Quick Facts...
- The term windrow was originally used to describe cut hay left in long
rows to dry in fields.
- One horse generates, on average, over 5 cubic feet (about 350 pounds)
of manure per week!
- Dynamic methods rely on mechanical turning of the windrow for aeration.
- Windrow composting is recommended for those operations that own or
have access to a bucket loader.
Horses provide utility and pleasure to many Coloradoans and visitors
to the state. However, the buildup of horse manure for operations with
horses on drylots or in stalls creates a management issue that cannot
be ignored. Too often manure or manure mixed with bedding is piled on
site for years without a plan for disposal or adding value to this raw
product. This stockpiling can become a pest breeding ground and a water
quality and nuisance issue. Some horse owners end up paying someone to
haul the material away or hoping that gardeners and landscapers will remove
it at no cost. In any case, horse manure is a resource to reuse. It serves
no purpose sitting in a pile indefinitely.
With minimal amount of equipment, time, and money, horse handlers can
implement an appropriate plan for composting this resource on site. Effectively
composting horse manure will increase its value for application to pastures
and for sale to farmers, gardeners, and landscapers.
What is a Windrow?
The term windrow was originally used to describe cut hay left in long
rows to dry in fields. Windrows of compost resemble these long rows of
hay but are mounds of material instead of a flat layer of hay. Windrows
typically begin as 4 to 8 feet tall, 10 to 20 feet wide, and 10 to 200
feet long. They typically decrease in volume as they mature. The shape
of the windrows allow for easy access to turn the material and provides
the best configuration for the air, moisture, and volume requirements
of the organisms that decompose the manure and bedding. The finished product
is brownish-black in color with most particles less than one half inch
in diameter. It has an earthy smell similar to healthy, fertile soil.
Is Windrow Composting Right for My Operation?
One horse generates, on average, over 5 cubic feet (about 350 pounds)
of manure per week! Add to that 3 to 6 cubic feet of bedding per week from
stalled horses and suddenly the volume and weight of this material becomes
too much to move by hand. While it is possible to do windrow composting
with a fork and a wheelbarrow, windrow composting is recommended for those
operations that own or have access to a bucket loader.
Advantages
- Compost can be added to sand in arenas to improve footing.
- Compost is an excellent soil conditioner. It improves the drainage,
structure, and nutrient holding capacity of all types of soils found
in Colorado.
- Composting improves manure handling by reducing the volume of manure/bedding
by 40 to 60 percent and enhancing uniformity.
- Compost is more valuable than raw manure/bedding for land application
because the process: a) creates a more stable form of nitrogen for sustained
release in the soil; b) lowers the ratio of carbon to nitrogen, preventing
nitrogen deficiencies in crops; and c) has the potential to kill parasites
and weed seeds.
- Compost is valued by organic gardeners and farmers and by landscape
professionals as a high quality soil amendment.
Disadvantages
- Requires time and money – must be turned and watered appropriately.
- Requires space suitable for forming and maintaining windrows.
- uburban and urban areas may be subject to nuisance odors from the
process (although odors are minimal if done properly).
- Colorado climate requires the addition of ample moisture to windrows
and a buffer (i.e., space, trees, etc.) against blowing particles in
some areas.
- Marketing of composting requires time and effort.
- Use of bedding in windrows requires the addition of a nitrogen source
to speed up decomposition of the carbon source (i.e., bedding) if the
carbon to nitrogen ratio (C:N) exceeds 30:1.
The Biology of Compost
Healthy compost is alive with organisms. An ecosystem of macro- and microorganisms
feed on the carbon sources that are put into the pile (manure, bedding,
etc.). There is a food chain that occurs in healthy compost piles from
decomposers to predators. Bacteria, fungi, actinomycetes, and basidiomycetes
do the bulk of the decomposition that creates the finished compost. Helping
them are nematodes, red worms, millipedes, sowbugs, and some types of
mites. Beyond these decomposers, a host of predators feed on them and
each other. These include springtails, protozoa, rotifers, soil flatworms,
centipedes, rove beetles, predatory mites, fomicid ants, and carabid beetles.
