15

Managing HorseManure byComposting

Recipe for SuccessfulCompostingLike animals, the microorganisms responsiblefor composting need food, water and air tosurvive. The goal of composting is to provide theideal environment and the proper balance ofnutrients needed by the microorganisms toencourage their growth. Components of this“recipe” for successful composting include anumber of key ingredients:

1) Availability of airMicroorganisms need air (oxygen) to be ableto decompose manure properly. To providespace for air to move in and out of the pile,manure should be combined with bulkiermaterials, such as wood shavings or strawbedding mucked from a stall, or even lawnclippings, leaves or hay. Infusing air into thepile is also accomplished by mixing andturning the pile frequently or by insertingperforated PVC pipes into the pile.

Why Compost?Many horse owners and urban horse facilities donot have access to enough land to make gooduse of raw manure by spreading. If you are oneof these individuals, composting providesanother option for managing horse manure.

Manure starts to decompose as soon as it hitsthe ground. Microorganisms in the soil,including bacteria, fungi, insects, worms andother creatures, break down the organiccomponents of manure and bedding into smallerparticles (Figure 10). In doing so, they recyclenutrients back into the soil, while releasingcarbon dioxide, water and heat.

Although manure can decompose on its own,composting is a method of speeding up thisnatural process. The breakdown of manure andbedding occurs much more rapidly in thecompost pile because the environment can bemade ideal for the microbes to do their work.The end result of composting is a dark, crumbly,earthy-smelling product similar to potting soil.

Composting is of particular interest to horseowners because, if it is done properly,composting kills parasites eggs and larvae anddestroys weed seeds in horse waste. Therefore,if the compost is later spread on pastures, thepossibility of re-infection is reduced.Composting also reduces the odor of themanure and can decrease the size or volume ofthe pile by 50 per cent. Finished compost can beused to improve soil quality or serve as a mulchor growing media for plant nurseries, gardeners,mushroom growers and worm farms.

Benefits ofcomposting

• Kills intestinalparasite eggs andlarvae

• Destroys weedseeds

• Reduces flies byeliminating theirbreeding ground

• Reduces odor

• Reduces volume ofmanure

• Serves as anexcellent soilamendment

• Produces anattractive productto use, give away,or sell to others

Figure 10. Soil microorganisms break downmanure and bedding to form compost.

16

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2) Moisture levelMicroorganisms grow best with the moisturelevel at around 50 per cent. The averagemoisture content of horse manure is 70 percent, but the manure may be closer to theideal moisture content when it is combinedwith soiled bedding.

3) Particle sizeSmall particles decompose faster becausethey have more surface area for microbialactivity. If you own a shredder or tub grinder,consider processing straw bedding, hay andother coarse materials before adding them tothe compost pile.

4) TemperatureAs microorganisms decompose manure andbedding, their body heat causes thetemperature in the pile to rise. A hot piledecays much faster than a cold pile. Greaterheat is necessary to kill weed seeds andparasites. Effective composting takes placearound temperatures of 55 to 65°C(Figure 11).

5) Pile SizeThe size of the pile influences whether thepile will hold heat. Small piles are usuallycolder and dry out faster. A pile of at leastone cubic meter (3.5 x 3.5 x 3.5 feet) is bigenough for year-round composting, even inthe winter cold.

6) NutrientsMicrobes use carbon, nitrogen and othernutrients from materials added to the pile tosupport their own growth. Nitrogen is themain nutrient found in manure; carbon is themain element found in bedding material. Thechallenge is to ensure the proper proportionsof carbon and nitrogen needed for successfulcomposting.

The carbon-to-nitrogen ratio (C:N) of amaterial is an estimate of the relativeamounts of these two elements. A ratio ofabout 30:1 is ideal for composting. Table 2shows the approximate ratios for somematerials commonly added to compost piles.

A mixture of one part manure with two partsbedding (by volume) usually gives areasonable mix for rapid composting.However, the amount and type of beddingcan alter the C:N ratio and influence themanagement needed for successfulcomposting (refer to the sidebar “BeddingTips.”)

Figure 11. Effective composting takes place attemperatures of 55 to 65°C (130 to 150°F).

17

Bedding Tips• Use less bedding…

Large quantities of bedding mixed withmanure can slow the composting processby contributing excess carbon andupsetting the ideal C:N ratio. Beconservative with the amount of beddingin your stalls and remove only soiledmaterial when cleaning. Installing rubberstall mats or rubber pavers can reduce theamount of bedding needed whilemaintaining the comfort of stalled horses.

