Spring has arrived and many fields are full of activity. April is a great time to seed alfalfa whenever the soil is fit. Shallow-seeded forages will germinate and grow very quickly with adequate soil moisture and just a few warm days. The key to getting a great alfalfa stand is proper soil preparation and timing of the seeding.
Field preparation prior to seeding
Proper soil fertility is important when establishing a new stand of alfalfa. Soil sampling and fertilizing based on soil test results helps ensure that a new stand will get off to a good start. An updated Iowa State University Extension and Outreach publication, “General Guide for Crop Nutrient and Limestone Recommendations in Iowa,” is a great resource when looking up alfalfa fertility requirements. The recommended soil pH for alfalfa is 6.8 to 7.
Weed management is also important when establishing a new alfalfa stand. Warmer weather allows weeds to germinate and grow rapidly. A burndown herbicide may be needed prior to seeding to control winter annuals and other early-emerging weeds. The Alfalfa Management Guide is a good reference for herbicide options. A good reminder before applying any herbicide is to check the crop rotation restriction intervals in order to make sure that alfalfa may be seeded after the herbicide application takes place. A good resource to check herbicide labels is www.cdms.net/label-database.
Seedbed preparation and planting
Proper seed-to-soil contact and planting depth are critical factors when planting alfalfa. Loose seedbeds can dry out very quickly. Deep tillage should be completed several weeks ahead of seeding so rains can settle the soil before final seedbed preparation. A cultipacker or roller is an excellent last-pass tillage tool. The soil should be firm enough for a footprint to sink no deeper than 3/8 to 1/2 inch.
Drilling spring forages is the preferred seeding method, but broadcast seeding can also be successful if wet conditions prevent field access with heavier equipment. Broadcast seeding may require a 10 to 15% higher seeding rate to account for poorer seed-to-soil contact that can reduce germination. If soil moisture is a concern, interseeding and no-till forage seeding can be successful, but weeds must be controlled prior to planting.
Seeding depth should be no deeper than ½ inch for heavier soils and ¾ inch for lighter soils. If seeding with a drill, it is recommended to set the drill at the ¼ inch depth. You should see approximately 10% of the seed visible on the soil surface. If you are seeing a smaller amount, the seed is being placed too deep, and you should adjust your seeding depth. Across the Midwest, 10 to 15 pounds of pure live seed per acre is generally recommended in most planting situations.
Alfalfa is typically sown with a nurse crop such as oats. Research has shown that oat seeding rates should be aligned with the producer’s goals. For highest grain yields, oat seeding rates of 2 to 3 bushels per acre should be considered. Highest silage forage yield may be achieved with seeding rates of 1.5 to 2 bushels per acre. If oats are planted simply for weed control or preventing soil erosion, there has generally been no advantage to seeding rates over 1 bushel per acre. When using oats as a nurse crop consider the information in he article “Oats as a Cover Crop for Alfalfa.”
Other considerations and links
Thickening up alfalfa stands or interseeding into an existing alfalfa stand is only recommended within 12 to 15 months of establishing a new stand due to autotoxicity concerns. When seeding a legume such as alfalfa, make sure the seed has fresh inoculum of the proper rhizobium. Additional information and articles on alfalfa establishment can be found on the University of Wisconsin Team Forage Alfalfa website.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on April 14, 2023. The information contained within may not be the most current and accurate depending on when it is accessed.