EAST LANSING, Mich. — Ideally, winter wheat is planted while the soil and air temperatures are still warm to insure the seedling can emerge quickly and uniformly in plenty of time to develop multiple tillers and a strong root system. In fact, beginning in mid- to late September, potential wheat yields tend to slip at least one bushel for every day planting is delayed. This relationship may not hold, however, once the calendar reaches late October as soil and weather conditions tend to play a more important role.
While the Hessian fly no longer poses a significant threat to wheat in Michigan, the fly-free-date is still a useful reference. The 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. When wheat is planted within a few days of the fly-free-date, seeding rates and fall-applied nitrogen rates should be reduced.
Attaining a consistent seed depth is important because it will increase the probability of even emergence. Usually, a planting depth of 1 to 1.5 inches is sufficient 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. Where planting depths of 2 inches or greater may be advantageous is when a coarse soil is very dry. In this case, seed should be planted as deep as possible in order to come in contact with moisture.
Michigan State University Extension’s recommendation is to plant between 1.4 and 2.2 million seeds per acre. Seeding rates on the lower end of the range should be reserved for fields being planted within a week of the fly-free-date. Using high seeding rates are discouraged when seeding relatively early as it may lead to overly thick stands that tend to lodging as the plant approach maturity.
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. The seeding rates should also be adjusted upward when seed is of questionable quality.
Table 1 identifies the pounds of seed needed based on the number of seeds per pound and your population target. For example, if the seed bag specifies 14,000 seeds per pound and the target seeding rate is 1.8 million seeds per acre, 129 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 emergence.
Table 1. Relating seed size and seeding rates to the amount of seed required per acre
|Seed size (seeds/ lb.)||Target seeding rates (millions of seeds per acre)|
|Amount of seed required (lbs./acre)|
* Seeds per acre / seeds per lb. = lbs. of seed per acre
Table 2. Relating target seeding rate per acre to seed and seedling numbers (for 7.5-inch row spacing)
|Target seeding rate (millions per acre)||Seeds per feet of row¹||Seedlings per feet of row²|
¹ Target seeding rate/ 43560 X 0 .625 = seeds per ft of row (7.5” spacing). Seeds per sq. ft. = target seeding rate/43,560.
² An estimated emergence rate is given in brackets as percent (the rate tends to decline as seed rates increase).
Hessian fly-free-dates for Michigan
— Martin Nagelkirk, Michigan State University Extension
For more news from Michigan, click here.