by Jochum Wiersma, Small Grains Specialist and Phyllis Bongard, Educational Content Development and Communications Specialist
With September just around the corner, we are approaching the optimum time for planting winter wheat in Minnesota. The optimum planting date windows are between September 1st and the 15th in the area north of I-94, between September 10th and the 30th south of I-94, and between September 20th and October 10th in the part of the state south of I-90.
Though seeds that just begin the germination process will vernalize (meet the necessary cold requirement to produce a spike in the summer), a much larger seedling typically has a better chance of overwintering and being more productive. In recent research, the early planted treatments have been more productive than those planted later than the optimal dates, though the difference was not always large, depending on the year and the variety grown. Below are key points to establish winter wheat successfully and give it the best chances to survive Minnesota's winter:
- Plant winter-hardy, adapted varieties - Use a winter hardy variety, especially if you are not planting into residue or you are seeding past the optimum planting window. Late planted seedlings will be small as winter approaches and will be more prone to winter injury, particularly if there is little snow cover this winter. A winter hardy variety will help reduce the risk of injury and be more productive when conditions are conducive to winter injury. Check the most recent University of Minnesota Variety Trials Bulletin for information about the winter hardiness of varieties currently available for planting.
- Plant winter wheat into standing stubble - Survival of winter wheat during the winter is enhanced when it is covered with snow during the coldest months of the year. Standing crop residues can effectively retain snow and help insulate the crop during the winter. Tall, erect flax and canola stubble works best, but any erect stubble that will retain snow is recommended. Abandoned stands of alfalfa that have been killed with glyphosate also work well. Even standing soybean stubble is capable of trapping some snow and reducing winterkill. Planting winter wheat into wheat stubble is not ideal due to the increased risk from residue-borne diseases. However, if disease management is planned, planting into wheat stubble is better than seeding into a clean tilled field.
- Calculate the correct seeding rate - An optimum stand for winter wheat in the spring is 23 to 25 plants/ft2 (900,000 - 1,000,000 plants per acre). Calculate a seeding rate accordingly, knowing that a poor seedbed and planting past the optimum window will mean a higher percent stand loss and/or more winterkill. If planting is delayed or conditions exist that may delay germination and emergence, the seeding rate can be increased by about 150,000 to 200,000 seeds per acre. However, there is no advantage to seeding more than 1.8 million seeds per acre.
- Apply phosphorus at time of planting - Phosphorus (P) fertilization can play a role in winter hardiness, especially if soil tests for P are low. Phosphorus helps develop strong roots and crown tissue, which will help the crop overwinter. The rate of P applied with the seed should be limited by the amount of nitrogen (N) in the fertilizer, since excessive N prior to freeze-up can reduce winter survival. In narrow rows, nitrogen should not exceed 15 pounds per acre with the seed, particularly if conditions are dry.
- Plant 1 to 1.5 inches deep - Adequate moisture for establishing winter wheat is often a concern as the soil profile is usually depleted of moisture in the fall. If there is little or no moisture in the soil's surface, planting shallow (1 to 1.5 inches deep) and waiting for rain is recommended. Furthermore, these relatively shallow planting depths allow for faster emergence when temperatures are rapidly declining.
- Avoid the "green bridge" - Avoid fall infections of Wheat Streak Mosaic virus, Barley Yellow Dwarf virus, Hessian Fly, and/or tan spot by not planting too early and ensuring the removal of any volunteer wheat and grassy weeds at least two weeks prior to planting.
- Choose the correct planting date - The optimum planting date windows are between September 1st and the 15th in the area north of I-94, between September 10th and the 30th south of I-94, and between September 20th and October 10th in the part of the state south of I-90.
- Consider treating seed with fungicides and possibly an insecticide - If the seed is going to lay in the soil for an extended period of time or if conditions favor disease development, a fungicide applied to the seed will help protect it. An insecticide may be beneficial if wireworms are likely to be present.