The 2005-06 wheat and oat season presented numerous challenges, including a dry fall that resulted in late emergence and vernalization issues, a late freeze, a very warm April, late rust pressure in Central Texas and a very dry spring.
These factors resulted in a lot of variability in yields and test weights across the state and within a given region.
When selecting a variety for the 2006-07 season, producers need to recognize the numerous abnormalities that occurred in the 2005-06 season and should not emphasize those results when selecting wheat varieties for the 2006-07 season. I strongly encourage producers to look at the two- and three-year averages for the varieties and to look at numerous relevant variety trial locations. Typically we conduct 20 or more wheat variety trials across the state each year.
Many locations showed good foliar disease ratings this year. Foliar disease resistance for wheat and oat varieties can and often do change annually. These ratings are the most current information on varietal resistance and should be used when selecting wheat and oat varieties.
Below are some general things to consider when selecting wheat and oat varieties.
Selecting the proper small grain varieties is one of the most important decisions a producer will make. This decision affects potential yield (forage and grain), seed quality (test weight and protein), disease and insect management, and maturity. It is important for producers to diversify varieties planted on their farms. Variety diversification spreads the risk associated with potentially devastating pests (rusts, Hessian fly, leaf curl mite, greenbugs) and yield loss from adverse environmental factors (freeze, drought, hail, etc.).
Producers should select no fewer than two varieties and preferably more. Variety selection should be based on a combination of sound data from university trials, county agent strip trials, and other reliable sources. Wheat varieties should be chosen based on multiple years of data (yield, pest package, test weight, and maturity). High yields over multiple years and multiple locations equates to a variety's ability to perform well over diverse environmental factors.
Stable yield performance is the best variety selection information. One thing to be cognizant of is decreasing yields and disease resistance over the two- or three-year time frame, which may reflect a change in disease resistance.
Interpreting the Data:
Each location is statistically analyzed using recommended procedures. The statistical analysis provides the mean, percent coefficient of variation (CV), and LSD values. Without considering these statistics, you may be misinterpreting yield data.
The mean is another term for the average. So, the mean value is the average of all the variety yields within the trial. The percent CV value indicates the level of unexplained variability present within the trial. A high CV value indicates a lot of variability existed within the trial. Variability may result from non-uniform stands, non-uniform insect or disease pressure, variability in harvesting, or other issues. When CV values exceed 15 percent, data validity becomes questionable and usefulness decreases.
The LSD value indicates if the varieties performed differently from one another within the trial. If the LSD value is 5 bushels per acre and the Variety A yielded 36 bushels per acre and Variety B yielded 30 bushels per acre, then Variety A is significantly better. The LSD value at a 0.05 level indicates that Variety A would yield better than Variety B in 19 of 20 trials conducted under the same conditions.