Winter wheat yield is affected by production practices, pest management, fertility, and weather. One production practice having a major impact on yield is seeding date.
Wheat seeded too early uses more soil water and nutrients in the fall, leaving less in the profile for yield production, and is more susceptible to insects and diseases. On the other hand, seeding too late reduces emergence, tillering, and winter hardiness.
The recommended seeding dates for Nebraska’s winter wheat vary substantially from one end of the state to the other — from Sept. 1 in the extreme northwest to Oct. 1 in the southeast tip — and have been proven and verified through years of research and farmer experience. Some years an earlier seeding may have an advantage, and some years a later date may have an advantage, but in the long term, the suggested seeding dates will give the highest average yield.
Recent seeding date studies
Seeding date research funded in part by the Nebraska Wheat Board is underway in western Nebraska. Some of the initial results from 2018 are found in the accompanying table. The ideal seeding date for a given year depends on the environment and available moisture. In 2018, early seeding at both McCook and Sidney had greater yields than later seeding dates.
The opposite was true in 2017. Much of the early seeded wheat in 2017 became infested with Wheat Streak Mosaic Virus because of the extended fall and warmer temperatures. In 2017, on-time seeding that followed the recommendations in the accompanying map performed the best. This research will be continued for another year before any changes are made to the current recommendations.
How seeding date affects tiller development
Date of seeding greatly affects development of tillers in winter wheat, the source of as much as 70 percent of the grain yield in a normal year. Seeding during the optimum period enables wheat to form sufficient but not excessive tillers. Early seeding results in too many fall tillers, which may compete with each other, become diseased, and deplete soil moisture so that grain yields are low.
Late seeding gives plants little time to develop tillers, resulting in an inadequate numbers of spikes (heads) for high yields the following spring. When seeding late, the seeding rate should be increased to compensate for the reduced number of tillers. Also, fertilizer placed with or near the seed promotes plant development.
Senescence and death may eliminate excessive tillers that form during the fall. Conversely, if too few tillers develop during fall, additional tillers may form during spring; however, the yield potential may differ between tillers that develop during fall and those that develop during spring.
Tillering also enables the plant to adapt to different conditions. Few tillers develop when moisture, nutrition, and other conditions are poor, whereas numerous tillers form when conditions are favorable. More tillers leads to increased yield potential.
The recommended seeding date represents a goal for seeding completion. As farm size and the number of acres increase for individual farmers, so does the length of time needed to complete seeding. The goal should be to have all wheat seeded by the ideal date. Plan your field order for planting accordingly. For example, plant higher elevation fields and those containing sandy soil first and leave lower fields and those with higher clay content until last.
Recommended Planting Dates
Several factors were considered when developing the existing recommended seeding dates. In the Panhandle, the dates depend on elevation. Producers can determine the ideal date for each field by knowing the elevation. Using a starting point of Sept. 15 for 3,500 feet, one day should be added for each 100-foot decrease and subtracted for each 100-foot increase in elevation. For the rest of the state, Sept. 25 or later seeding dates are recommended to avoid Hessian fly infestation.
The map is a guide rather than an absolute deadline. Each producer should make changes to ensure the planting dates fit the conditions of his or her farm.
For more information on; how planting date affects fertilizer use, disease problems, and yield visit the Wheat Issue of Nebraska Extension’s CropWatch Website: https://cropwatch.unl.edu/2018/august-31-2018.