www.ag.ndsu.nodak.edu • 1

NM-1407

MAY 2009

North Dakota State UniversityFargo, North Dakota 58108

Land Applicationof Manure

and Environmental Concerns

Shafiqur RahmanAssistant Professor, ExtensionWaste Management Engineer,

North Dakota State University

Ron WiederholtNutrient Management Specialist,

Carrington ResearchExtension Center,

NDSU

Ying ChenProfessor, Department ofBiosystems Engineering,University of Manitoba,

Canada

As of January 2008, 1.81 million head of cattle, 182,000 headof hogs and 1.9 million turkeys were raised in North Dakota(NASS-ND, USDA 2008). These livestock and poultry facilitiesare generating substantial amounts of manure and wastewater,which pose a considerable challenge for livestock producers.

The most common manure disposal method is land applicationbecause animal manure contains nutrients and organic matterthat can be applied to meet crop nutrient requirementsand improve the soil’s physical and biological conditions.However, to meet the nutrient requirement of crops, applyinglarge quantities of manure (tons/acre vs. pounds/acre withcommercial fertilizers) is necessary.

2 • NM-1407 • Land Application of Manure and Environmental Concerns

If manure is not applied properlyto fields, the potential for surfaceand groundwater pollutionincreases from runoff and leaching.Similarly, field application ofmanure also poses odor and airemissions concerns (ammonia,NH3) depending on land applica-tion methods (for example, surfacevs. injection) and equipment(sweep, chisel, disc tools, etc.).

Some of these concerns resultingfrom land application of manurecan be minimized by adoptingbest management practices.The aim of this publication is toprovide producers and manureapplicators with information onhow to minimize environmentalconcerns associated with landapplication of manure.

Manure can be applied bybroadcasting or surfacespreading, surface incorporationand subsurface injection. Of these,surface spreading is low incost but produces higher odorand ammonia losses. Surfaceapplication also poses the greatestchallenge in uniform application.

Odor from land spreading ofmanure is not always a seriousconcern in North Dakota.However, in the long run, it mightbe an environmental issue andnuisance to rural populations asmanure application continuesto increase because of increasedfertilizer values.

Typically, partial or full incorpora-tion of manure provides a betteralternative to reduce odor, surfacerunoff and ammonia emissions ascompared with surface spreadingwith no incorporation.

Subsurface injection of manure isthe best option to minimize runoff,odor and ammonia emissions.

Studies show that injection ofmanure can reduce odor emissionsby 85 percent and ammonia volatil-ization by 90 percent. In addition,subsurface injection reduces thechance of crop contamination andpathogen activity. Furthermore,manure injection techniquesprevent surface runoff, increasewater infiltration and improveroot development due to soilloosening and aeration of the soil.

Manure TypesBased on livestock facilities,manure can be handled and storedas a liquid (less than 5 percentdry matter), slurry (5 percent to10 percent dry matter), and solid(more than 15 percent dry matter).Figure 1 shows relative consistencyof various types of manure asexcreted by the common animalspecies. Depending on manureconsistency, manure applicationequipment and applicationmethods differ significantly.

Manure ApplicationMethodsBroadcasting or surfacespreading (Figure 2)This is a common method of solidor liquid manure application inNorth Dakota but it has the highestrisk of runoff, particularly whenliquid or slurry manure is notincorporated or when applied onfrozen or snow-covered ground.According to the “North DakotaLivestock Program DesignManual,” manure should not beapplied on frozen, snow-coveredor saturated soils if runoff is likely.

Some studies also suggest that evenwith immediate incorporation,pollutants are more susceptibleto surface runoff if not injectedbecause incorporation may exposesoil to erosion and pollutants canbe carried off-site with sedimentsin the runoff.

