From the Fields…COnsider performance in seed selection
By Jim Morrison
By Jim Morrison
Extension Educator, Crop Systems
University of Illinois, Rockford Extension Center
Farmers are in the process of making important seed selection decisions. With a wide variety of seed demonstration plots and booklets available, plus the farmers own experience, especially aided by yield monitors, the task of variety selection can be overwhelming.
It is impossible to get an exact measure of performance when conducting any test of plant material. Harvesting efficiency may vary, soils are not uniform, and many other conditions may produce variability. Results of repeated or replicated tests are more reliable than those of a single year or a single-strip test.
When one hybrid or variety consistently outyields another at several locations and for more than one year of testing, the chances are good that this difference is real and should be considered in selecting a variety. However, yield is not the only factor. One should also consider maturity, lodging score or stalk strength, plant height, disease and insect resistance, etc. Keep in mind the tillage system and the row spacing that will be used, and whether to grow a genetically modified crop cultivar.
As an aid in comparing corn, soybean, and forage varieties within a single trial, the University of Illinois Department of Crop Sciences has used certain statistical tests.
One of these tests is the least significant difference (L.S.D.) and is included in variety test booklets.
When two entries are compared and the difference between them is greater than the calculated L.S.D. value, the entries are said to be significantly different. The L.S.D. can be expressed as bushels per acre or tons per acre. If the 10 percent L.S.D. is used, decisions are true nine out of 10 years. A 30 percent L.S.D. will be true seven out of 10 years. The 30 percent L.S.D. is a smaller number and will include fewer varieties in the top group.
Now, how does one use this statistical measure? Decide the L.S.D. level that is best for your farm and find the highest yielding variety at a given location, maturity group, etc. Subtract the chosen L.S.D. level from the highest yielding variety. Every variety with a greater yield than the resulting number is statistically the same as the highest yielding variety. Consider the merits of the varieties in this group when making final variety selection decisions.
Copies of University of Illinois corn, soybean and forage variety trials from 2000 are available at local Extension offices. The variety data is also available on the Internet at HYPERLINK: