SECTION 4 Application of Manure - Province of …...should be based on crop nutrient requirements or removals. The goals of using livestock manure as a fertilizer should be to: ®maximize

4.1 Manure – An AgronomicResource

Manure is both a natural by-product of livestockproduction and an excellent source of plantnutrients. The use of manure as a fertilizer forcrop production is a very beneficial way torecycle manure nutrients within an agriculturalsystem. Most livestock operations are on orsurrounded by, large areas of productiveagricultural land where manure can be appliedin a sustainable manner. In many instances,manure can be a substitute for commercial,inorganic fertilizers. Manure not only acts as asource of plant nutrients but, through theaddition of organic matter, it also helps toimprove soil tilth, structure, aeration and waterholding capacity.

Manure application is a sustainable agriculturalpractice. To maximize the benefits of manurenutrients, prevent crop damage and minimizethe risk of pollution, manure application ratesshould be based on crop nutrient requirementsor removals.

The goals of using livestock manure as afertilizer should be to:

maximize the use of the manure nutrients bycrops

minimize the risk of polluting surface waterand groundwater

4.1.1 Manure as a fertilizer

Manure contains both macro- and micro-nutrients needed for crop production inorganic and inorganic forms. Inorganicnutrients are readily available to thegrowing crop, while the organic nutrientsbecome available gradually over time. Acrop responds to inorganic nutrients in soil,whether they originate from manure orcommercial fertilizer.

As not all of the nutrients are available atthe same time, proper management isneeded to ensure sufficient nutrients areavailable when required by the crop. Thiswill maximize nutrient use as well as cropyield and crop quality.

4.1.2 Manure content

A large proportion of the nutrients in livestockfeed is excreted and not used by the animal.There are many factors that affect the nutrientcomposition of manure including the type ofhousing system, whether or not bedding isused, the type of bedding, the age of theanimals, the feeds and feed supplements thatare being used and the type of manurestorage and handling system. The results ofthe manure nutrient analyses can be greatlyaffected by how the manure sample is taken.Information on how to take a manure sampleis provided in Section 4.3.2. Typical nutrientconcentrations for liquid and solid pigmanures are provided in Tables 4a and 5.

ManureApplication of

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SECTION 4FA R M P R A C T I C E S G U I D E L I N E S F O R P I G P R O D U C E R S I N M A N I TO B A ( A P R I L 2 0 0 7 )

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FA R M P R A C T I C E S G U I D E L I N E S F O R P I G P R O D U C E R S I N M A N I TO B A ( A P R I L 2 0 0 7 )

A P P L I C A T I O N O F M A N U R E

These tables provide data on nutrientconcentrations in manure prior to theadoption of phytase use to reduce thephosphorus (P) content of the manure. Table4b contains nutrient data collected after theadoption of phytase use by the pig industry.

Housing system – The type of housing systeminfluences various management practicesincluding the quantity of washwater andbedding that is used. These differences willbe reflected in the moisture and nutrientcontent of the manure.

Animal age – As pigs grow, their ability toconvert the nutrients in feed to body tissuechanges. Pigs that are actively growing willutilize some nutrients more efficiently thanmature animals.

Feed type – The nutrients in pig manure arepredominantly excess and undigested feednutrients that have been excreted by the pig. Therefore, the nutrient content of manure isdirectly affected by the nutrient content ofpig feed. Some of the nutrients in the feedare in a form that is not available to the pig

and are excreted in the manure. If a ration isunbalanced, the pigs can not use all of thenutrients and the nutrients will also beexcreted. Various feeding strategies, such asmulti-phase feeding and the use of enzymes,can be adopted to minimize the amount ofnutrient excreted by the animal.

Manure storage, handling and application –The manure handling system (e.g. liquid vs.solid) and storage type and duration affectthe nutrient content of manure. Cropnutrient availability depends on theequipment selected to apply manure, thetiming of application, post application fieldoperations (such as tillage) and weatherconditions during and after application.Nitrogen is the nutrient most affected by thevarious components of the manuremanagement system.

NitrogenThe nitrogen (N) content of manure is highlyvariable. A manure analysis is required todetermine how much N is in the manure andin what forms. A proper manure analysiscontains three N measurements:

Table 4a: Nutrient (kg/m3 Or kg/1000 L) And Dry Matter (%) Content For Liquid Pig Manure1 (Pre-phytase Use)

Parameter2Farrow Nursery Finisher Farrow to Finish

Avg Min Max Avg Min Max Avg Min Max Avg Min Max

Total N 1.7 0.6 6.5 2.7 1.5 4.6 3.4 1.5 6.4 2.8 1.2 4.0

NH4-N 1.2 0.5 3.2 2.0 1.3 3.0 2.6 1.2 4.1 2.4 1.1 3.4

Total P2O5 1.5 0.1 12.7 2.7 0.3 5.9 2.3 0.1 8.1 2.4 0.3 4.8

Total K2O 1.2 0.3 4.2 2.0 1.5 2.4 1.8 1.1 3.2 1.7 0.8 2.1

Dry Matter 3.0 0.3 38.6 3.1 1.1 5.6 3.7 0.0 11.8 2.1 0.6 4.0

1 Values are on an as-is basis (i.e. untreated). See Appendix C for imperial units. SOURCE: Racz and Fitzgerald 2001. Nutrient and Heavy MetalContents of Hog Manure – Effect on Soil Quality and Productivity. Proceedings: Livestock Options for the Future. Results based on 37, 11, 92 andfive samples for farrow, nursery, finisher and farrow to finish, respectively.

