What is the carbon to nitrogen ratio of dried grass clipping

Enterprise, AL(Zone 8b)

I have been all over the internet looking for a reliable answer to this question. I have found forums saying it is a brown others saying it is still a green. I have done search after search to find a university study that states what the actual carbon to nitrogen ratio is for dried grass clippings. Everywhere I find the ratio listed for green grass clippings and sometimes implied for dried but not made clear. Example grass clippings 15,20:1. Does that mean green is 15:1 and dried is 20:1 or is that for different varieties of grass for green clippings? I find some places saying grass does not lose much nitrogen as it dries and others showing over 90 percent nitrogen loss during drying. Does anyone have a source for the actual carbon to nitrogen ratio of dried grass clippings?

Anne Arundel,, MD(Zone 7b)

Since you have searched well, I think nothing exists. Conditions during the drying are going to vary and could make a huge difference. I would think the range stated is because of the nature of nitrogen going away easily and the variability of how much water was in the clippings that were tested etc.

Enterprise, AL(Zone 8b)

I did find that dried grass clippings are about 3 per cent nitrogen. So if they can state that why not a carbon to nitrogen ratio of the same dried grass clipping? Still looking for the answer. I suppose it is really not that important, but somethimes I just wonder about things. I also found that dried grass clippings lose over 90 per cent of their nitrogen. However at 3 per cent that is still more nitrogen than manure has in it I think.

Enterprise, AL(Zone 8b)

Never give up! I finally found the carbon to nitrogen ratio for dried grass clippings, 50:1.

I realize that this is a very variable figure but it gives me a good ball park figure to go by, and answers the question should it be a green or a brown. With that carbon to nitrogen ratio, it should be used as a brown, even with the three percent nitrogen.

Also found this nifty compost calculator:

Unfortunately two of my most used ingredients: dried grass clippings and dried shredded leaves are not included, but I still find it interesting and a good general guide.

This site has lots of info about composting:

Anne Arundel,, MD(Zone 7b)


That calculator is fantastic. I've never come across one. It will make it really easy for me to better visualize the proportions I need. Have to guesstimate on the shredded leaves. Depending on the type of leaves, I think shredded could have 2-3 - ? times as much carbon mass as loose.

I just read the Wood Chip Backyard Biology page. One of the most clearly written concise I have read on that subject. A++.

This message was edited Feb 23, 2013 11:26 AM

Enterprise, AL(Zone 8b)

Check out the "Links to Compost and Organics Information" at the bottom of that page lots more good stuff about composting!

Everett, WA(Zone 8a)

I found this link to a short table of Estimated Carbon-to-Nitrogen Ratios.

It doesn't mention DRIED grass clippings, and says "60:1" for leaves, which must mean "dried leaves".

Anne Arundel,, MD(Zone 7b)

Hay- that is sort of a dried grass, right? That is 25/1.

Everett, WA(Zone 8a)

I saw "grass clippings" at 20:1 and thought "those must be green grass clippings".

I didn't notice hay. I saw straw3 at 75:1, but straw should be the long stems, not the stems.

I usually start with much more brown than green. Then I add kitchen waste and coffee grounds in the right- center part, for as many weeks as it takes until it looks "rich", then starts to look a little gooey.

Then I mix a little of the "leaner" surroundings back into that area and set it aside (to the right) to finish.

Then I add the kitchen waster to a new "center" that's a little farther to the left.

Belmont, CA

I too have been looking for a reliable nitrogen ratio for dried grass. I found the value on the Compost Junkie sight as well, but being only one source with no references, I hold it suspect. I have adapted the compost calculator from WA State U (https://puyallup.wsu.edu/soils/compost-mix-calculator/) to match my feedstock so I can calculate my compost recipe ratios. I have a lot of dried grass as our school district gardeners bring me all their grass clippings (and dried leaves), which I dry out on a raised drying bed made from pallets and hardware cloth. Storing fresh grass clippings is messy and smelly, and I didn't want to pass on this free local feedstock. Back to the point - I'm still looking for a reliable ratio for dried grass. I'm currently using a 40:1 ratio in my calculator, which makes it a brown, but this ratio was extrapolated from other similar feedstock numbers. Our local Office of Sustainability just provided me funding to implement a worm composting system for a 1,100 student middle school, and in the grant I included funding to have my dried grass clippings analyzed by a soil lab. I'll post my lab results once I get them.
Keep on doing the rot thing.

Thumbnail by OrganicRusty

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