The Pros and Cons of Overseeding Alfalfa into Alfalfa

A thin alfalfa stand is a common occurrence as that stand ages. Unfortunately, thinning of an alfalfa stand also can occur in young stands. So what’s a producer to do?

One theory is that overseeding alfalfa into alfalfa will not only prolong the life of an alfalfa stand but also will correct any deficiencies present in a stand. While this method of improving a thin stand has some proponents, there are risks to it, as well. Here are some things to look out for when considering this method:

  1. As a slow-growing perennial, alfalfa has a difficult time competing with existing plants and weeds for things like water, nutrients and water. Further, soils in fields that are well established do not germinate well.
  2. If the reason for plant loss in the first place is not determined than it is likely that it will impact the newly planted alfalfa, as well,
  3. Alfalfa produces autotoxins that suppress growth of alfalfa seedlings in existing stands.

Under certain conditions, however, overseeding alfalfa into existing alfalfa stands will help to reduce thinning. These include alfalfa stands that have been damaged by flood or frost.

Thankfully there are other methods for improving alfalfa stands that are thinning. One successful method is to overseed with grass forage such as berseem clover, fescue, oat hay, orchard grass and ryegrass. These types of annual and perennial forages are planted in the late fall or winter and will quickly grow and push through dormant, established alfalfa to fill in thinning and weak alfalfa stands.

When overseeding with grass forage it is important to keep in mind that mixed hay may not be acceptable for livestock feed for the dairy industry and instead will be more appropriate for horses. It also is important to note that when grasses are mixed with alfalfa, the grasses will likely, over time, take over alfalfa.

In the end, if you are committed to overseeding alfalfa into alfalfa, keep the following in mind:

  • If you are overseeding alfalfa into young stands it is important to pay close attention to herbicide limitations, seed depth, tillage and timing.
  • Overseeding into older stands is less successful but may be possible under mild conditions.