• If you use straw bedding…The porous, spongy consistency of strawusually provides close to the right amountof free air space within the pile. However,the large particle size might delay thebreakdown of straw. If a shredder orchipper is available, consider processingstraw bedding before adding it to thecompost pile. The addition of nitrogen tothe compost pile may be necessary if largeamounts of bedding are used.

• If you use wood chips or sawdustbedding…Wood bedding products contain very littlenitrogen and a lot of carbon. Therefore, itmay be necessary to add supplementalnitrogen to facilitate proper composting,particularly when large amounts ofbedding are used. Wood chips are lesslikely to compact the pile, compared tofiner sawdust. If you bed on sawdust, youmay need to add other bulking materialsto improve aeration. The advantagesawdust has over straw and wood chips is asmaller particle size. In fact, if managedproperly, sawdust will compost faster thancoarser bedding materials.

Locating Your CompostPileThe first step in setting up a composting systemis choosing a location. When choosing alocation, consider the following:

1. Select a fairly flat site

2. Avoid low lying areasPooled water, especially around manure andcompost, will cause odour and fly problemsand will increase the risk for runoff tocontaminate water sources.

3. Locate the compost pile away fromgroundwater and natural open bodies ofwaterIn Alberta, compost sites cannot residewithin 100 meters (330 feet) of any spring orwell and must be located at least 30 meters(100 feet) from any open body of water, suchas a stream, lake, river or slough. For moreinformation on guidelines and regulations,refer to the chapter on “Manure Storage andHandling” in this manual.

4. Locate the pile where water can beaccessed if necessaryWater may be needed to maintain theappropriate moisture content of the compostpile and will need to be located convenientlyin the unlikely event of a combustion fire.

5. Be considerate of your neighborsA well-managed pile will not have a foul odoror attract flies. Nonetheless, try to locateyour bins out of view and downwind fromneighbors.

6. Allow room to maneuver equipment tobuild and turn the pile

Choosing a CompostingSystemThere are several ways to design an on-farmcomposting system, and no single one isappropriate for all sizes and types of equinefacilities. You can tailor your composting systemto meet your needs depending on how manyhorses you have, the space and equipmentavailable and how intensively you plan tomanage the pile.

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Free-standing Compost PilesMaking compost does not necessarily require aspecial structure to house the materials. Asimple, free-standing pile can be turned into aneffective composting system and works well forone- or two-horse operations (Figure 12). Thepile grows as manure and bedding arecontinually added to the top or sides of themass. When the pile gets too big, additionalpiles can easily be created.

Frequent turning of the pile will hasten thecomposting process and help reduce parasitesand weed seeds. However, many people prefer aless labor-intensive approach of building a newpile once or twice a year, turning the pile two orthree times, then letting it take a year or so tomature. In this case, parasites and weed seedsmay not be adequately destroyed.

Free-standing piles are usually the least costlyoption for composting because they do notrequire special structures or equipment.However, free-standing piles will require morespace and careful consideration of location toprevent leaching and water contamination.

Windrow CompostingManure and bedding can also be formed intolong, horizontal piles, or windrows, forcomposting (Figure 13). The windrow pile istypically about 1.5 to 2 meters tall (5 to 6 feet)and 2 to 3 meters wide (6 to 10 feet). Materialsare added at the end of the pile, allowing thepile to grow to any length.

Figure 12. Free-standing compost pile.

These piles are generally turned with front-endloaders or specially equipped tractors, althoughthey can also be turned by hand. Windrowcomposting works well for people with largeherds and lots of space.

Figure 13. Composting manure in windrows.

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Basiccomponentsof allcompostingsystems:

1. Adequate space forstorage andcomposting.

2. A set of two ormore bins or free-standing piles largeenough to maintainelevated internaltemperatures.

3. A mechanism forturning the piles ormoving thecompost from binto bin, such as apitchfork or a smallfront-end loader.

4. A water faucet orpump/water tankcombo and a spraynozzle.

Multiple Bin Composting SystemCompared to stacking manure in a pile orwindrow, decomposition is best and space isused more efficiently if the materials are placedin bins or some type of enclosure (Figure 14).

