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northeastern Ohio | Good advice!
Alfalfa breeders have told me that they have bred the autotoxicity out of modern alfalfa's in order to make stands last longer. But as you noted, there are more factors at play than just autotoxicity. Here is a post I wrote on Agtalk back in 2013: https://talk.newagtalk.com/forums/thread-view.asp?tid=377396&mid=299...
Alfalfa thins out due to disease, fertility, bugs and physical damage. Physical damage and bugs can be easily overcome by reseeding and spaying for pests. However, disease generally requires time for the disease load to reduce. Rotating to a different crop (grass crops like corn are better than other legumes) can help in reducing disease pressure. Fertility also takes time, especially deep fertility that is required by alfalfa. Yes, you can put all the nutrients on and even mix them into the top few inches, but it takes time for them to reach the depths that alfalfa require. It also takes time for the nutrients to be mineralized and released at those depths.
Another post from 2024: https://talk.newagtalk.com/forums/thread-view.asp?tid=1176421&mid=10...
There are several issues that cause stand thinning:
1) physical damage to the plants
2) disease
3) competition
4) nutrient availability (and pH) at root depth (including water)
The first issue will not affect future stands, but the other 3 will.
By killing the remaining alfalfa plants now, you can break the disease cycle by allowing a winter as well as time to reduce the disease pressure.
Competition is weeds or other species in you mix. I would do a full stand kill and plant wheat this fall (or oats in the spring).
Pull some soil samples and split each core in half (0-3" and 3-6"). If you need to address deep nutrient issues, then you need to get nutrients/lime on now in order to allow time for them to work their way down the soil profile in no-till ground.
A single alfalfa plant can dry out the ground around it. This makes it difficult for new seedlings to compete when the existing plant has a deep tap root to find water when it needs it.
Once you take care of the above issues, you can reseed alfalfa.
Edited by Jay NE Ohio 8/25/2025 18:13
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Something new about autotoxicity in alfalfa
