Feed Your Soil for Free While Helping a Horse Rancher

Garden soils need organic matter to hold moisture, slowly release nutrients, add to soil tilth so roots can be cozy and get at soil particles... There are lots of horse stables and pastures where I live in N. Central Florida, as well as high temperatures which lead to fast decomposition of organic matter in these sandy well-drained soils, so my garden needs a healthy - pow! - shot of nutritious organic matter every fall.

Horse farmers have huge piles of free horse manure, urine and straw that get cleaned out of stables that can get them in trouble with the department of environmental protection because of the nitrogen that can leach out and go to creeks and streams in heavy rains.  USDA or state agents go on visits to farms to see how their poop piles are doing, and the smaller they are the better.

This instructable tells you how to
1. find free fresh horse manure
2. get it to your house
3. add it to your soil as a mulch, or as a soil amendment for future plants.

You will need:
1. station wagon OR pickup truck with some big tarps
2. a few shovels
3. a hearty friend who likes poop
4. recycle bins or wheelbarrow

The best bet is to find a horse boarding stable, as they have lots of horse owners coming in and out... call or drive up and ask if they have some manure they'd like to get rid of. You'd be willing to remove their waste problems for free. If you're lucky, you'll find some composted manure. (Some pay to have it hauled to a landfill, or spend energy and tractor time composting it.)

A 1000-lb horse creates 50 lbs of poop and pee per day!

This partially decomposed horse manure has a very high Carbon (C) to Nitrogen (N) ratio because there is a lot of straw (high carbon) mixed with the manure and urine (high nitrogen). Microbes reproduce and build themselves out of carbon and nitrogen, so if there is a high carbon content relative to nitrogen, microbes will take advantage of all that carbon and eat all the nitrogen they can get to make more of themselves.  A microbe cell C:N ratio is around 25:1.  So if your poop has a C:N ration higher than this (it's typical for manure with bedding to have C:N ratio > 30:1), there will be no nitrogen available to plant roots.

If you use cow manure from a dairy or feedlot, the C:N ratio will be much lower.

This means that if you mix this partially decomposed manure into the soil and put in plants right away, the plant roots might get some phosphorus and potassium, but there won't be any nitrogen for them to take up because the microbes will be eating it all so they'll turn yellow being starved for N! 

Use the recycle bins or wheelbarrow to move your mulch from vehicle to garden.

You can mulch plants by putting the partially decomposed manure on TOP of the soil. Here it will serve to contain moisture in soil and keep cold freezes from hurting roots.  As the manure decomposes, nutrients will go down into the soil and feed the plants over time. Sort of a slow release fertilizer, but some of the nitrogen from this mulch will be release to the air as ammonia, so not all the nitrogen will stay in the manure.  This manure will slowly break down and you can mix it into the soil later to improve soil texture, microbial habitat and moisture retention. 

Check out the mulch! You can see if it is broken down a bit. Mine has been decomposing...

In an uplanted plot, you can mix in the manure to let it finish decomposing there. I put about 3 inches over the bed, mix it in the top 3-4 inches of soil.

General rule is to put 1 lb of manure for every square foot of soil.  A 5 gallon bucket holds about 25 lbs of manure (depending on moisture).  I read in several places that you should not wait to incorporate the manure, as a lot of nitrogen will evaporate from manure as ammonia.