At least two bins are recommended for smalloperations that support just a few horses, or forthose with no mechanical equipment. In thisscenario, the first bin is filled to capacity andperiodically turned and mixed with a shovel orpitchfork to promote composting. When thefirst bin is full, materials can be added to thesecond bin.

Larger facilities or those equipped with a smalltractor or front-end loader, should considerbuilding three or more bins. A series of binsallows the containment of waste at differentstages of the composting process.

In a three-bin system, manure and bedding arepiled into bin one until it is full. The material isthen shifted into bin two for holding andcomposting. Meanwhile, bin one can be refilled.When bin one is full again, materials in bin twoare shifted into bin three, and materials in binone are shifted into bin two. Shifting materialfrom one bin to the next serves as part of theturning and mixing process. Ideally, by the timebin one is full again, materials in bin three willbe completely composted.

The size of the bins will be dictated by severalfactors:

• the amount of manure and bedding produced

• how long the materials will remain in the bin

• the equipment, if any, the bins will have toaccommodate

Ideally, your bins should be large enough toaccommodate all the waste materialsaccumulated for several months of composting.Refer to the sidebar “Determining Bin Size.”

The materials needed for the construction ofsuitable bins will depend on the size of binsdesired and whether they need to accommodatemechanical equipment. Bins constructed from2 x 6" (untreated) boards and heavy-duty postswill hold up the best. Bins with a wooden floorwith small spaces between boards that allow airto move from underneath the pile performbetter than bins built directly on the ground. Aconcrete floor and strong walls are handy forlarger bins that will accommodate mechanicalequipment. A gravel access is convenient forloading or using a wheelbarrow to bring themanure to the heap.

Covering the compost bins with a permanentroof, plastic sheet or tarp is recommended.Protecting the pile from rainwater and snow willhelp you regulate the proper moisture level bypreventing piles from becoming too wet in thewinter or too dry in the summer. Covering willalso prevent rain and snow melt from leachingcontaminants from the pile and creating apollution hazard.

Figure 14. Multiple bin composting system.

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Determining Bin Size• Calculate the amount of manure and bedding produced (see Tables 3 and 4 for Example Calculations)

An average 500 kg (1100 lb) horse produces 22 kg (0.81 ft3) of manure plus bedding each day. If soiledbedding is combined with manure, the total volume generated each day can easily double(44 L or 1.6 ft3) or triple (66 L or 2.4 ft3). Alternatively, you can count the number of wheelbarrow loadsgenerated from your operation each day and estimate the capacity of each load. Keep in mind these arejust estimates and may increase or decrease depending on the volume of stall waste produced.

• Determine how long the materials will remain in the binThe use of only one or two bins usually means the materials will remain in the bins for longer periods(three to six months). When using three or more bins, each bin should provide enough space to housematerial generated for a two-month period. The volume of material in each bin will decrease over timeas materials degrade, so subsequent bins may be slightly smaller if necessary.

• Plan for extra bin space if your operation will house more horses in the future.

What can youcompost?

• Manure mixed withbedding from stalls

• Manure picked upfrom pastures,corrals, arenas andtrails

• Old, moldy orunwanted hay

• Grass clippings

• Leaves

• Householdvegetable wastes

Things tokeep out ofthe compostpile:

• Weeds

• Baling wire ortwine

• Syringes andneedles

• Soda cans andother trash

• Shoes, nails andother metals

• Plastic

• Cedar wood(resistant to decay)

Managing Your Compost PileComposting does demand some time and attention. Management of the compost pile can be keptsimple or be quite sophisticated and should be customized to fit your specific situation and goals.Remember that some trial and error is an essential part of developing a successful compostingsystem.

Building the PileA minimum pile size of one cubic meter (3.5 x 3.5 x 3.5 ft) is needed to achieve compostingtemperature. The pile can be bigger and will obviously be dictated by the type of composting systemyou choose and the space available. The minimum pile size may be created all at once or amassedover several days, and the pile allowed to grow from there.

Add manure and bedding directly to the compost pile as you clean your horse stalls. This is also thebest time to add water if needed. Manure picked up from riding rings, arenas, trails and corrals canalso be added directly to the pile. Avoid picking up too much dirt along with the manure, and keepall trash out of the pile.

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21

Wintercompostingtips:

• Composting canstill take place inthe center of largepiles in the winter.

