After broad beans

Discussion in 'Planting, growing, nurturing Plants' started by Peter Warne, Oct 14, 2007.

  1. Peter Warne

    Peter Warne Junior Member

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    We've had a mighty crop of broad beans - after waiting so long for them to put out some beans that we were on the point of hacking them down. I think maybe our extra cold snap could have made them produce more.

    Now they have finished, and it's time to cut down the plants. I've pulled up a few and seen that their roots are covered with the little white balls which I suppose are nitrogen nodules. Should we leave the roots in the ground or what? Digging the stems and leaves in would take really deep turning of the soil, and I'm not keen on disturbing the soil so deeply. Can we just leave the stems and leaves on top of the soil to break down, or are we missing out on some of the nitrogen fix that way? How soon can we plant something else there? Should we chuck some straw over the whole lot to stop it evaporating in the air?

    Any advice?

    Peter
     
  2. sweetpea

    sweetpea Junior Member

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    Peter, lucky you! There was enough of the bacteria that allows those nodules to grow in your soil. :)

    It's best to leave those roots in the soil, put a mulch over the top so the microbes have a damp environment to start chomping on those nodules. The root fibers and all of the organic matter in your soil will help hold that nitrogen in place once the nodules break down. Also, putting a layer of wood ash under the mulch will also help hold the nitrogen.

    Remember, nitrogen is a gas, and if you pull up those nodules, and they break down where they are surrounded by air in a compost pile, or air in general, poof, there goes your nitrogen.

    The chemical properties of ADsorption create conditions where the nitrogen will chemically cling to the pores in certain kinds of organic matter, like crushed wood charcoal, composted leaves, etc., and then the little teeny plant root hairs can get in touch with that nitrogen, and start using it. :)
     
  3. Peter Warne

    Peter Warne Junior Member

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    Thanks Sweetpea - we've put a layer of charcoal filled soil over the stubble, and a thick layer of straw over that. Now we'll leave it fallow for a little while. I also checked out that word adsorbtion, and watered the whole lot well to help the nitrogen transfer to the bits of charcoal. Thanks again for the very useful suggestions.
    Peter
     
  4. christopher

    christopher Junior Member

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    Peter,

    Everything Sweetpea says!

    Another good reason to leave the roots in is that as the roots decay, the nitrogen is released, some carbon is sequestered in the soil, and oxygen can flow through the cavities left by the decomposing roots and nodule, which is good for the soil biota.

    Christopher
     

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