windfall of composted manure

rdgardener(7a)May 29, 2012

This weekend my husband and I scooped up a huge amount of cow manure and various stages of decomposed hay from my Dad's lot. I'm not really sure how to incorporate it into my garden plot which is nothing but barely there grass at this point. I am okay with putting it on there and leaving it till next spring, though I'd prefer to plant a fall garden in a few months if possible. I think I may need to plant some type of cover crop or it will look like some of the other lots that are knee high in bermuda grass and "weeds." I have 11 chickens and 9 guineas that I can employ for incorporating the organic matter. Any suggestions?

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I have what I call my experimental garden (which is empty now). I have tested questionable amendments (hay mainly). If I were going to plant a green manure crop to till in I would not be concerned at all. For this time of year I like buckwheat, it grows fast, easy to work with and the bees like it.


    Bookmark   May 29, 2012 at 9:21AM
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Okiedawn OK Zone 7

If it is fully decomposed so that the manure is fine and crumbly and looks like compost or rich soil and the hay is heavily decomposed, you probably could incorporate it into your garden plot now and plant into it for fall. If it is fully decomposed, the heat of decomposition should have reached high enough temperatures to kill weed seeds and nasty E. coli bacteria and other stuff that you wouldn't want in your garden where food is grown.

However, if the manure is still chunky and is not yet completely broken down and the hay still resembles hay more than compost, then it would be wiser to pile it up in a big compost pile, mix grass clippings and other garden debris with it this summer, and let it fully decompose as a hot compost pile this summer, fall and winter and add it to the garden before planting in winter or spring. When you have cow manure, it is essential it was hot-composted to kill pathogens, and not just cold composted by laying on the ground or in the barn or whatever.

The other issue is that if your Dad used Grazon or any other similar herbicide (the pyridine carboxylic acid types) on his hay pastures or purchased hay from anyone who used those herbicides, then there is a possibility of herbicide contamination that could make its use in a veggie garden a huge mistake. Beginning around 2000, contaminated hay mulch and composted cow manure, including some commercially bagged and sold compost and/or manure as well as compost from some cities' recycling programs, began killing gardens on the east coast and west coast and then spread sporadically across the country. Eventually it was determined that a specific class of chemical herbicides (I believe the first year it was picloram that was the issue and later they discovered that some other similar herbicides persisted in soil as well) were persisting in strong enough concentration to contaminate hay and manure. These chemicals were surviving going through the cows' digestive tract and were surviving being composted.

Municipalities and commercial composters became pickier about using materials that had been treated with those herbicides, and home gardeners learned to use the same caution when using any hay or manure product, and it all died down, though there still were scattered reports of herbicide-contamination killing garden plants here and there---just not on a large-scale like before.

Then a couple of years ago, maybe in 2008 or 2009, it happened again, but this time in Britain and with a "new" chemical herbicide that was very similar to the previous one that caused the trouble. Gardens died, gardeners were infuriated, the manufacturer of that herbicide stopped selling it (I don't know if they later resumed) in Britain, etc. Within less than a year, that same herbicide began killing gardens where the gardeners were using purchased cow manure or purchased compost or hay mulch in parts of America that happened to contain the same herbicide residues that had caused trouble in Great Britain the year before.

So, the threat of contaminated compost and manure remains and we all have to be vigilant about making sure we do not use compost, hay, straw, grass clippings (these herbicides are often used on municipal parks grassy areas and golf courses to kill broadleaf weeds) or manure that contains residues of these herbicides.

This may not sound like a big deal, but it is. Some folks who had their garden killed by the herbicide contamination found they could grow nothing but grass or grain crops in that soil for several years, and most people want to grow a wider variety of veggies, including those with broad leaves.

Last year some friends of ours gave me 206 bales of prairie hay to use as mulch, and reassured me that they'd never sprayed that pasture. Still, I worried about contamination because their hay grows on a family farm divided between the adult children after their parents died, and I worried that one of the siblings might have sprayed their part of the farm without their knowledge while spraying his or her own part of it. So, I cut up random samples into little pieces, mixed it 50/50 with fresh soil-less mix straight from a new bag, and put it into paper cups. I then sowed bean and southern pea seeds into those cups to see if they would grow. (Beans grow quickly and react quickly to herbicide-contamination so they are a good test item.) The hay proved out fine and I have been using it ever since as mulch and as an ingredient in my huge compost pile.

