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Inside Grundy County

Source of Unbiased Yield Information

December 17, 2011
Bill Arndorfer - Butler-Grundy County Extension Educator , Reinbeck Courier

There is a lot of corn hybrid and soybean variety information available for farmers to use to help make hybrid and variety decisions in their farm operations. One source farmers can turn to for unbiased performance data is the Iowa Crop Performance Tests from Iowa State University and the Iowa Crop Improvement Association. You can access the performance results at:

So how does this work? There are six testing districts throughout Iowa with three testing sites within each district. Districts also have an east/west overlapping region which allows four testing locations per district. Corn entries are subdivided into experiments based on relative maturity, providing an early season and full season test within each district. Soybean entries are likewise subdivided based on maturity group within each region. Soybean entries with various herbicide traits are placed into the same tests as conventional soybean entries.

Seed companies, Iowa farmers, and the Iowa Crop Improvement Association may include entries in the Iowa Crop Performance Test-Soybeans. The Iowa Crop Performance Test-Corn contains hybrid entries from seed companies, the Iowa Crop Improvement Association and Iowa State University. All entries from these entities are made voluntarily and the seed used to plant entries are submitted by the originators.

Testing procedure for corn is as follows: each entry is replicated four times in four row plots with a planting rate of 34,500 kernels in thirty inch row spacing, plot length of twenty feet and planted row length of 17.4 feet. The center two rows are harvested with a combine and no gleanings or dropped ears are included in the yield data. Moisture determination is made from each plot and yields are corrected to 15.5 percent moisture for shelled corn. Yield determinations are based on a twenty foot plot which includes the planted row plus the alley. This is because area in alleys may contribute to the yield of plants at the ends of planted rows.

Soybean entries are grown in four row plots with thirty inch row spacing. The plot length is twenty feet with a planted length of 17.4 feet. The seeding rate is eight seeds per foot or 140,000 seeds per acre. Four replications of the entries are used at each location. Conventional herbicide products are used for weed control at each location and plots are sprayed for soybean aphids, bean leaf beetles and fungal pathogens as needed.

It is important to select hybrids and varieties having stable performance over a range of environmental conditions. High yields for two or more consecutive years indicate stable performance. If two year means are not available, regional averages consisting of several locations should be used to make selection decisions. Variety performance data from a single location has very low predictive probability and should not be relied upon for hybrid selection decisions. Supplemental yield and agronomic information about specific varieties may be obtained from seed dealers, crop consultants and neighbors who have grown these varieties.

For a copy of the corn and soybean yield trials, check out the crop testing website listed above or contact the Grundy office of ISU Extension at 319-824-6979.



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