Obtaining free Nitrogen, by using Nitrogen fixing bacteria, is something that anybody looking for a more sustainable way of growing should be aiming for. There’s plenty of it in the atmosphere, so why use energy, effort, and money to get it, when there is an army of microbes waiting to do it for you, for free.
It was my intention to write an article about the Nitrogen cycle, but I came across this excellent post by Wiley, from Citysown, and realised that I couldn’t have written it better. So why not read his article . . HERE
.Using Nitrogen fixing plants makes a lot of sense, and is in line with the Permaculture Principle of Use and Value Renewable Resources and Services (Holmgren) or Use Biological Resources (Mollison). In traditional agriculture, Nitrogen fixing plants were grown as part of a rotation, whereas in Permaculture, we are trying to integrate them in our planting schemes. Examples include the following. Rice or wheat grown in a permanent bed of white clover, like Fukuoka/Bon Fils. Using permanent beds of clover, and growing vegetables within it. Intercropping legumes with other plants, as in the three sisters grouping of squash, beans, and corn. Alley cropping agroforestry systems, using rows of Nitrogen fixing trees, to flank alleys of other crops. Integrating Nitrogen fixing trees and shrubs within Forest Gardens, soft fruit systems, and new woodland plantings.
In all of the examples above, the key is to manage the Nitrogen fixers to prevent them from dominating the other plants, although many of them also have value as food producers, fuel, animal forage, and bee forage. In most cases, that involves cutting the plants back, and using the material as mulch, sometime called ‘chop and drop’. When the top growth is cut back, the plant root prunes itself, shedding roots to balance the loss of above ground material. This gives a double dose of Nitrogen, from the branches and roots, made available to other plants, after decomposition by microbes.
My recent tree planting has been predominately of Italian Alder, a non leguminous Nitrogen fixer, planted as a support tree. I have also planted white clover in some of the vegetable beds, to grow with other crops, to see how effective it is as a living mulch.
Hopefully, more of us will see the benefits using Nitrogen fixers, to help obtain free plant food.