August 8, 2008

Variety selection is one of the most important decisions a winter wheat grower has to make. The right or wrong decision can enhance or negate all other factors in profitable wheat farming. When selecting seed, consider these variety characteristics: yield potential, maturity, winter hardiness, straw strength, coleoptile length, plant height, lodging and shattering, seed size, test weight, disease and insect resistance, herbicide tolerance, milling and baking quality and enhanced traits.

Balance Risk with Complementary Varieties Complementation means getting consistent performance by planting multiple varieties which offset each other's strengths and weaknesses. This should be basic to your crop planning. An example of complementation might be growing a high yielder with less winter hardiness and a variety that yields a bit less but has good winter hardiness. Because there is no single perfect wheat variety for all production systems or in all years, using complementary varieties will enable you to realize the greatest benefit from a specific variety's strengths and offset, to a high degree, its potential weaknesses. This compensation improves the opportunity for yield stability and profitability of your entire wheat production system. The number of complementary varieties that are grown as part of a wheat farming enterprise and the acres planted to each variety will depend entirely on specific production conditions and any special needs (common diseases or insects, etc.). Farmers who do not have enough acres to justify planting several varieties, may want to consider using a blend of three or four varieties. Also, tenants whose landlords don't have enough acres to justify planting several varieties could reduce risks by planting a blend. There are four steps in developing and updating your wheat farm's variety complementation strategy:   Identify your workhorse varieties. These are the varieties you now grow on a majority of your wheat acres because they have a reliable and proven record of performance over several years in your preferred production management system.   Complement your production needs and limits. Select a variety or varieties that have characteristics needed for specific production practices (e.g., straw strength or height) and typical soil conditions. Choose varieties that offer the best level of protection from expected diseases and other yield limiting factors common to your growing conditions or area.   Complement with a range in maturity. The major limiting factor to wheat production in Nebraska is the short grain fill period (from 2.5 to 4 weeks). Because you can never be sure about the weather during that critical time of year, select varieties that will mature earlier (or later or some of both) than your workhorse variety. A spread of maturities also will allow you to stagger your harvest schedule and take maximum advantage of your available equipment, plus reduce losses to yield (e.g., from shattering) and end-use quality (e.g., from weathering).   Complement with different genetic families. Varieties with closely related genetic backgrounds often can be susceptible to the same diseases and production stresses. You can lower those risks by selecting varieties that share 50% or less common parentage with your workhorse variety and each other. Varieties with similar backgrounds often can be susceptible to the same disease, insects and production risks. See the fall Nebraska Seed Guide (EC103) for a list of many of the winter wheat varieties and their predominant genetic family. Robert N. Klein Cropping System Specialist

Grain Quality

The major use of the Nebraska wheat crop is as a bread wheat for human consumption. Therefore, it is important that the grain meets the expectations of millers and bakers to produce a quality end product. Quality is determined by both variety and growing conditions. Hard white wheat has excellent potential to be a successful crop in Nebraska. It has significant advantages over hard red winter wheat.

Whenever they have a choice, millers, baker and consumers prefer white wheat which can also be used for noodles and other food products. This preference is particularly strong in some international markets which buy wheat from the United States. Producers should check on their local markets for hard white wheat and if available consider the production of hard white winter wheat. Producers should encourage those markets that are not now accepting hard white wheat to consider accepting this wheat.

Yield Potential

Harvested grain yield is one of the most important factors to consider when selecting varieties. Results of UNL variety tests are the best and most publicly available information on how specific varieties have performed under Nebraska conditions. The results of variety tests across the state are included in the Fall Seed Guide (EC103) available at your local extension office. The guide also contains additional information on wheat production and lists growers of certified seed. The variety test and/or guide is also available on the Web at http://varietytest.unl.edu/winterwheat.html

Yield varies from year to year and location to location as a result of environmental factors (soil, rainfall, temperature, etc.). Thus care needs to be taken when interpreting the yield data from variety test plots. The more locations tested and the more years represented, as well as the extent of similarity between the test and grower's field environments, the more reliable the information will be.

Agronomic Characteristics

Maturity. Early maturing varieties are likely to escape damage from hot winds, drought and rust infection; however, they are more subject to late spring freezes. Producers with large acreages can spread out risk and harvest by using varieties of differing maturity.