Often no-till management ispracticed to minimize soil erosion

Figure 1. Relative consistency of various types of manure(Fulhage et al., 2001)

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in runoff, but it is incompatiblewith surface manure applicationdue to concerns with odor andnutrient losses. Also, accordingto the “North Dakota LivestockProgram Design Manual,” manuremust be injected or incorporatedwithin eight hours if appliedwithin one-half mile of an occupiedresidence (other than the owner’sresidence), building or publicarea where people may be present.

Manure injectionAn alternative to surface spreadingliquid manure is to apply it belowthe soil surface. Injection is awidely accepted best managementpractice in North America andEurope. However, it is not widelypracticed in North Dakota due tothe fact that most of the manureproduced is in solid form.

Many injection tools are availablefor liquid manure, but no injectiontool is commercially available forinjecting solid manure.

Recently, Hubert Landry of thePrairie Agricultural MachineryInstitute (PAMI) has developeda prototype of a solid-manureinjection unit (Figure 3), which caninject solid manure successfully.This new technique will be abreakthrough to inject solid manurewhile minimizing environmentalconcerns associated with surfacespreading of solid manure.

For liquid manure, different typesof injection tools (for example,knife, tine, disc, sweep, etc.) arecommercially available. However,sweep injection tools (for example,a V-shaped winged tool) providebetter mixing of manure and soilas well as minimizing manureexposure to air because of quickadsorption and distribution ofliquid manure into loose soil

Figure 2. Surface spreading/broadcasting application unit for solid (left) and liquid (right) manure

Figure 3. Solid-manure injection system(Hubert Landry, Prairie Agricultural Machinery Institute, PAMI)

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(Figure 4). Minimizing exposureof manure to air will decreaseodor and ammonia emissions.In addition, injection of liquidmanure can reduce runoff by up to94 percent (Ball Coelho et al., 2009)and often results in greater yields.

Other manureapplication optionsBecause of the heavy loads, bothsurface spreading and injectioncause some soil compaction,especially in wet soil conditions.Drag-hose manure applicationsystems provide an alternative thatlessens soil compaction (Figure 5).This system pumps manure froma lagoon through flexible hosesto a manure distributor mountedon the tractor and then it isdeep-injected into the soil.

These deep-tillage tools alsohelp break up the plow pan fromprevious tillage events. However,this system is not widely used byindividual producers due to highinvestment costs, but customapplicators are available. Also, thissystem is not feasible in standingcrops since the drag hose can causephysical damage to crops.

Gaining in popularity is theAerWay SSD® (Figure 6),a shallow incorporation tool thatis very effective in minimizingsurface runoff and leaching ofpollutants through soil macropores.Several researchers have indicatedthat the AerWay system can beused as a best managementpractice to minimize both surfaceand subsurface water pollution.Others also indicated that thistool can be used to minimizeodor and air emissions.

Figure 4. Equipment options for injection or direct incorporation(Jokela and Cote, 1994)

Figure 5. Drag-hose manure application system

drop tubeshank

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With the AerWay system, liquidmanure is released into cavitiescreated by tines that rapidlyabsorb liquid manure resultingin minimum exposure to the airreducing odor and runoff. Recently,this injection technique has beenstudied on grassland and itconserved more ammonia thanbroadcasting or surface banding.

EnvironmentalConcerns andManagementPracticesThe main environmental problemcaused by land application ofmanure is water (runoff of nutrientsand leaching) and air pollution(odor and ammonia emissions).The following sections brieflydescribe these concerns andmanagement options.

Water QualityAs stated previously, landapplication of manure is thepredominant method of manureutilization. Excessive rates orinappropriate methods of manureapplication that lead to surfacerunoff are the main culprits ineutrophication of surface watersystems. Eutrophication is causedby high rates of phosphorus (P)addition to the water systems.

Similarly, land applicationof manure can contribute togroundwater contamination fromnitrate leaching. The amount ofphosphorus delivery to runoff isinfluenced by the P source, soil Plevel, rate and method of manureapplication, field slope anddistance to surface water(Daverede et al., 2004; Allenand Mallarino, 2008).

