Source: Jim Shroyer, Extension Agronomy State Leader; Becky Miller, Director, K-State Wheat Quality Laboratory; and Jane Lingenfelser, Kansas Crop Performance Test Coordinator, Kansas State University
Protein levels below 12.5 percent in hard red winter wheat were common last year in the Central Plains, and have been occurring again this year in many areas. Marketing hard red winter wheat that has lower protein levels has become a problem, and is a factor in the decline in wheat prices over the past year.
If producers have not yet harvested their wheat, they may want to have the crop tested for protein prior to harvest. If protein content is especially good, producers may want to alert their grain elevator before hauling their wheat to market. If producers have on-farm storage, they may also choose to hold onto the wheat in hopes that demand will increase throughout the year for high-protein hard red winter wheat.
Wheat protein content stabilizes by the time the wheat reaches the end of the soft dough stage. Once the wheat kernels have matured and dried to 10 percent to 14 percent moisture, the protein content can be accurately determined in the field by using a hand-held NIR device. Producers can also send a sample of their wheat before harvest or at any time to K-State's Wheat Quality Laboratory for protein analysis. The cost is $15 per sample. Results are generally provided within a day of receipt of the sample.
For detailed instructions on how to submit a sample of wheat to the K-State lab for protein testing, go here
The main factors that determine protein content in wheat are:
Variety. Performance test data from K-State consistently show about a 2-3 percent difference between varieties with the lowest protein content and the highest protein content.
Environmental conditions. Protein and starch are the most important constituents of the wheat kernel. Most of the protein comes from nitrogen previously accumulated in the leaves, and most of the starch is from sugars made by photosynthesis during the grain-filling period. The nitrogen moves into the filling kernels to form protein during early grain development. As a result, if yields are low because the kernels do not fill properly, the grain is high in protein. Drought and high temperatures are usually responsible for this condition. If the grain fills normally and yields and test weights are high, grain protein is frequently lower because it is diluted by other materials. Of course, under good growing conditions, grain protein can be increased with nitrogen fertilizer.
A comparison of wheat protein levels in past years as reported by Kansas Agricultural Statistics shows that in a given year, protein content can vary by about 2 percent overall between areas of the state with good growing conditions and high yields compared to areas with stressful growing conditions and low yields. The more stress, the higher the protein content. A good example can be found in the 2004 crop.
Relationship Between Protein Content and Yields in Kansas, 2004
Average yield (bu/acre)
Protein Content (%)
Northwest (most stressed)
Southeast (least stressed)
Summary of growing conditions for 2004 crop: Condition was above 50 percent good to excellent all fall until dropping slightly by the end of November to 47 percent good to excellent. Condition declined over the winter due to dry conditions. On March 7, 34 percent was rated as poor to very poor. By the end of March, 7 percent either had not emerged or was lost to winterkill. On April 25th, 30 percent was in poor to very poor condition compared to 16 percent in 2003. Crop progress was ahead of normal during the spring with 84 percent jointed on April 25th, compared with 80 percent the previous year and 75 percent for the 5-year average. Heading began by late April and progressed ahead of normal during May. Damage from freezes in early spring became evident during May. Harvest continued ahead of average throughout June despite some scattered showers. Heavy rains in July slowed harvest and led to wheat sprout in the northern third of the state.
Nitrogen fertility. Nitrogen (N) availability is one of the key management factors in protein content. Good nitrogen management throughout the growing season can help increase protein content of any variety. This is a big topic, and will get a full article of its own in a future e-Update this summer. Reports from some western states indicate that, at times, late-season N applications can increase protein by up to about 0.5 to 1.5 points. But results are inconsistent. The actual result depends on available soil N levels at the time of application, yield level, and whether the late-season N application causes leaf burn.