Nitrogen Fixing

I know that beans, peas, clovers, leguminous type plants fix nitrogen. I also know that you can then use that nitrogen to enrich the nutrient base in the soil for other plants. At least, I *thought* I knew, so I grow lots of nitrogen fixers and enjoy lots of peas and beans.

BUT I have just read that if you allow them to flower and set seed then they use up that nitrogen and don't give it to other plants. Bang goes the harvest of peas and beans then. Bang goes the seed saving. I was astonished to learn this new cruel twist in the tale of nitrogen fixing. So what to do?

Alison Freeth-Thomas wrote:
BUT I have just read that if you allow them to flower and set seed then they use up that nitrogen and don't give it to other plants. Bang goes the harvest of peas and beans then. Bang goes the seed saving. I was astonished to learn this new cruel twist in the tale of nitrogen fixing. So what to do?

don't worry too much: some nitrogen remains. also, if your nitrogen-fixers are mixed in with other plants, some nitrogen can be used by the other plants during growth.

and just because much of the nitrogen goes into the protein in the seeds doesn't mean that it's permanently unavailable to other plants. you eat these seeds, yes? using urine in the garden is one easy way to put a lot of that nitrogen back in the dirt. composting feces is another.

all told, these methods will provide a bit less nitrogen than discing in legumes inoculated with high-yielding rhizobium, but the nitrogen that is fixed won't immediately vaporize and be lost to the atmosphere, so I think you'll come out ahead.