But don’t worry; none of these organisms are horse pests.
To make a good finished product, you must create the ideal environment
for the primary decomposers (bacteria, fungi, actinomycetes and basidiomycetes).
Dynamic windrow composting is one way to create and maintain these conditions.
How Do I Make Compost Using This Method?
It is important to distinguish between dynamic and static windrow methods.
Dynamic methods rely on mechanical turning of the windrow for aeration.
Static methods utilize perforated pipes to bring the air into the windrow.
These pipes are either open ended, allowing air to diffuse into the windrow;
or capped with blowers that force air into (and in some cases out of)
the windrow. Both processes are similar in their management goals, differing
only in how they bring oxygen to the organisms in the windrow. For more
information on static methods of composting see fact sheet 1.226, Composting
Horse Manure in Static Windrows.
Where to Put the Windrow
The ideal location for a windrow takes into account the following:
- Proximity to drylots and stalls to minimize transport;
- Access to a pressurized water source to add supplemental water;
- High, level ground away from surface and ground water sources (i.e.,
flowing and dry creeks, rivers, irrigation ditches, springs, ponds, lakes,
and areas with a high water table) to minimize potential surface and ground
water contamination; and
- Sufficient area to maneuver equipment and accommodate the volume
of manure to be windrowed – at least 10 feet on all sides of the
windrow (see Table 1).
| Table 1: Maximum length of piles for
manure vs. manure with bedding. |
| Number of Horses |
Length – Manure Only |
Length – Manure and Beddinga |
| 10 |
94 feet |
195 feet |
| 20 |
195 feet |
389 feet |
| 30 |
292 feet |
584 feet |
| 40 |
389 feet |
779 feet |
| 50 |
487 feet |
973 feet |
| 60 |
584 feet |
1168 feet |
| 70 |
681 feet |
1363 feet |
| a50 percent manure and 50 percent
bedding. |
| + Based on a windrow formed to 6 feet high
and 10 feet wide (capacity of most small tractors with bucket loaders)
and will decrease as height and width increase (12 feet tall and 20
feet wide maximum). |
| ++ Length is maximum needed (based on 1
horse producing 0.8 cubic foot of manure per day) and does not need
to be one continuous windrow. |
How to Get Started
Uniformity is important to ensure an even, predictable composting process.
If you are using varied sources for your windrow (i.e., manure only; manure
and several types of beddings [pine sawdust, woodchips, shavings, straw,
etc.]) try to mix them together until you see no pockets of the various
sources. If you can regulate bedding types, try to use only one.
Once your windrow is uniform, determine if supplemental nitrogen is necessary.
Take a sample to a laboratory for analysis of carbon and nitrogen levels.
An acceptable carbon to nitrogen ratio (C:N) for composting is 30:1. Horse
manure sampled in Colorado has a C:N of 21:1, on average, making it an
ideal compost material. If you have wood chips or sawdust in your windrow
mix you will create a C:N that can approach 400:1. This C:N can double
the time necessary to decompose the material thus increasing your labor
and machinery costs for turning it. For more efficient composting, use
Table 2 to determine how much N to add per cubic yard of material.
As you build the pile with your bucket loader, add the N source evenly
over 1 foot thick layers of material. You may have better results if you
dissolve the N fertilizer in water before applying it. This is an ideal
time to add moisture to the new portion of the windrow. Moisten the manure/bedding
so that it feels moist to the touch but no water comes out when you squeeze
it (like a damp sponge, about 40 percent moisture). Moisture is essential
for the health of the compost organisms and to prevent spontaneous combustion
of the windrow. Warning! Manure and bedding are difficult to wet once
they completely dry out!
Each time you gather manure and bedding, go through the above process,
adding to one end of the windrow only. In this way you can build
a windrow that can operate continuously and mature in one direction along
its length.
