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Field Fodder: Know the recommended seeding rates

March 11, 2019

3 Min Read
tractor in alfalfa field
SEEDING ALFALFA: Now is a perfect time to evaluate your plans for alfalfa seeding this year.

By Kimberly Kassube

After enduring a cold and snowy Wisconsin winter, we all may be anxious to jump in the tractor and get out to the fields by the time spring arrives. However, now is a perfect time to step back and evaluate your plans for alfalfa seeding this year.

It is recommended that the rate for seeding alfalfa in Wisconsin is 12 to 15 pounds per acre. This rate does not account for expected mortality, emerging ability, seed weight, seed germination, seedbed condition, depth of planting and planting equipment.

It is important to keep in mind that the recommended rates are for pure live seeds (PLS). A quick check of the seed tag and some math can ensure that you are applying the correct rate to your fields. The two numbers to look for on the label are the percent germination and the percent purity. Once you have those numbers, plug them into the following equation:
(% germination x % purity) ÷ 100 =  % PLS

With the popularity of seed coatings in the industry, this can be a useful calculation. For example, if you have a 92% germination, but your purity is lower due to the seed coatings, making it around 78%.

Your calculation would look like this:
(92% germination x 78% purity) ÷ 100 = 71.8% PLS

A PLS % of less than 90% PLS requires an adjustment in seeding rate. If your plan was to seed 12 pounds of alfalfa but your PLS is 71.8%, as we calculated above, we would perform the following calculation to determine the correct rate:
12 pounds ÷ 71.8% PLS = 16.7 pounds

The 16.7 pounds would be the new seeding rate to achieve the desired stand.

Delay checking winterkill
Assessing winterkill too early in spring may not be as accurate as waiting until mid-May. However, you can still dig up plants if you suspect winterkill has occurred. Remember that a healthy crown has minimum discoloration and is cream-colored, while an injured or diseased root is brown or black. Please refer to the Extension bulletin "A3620 Alfalfa Stand Assessment" for a more in-depth look at assessing your alfalfa stands.

After doing an assessment and determining that a stand is not viable enough to keep on its own, you have several options, the first being reseeding the field with alfalfa and starting a new stand. However, this may not be economical, and autotoxicity could be an issue depending on the age of the alfalfa stand. If your plan is to extend the stand for another year, you may consider overseeding with cereal grains, grasses or clovers. Clovers will provide a high-quality forage but may not yield as much as grass. Cereals will provide yield, but the quality may not be high enough for lactating cattle.

The following are suggested overseeding rates, although your actual seeding rate will depend on your chosen seeding method: orchardgrass and Italian ryegrass, 5 to 10 pounds per acre; red clover, 6 to 10 pounds per acre; oats, 50 to 75 pounds per acre; and sorghum-sudangrass, 20 to 30 pounds per acre.

Questions? Visit the Extension Team Forage website or contact your county Extension educator.

Kassube is the Shawano County (Wis.) Extension agriculture educator.

 

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