Shop Products
Houzz Logo Print
wazzamcg

C:N Ratio Question and Blood & Bone

wazzamcg
9 years ago

Hi

I can get access to Horse manure (fresh), Coir Dust (dry & fine) and Bagasse (shredded sugar cane mulch) relatively cheaply.

I have found their carbon content and how much I want to use of each as shown below;

Horse manure 30:1 & 30Kg
Coir 100:1 & 6Kg
Bagasse 170:1 & 22Kg
Blood & Bone 3.25:1 & ? Kg

I understand how the C:N ratio concept works roughly but need further help.

How much Blood and Bone meal do I need to get to the perfect 30 to one ratio (in Kgs)?

I would be happy if someone could show me the math or any further advice. Thanks.

Cheers
wazzamcg

Comments (6)

  • toxcrusadr
    9 years ago

    Are you sure horse manure is 30:1? I guess it could be if it had a lot of high carbon bedding in it. Usually manure is high in N, below 20:1.

    There are probably online calculators for this, but there is a quick and dirty way if I can remember how to do it.

    When you mix this up, observe the temp and odor and see if it really is as you intended. Always observe and adjust.

  • toxcrusadr
    9 years ago

    You can do an approximate calculation using a 'parts' method. Multiply the kg of each material by its C and N values to get 'parts' of C and N from that amount of that material. Do this for all 3, add up the C's and N's and divide. This will give you a C:N ratio for your mix. I get 5240 parts C and 58 pars N for a ratio of 90:1.

    Calculating exactly how much 3:1 meal to add is more complicated, but you can do it by trial and error. Say you add 10 kg of the meal - that's 32.5 parts additional C and 10 parts N. Add those to your original totals, divide again and get a new ratio. A few trial and errors will get you close.

  • wazzamcg
    Original Author
    9 years ago

    Hey toxcrusadr

    I did a quick google and it seems the majority say Horse manure is 25:1 not 30:1. Thanks.

    The math suggested that I would need 120kg of Blood & Bone with the original figures - which seemed wrong to me, thats why I required some help. Thats alot of B & B in my books. I will continue to search for the answer.

    I have noted that alot of people just compost the horse manure with no further additions.

    Regards
    wazzamcg

  • renais1
    9 years ago

    The math is correct: if you want to get to a 30:1 ratio, you'll need about 127 kg. blood and bone meal. However, in my experience, there is not a need to use so much material. I just mix materials together, trying to get what nitrogen I can, and let it begin to rot. I usually have far more browns than greens, and often am dealing with many hundred pounds of high carbon browns, so I don't want to add too much supplemental nitrogen from fertilizer. Once I mix the materials, and I've let them rot for a few weeks, I sometimes sprinkle some high nitrogen fertilizer on the mix. The nitrogen addition really helps to spur on the decomposition, but I put no where near enough to get to an initial 30:1 ratio. I might put a pound of nitrogen fertilizer on 400-500 pounds of a high brown mix. For me, this is enough to make a quality compost.
    Renais

  • wazzamcg
    Original Author
    9 years ago

    I'm going to re-visit the materials and will probably cut out the sugar cane mulch as I will likely be using that as a mulch not compost as such. That should lower the amount of B & B used (it's expensive) and add some urea as you suggest.

    I will repost the formula soon - getting more comfortable with the C:N ratio for composting.

  • wazzamcg
    Original Author
    9 years ago

    Okay, the following is the new compost recipe.

    Horse Manure 25:1 @ 30Kg
    Chicken Manure 7:1 @ 6Kg
    Coir (Dry) 100:1 @ 6Kg
    Blood & Bone 3.25:1 @ 10 Kg

    I intend to add some gypsum, potassium sulphate and epsom salt as well, but since they have no carbon in them I have not listed them.

    If I have done my math correct I will need 10 Kg of Blood & Bone and end up with a C:N Ratio of 27:1. Could someone confirm I have done this correctly please.

    Thanks.

Sponsored
Ed Ball Landscape Architecture
Average rating: 4.8 out of 5 stars30 Reviews
Exquisite Landscape Architecture & Design - “Best of Houzz" Winner