Dr. John Yost, OSU Extension Educator ANR, Wayne County
The fall 
is a critical time in our yearly forage management calendar. Regardless of how the growing season has progressed, your fall management practices will set the stage for getting the next spring off on the right foot. In this article, we will give some recommendations on soil fertility, fall planting of new alfalfa stands, and when to take the last forage harvest for the season.
Your soil fertility program is far and above the most critical component of your alfalfa management. While current weather conditions and harvest timing will most influence the quality of a single cutting, a well-balanced fertility program will ensure that the plant has the available resources to perform within its environment. Again, the goal is to finish the growing season with a healthy plant that has had sufficient time to accumulate top growth that will protect the crown from cold temperatures during the late fall and winter. Allowing for enough top growth will also allow the plant to increase its energy reserves to initiate rapid growth in the spring.
We have to begin any soil discussion with a reminder to soil test. As you implement your testing procedures, remember that you are submitting a few ounces of soil to the lab, and you will take those results and develop recommendations that will apply to the whole field. You need to have a high level of precision between sampling years so that you can accurately track your progress. Whether you use whole field, grid, or zone sampling, incorporating GPS technologies to mark sampling locations will help increase your accuracy. At a minimum, you should be collecting 15 cores for every 25 acres. These cores can be combined to create one pooled sample for submission to the lab. To determine soil nutrients, you need an 8-inch core, or if you are only interested in pH, you can sample the top 4 inches. Remember to remove the surface layer of soil so that crop debris is not included. Soil sampling should be done at least every 5 years, and recommended fertilization can be estimated off crop removal rates. For every ton of alfalfa harvested, you are removing approximately 12 pounds of P2O5 and 49 pounds of K2O. The recommended soil test ranges for phosphorus and potassium are 30 to 50 ppm and 120 to 170 ppm, respectively. Subsoil pH should be approximately 6.8.
When considering a fall alfalfa seeding, it is important to have pH and soil nutrients at the recommended levels. This will facilitate rapid stand establishment, so that the plants are prepared for the coming winter. Most importantly, if soil pH is below a 6.5, you may need to consider making your lime application and delaying planting until next spring. If soil fertility is adequate, a fall seeding of alfalfa can be the most productive. In the fall, there will be less weed pressure and a nurse crop is generally not recommended as compared to the spring. Weeds that emerge with the crop are the most damaging. Your goal should be for the first 60 days after planting to be weed-free. If you will be no-till seeding, it is important to control existing vegetation prior to planting, especially perennial weeds. You can determine which herbicides to use, based on your existing weed populations, by consulting the 2024 Ohio, Indiana, and Illinois Weed Control Guide. Seeding rates can range from 10 to 20 pounds per acre depending on planting method and soil type. If no-till seeding, you should be in the 15 to 20 pound range, and when seeding into a prepared seedbed, you can reduce seeding rates to 10 to 15 pounds per acre. Your planting depth should be ¼ to ½ inch. When no-till seeding, make sure that your no-till coulter depth is not deeper than your seed placement depth.
It is unlikely that you will have an opportunity to harvest your fall seeding prior to winter dormancy. The recommendation is to complete planting 8 weeks prior to the first expected frost. In established stands, the last cutting should be made no later than 6 weeks prior to the first frost. For most of northern Ohio, the first potential frost date is October 6th. Once the plants have entered winter dormancy, they have stopped photosynthesis, and it is possible to take a post-dormancy harvest. This isn’t recommended for newly seeded stands. As mentioned previously, it is important to ensure that there has been sufficient growth to help the plant overwinter and initiate growth next spring. Sufficient top growth will help protect the crown from heaving. The added benefit of the top growth is supporting any snow load, which can insulate the crown when temperatures drop below 25oF.