Newbie compost questions

uscjustoMay 20, 2013

I read the ratio should be 50/50 green and brown.

People refer to leaves as brown, but what if they are freshly pruned or fallen from a tree and not dried out yet. Are those leaves considered green if they have not dried out?

Are UNused coffee grounds the same as used coffee grounds?

I use Scott's lawn fertilizer with crabgrass killer on my lawn. Would it be bad for me to use my lawn clippings in my compost pile?


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Yes the crabgrass killer could be a problem. You wouldn't want to put it on vegetables and it could possibly still be effective after composting even if you use it on non edibles. Coffee grounds are actually green and I believe the leaves are still browns even if they are still green! Composting is color blind. It will take longer to compost green leaves though.

    Bookmark   May 20, 2013 at 6:13PM
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The ratio depends upon what you use for browns and greens. What you are trying to do is achieve a carbon:nitrogen ratio of about 30-40:1 by weight. If you search 'compost carbon nitrogen' you will find many tables for various C:N ratios of compostable materials. Adjust the ratio of your feedstock to get the right end result.

The classic ratio is about 2 parts browns (leaves) to greens (kitchen trim). The greens are anything with a C:N ratio of ~ 20:1 or less, the browns are those with a C:N ratio of ~ 30:1 or greater. Manures have very low C:N ratios, kitchen trim is about 20:1, wood products can be as high as 500:1.

Coffee grounds, used or unused (really?) are green. Leaves, green or brown will be browns.

If the fertilizer you are using is Scotts with Halts, the Halts is pendimethalin, which is a pre-emergent herbicide. It will ultimately decompose, but it can take months - it's half life in soil is ~ 90 days. It tends to bind tightly to clays and soil organic matter, and is considered not subject to microbial degradation in soil. According to one study, pendimethalin is most likely tightly bound with humic products formed during composting (link below). If it remained there, it shouldn't be much of a problem. However, given that is translocates to plants via roots, and is not readily broken down by microbial degradation, I would keep treated grasses out of my compost.

Here is a link that might be useful: What happens to pesticides during the composting of yard trimmings ?

    Bookmark   May 20, 2013 at 7:38PM
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I'm thinking I should discontinue my use of weed killer on my lawn so I can use my grass clippings in compost.

I said unused coffee grounds because I don't drink coffee but I just found a can of grounds in my pantry that I have no use for.

    Bookmark   May 20, 2013 at 8:42PM
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If you stop using herbicides on your lawn, and give it a season before you use them, then you are surely fine.

I did organic lawns when I lived in MI - it worked extremely well and I had as much grass to compost as I wanted. In SE TX, I tried several times and the pest pressures plus environmental conditions (heat and humidity) left me concluding that it just isn't feasible or practical if you want or need a turf lawn. As a result I am strictly a mulch cutter, which given our soils is probably the best use for the clippings anyway. In fact, I don't know anyone who ever bags clippings, save a winter clean-up.

    Bookmark   May 20, 2013 at 8:51PM
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I bag the clippings from just the first few turns of my mower so the grass/weed tops don't go into my flower beds. They look unsightly and possibly spew weed seeds into my mulch! Also when it rains for a week straight and the grass is so high it makes big clumps. That is the kind of rain we've had in TN the past week or two.

TXEB with your knowledge of soil, do you have any experience with Bayer systemic products? I used the Bayer 3 in 1, which is a fertilizer and systemic pesticide and disease treatment. I stopped using it two years ago when I went organic. I called the company and they say it completely dissipates in the soil in 30 days. I wonder how long I should wait to plant edibles near my roses and much leaching there is in the surrounding soil. I realize this is a long shot but thought I'd ask. Your past posts have been incredibly detailed.

This post was edited by bibbus on Mon, May 20, 13 at 21:28

    Bookmark   May 20, 2013 at 9:19PM
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First, I'm not a soil guy - just a chemist.

If you used a Bayer systemic insecticide in a retail product I would guess it was Imidacloprid. If the product you used contained Imidacloprid as the insecticide, I would be very skeptical of the 30-day period in soil.

