Alfalfa friend or foe?

I work for a Co-op, so I get a pretty good price on organic alfalfa pellets.  For the most part I use them when I'm filling a new hugel beet raised bed. My thinking was the wood will rob nitrogen, so  give it extra so the plants don't suffer.  This has worked very well for me. I don't know if I right or wrong, just that I have healthy productive plants.
I usually fertilize two times a year. I sprinkle a mix of what I have before spring and fall planting. Sometimes if I don't have other nitrogen source, I will add some alfalfa pellets to the mix. Again I keep doing it because of the healthy productive plants. Not to say I don't have a non productive plant now and then, or that nothing ever goes wrong, because of course I do.
Yesterday a long time gardener/pro told me to get old alfalfa from someone and mulch around my fruit trees, not only will it help with water retention, but it's a super at suppressing weeds.  He said farmers can't even grow it in the same place for more than 3 years in a row because nothing will grow. I was going to do just that, happy to have a great mulch.  
Then I started to think about all the time I put alfalfa in my raised bed.
My question is have I slowly been poisoning my veggie beds?

Jen,

Your friend may be talking about alfalfa autotoxicity, it inhibits the new growth of alfalfa, don't think it bothers other plantings.

From Google,

Alfalfa autotoxicity is a phenomenon where established alfalfa plants produce chemicals (medicarpin and phenolic compounds) that inhibit the germination and growth of new alfalfa seedlings, causing stunted, reduced stands. It poses a severe risk when reseeding old stands, often necessitating a delay of 1–3 weeks or rotation to another crop.

Alfalfa is a good nitrogen source as plant protein is nitrogen.

AI Overview

To convert protein percentage to nitrogen (N) percentage, divide the protein percentage by the nitrogen-to-protein conversion factor (typically 6.25, which assumes proteins are 16% nitrogen). The formula is: % Nitrogen = % Protein / 6.25. For example, 20% protein equals roughly 3.2% nitrogen


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I have never heard of  alfalfa being toxic to itself. I have alfalfa growing in my yard and comes back on its own year after year. Its an amazing green mulch.

Unless folks are growing large amounts of alfalfa, I feel there is no concern about alfalfa especially pellets.

I have always read the alfalfa is an excellent organic soil amendment as it add some many nutrients.

If folks are planning to grow alfalfa and have a deer population then folks might not be successful as deer love alfalfa.