The highest risk of P losses inrunoff is likely when manure isbroadcast on the surface andfollowed by intermittent rain.Broadcast or unincorporated

manure concentrates P at the soilsurface, where it may be easilytransported with runoff water.

Runoff transport of P frombroadcast or unincorporatedmanure increases with theapplication rate; however, thepotential P loss will declinethrough time as more soluble P inthe manure interacts with the soil.On the other hand, incorporationor injection of manure into thesoil reduces runoff significantlywithout increasing the risk ofsoil erosion.

Therefore, selection of applicationmethod plays an important role inminimizing water quality degrada-tion. Manure application must bemade in a manner that does notcontribute to water pollution.

In North Dakota, zero till is awell-accepted management practicewhere continuous macropores(earth worm channels, cracks, etc.)are more highly developed thanin tilled soils.

Recently, tile drainage is gainingacceptance in North Dakota toreduce salt accumulation andstanding water issues. Underzero-tillage and tile-drainageconditions, established macroporesfavor rapid movement of pollutantsby establishing preferential flowpathways. These pathways aredirect conduits that allow forthe flow of surface-appliednonincorporated liquid manuremovement to ground water andtile lines (Thiagarajan et al., 2007).

Because of the high risk ofpreferential flow in establishedzero-till fields, manure shouldbe subsurface injected or surfaceapplications should be followedby light soil stirring.

Figure 6. AerWay SSD® injection unit

6 • NM-1407 • Land Application of Manure and Environmental Concerns

Excessive rainfall following manureapplication also plays a key rolein nutrient runoff. For example,P concentration is much higher inrunoff water within 24 hours ofmanure application than runoffdelayed for a few days (10 to16 days) after manure application.Therefore, delaying manureapplication before a forecastedrainfall event can decrease sharplythe risk of P loss from surface-applied liquid manure andminimize environmental concern.

Air QualityMost air quality complaints areodor nuisance concerns frompeople who live near concentratedanimal feeding operations (CAFOs).

Odor from CAFOs is producedprimarily by incompletefermentation of livestock manure.Unfortunately, odor is not causedby a single substance, but a largenumber of compounds includingammonia, hydrogen sulfide andother volatile organic compounds(VOCs) (Laor et al., 2007).

Odor can be generated fromlivestock housing, manurehandling and storage systems,and during and following landapplication of manure to the land.Of these, approximately 50 percentof the ammonia (NH3) emissionsoccur from surface spreading ofmanure (Portejoie et al., 2003).

Emissions of ammonia are respon-sible for the acidification andeutrophication of deposited ammo-nia in the environment (Koerkampet al., 1998). Ammonia emissions

also decrease the nutrient value ofmanure and represent a significantloss of fertilizer value.

Studies suggest that injection ofmanure below the soil surface canreduce ammonia volatilization byabout 90 percent compared withsurface application.

Like NH3, hydrogen sulfide (H2S)is a pollutant gas that is colorless,heavier than air and highly solublein water and has the characteristicodor of rotten eggs at lowconcentrations. H2S is producedwhen sulfur (usually added as afeed additive or naturally occurringin drinking water) bearing organicmatter is decomposed by anaerobicbacteria and sulfate is reducedto H2S.

Any excreted sulfur that is not inthe form of hydrogen sulfide isreduced to H2S. Although emis-sions of H2S from land applicationis not well-documented, odor(which is a complex compound)complaints from land applicationare a concern and the odor can berecognized from distances.

Control StrategiesThe livestock and poultry industryis a smaller proportion of ag vs.crop production in North Dakotayet is vital to the state’s economy.As the livestock and poultryindustry expands, manurehandling and management may bean issue in the foreseeable future.However, modification of currentmanure management practicesand application methods canreduce environmental concern.

Emissions control during landapplication is the most effectiveway to minimize ammonia loss andretain fertilizer value. For example,incorporation of manure into soil orinjection below the soil surface canminimize both odor and ammoniaemissions when compared withsurface spreading.

