By Carrie Knott, Extension Agronomist
The optimal planting window for winter wheat in Kentucky is quickly approaching: Oct. 10-30. Prior to the physical planting of wheat, growers must make several critical decisions to maximize wheat grain yield and profitability the following June. The first is variety selection.
In Kentucky, there is an annual risk of Fusarium Head Blight (caused by Fusarium graminearum) infection of wheat. This disease not only reduces yield, but it also produces a toxin in the grain (vomitoxin or deoxynivalenol), which can result in considerable price reduction when delivered to the grain elevator. The best way to reduce the risk of Fusarium Head Blight is to grow a moderately resistant variety. If the seed representative you are buying your seed from does not know how resistant a variety is to Fusarium Head Blight, it is best to choose another variety with known resistance.
Seed depth and seeding rate are also very important. The optimal planting depth for wheat seed is 1-1.5 inches with good seed-to-soil contact. These depths help reduce the risk of winter injury and heaving. Heaving occurs during periods where soil freezes and thaws. During these freeze/thaw cycles, the wheat seed can be pushed closer to the soil surface, causing plant injury and possibly death, which can ultimately reduce plant stands and grain yield. When soil conditions are extremely dry at planting, wheat seed can be planted up to 2 inches deep to access soil moisture. Do not plant wheat seed greater than 2 inches.
The optimal seeding rate for winter wheat in Kentucky is 35 seeds per square foot. Some farmers prefer to use pounds of seed per acre. When using pounds per acre, seed size is critical. Wheat seed size varies considerably and this option must be determined by counting the number of seeds per pound (usually on seed tag).
Seeding rates based upon weight alone can result in plant populations that are too high or too low, depending on seed size. Seeding rates that are too high result in high plant populations that are prone to lodging (falling over in the field) and have lower grain yield. Seeding rates that are too low may result in low plant populations and reduced yields.
Example 1: Seeding rates in pounds per acre for three winter wheat seed lots with different seed sizes.
The desired plant population per acre is 1,524,600 seeds per acre: 35 seed per square foot x 43,560 square foot per acre.
Seed Lot 1: 10,000 seeds per pound = 152.64 pounds per acre
Seed Lot 2: 11,000 seeds per pound = 138.6 pounds per acre
Seed Lot 3: 12,000 seeds per pound = 127.05 pounds per acre
Seed germination of the seed lot is another critical consideration prior to wheat planting. To be sure that the optimal plant population of 30-35 plants per square foot is achieved, seeding rates must be adjusted for seed germination at planting. To adjust your seeding rate for the seed germination rate, divide your desired plant population by the germination rate of your seed.
Example 2: Adjusting winter wheat seeding rate for seed germination.
Desired seeding rate: 35 seed per square foot. Seed germination rate: 92%.
35 seeds per square foot ÷ 0.92 = 38 seeds per square foot
Many winter wheat fields are no-till production systems, where the residue from the previous crop remains on the soil surface at the time of wheat planting. In Kentucky, most winter wheat follows corn. Proper seeding depth and rate is especially important and challenging in no-till production systems. Ensuring that residue from the previous crop is uniformly distributed throughout the field will help with uniform wheat planting and emergence, which is necessary for high wheat yields the following summer.
Fall Nitrogen Applications
The final consideration for this season’s winter wheat planting is fall fertility. In most years fall nitrogen (N) applications are not necessary for wheat. However, this year we have had considerable rainfall and even flooding of fields that do not typically flood. These conditions likely depleted much of the N that would usually be available to the wheat crop in the fall. If you are in an area that received excessive rainfall or your fields were flooded at least once this season for several days or longer, you may want to consider a fall N application of about 20-30 pounds per acre. Do not exceed 40 pounds per acre.
For more information, consult "A Comprehensive Guide to Wheat Management in Kentucky."