• Composting willoccur at a slowerrate in the winter(four to fivemonths, comparedto two to threemonths in thesummer). Makesure you haveadequate storagespace for stallwaste.

• Keep piles large(at least one cubicmeter) to maintainadequate heat forcomposting.

• Turn piles lessfrequently in thecold wintermonths. Turningpiles duringextremely coldweather may resultin a slowerrebound back tocompostingtemperatures or atotal shutdown ofthe wholecompostingprocess.

• If you are notalreadycomposting, winteris not the best timeto begin. Instead,establish yourcomposting systemwhen the weatherwarms up in thespring.

but it also ensures that weed seeds and parasitesin the cooler sections are destroyed by bringingthem into the center to “cook.”

Depending on your composting system and theamount of manure generated, the pile can bemixed and turned by hand with a pitchfork ormechanically with a small front-end loader.

Frequent turning accelerates the compostingprocess; the more it is turned, the faster the pilebreaks down. Turning may be done on a weeklyor monthly basis, or turning may be based onthe measured temperature of the pile. If usingtemperature as a guide, you should turn pileswhen temperatures fall to 43°C or when theyrise above 65°C.

Alternatively, your composting system mightdictate your turning schedule. For example, ifyou have a multiple bin system, turning mightoccur as you shift the heap from one bin to thenext.

Weather conditions might affect your turningschedule. The pile will take longer to reheat inthe winter, so you may not want to turn thecompost as often. Monitoring the temperatureof the pile will be helpful in deciding when toturn the pile during the cold winter months inAlberta.

Monitoring the Temperature of thePileYou should monitor the temperature of the pileweekly to ensure active composting is takingplace. Effective composting temperatures rangefrom 55 to 65°C. The center of a properly madeheap should reach such temperatures within aweek during the summer. In cooler seasons, itmay take up to a month to reach effectivecomposting temperatures.

To destroy parasites and weed seeds,temperatures of 55 to 65°C should bemaintained for at least 21 days. Piles that aretoo cool (below 55°C) break down more slowlyand do not kill parasites or weed seeds. Pilesthat are too hot (above 71°C) kill thecomposting microorganisms and result in anextremely foul-smelling pile.

A temperature probe can be used to eliminatethe guesswork. Long-stemmed compostthermometers are available at most hardwareand garden supply stores (Figure 11).

Turning and Mixing the PileThe most active site of composting takes placein the hotter center of the pile. Therefore, thepile needs to be turned and mixed to expose thematerial from the cooler, outer edges to the hotcenter. Turning not only helps aerate the pile,

22

of bedding used, the weather and if the compostis protected from rainfall. The more dry beddingincluded in the mixture or the warmer and dryerthe weather, the more likely it is that you willhave to add water. Make it a habit to check themoisture content when you turn the pile, orcheck more frequently during hot, windysummer days.

Can the Compost PileCatch Fire?Despite the high temperatures that developin a compost pile, the pile will only ignite ifthe hot zone is next to a dry zone. So, it isimportant to keep the pile mixed and at theproper moisture level (50 per cent).

Adding Extra Nitrogen to the PileThe more bedding you use, the more likely it isthat you will need to add supplemental nitrogen.Bedding contributes primarily carbon to thecompost pile. The use of too much beddingoffsets the ideal C:N ratio and slows thecomposting process.

Because of the high C:N ratio of wood products,supplemental nitrogen may also need to beadded to the pile if you use shavings or sawdustbedding.

Commercial fertilizers, such as urea, ammoniumnitrate or another high-nitrogen fertilizer, canbe added to the pile to provide supplementalnitrogen. Ideally, nitrogen should be sprinkledon each wheelbarrow load of manure dumpedon the pile each day. Alternatively, nitrogen canbe mixed into the pile when it is turned.

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As an alternative to frequent turning, PVCpipes can be inserted into the center of thecompost pile like chimneys. Drilling severalholes (1 cm or ½-inch in diameter) along eachpipe (at approximately 15 cm or 6-inchintervals) will allow air to enter the pilepassively.

Occasional turning of the pile may still beneeded to get manure from the outside into thecenter, so the heat from the composting processcan destroy parasites and weed seeds. It maytake longer to compost a pile aerated by PVCpipes compared to a pile that is actively mixedon a regular basis.

