Understanding Carbon:Nitrogen ratios

Discussion in 'Plants: Science and Cultivation' started by mmesford, Jun 5, 2014.

  1. mmesford

    mmesford Member

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    Hi. I'm curious about nitrogen ratios, especially for composting. I've always understood that green meant higher nitrogen and brown meant more carbon. When I look a little deeper it seems to get complicated fairly quickly. Is it possible that a green leaf has a lower C:N ratio than the same leaf does when it's dried? Does nitrogen evaporate?

    Mike
     
  2. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    Are you looking at something like this website on C/N ratio re: composting from Cornell? It includes mention of the loss of carbon once processed to carbon dioixide.

    If you want to adjust the C/N ratio of your compost pile, you then need to know the moisture content of both the pile and what you are adding to it in order to calculate what amount to add in order to adjust the ratio.
     
    Last edited: Jun 5, 2014
  3. mmesford

    mmesford Member

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    Wow, that's even more complicated! I'm only trying to get a general sense of the subject. But the second line of the article points up my confusion: "Grass clippings and other green vegetation tend to have a higher proportion of nitrogen (and therefore a lower C/N ratio) than brown vegetation such as dried leaves or wood chips." One would assume the term "other green vegetation" includes leaves. So when they're green, they have a higher proportion of nitrogen. But when they're brown, they have a lower proportion. This supports my idea that the nitrogen content is reflected in the color, at least to some degree. And since nitrogen is a gas, it must evaporate as the green material turns brown.

    Mike
     
  4. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    Hmm. I agree, that does seem confusing. I think the Whatcom County Extension has a more approachable explanation: Compost Fundamentals
     
  5. mmesford

    mmesford Member

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    Thanks for the links. That last looks a bit more approachable.
     

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