Wednesday, May 14, 2014
Evaluating Winter Wheat Plant Stands
One of the hardest decisions with growing winter wheat is evaluating the amount of winter kill and making the decision whether to keep a stand. Winter wheat is planted in the fall and develops in the spring during relatively ideal conditions for tiller development. Therefore the optimum plant stands of winter wheat can be less than that of spring wheat. A stand of 900,000 - 1,000,000 plants/acre or 21 - 23 plants/ft2 will be enough to maximize grain yield.
Some winter kill is to be expected in Minnesota. This past winter was cold even by Minnesota standards. The extreme cold, combined with little snow cover in parts of the state, and that the fact some of winter wheat was planted on prevent plant acres that had little or no standing stubble to collect the limited snow that fell, means that winter kill is very likely this year. Roots are generally less winter hardy than crowns and regrowth may be very slow, even if roots and shoots appear dead.
The very cool and wet weather to date has meant that fields have been very slow to green up and have just started to put on new leaves and tillers. This past week was probably the first time that evaluating surviving plant density was fairly straightforward. The problem that remains, however, is that winter survival in all likelihood will variable within a field and depending on topography (windblown hilltops having less stand than protected areas of the field). If stands are reduced uniformly across the field, stands of 17 plants/ft2 can still produce near maximum grain yields. Even stands as low as 11 plants/ft2 can still produce a 40 bu/A yield.
Given the lateness of the spring and the likelihood that anything else that is planted will be planted later than optimum creates another incentive to stick with a less than ideal stand of winter wheat. Consider interseeding spring wheat to fill large gaps but be prepared for the fact that spring wheat matures later than winter wheat so harvest will be problematic. Furthermore, mixing wheat classes can cause problems at the elevator. Planting winter wheat into large gaps can also be an option. Winter wheat planted in the spring will not vernalize so it will not produce a head (or there will be fewer late heads), but will provide ground cover until harvest.