Winter Hardiness. Wheat is most likely to be damaged by cold temperatures: 1) just after heading, 2) in the spring after growth starts, and 3) in the fall before wheat hardens. Varieties differ in their susceptibility to freeze damage.

Straw Strength. Good straw strength is important to keep wheat from lodging. Also, standing stubble traps more snow and benefits the following crops. Stripper headers on combines work best with varieties having good straw strength.

Coleoptile Length. The coleoptile is a leaf sheath that surrounds and protects the first true leaf as it grows from the seed toward the surface. If the coleoptile is shorter than the depth of planting, emergence will become difficult. The young seedling might not reach the surface and ultimately will die, resulting in stand loss. With the introduction of semi-dwarf varieties, depth control became even more important because of the shorter coleoptile of semi-dwarf wheat compared to conventional height wheat varieties.

Height. There is a fairly good correlation between overall plant height and coleoptile length; taller varieties tend to have longer coleoptiles. More stressed environments frequently require a taller wheat variety for emergence and combine harvest.

Lodging and Shattering. Since wheat is harvested with the combine and harvesting must wait until the crop is ripe, varieties that are less likely to lodge or shatter are preferable. The shorter (semi-dwarf) varieties usually are less susceptible to lodging. Varieties with upright stature incur less hail damage (shattering).

Disease and Insect Resistance. Genetic resistance to insects and diseases is an excellent control method when such resistance is available. Hessian fly, wheat streak mosaic, soil-borne mosaic, Russian wheat aphids, stem, stripe and leaf rusts, and other pests can, and do cause serious losses in the Nebraska wheat crop at times. Use of resistant or tolerant varieties, plus good cultural practices, can minimize the losses.

Herbicide Tolerance. Varieties are now available that are tolerant to a specific herbicide. For example, Clearfield wheat varieties are tolerant of Beyond herbicide. Beyond may be used to selectively control weeds such as jointed goatgrass, rye and cheat in Clearfield wheat varieties. Beyond herbicide will kill non-Clearfield wheat varieties.

Acid Tolerance. Some Nebraska soils are becoming more acidic as a result of using nitrogen fertilizers. Acidic (low pH) soils have more free aluminum which can burn root tips and lead to poor vigor. The wheat producer should be aware of the soil pH and mineral content of the soil. Wheat varieties differ in their ability to tolerate low pH soils and alkali.

Seed Size and Test Weight. Planting larger seed will require higher seeding rates to achieve the necessary plant population (plants per acre). Seed should have a minimum test weight of 57 lbs/bu, preferably greater. Winter wheat seeding recommendations should be changed from a lbs/acre rate to seeds/acre rate. The number of winter wheat seed in one pound can range from more than 20,000 to less than 10,000, depending on the variety and the year produced. All seed should be cleaned and the small and cracked seeds eliminated. Shriveled seed can reduce yields because germination is slower and emergence less.

Seed Protein and Phosphorus Content Seed protein is another factor linked to increased plant vigor and higher grain yields. Actually, it is not the percent protein in the seed that has the greatest influence on seed quality, but rather the amount of protein contained in each kernel. For example, seed that has a thousand kernel weight (TKW) of 34 grams (13,500 seeds per pound) with 11% protein contained 3.7 mg protein per seed. A seed lot with a TKW of 20 grams (22,700 seeds per pound) with 13% protein would only contain 2.6 mg protein per seed. In this example the larger seed with a lower protein percentage would actually provide more protein per seed (and consequently more protein per seedling) than the smaller, higher protein percentage seed lot. Again, seed size should be the overall determining factor for seed lot selection. However, all things being equal (variety, seed size), producers should look for high grain protein in seed lots.

There is continuing interest in the phosphorus (P) content of wheat seed and how this might influence plant vigor and yield. Given the fact phosphorus is involved in energy production and energy transfer, this would be logical; however, much like protein, it would be the amount of phosphorus present in each seed that is important, not simply the percentage of phosphorus in a seed lot. Since the phosphorus percentage of seed lots are not normally reported, producers should consider seed size first and protein second.

Grazing Potential. In a study conducted near Sidney during the mid-1990s, six wheat varieties were evaluated: four were standard height and two were semi-dwarf. While some differences among the varieties were observed for various traits in specific years, there were no consistent or overall trends for superior forage performance by any of the varieties over the three years of the study or for standard height wheat versus semi-dwarf. Since there was little difference in forage yield, we encourage planting the one with the most yield potential.

Robert N. Klein
Cropping System Specialist