In a perfect world, all wheat would be planted at the ideal time. But several factors can cause producers to plant wheat either earlier or later than the recommended time – including grazing intentions, weather delays, and late row crop harvest, said said Kansas State University agronomist Doug Shoup.
"Wheat yield potential is greatest in south central Kansas when planted between Sept. 25 and Oct. 20, and in southeast Kansas when planted between Oct. 5 and Oct. 25," said Shoup, who is the southeast area crops and soils specialist with K-State Research and Extension.
When wheat is planted earlier than that, the plants often produce too many fall tillers, he said. The result is an increase in competition between plants, which reduces the number spikes and overall yield in the spring. In addition to tiller competition, wheat planted early generally has a higher incidence of insects and disease.
"Hessian fly, aphids, and wheat curl mites are more likely to invade earlier-planted wheat, causing damage and vectoring viral diseases such as barley yellow dwarf and wheat streak mosaic," Shoup said. In that situation, management practices should be adjusted somewhat.
"If planting early, the best management practice against insects and disease is to select resistant varieties with good yield potential," he added. "Systemic insecticide seed treatments may provide a benefit against some insects and the viral diseases they vector; however, these can be costly and are an added expense if insects are not present."
On the other extreme, if planting is delayed past the optimal window, the yield potential also will likely be reduced unless the growing conditions are favorable. Planting later in the season will reduce the number of highly productive fall and productive spring tillers, reducing the overall yield potential, the agronomist said.
If planting later than optimal, producers should increase their seeding rate to account for the limited time for fall tiller production by individual plants, Shoup added. Planting extremely late, into the winter, is not recommended as yield potential will likely be very limited unless growing conditions are favorable, he said.
More information is available at county and district K-State Research and Extension offices and in K-State´s Wheat Production Handbook, C- 529, at: http://www.oznet.ksu.edu/library/CRPSL2/c529.pdf .