Sept. 3, 2010

Wheat yield during a particular season is mainly determined by the

• variety,
• management and the level of input, and
• environmental factors affecting wheat yield during the season.

Of these factors, producers have the most control over the variety selected. The variety can make all the difference between a very good season or a disappointing one.

To assist with variety selection, the UNL Variety Testing Program provides useful information on winter wheat varieties sold in Nebraska based on field trials conducted throughout the state. Wheat varieties tested by the program come from

• UNL wheat breeding program
• Public breeding programs from surrounding states
• Private seed industry

The Nebraska Wheat Board partially supports the testing of wheat varieties from out of state public wheat breeding institutions.

Accessing Wheat Variety Test Results

The results of these wheat variety tests are made available through the UNL Variety Test website and the UNL Fall Seed Guide (EC 103), available from your local Extension office. The Fall Seed Guide also contains information from the Nebraska Crop Improvement Association on certified seed sources and private industries developing and marketing wheat varieties in Nebraska.

The variety testing program provides unbiased third party information in the performance of each wheat variety marketed in Nebraska. This information can be used to make informed decisions when selecting varieties to plant. Test results from various locations are provided for a number of varieties for yield, test weight, seed size, and grain protein. Other important characteristics included are relative values for maturity, winter hardiness, straw strength, coleoptiles length, and disease and insect resistance.

Table 1 shows where trials were conducted this season, sowing date, harvest date, highest location yield, and the mean yield of the top five varieties tested at the location. Table 2 shows top yield performers by site, as well as within regions and across regions. It helps provide a general idea of how various varieties performed, including in organic trials.

When the yield reported for the top five doesn’t significantly differ from the current variety (ies) used on a farm, it may not be necessary to look further if yield is the only criteria for selection. Use the LSD (Least Significant Difference) value to evaluate whether the observed difference in performance between varieties is significant. LSD values are shown on the web with individual site analysis or in the seed guide with across site and across year analysis. A 5% LSD value indicates a variety would yield better than the other variety at least 95 of 100 times due to real difference. It must be clear that the LSD values are shown only when there is significant difference between varieties.

The seed guide is a good source for varieties that have top performance across season (last five years) and across location. It is highly recommended that you consider across location and across year yield stability in selecting a variety to grow.

2010 Conditions Affecting Variety Trial Results

There are some peculiar situations specific to the growing condition of this past season worth noting when selecting varieties using the variety testing data. Stripe rust was reported to be dominant across the state where wheat was grown. Stripe rust incidence (percent of diseased plants) and severity (percent of diseased area on a plant) varied from field to field reaching over 70% for both incidence and severity at some locations. Other diseases observed were blotch, tan spot (especially in fields with wheat stubble on the ground surface), leaf rust, isolated cases of stem rust, glume blotch, loose smut, and black chaff. Excessive, prolonged wet weather favored development of higher levels of disease this year compared to the previous three years. Wheat harvesters have reported wheat stem sawflies, particularly in the Panhandle.

Hail damage was observed in a number of locations particularly in the west with a wide range of reported yield loss. Plots where yield trials were located reported up to 70% loss due to hail damage. Two trial locations were not harvested due to hail damage.

Harvest was complicated by heavy rain. The delayed harvest due to rain resulted in bleached kernels, lower kernel weight and low grain protein.

Complementary varieties are important when selecting additional varieties to grow. One definition of complementary varieties is that they come from diverse parentages. Please refer to the following link for more detailed discussion on variety complementation strategy.

Wheat Variety Selection Tips

Management information for all testing sites is given in the Fall Seed Guide (EC101), available now from local Extension offices. Producers are encouraged to relate the information given for the sites they’re interested in and consider how varietal response might transfer to their farm condition and management

One advantage with comparing wheat test data over some other crops is the ease of finding three- to five-year averages. Wheat varieties have a longer field life than other crops such as corn. It is appropriate also to look at variety performance at different variety trial locations even when the location characteristics are different. Typically we conduct more than 20 wheat variety trials across the state each year. We have two sites in Wyoming this year across the state line. Wheat trials are tested under rainfed, irrigated, and organic conditions. This gives an additional option for evaluating how some cultivars respond to a change in management.

• Look at how a variety performed over several counties and several years. Information from one season to another and from one site to another varies with seasonal weather variation and associated effects on disease and pest dynamics. Comparing several sites and years can provide a more realistic average. Emphasize varieties that perform well over years and across locations. They’ll have more stability of performance and may do well under your specific conditions.
   
• Consider factors such as soil type, seasonal rainfall amount and distribution, temperature, and management factors such as plot history, crop rotation, previous crop, residue management, tillage etc. These will have a significant effect on varietal performance in terms of yield, grain quality, and disease reaction.
• Emphasize varieties that showed good disease and pest ratings at locations nearest to your farm or at locations with growing conditions similar to yours.
   
• Depending on your farm condition and management style, consider potential benefit from stalks and crop aftermath.
   
• Look for other agronomic characteristics that fit your management and production objective such as what you want to do with stables.
   
• Also consider secondary benefits such as feed value after the field is harvested.

Teshome Regassa
Extension Educator, Crop Variety Testing