Much of the winter wheat crop is expected to have survived the winter relatively well. However, there undoubtedly will be some areas that for one reason or another were damaged by drought, wind erosion, sitting water or for other reasons.
As the winter wheat begins to grow, producers should be able to accurately assess their stands, and the degree of winterkill that may or may not have occurred.
Evaluating a winter wheat stand early consists of two aspects, plants per square foot, and how uniform the stand is. Yield is directly affected by the number of plants per square foot in the field. Optimum plant stands for winter wheat are said to be 20 or more plants per square foot. If uniformly distributed, 5-6 plants per square foot is considered to be the minimum. Winter wheat has the ability to compensate for lower plant densities by tillering, but there is a limit to that ability, and the plants must be uniformly distributed to take full advantage.
To evaluate a winter wheat field early in the season, you should make several assumptions. If we assume 1 million kernels per bushel, 25 kernels per head, and 5 tillers per plant, 8 plants per square foot would produce 44 Bu/Acre. Main stems often produce more than 25 kernels, but secondary tillers will bring the average down. High plant populations typically produce fewer than 4 tillers, whereas low plant densities will likely result in considerably more. Each producer will need to decide what yield potential is adequate for their operation.
The general recommendation for nitrogen fertilization is to have all or most of the nitrogen applied before jointing. Usually the head size of the plant has been determined by early jointing. Providing optimum nutrients up until that time will help the plant pollinate and fill potential kernels, as long as other environmental factors do not limit pollination or kernel fill. There is some thought that nitrogen applied early will stimulate tillering, although possibly to a limited extent. Nitrogen applied after tillering can contribute to kernel fill and protein, if other factors such as moisture are not limiting. Nitrogen application should be delayed until the soil is no longer frozen but dry enough to support traffic. If the spring is wet, the window of opportunity may be narrow enough that getting it on early will help insure that the nitrogen is available before jointing occurs.
Weed control becomes more important with a thin stand of wheat. If the crop is planted into wheat stubble, adding a half rate of fungicide with the herbicide may help maintain secondary tillers and subsequent yield potential.
Stripe rust, powdery mildew and tan spot infested some winter wheat fields last fall. If early wheat scouting indicates that diseases are present, fungicides may need to be added to the herbicide at early herbicide application time. For more information refer to http://igrow.org/up/resources/03-3013-2016.pdf.
South Dakota State University, South Dakota counties, and USDA cooperating. South Dakota State University adheres to AA/EEO guidelines in offering educational programs and services.
Ruth Beck
SDSU Agronomy Field Specialist
412 West Missouri Ave.
Pierre, SD 57501
605-773-8120