I knew that I personally would have been devastated if the hay was contaminated and ruined the garden soil I've been working to amend and improve for 14 years now.

I am sure you Dad will remember if he used Grazon or any of the similar products that contain these persistent herbicides, but if he often purchases hay for feed, he may not know if that hay was raised with the use of those herbicides.

Assuming your manure and hay are fully composted and contain no herbicide residues, you could layer it on top of the ground now where you want to garden this fall. If you're worried that it all will turn into a big weedy area, put down a layer of cardboard on the ground first to smother out grass and weeds currently in the area. Then layer on the manure as thickly as you'd like. Then, pile something else on top, like grass clippings, spoiled hay or chopped/shredded leaves, etc. to keep the seeds, if there are any, in the composted manure from sprouting. Water it occasionally just enough to wet it down with some moisture--you don't want it all soggy. The moisture will help it heat up and finish decomposing if it is currently only partially decomposted.

Watch it for the next month. If seeds start sprouting in it everywhere, then it isn't fully composted and will give you horrible weed problems and needs to be completely composted before it is used unless you just really enjoy weeding.

Be sure you always wear gloves while handling it. It is never a good idea to handle manure bare-handed because of E. coli and other disease pathogens that can be present in cow manure.

Chickens and guineas likely will dig through it and pick out weed seeds and insects, so there's no reason not to let them help stir it up and break it down. When you clean out their coop, you also can put their old bedding and manure on your compost pile to help it heat up and break down.

I once made the mistake of using not-quite-fully-composted manure that a farming/ranching neighbor gave me without waiting for it to fully decompose. It was the biggest weediest mess you've ever seen in my garden that year and I spent years getting rid of all the weeds that manure brought into my garden. It is not a mistake I've ever made again.

If you pile the manure on the ground, and it seems really well broken down and a gazillion weed seeds don't sprout from it, then there's no reason not to plant a fall garden area into it. I assume you're going to dig it into the existing soil or rototill it into the soil. That is assuming you are confident there is no herbicide contamination.

If you haven't tested the garden soil where you intend to put the manure and have no idea if it contains adequate nutrition for a garden, it would help to get a soil test first so you know what you're dealing one. Soil tests through OSU are inexpensive and are a good starting point.

In the article linked below you will find the listing of chemical herbicides known to break down slowly and contaminate farm fields and gardens. It is a whole lot easier to proceed slowly and with caution and make sure your manure or hay doesn't contain these residues than to spend up to the next 4 years or so not being able to grow much of anything in herbicide-contaminated soil.

When I purchase hay from a feed store now, I only purchase alfalfa because it is a legume and this class of herbicides are not sprayed on legume fields because, of course, they would kill the legumes. If your hay contains obvious legumes, it likely wasn't sprayed with these herbicides.

Hope this helps,


Here is a link that might be useful: Herbicide Contamination

    Bookmark   May 29, 2012 at 9:49AM
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Question...about horse manure...I have a 40lb (dog food) bag of it (mixed with some stall and paddock cleanings) that is about 3/4ths composted. If I have that bag sealed and left out in the heat, will it go ahead and finish itself off? Is there any other reason I wouldn't want to do that? If it's not a good idea I'll just mix it into my other compost bins, but I kind of wanted to keep it separate.

Thanks, manure experts :~)


    Bookmark   May 29, 2012 at 5:24PM
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Okiedawn OK Zone 7

Sharon, I haven't tried composting manure in a bag, but imagine it would work. I'd suggest poking holes in the bag. They don't have to be big...say, maybe the diameter of a dime or even a No. 2 pencil. You want to encourage air flow because it will aid in decomposition. I have filled black trash bags with chopped and shredded leaves in the fall, moistened them (not to the point of being soggy) with water from the hose and lined them up behind the barn out of sight all winter. When I opened them in the late winter to add to raised beds, they were a lovely, rich, composty leaf mold that was wonderful for the soil. I don't see why composting horse manure in a bag would be any different.


    Bookmark   May 29, 2012 at 11:26PM
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Thanks a bunch, folks! I decided to sheet mulch it and the chickens are doing a mighty fine job of sanitizing it. I'm going to be planting some cover crops in that entire area to improve soil structure and composition. This forum is a gem for me!

    Bookmark   June 23, 2012 at 12:56PM
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