Q. I’d like to plant a few manageable nitrogen fixing plants and go about fertilization without chemicals, if possible. Can you recommend any?
A. There is a misunderstanding in the general horticulture community about what nitrogen fixing plants can and can’t do. Nitrogen fixing plants, those plants which can take nitrogen from the air and convert it to nitrogen that a plant can use, do not produce enough nitrogen to support other plants nutritionally that most gardeners might be comfortable with.
If you are looking for a trickle of nitrogen to your trees, then perhaps selecting the right nitrogen fixing plant might provide some benefit to your trees. But most nitrogen fixing crops or plants actually require additional applications of nitrogen to perform at its higher levels of production.
Nitrogen fixing plants, in my opinion, give the greatest benefit in what we call it green manure crop. These are plants that are grown to a certain stage of maturity and then recycled back into the soil. These plants take nitrogen from the air and also nitrogen from the soil and put it into a form that can slowly decompose.
The decomposition of nitrogen fixing plants in soils allow the nitrogen that they have fixed from the air and the soil and converted into forms that slowly release this fertilizer over time. So another words, they take nitrogen that would otherwise might be lost in the environment and give crops a better chance of utilizing it.
If you are a permaculturist or a gardener who puts more value into sustainability than the appearance or total production of their garden, then you might be able to appreciate what some of these nitrogen fixing plants can do for trees.
But if you are expecting to have a level of production and visual quality of fruit that you could buy from a grocery store or a farmers market, you will probably be disappointed. This does not mean that the fruit will not taste good or it will have a decreased level of nutrients.
In fact, the opposite might occur in some fruits but you should not expect the level of production to compete with neighbors who are growing organically or conventionally.
I have attached a link from New Mexico State University that talks a little bit about this.