As the microbes begin to digest the material, heat is released from the
decomposition process. Temperature and moisture must be monitored at least
weekly for optimal composting conditions.
| Table 2: Pounds of pure N and N sources needed per
cubic yard of material to lower C:N to 30:1. |
| Manure and Bedding Mix |
Nitrogen |
Ammonium Nitrate |
Urea |
Bloodmeal |
Alfalfa Hay |
| 75% Manure/ 25% straw |
None Required |
None Required |
None Required |
None Required |
None Required |
| 50% Manure/ 50% straw |
2 lbs. |
6 lbs. |
4 lbs. |
17 lbs. |
67 lbs. |
| 75% Manure/ 25% sawdust |
None Required |
None Required |
None Required |
None Required |
None Required |
| 50% Manure/ 50% sawdust |
6 lbs. |
18 lbs. |
13 lbs. |
50 lbs. |
200 lbs. |
75% Manure/ 25% chips/
shavings |
None Required |
None Required |
None Required |
None Required |
None Required |
50% Manure/ 50% chips/
shavings |
6 lbs. |
18 lbs. |
13 lbs. |
50 lbs. |
200 lbs. |
| +For horse manure calculations only – C:N for straw
80:1, all others 400:1 |
++33 percent N in ammonium nitrate, 46 percent N in
urea, 12 percent N in bloodmeal, and
3 percent N in alfalfa hay. |
Turning and Monitoring the Windrow
Turning. During the initial stages of decomposition, bacteria
dominate the process and require a lot of oxygen. These same bacteria
are responsible for the heat that the windrow produces. Turning the pile
with a bucket loader does several things:
- Releases heat and gases (some gases are toxic to the compost organisms);
-
Fluffs the pile to increase passive air exchange and add fresh air (oxygen);
and
- Mixes the materials and brings the outer layers of the windrow to
the center where they can be exposed to temperatures that kill parasites
and weed seeds (145 F).
Temperature. Heat is necessary for fast decomposition, but it
evaporates the moisture in the pile and reduces microbial activity above
140 F. Heat in a dry pile can result in spontaneous combustion (fire).
Therefore, turning the pile as soon as internal temperatures (monitor
with a 3 foot long compost thermometer) reach 145 F is critical.
Monitor the temperature every 20 feet or less along the length of the
pile (determined by the age of sections of the windrow). As oxygen levels
drop below 5 percent, decomposition slows, and temperatures decrease.
When temperatures drop to 120 F, turn the pile and check for moisture.
The frequency of turning decreases as the compost matures.
Moisture. Microbial activity diminishes as moisture drops below
“moist sponge” levels. Sufficient moisture levels may be reached by applying
water to the top of the windrow. However, it may be necessary to open
a section of the windrow with a fork or bucket loader and spray it with
water. Another way is to use a watering probe. This is a thin perforated
pipe that attaches to a garden hose and is pushed into the pile. Water
is injected into the pile, minimizing losses to evaporation and runoff.
Check for moisture from a few inches beneath the surface to the center
of the windrow when turning.
Curing
When temperatures fall below 120 F after turning (assuming proper moisture
levels exist) the windrow has moved into its curing stage. Curing is critical
to finish the life cycle of oxygen consuming microbes, shift the pH toward
neutral, increase levels of nitrate-nitrogen, and allow for the recolonization
of soil microorganisms. The enhancement of these qualities ensures a market-ready
product. When windrow temperatures reach air temperatures, the curing
is complete (about one month). Now the compost is ready for use.
References
- Davis, J.G., and A.M. Swinker. 1996. 1.219, Horse Manure Management.
Colorado State University Extension.
- Rynk, R., et al. 1992. NRAES-54, On-Farm Composting Handbook. Northeast
Regional Agricultural Engineering Service.
- Card, A.B., J.V. Anderson and J.G. Davis. 2002. 1.224, Vermicomposting
Horse Manure in Windrows. Colorado State University Extension.
- Card, A.B. and J.G. Davis. 2002. 1.226, Composting Horse Manure
in Static Windrows: Passively Aerated Windrow Method. Colorado State
University Extension.
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