Hello all,
My name is Eric and I am new to posting on this informative website. Although I have lurked through these threads many times before and always been impressed by the collection of knowledge here. This post is specifically about my idea relating to nitrogen fixation and nitrogen tie-up, and whether there has been any work in this area.
The basic premise is to grow a
native nitrogen-fixing plant in a
raised bed amended with large quantities of high-carbon material like sawdust, oak leaves, or
wood chips that exclude ramial chipped wood. This would tie up most if not all of the available nitrogen in the soil, which is the goal. Nitrogen fixers will preferentially scavenge nitrogen from the soil over fixing it from the atmosphere due to the heavy
energy cost, thus this bed is designed to force them to fix most, if not all, of their nitrogen needs by removing available nitrogen in the soil. However it will not affect any other nutrients, and the plants will be placed in a full-sun location and given plenty of
water; as the main goal is to eliminate all stressors except the nitrogen tie-up. They could then be harvested at the optimal times and the nitrogen-rich biomass used for liquid
feed or worked into the soil as green manure. In addition, the high-carbon materials will slowly be broken down after an undetermined amount of plantings, and the nitrogen present in that soil will return from being tied up, meaning almost all the nitrogen gained in the biomass from the plantings will be fixed nitrogen.
It will also be wise to inoculate them with the proper rhizobia, and it will be necessary to add a slight amount of nitrogen fertilizer of some kind to the bed at germination. This is to ensure that the seedlings will have
enough nitrogen to survive the gap between the energy stored in the seed,
to established nodules, and sufficient photosynthetic reserves/capacity for nitrogen fixation. Normally I would want to vary the particle size of the wood chips in the bed to form a gradient, but since the primary goal of this bed is not wood chip decomposition, I do not think that's necessary.
It sounds complicated to grow some nitrogen-rich biomass, but my line of thinking was that it could be used to not only break down high
carbon materials over time but also provide a source of nitrogen that is completely from the atmosphere with very little to none being extracted from the soil. For my area, the annual legume Partridge
Pea (Chamaecrista fasciculata) is an excellent and productive plant. I have not had the opportunity to try this yet but please let me know if you have any thoughts!
All the best,
Eric S.
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