Nitrogen fixation into a pot using beans?

So I'm growing anual plants with a very short vegatative period that would benefit from a N boost. I planted them in 5' inch pots with regular potting soil and sowed 4-5 beans at the same time (but just learned beans are poor fixators http://aces.nmsu.edu/pubs/_a/a-129.pdf) in hopes for some nitrogen fixation as green manure. I was hoping to chop n' drop once the beans started flowering but it might be too late, how long will it take from the chop n' drop till the main plant uses the nitrogen from the leftover rhizobium and mulched plant matter?

Hi Edward,

Here's my experience on these issues:

1. legumes in pots using potting soil doesn't always work so well- the seeds need mircorhizi to get them to florish and the potting soils I've used (given they are the cheap stuff) don't seem to do it. If it's a new pot and new soil, I'd say wait a year before trying beans unless you can dig up a clump of earth from the garden and add it in (or purchase innoculated seeds)

2. Flowering is usually a good time to cut and drop. That's when the plant is the most mature, but hasn't started allocating all of it's resources for the next generation.

3. Decomposition and availability of nitrogen to the adjacent plants depends on the area and the soil. If you have avid slugs, snails, and worms, it will probably decompose fast. If the soil is dry, hard, and/or cold it's likely not very bioactive and decomposition will take longer. The good news is you are setting up the soil for years to come of happy plants.

4. A real easy and cheap quick nitrogen boost is at your local coffee shop. Ask them for their used coffee grounds. Sprinkle just a little on top. But, the truth is, if you are using a new compost mix or potting soil and you are not over-watering (nitrogen leaches out of the soil pretty readily), you probably won't need a nitrogen boost for your first season. Look at the color of the water leaking out of the bottom of the pot. If it's coffee colored or light coffee colored you probably have enough nitrogen.

I hope that helps!