What I know about the stuff is that it's degradation in soil is highly variable. It has been widely studied, and the reported half-lives in soil vary from ~90 days to several years, depending upon conditions. It's primary mode of environmental degradation is via aqueous photolysis - in aqueous solution and sunlight the half-life is hours. Rather than complicate the question, it can persist in soil for a year or more, depending upon a number of variables. The amount that is left as residual at any time will depend upon how much was applied, and how it was applied (directly in soil vs liquid spray, vs other?).

All that said, Imidacloprid is used and included in a number of garden insecticides. When applied as a liquid to row crops the intervals between application and harvest are variable, but at garden application rates, which I would guess are lower than what is used for roses, the pre-harvest interval is usually about 21 days. If you applied less but no more than what would be typical in a registered veg garden application, then 21 days should be adequate. If you applied more or it was incorporated into the soil, then to it would take longer to reach soil comparable residual levels. So the answer is, it depends.

How long ago and in what form did you use the stuff, and do you know if it contained Imidacloprid?

    Bookmark   May 20, 2013 at 10:12PM
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The ratio of green to brown is not fixed and it depends on what you have. Animal manures should be mixed with vegetative waste about 1 part manure to 3 parts vegetative waste. A general rule of thumb is that anything with a Carbon to Nitrogen (C:N) ratio less than 30 to 1 is a green and anything higher is a brown.
Green leaves can be a green as long as the C:N ratio is less than 30:1. However, I have seen leaves that are fairly old that have retained the chlorophyl that makes them green and probably they do not have much Nitrogen left. Freshly fallen leaves with a C:N ratio of 40:1 are close to being a green while old leaves with a C:N ratio of 80:1 would be a brown.
Unbrewed coffee grounds will be about the same as brewed coffee grounds.
There is much information available about some "weed" killers having adverse affects on vegetable gardens when products they were used on are used as mulches or are composted. While I have seen nothing to indicate Pendimethalin is one that may well mean that no one has looked.

Here is a link that might be useful: Pendimethalin

    Bookmark   May 21, 2013 at 7:23AM
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Here's a bit more on pendimethalin.

There's a link below to the label for an ag version from Helena. On the label you will see it is registered for use on the following crops:


For crop rotations (see page 11 of the label pdf), listed crops above may be replanted in the same season. Other crops (e.g., sugar beets, red beets, spinach ...) noted have rotation schedules varying from 4 to 20 months following application of pendimethalin depending upon crop following, rainfall after application, and time of year that it as applied.

Here is a link that might be useful: Pendimethalin label

    Bookmark   May 21, 2013 at 9:04AM
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The solution for clippings you don't want to compost is to use a mulching mower, or even a regular mower with a side chute, and recycle them back into the lawn.

I am not so sure that green leaves are a brown. I've seen piles of freshly shredded green tree limbs and leaves heat up and steam. That means the C:N ratio was not too far over on the brown side.

Compost piles are very forgiving, though. You don't have to be terribly precise.

    Bookmark   May 21, 2013 at 12:25PM
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I guess I can use grass clippings from my treated lawn in my compost pile if I intend to only use the compost on the lawn, and not into my vegetable garden right?

The weed killer residue on my grass clippings won't affect the composting procedure?

    Bookmark   May 21, 2013 at 8:12PM
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Sure - if it came from the lawn, it can go back there. But like Tox said, the easiest way is to mulch cut, let them fall and decompose right there.

    Bookmark   May 21, 2013 at 8:17PM
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Another newbie question. Do bones belong in composting at all?

    Bookmark   May 24, 2013 at 6:08PM
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Not in my compost ! But then, I don't put animal products in my compost.

Most animal bones won't decompose much under composting conditions, unless you wait a very, very long time. The exception might be fish bones.

Separate from bone are exoskeleton shells that are primarily chitin (shrimp, lobster, etc.). Those will decompose, but somewhat slowly.

    Bookmark   May 24, 2013 at 6:58PM
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