Since the ratio is "to one" then saying, "carbon to nitrogen ratio of leaves (from deciduous trees) is 30" is the same thing as 30:1.

As to the amount of browns to greens, the amount will vary based on their C:N ratio but as a general rule (and I mean that in the most general sense) I basically go by volume that's about 4:1 (C:N) and adjust as needed from there.

tj

Let it be known though that you only need to worry about perfect ratios if you are trying to hot compost. I use what I have available which differs depending on season. The only things you need to compost is moisture, time and a little manual labor. For example most of my compost material this past summer was weeds and grass clippings. I have two large piles at the back side of my garden. The earlier spring pile has broken down quite a bit with just turning and rain (and it hardly rained here this summer just outside of Boston). I am in no hurry for it to finish so we will see how it is come spring.

Another thing to remember just as a baseline is that browns will compost all by themselves given water, air, and a lot of time. Adding greens speed the process, and turning speeds it up more. So greens are optional.

A pile of greens, on the other hand tends to quickly use up their limited carbon and then turn into a slimey smelly sludge. Some browns are required to regulate the bacteria and keep air pockets open.

So err on the side of browns, then add enough greens to get some heat. Or don't, and just let the pile take its time.

You can always try an experiment. Make a pile with 3 parts grass clippings to one part leaves and see what happens. I predict an ammonia plume. :-]

Better to err on the brown/slow/cool side than to lose the nitrogen, unless you're either in a hurry or trying real hard to kill weed seeds or particular pathogens in your pile.

I wanted hot composting - as hot as possible - because I foolishly decided to compost some couch grass instead of taking it to the local green waste place. I was making the trips anyway. Why do I make these hare-brained decisions???

Thanks everyone and thanks kmmq for mentioning: There is a difference between the Carbon to Nitrogen ratio which is 30 parts Carbon to 1 part Nitrogen and the ratio of browns (usually high Carbon) to greens (usually high Nitrogen) which should be in the 2 to 3 parts Carbon to 1 part Nitrogen.

Something that puzzles me is how fresh grass clippings heat up beautifully while just sitting there waiting to be 'used'. I stole a huge pile of them while at the green waste place so that I could resucsitate my failing compost heaps. When I poke around in them I can see the couch starting to come back to life now that the weather is warming up.

What I really need is a tractor. And more space to maneuvre it.

The biggest problem with grass is that it is inherently small in size when cut. The tiny blades of grass mat down and do not allow much oxygen in. You need oxygen for a healthy hot compost. Blades of grass also break down quickly so initially the pile will heat up but once most of the oxygen is used up the anaerobic bacteria takes over and instead of composting the grass pile you begin fermenting it.

The Carbon to Nitrogen ratio of fresh grass clippings is about 19:1 and the moisture content of those clippings is about what is needed to get the bacteria that will digest them working which is why grass clippings will heat up quite rapidly, but that is also why you can get that strong ammonia odor from a pile of composting grass clippings. The hotter the pile gets that faster the bacteria are working and the more air they are using which means that pile could enter the anaerobic (in the absence of air) stage and then you get a quite putrid (sewage like) odor.

The same thing can happen anytime the Carbon to Nitrogen ratio is too low, not in the 30:1 range and that can happen when the mix of material, 3 parts of high Carbon material to 1 part high Nitrogen material, is not observed. That ratio has been known for eons and was taught to Sir Albert Howard over 100 years ago in India where the Hunza's practiced composting.

kimmq is kimmsr

Oh, was that that Attila guy? Attila the Hunza?

Never mind, I'll let myself out. :-P

Interesting that grass clippings have a C/N ratio of 19:1

Looking at them I (for some weird reason) assumed that their N content was far far greater.

I have started to weed my compost heap. I can't believe how idiotic (or just overly optimistic) I was.

The C:N of grass clippings can vary by quite a bit. I've seen some indicate ranges from 12-25:1.

You also need to factor in time. The longer the grass clippings stay uncomposted the more nitrogen the clippings lose. It does not take very long for grass clippings to turn completely brown.