Seeding the 2020 winter wheat crop

 

 

Ideally, winter wheat is planted while the soil and air temperatures are still warm to ensure the seedlings can emerge quickly and in plenty of time to develop a couple of tillers and a strong root system. In fact, beginning in late September until late October, potential wheat yields tend to slip at least one bushel for every day planting is delayed.

 

While the Hessian fly no longer poses a significant threat to wheat in Michigan, the fly-free-date is still a useful reference (see table below). The standard fly-free-date is during the first week of September in the northern Lower peninsula, around mid- September in mid-state areas and approximately the third or fourth week of September for southern Michigan. Highest yields are often attained when seedings are made within two weeks following the posted fly-free-date, assuming heat unit accumulation is near normal in October and November. When wheat is planted within a few days of the fly-free-date, seeding rates and fall-applied nitrogen rates should be significantly reduced to avoid excessive growth.

 

 

 

Fertilizer nitrogen may not be necessary where wheat is planted early on fine to medium textured soils following soybeans or dry edible beans. For coarse textured fields or where planting is delayed, the standard Michigan State University recommendation of 10 to 30 pounds of nitrogen may be warranted.

 

Phosphorus rates should be determined using soil test results and the “Nutrient Recommendations for Field Crops in Michigan” (MSU Extension bulletin E2904) or using calculations on the MSU Fertilization Recommendation Program. Generally, soils having phosphorus levels of 50 ppm (100 pounds per acre) do not require additional fertilizer phosphorus. Soils testing lower than this sometime exhibit a significant improvement in fall growth with additions of 20 or more pounds per acre of the nutrient.

 

Potassium fertilizer is usually broadcast applied in the fall. The actual rates are dependent on soil test levels, soil cation exchange capacities and yield potentials. For soils testing medium for potassium (75 to 100 ppm), approximately 100 pounds per acre of potash may be enough.

 

 

Attaining a consistent seed depth is important in that it will increase the probability of even emergence. Usually, a planting depth of 1 to 1.5 inches is enough in heavy soil. Deeper seed placement may have an advantage when some types of winter stresses occur, but usually this is outweighed by the advantage in more rapid emergence posed by more shallowly placed seed. The exception may be where a coarse soil is very dry. In this case, seed should be planted as deep as possible to reach moist soil.

 

 

The recommendation is to plant between 1.2 and 2.2 million seeds per acre. Seeding rates on the lower end of the range should be used when planting within a week of the fly-free-date to avoid overly thick stands that can promote disease development and increase the likelihood of lodging the following season. As the calendar advances, seeding rates should become progressively higher. If planting continues into the second half of October, the seeding rate should be increased to at least 1.8 million seeds per acre.             

 

Table 1 identifies the pounds of seed needed based on the number of seeds per pound and your population target. For example, if seed size is 12,000 seeds per pound and the target seeding rate is 1.4 million seeds per acre, then 117 pounds of seed would be needed per acre. Table 2 is useful for assessing the number of seeds being dropped by each row unit (7.5-inch row spacing) and for evaluating actual seedling density. So, with the 1.4 million target, a 7.5-inch drill would drop approximately 20 seeds per foot and, assuming a 92% emergence rate, lead to an estimated 18.5 wheat seedlings.

 

 

Growers would do well to take advantage of prevented planting acreage by planting relatively early. However, an exception probably should be made where the field was also wheat in 2018 (i.e., a wheat – prevented planting – wheat rotation). Based on experience in Michigan, wheat in this tight rotation may face an elevated risk of root and crown disease such as take-all. To lessen this risk, seeding in this rotation should be postponed for a couple weeks beyond the Hessian fly-free-date so that the soil-borne root and crown diseases have less time to infect the wheat seedlings.

 

Prevented planting acres will not likely require any additional fertilizer nitrogen as the nutrient has been mineralizing all summer. Without the normal crop removal, it is reasonable to suggest that at least 20 pounds of nitrate nitrogen will be available on fine to medium textured soils (if taking a soil sample before seeding, request the laboratory to include a nitrate analysis). Phosphorus and potassium levels may also be adequate if it was applied last fall or spring for a crop that was never planted.

 

 

 

Michigan farmers are facing difficult planting and farm management decisions after weeks of unrelenting rainfall. MSU Extension has educational resources and programs to help farmers as they deal with delayed planting issues.