety trials for specific field crops in Iowa, both past and present.
Note: Yield publications included in this guide have been cited and mentioned in other publications; however, the ISU Library does not yet have copies of all of them.
Variety yield tests (or crop performance tests) are experiments in which different varieties of crops are analyzed to see which varieties produce the best yields. These results are then used to alert farmers in the area to best practices for growing specific crops and recommended varieties for specific geographic areas and soils. Some tests also studied other varying conditions (such as different types of fertilizer, soils, crop rotations, etc.) on yields. The original intent was to increase yields and help farmers make more informed decisions for higher profitability. In later years, chemical composition tests and industrial use research also helped increase demand for specific crop varieties. Variety and seed testing by agricultural experiment station researchers at U.S. universities has served as an independent, unbiased test validating the viability of commercial varieties; however, variety testing has also been conducted by many different private agricultural companies.
Individual varieties have the ability to influence not only yield amounts but also composition and quality of the crop, and ease of harvesting. If a variety does not work well or is not profitable, farmers are much less likely to plant it again. Beyond yield amounts, variety tests can also include valuable information on maturity dates, lodging and chemical composition. These in turn can be used in further research studies on topics such as digestibility of feed grain varieties, quality of oil or seed, nutritional value (for livestock and humans), and industrial uses for grain, seed or oils.