Status of the winter wheat crop
There is increasing interest, and concern, about the winter wheat crop in much of South Dakota. As addressed in this column two weeks ago, it will be difficult to accurately assess your winter wheat stand until the plants break dormancy, or in many cases, until the seeds germinate and emerge. Based on historical soil temperatures, that will likely occur in mid to late-March. The statement, until the seeds germinate and emerge, is of course due to much of it being planted into dry soil, some of which is still dry.
Based on soil temperatures at several of the automatic weather stations this winter and limited field inspections, it appears that much of the winter wheat that germinated last fall may have escaped winterkill, at least in south-central South Dakota.
Two major concerns seem to remain. Many areas in South Dakota are seriously lacking topsoil and/or subsoil moisture. Seeds that germinated last fall, and those getting just enough moisture to germinate this spring, could grow for a short time once soil temperatures raise to 39 degrees F or higher, and then dry out if additional precipitation is not received within a short time after.
There are also fields that lack topsoil as well as subsoil moisture, and winter wheat planted into dry soil also has the risk of not completing the vernalization process. Neither seedling growth nor tillering is required for vernalization to occur. This process can begin in seeds as soon as they absorb water and swell, and be complete if a period of about 3 weeks passes when the soil temperature at the seed/seedling level remains below about 48 degrees Fahrenheit (F). The exact length of time and temperature varies by variety, and is correlated closely to winterhardiness and relative maturity. The more winterhardy and later maturing a variety is, the longer the time required and the lower the soil temperature the seed/seedling must be exposed to. The vernalization process must be completed for winter cereals to joint and produce a seedhead.
As the month of March progresses and we move into April, the likelihood of a three week period with soil temperatures consistently below 48 degrees F diminishes. Historically, soil temperatures have varied from one year to another on any given date at each weather station during this time period. That makes it difficult to predict how late in the spring a winter wheat seed could absorb moisture, germinate and complete vernalization. If these dry fields do not receive enough moisture by late-March to begin the germination process, the rare occasion of winter wheat planted in the fall and not vernalizing may occur in 2013.
Significant precipitation in the near future would relieve a host of potential problems. Again, before destroying a winter wheat field, contact your crop insurance agent. They can explain your options and the requirements to maintain insurance coverage. Also, avoid inter-seeding spring wheat into winter wheat as this would result in mixed wheat at harvest and result in marketing problems and almost certain price reduction.