Sounds like you're trying to store moist manure, and do it largely anaerobically. That's a recipe for awful smells and probably pathogen breeding as well. Just pile it up and let it dry out.

But if you're going to compost it, do it while it is wet. By the time it dries out, a lot of the urea in it will have decomposed.

Why store that manure until next spring? Even in a covered container that manure will loose valuable nutrients. Best to put that manure in the soil now.

OK how long after I mix the manure into my tomato and flower garden soil can I plant?

taras, if you go up to the search box and type in 'horse manure', you will find LOTS of discussions about it here in this forum. Not all are in favor of fresh horse manure in the garden for a variety of reasons. Might be a good idea to do a little research before dumping it into your soil.

Fresh manure is rich in urea, and will outgas ammonia rapidly. That can cause nitrogen burn for plants, but it's terrific for compost.

If you apply manure directly to a garden bed, I'd leave it a month or two before planting. Basically, what you're doing is in situ composting.

Storage of manure is a big deal for the agricultural community, but they're not doing it for soil improvement. They're doing it to wait for someone to haul it away.

How long to wait depends on how old that manure is. If it is fresh, and still has that strong manure aroma, wait a month or two. However if that manure is somewhat older and has no aroma a week or two would suffice.

It also depends on how much organic material is in the soil to help stabilize the Nitrogen that manure has.

One problem with horse manure is that horses have inefficient digestion and swallow their food lightly chewed. There are weed seeds in it and they will sprout in your garden. At least give the weeds time to sprout so you can kill them off before you plant anything.

Stable litter is the mix of urine, manure and straw cleaned out of stables. Way more nitrogen and needs to compost a bit unless you are making an old-fashioned pit for growing squash in a cold climate.

I would compost that with some leaves or other browns (straw, newspaper, sawdust/wood shavings, cardboard, etc.) this summer and add it to your garden in the fall. If you started a pile now and turned it a couple times, it would be ready in time for some fall crops - greens, lettuce, root vegetables, etc. that you can plant in late summer/fall.

Use something else to amend your garden for planting now.

And compost that stuff in an open pile or bin, not a sealed can.

I don't have the room for an open pile; I live in the Bronx and my "farm" is about 10' x 10'. I plant veggies in the "farm" and have a small area in front for flowers. I'm turning it into my garden soil now and will wait a month or so to plant. I appreciate all the help.

You can vermicompost manure in a box or bin in the same amount of space as what you're proposing. It would need to be somewhat open to the air, of course, and may work better if oriented vertically rather than horizontally, which maximizes surface area. Here are some simple worm bin ideas (the text here is not the greatest, but the pictures give you a good idea of what's possible to build): http://theselfsufficientliving.com/10-helpful-worm-composting-bin-ideas-plans/

Thank you; some doable ideas on that site

You can also make a tall skinny cylinder out of wire fencing and hide it behind a bush or anywhere. Some people put them in the center of a garden bed and let the nutrients leach out of the compost into the garden while it does its thing. Barely takes more than a square foot.

Where did you get the manure if you live in the city? If it is from race horses I would think twice before using it. They pump more pharmaceuticals into race horses then into any other animal used for labor.

Another thing with horse manure is whether they used ag lime to control odors in the barn. This can make it highly alkaline. Composting tends to neutralize pH but there is a limit.

Based on the number of degradation and dilution and media transfer steps, I'm not too worried about animal pharmaceuticals affecting the health of vegetable gardeners. JMHO.

I get the manure from NYPD stables. I've decided that at the end of this growing season I'll go back to the police stable and pick up 2 more bags and dump them on top of my "farm" and let it compost over the fall and winter. Good idea?

You might as well dig it in, rather than dumping on top. If you dig it in, the ammonia volatiles that will come off of fresh manure will turn into soil nitrates that will benefit the plants. If you just leave it on top, that ammonia will just blow away. In situ composting is the way to go, especially if you don't have space for a separate, deep, compost pile. It'll be all done in the spring.

Police horse manure - now that ought to be a conversation piece with your neighbors. From the size of your patch, I'm assuming you have neighbors pretty close in? In that case, the conversation about you spreading fresh manure might not be the most pleasant.

Surprised the NYPD stables don't divert their manure to a composting operation already, though. Does NYC have (finished) municipal compost you can acquire for free?

No. I don't know of any municipal compost stations in NYC. The NYPD stable that is near my house, actually throws out the manure. They welcome anyone to drive in and take all they want. This was my first trip to the stable and I really didn't get that much manure so the "aroma" wasn't overwhelming; by the 2nd day there was no smell at all. I'm hoping that my next trip in the fall will be the same. I will, as advised, bury the fall load. My 10' x 10' farm does not take a whole lot of effort to turn the manure into.

If you bury the manure, it won't smell. If you keep it in a covered garbage can, you and your neighbors will be wearing clothespins on your noses. I'm pretty sure NYPD does divert their horse manure to a municipal NYDS composting operation. Big Reuse in Queens has an enormous such operation, and I think there is a smaller one in Manhattan. NYPD is just saying that you're welcome to come by and get some before they divert it there.

Whether or not any animal manure smells depends on many factors, most of which relate to the freshness of the manure as well as the amount. Manures with very little to no odor may have had most all of the nutrients released, since that "aroma" is an indication of what is happening with the manure.

When we say that manure, or compost, has "matured" or "stabilized" we mean that it has reached a point where the decomposition processes are substantially finished. This does not mean that the (plant-available) nutrients have all been "released."

For instance, aerobic decomposition and vermicomposting promote the conversion of nitrogen to nitrate, which unlike ammonium does not evaporate into the air but does dissolve and disperse in water. (That's why finished compost "keeps" longer when covered against rainfall but does not need to be sealed off from the air.)

Fresh manure gives off hydrogen sulfide, ammonia, methane and CO2. Of these the first two are the stinky ones. The more you can aerate and oxygenate the manure, the more the volatile compounds will dissipate and the more aerobic decomposition that does not produce these noxious odors will take over. The tricky bit here is that you can't avoid the smell being produced by the initial dissipation. Small volumes of manure are easier to aerate faster and more thoroughly.

Definitely dig some of that into the garden in the fall!