By Emma Heiden
University of Minnesota Extension
There are many things to do and to consider when seeding mid-July to early August alfalfa. Seeding during this time is great if you have land available because it can be great for getting ahead of annual weeds and potentially increasing your first-year yield compared to spring seeding. With late summer seeding you typically have less herbicide use and it is a good time for the alfalfa-grass mixture.
When picking what field to seed, keep in mind auto-toxicity of your field. You do not want to plant your new seeding into a field that has had alfalfa on it for the past two years.
Knowing your soil pH and nutrient levels is very important to avoid any deficiencies and get the best results from your seeding. You want to know these levels before you plant so you have the ability to fix them easier. A neutral level for soil should be 6.5 to 7.1 when seeding alfalfa. Potassium at 150-175 parts per million and phosphorus at 25-30 parts per million should be the minimums you should be seeing on a soil test.
When seeding alfalfa, ideal seedbed conditions are minimum residue, firm and smooth soil. A rule of thumb to follow from the University of Minnesota Extension is if your heel sinks more than ½ inch into the soil before seeding use a cultipacker to firm the surface or a press wheel drill with depth control. Alfalfa should be seeded around 3/8 inch in medium to fine soil and 5/8 inch for more sandy soil.
Make sure you are seeding with the correct Fall Dormancy (FD). They run from 1-11 and it means the measure of fall growth. Fall Dormancy 3 is commonly used here in Minnesota for baling hay. Overall, fall dormancy 2-4 are recommended for Minnesota’s harder winters.
It is recommended to seed from August 1 to September 1 for the southern region of Minnesota and July 20 to August 1 for the northern region of Minnesota.
If you have questions about this or any other horticulture, agriculture or natural resources topic, please reach out to your local Extension educator. Fillmore and Houston County residents can call (507) 765-3896 or (507) 725-5807.