Adding Water to the PileAll materials in the pile must be moist, but notsoaking wet. The moisture level can be gaugedby squeezing a handful of compost. Compostthat contains an adequate amount of moisturewill feel like a freshly wrung out sponge. If waterruns out of the pile or if you can squeeze waterfrom a handful of compost, it is too wet. In thiscase, you will need to add straw, tree leaves,shredded bark or old hay to dry the pile. If thecompost does not feel moist, you need to addwater.

One of the biggest mistakes people make isputting a lot of water on the pile all at once,then ignoring the pile. Adding a little watereach day is much better than letting the pile getdusty and dry, then trying to re-wet it back tothe 50 per cent range. Consider watering yourcompost with a garden hose when you turn thepile. Or, an easy way to add water is just to hosedown the manure in your wheelbarrow beforeyou dump it into the pile.

The actual amount of water needed will varysubstantially depending on the kind and amount

How long willit take tocompost?

Depending on theamount of materialsand how diligent thehorse owner is inturning the compostpile, composting cantake several months.A well-managed pilewill break down thefastest—as quickly as60 days—althoughthe average time is120 days. Piles thatdo not have thecorrect mix or are notmaintained breakdown much moreslowly, taking 6 to 12months or more. Inthe winter, properlymanaged piles mayrequire 4 to 5 monthsto compost.

23

When adding supplemental nitrogen, a goodrule of thumb is 1.5 kg of nitrogen per tonne ofstall waste (3 lbs per ton). A ton of stall waste isequivalent to a pile approximately the size of anaverage washing machine. Table 5 lists severaldifferent sources of supplemental nitrogen andthe amounts to add per tonne (or ton) of stallwaste or the amount per horse per day.

Putting Compost to UseAfter you have successfully produced compost,you need to think about what you will do with it.In many cases, compost is a more attractiveproduct than raw manure, making it easier togive away or sell to others if you cannot use ityourself.

Properly prepared compost has many uses:

• Soil Amendment. Although compost containsnutrients, its greatest benefit is in improvingsoil characteristics. Composted horse manurecan be used to increase the organic mattercontent and the water and nutrient-holdingcapacity of sandy and heavy clay soils.

• Growth Media. Finished compost can be usedby plant nurseries as potting soil and is anexcellent media for the production ofmushrooms and fish worms.

• Mulch. Compost can be a valuable mulchingmaterial for garden and landscape plants. Andif used as mulch, the compost need not becompletely finished.

• Slow-release Fertilizer. When applied tolawns, cropland or pastures, finished compostcan supply a modest amount of nutrients thatwill be released slowly over time. Sincecompost is already broken down, it does notdeplete the soil of nitrogen needed by plantsto grow. Nitrogen depletion can occur whenuncomposted horse waste (or unfinishedcompost) are spread on fields. And becausecomposting kills parasites and weed seeds, therisk of re-infection is reduced. Additionalfertilization may be necessary to obtainacceptable growth yields when compost isapplied as fertilizer.

If applying finished compost to cropland(Figure 15) or pastures, it should be appliedonly at recommended rates and to plants andsoils that can use the nutrients. For moreinformation on testing your soil and compost, aswell as guidelines for spreading compost onpastures and cropland, refer to the chapter“Managing Manure by Spreading on Croplandor Pasture” in this manual.

Figure 15. Harrowing horse manure compostdistributes the nutrients more evenly across thefield.

24

Is it Ready?• Finished Compost

When manure and bedding are completelydegraded, they are termed “finished”compost. Finished compost will not heat upanymore and has an earthy smell and acrumbly soil-like texture. Properly producedcompost will also be less likely to containparasites and weed seeds. Because of thischaracteristic, finished compost can be safelyused in gardens or applied to cropland orpastures.

• Unfinished CompostDecomposition will take place even if acompost pile is ignored after it has been built,but at a slower rate. Decay will be slower,cooler and less effective at killing weed seedsand pathogens. Manure and bedding that arenot allowed to decompose fully are termed“unfinished” compost.

TheBottomLine• Composting provides a

viable option for managinghorse manure.

• Properly prepared compost has many uses asa soil amendment, growing media, mulch orslow-release fertilizer.

• Compost may be a more attractive endproduct, compared to uncomposted stallwaste, making it easier to give away or sell.

• Composting kills intestinal parasite eggs andlarvae and also destroys weed seeds, reducingthe risk of re-infection if compost is spread onpastures.

• On average, a well-managed pile can becomposted in two to three months in thesummer or four to six months in the winter.

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