As mentioned before, zero tilland tile drainage are prone topollutant movement to surface andgroundwater due to continuousmacropores. Manure should not beapplied on frozen, snow-coveredor saturated soils if runoff or tiledrainage is likely.

Several studies indicated thatpartial incorporation or aerationwill result in reduced pollutantmovement in tiled water due tothe disruption of macroporesfrom the tillage action of tools.

Similarly, partial incorporationor aeration also reduced surfacerunoff as well as odor andammonia emissions. Therefore,manure management practices area unique opportunity to mitigateenvironmental concern associatedwith manure application.

Any reduction of ammoniaemissions from land-appliedmanure would be the mosteconomically effective first stepto reduce ammonia emissions.

Apart from manure applicationtechnology, a number of othermanagement practices exist thatcan reduce NH3 emissions at littleor no cost. For example, ammoniaemissions are likely to be higherif manure is applied during hot,

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dry and windy weather. Similarly,emissions can be reduced notably(up to 25 percent) during summerapplication if liquid manure isspread in the evening rather thanduring the daytime.

However, increased humidityin summer evenings may causelong-distance transportation ofodorous compounds. A shift in thetime of manure application mayhelp minimize odor and ammoniaemissions if done at the right timeof year.

Furthermore, depending onweather, if liquid manure isapplied shortly before or duringa slight rain, emissions arereduced considerably becausethe ammoniacal fraction of themanure is washed into the soil.However, applying manure at thistime increases the risk of runoff ifthe rain is heavier than expected.Therefore, watching the weatherand spreading manure at a timewhen the weather is more favorableis better.

No one single method is goodenough to reduce emissions andrunoff completely. Producersmay need to adopt multiple bestmanagement practices to minimizeenvironmental impacts resultingfrom land application of manure.Finally, to minimize environmentalconcerns associated with manureapplication, livestock producersand stakeholders need to be awareof the issues.

ReferencesAllen, B.L., and A.P. Mallarino. 2008.

Effect of liquid swine manure rate,incorporation, and timing of rainfallon phosphorus loss with surfacerunoff. Journal of EnvironmentalQuality, 37: 125-137.

Arogo, J., R.H. Zhang, G.L. Riskowskiand D.L Day,. 2000. Hydrogensulfide production from storedliquid swine manure: a laboratorystudy. Transactions of the ASAE.43: 1241-1245.

Ball Coelho, B.R., R.C. Roy, A.J. Bruin,A. More and P. White. 2009.Zonejection: Conservation tillagemanure nutrient delivery system.Agronomy Journal. 101(1): 215-225.

Daverede, I.C., A.N. Kravchenko, R.G.Hoeft, E.D. Nafziger, D.G. Bullock,J.J. Warren and L.C. Gonzini. 2004.Phosphorus runoff from incorpo-rated and surface-applied liquidswine manure and phosphorusfertilizer. Journal of EnvironmentalQuality, 33: 1535-1544

Koerkamp, P.W.G.G., J.H.M. Metz,G.H. Uenk. V.R. Phillips, M.R.Holden, R.W. Sneath, J.L. Short,R.P. White, J. Hartung and J. Seedorf.1998. Concentrations and emissionsof ammonia in livestock buildingsin Northern Europe. Journal ofAgricultural Engineering Research.70: 79-95.

Laor, Y., A. Shabtay, U. Ravid, R.Baybikov and H. Eitam. 2007.Changes in VOCs emissions fromfecal manure throughout the lifecycle of beef cattle. ASABE PaperNo. 074003, St. Joseph, Mich:ASABE.

Portejoie, S., J. Martinez, F. Guiziou andC.M. Coste. 2003. Effect of coveringpig slurry stores on the ammoniaemission processes. BioresourceTechnology. 87: 199-207.

Thiagarajan, A., R. Gordon, A. Madaniand G.W. Stratton. 2007. Dischargeof Escherichia Coli from agriculturalsurface and subsurface drainagewater: tillage effects. Water Air SoilPollution, 182: 3-12

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