2 Total N refers to all forms of nitrogen in manure, but typically only includes ammonium N (NH4-N) and organic N. NH4-N is the inorganic, readilyavailable form of nitrogen in manure. Total P2O5 refers to all forms of phosphorus in manure expressed in the fertilizer equivalent (P content x2.3). Total K2O refers to all forms of potassium in manure expressed in the fertilizer equivalent (K content x 1.2).


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total nitrogen

ammonia (or ammonium) nitrogen

organic nitrogen

As the term suggests, total nitrogen is anestimate of all of the N contained in themanure. It includes ammonium N, organic Nand any nitrate N that may be present. Notall of this N will be available to the cropfollowing application.

Ammonium nitrogen (NH4-N) is thepredominant inorganic form of N in manureand it is immediately available to the cropfollowing application. It may be expressedas either ammonium or ammonia on the soiltest report and it is the same form of N as isin ammonium-based commercial fertilizers.Ammonium N is very susceptible toatmospheric losses through volatilization.

Nitrate nitrogen (NO3-N) is another inorganicform of N. Although soil can containsignificant quantities of nitrate N, it istypically present in manure in very low orinsignificant amounts.

Organic nitrogen is determined indirectly bycalculating the difference between total Nand ammonium N. Organic N is slowlyreleased to the crop and can have asignificant impact on the N-supplying powerof the soil if it is allowed to build up afterseveral years of manure application.

Organic N = Total N – Ammonium N

In liquid manure, a larger fraction of thetotal N is typically in the ammonium formthan in solid manure. The N in solid manureis mostly in the organic form. This has greatbearing on the N value of the manure as afertilizer and manure nutrient management.As well, many solid manure systems uselarge amounts of bedding materials that arehigh in carbon (C). This can increase thecarbon to nitrogen ratio (C:N) in the manuresignificantly. A high C:N ratio in manure candelay the availability of the N to the cropfollowing application.

PhosphorusThe phosphorus (P) content of the manure isalso highly variable. Pig manure is a mixtureof organic and inorganic P. Studies have

Table 4b: Nutrient (kg/m3 Or kg/1000 L) And Dry Matter (%) Content For Liquid Pig Manure From Operations (Phytase Use)

Parameter2Farrow Nursery Finisher

Avg Min Max Avg Min Max Avg Min Max

Total N 2.2 0.4 6.0 2.7 1.1 5.6 3.4 0.4 6.7

NH4-N 1.6 0.4 2.7 2.0 0.6 3.3 2.4 0.4 4.7

Total P2O5 1.5 0.0 9.4 1.1 0.1 4.7 1.5 0.0 6.5

Total K2O 1.3 0.7 2.0 1.9 1.3 2.8 1.8 0.1 3.4

Dry Matter 2.1 0.3 9.1 2.2 0.6 7.4 3.4 0.4 11.21 Values are on an as-is basis (i.e. untreated). See Appendix C for imperial units.SOURCE: Industry co-operators. Results based on 132, 58 and 181

samples for farrow, nursery and finisher, respectively.2 Total N refers to all forms of nitrogen in manure, but typically only includes ammonium N (NH4-N) and organic N. NH4-N is the inorganic, readily

available form of nitrogen in manure. Total P2O5 refers to all forms of phosphorus in manure expressed in the fertilizer equivalent (P content x 2.3).Total K2O refers to all forms of potassium in manure expressed in the fertilizer equivalent (K content x 1.2).

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shown that the relative proportions of organicP ranges from 20 to 50 per cent of the total P,depending upon the age of pig, diet, andproduction system. The balance which isinorganic P ranges from 50 to 80 per cent. However, manure analyses routinely measureonly total P. Most of the P is contained withinthe solids, which tend to settle to the bottomof the liquid manure storage resulting in anincreasing concentration of P with depth. Thismakes obtaining a representative manuresample very difficult. As the organic portion isonly slowly available to the crop and some ofthe inorganic fraction is readily bound to soil,not all of the P in manure is available to thecrop following application.

Organic Matter (Carbon)The application of manure to cropland canhelp maintain or improve soil organic matterlevels and improve soil tilth, soil structure,water infiltration, nutrient and water holdingcapacity and reduce soil erosion. When thesoil is tilled and fields are cropped, a portionof the organic matter is broken down and lost

from the field. Organic matter is also lostfrom upper hill slope positions when topsoil istransported down slope by repeated tillage.

The use of commercial, inorganic fertilizersdoes not replenish the lost organicmaterial. Depending on soil type, a steadydepletion of soil organic matter can resultin a soil structure that is more susceptibleto erosion and crusting. Application ofmanure, particularly solid manure, will helpto slow or reverse this trend of degradingsoil quality and potentially improve cropyields as a result.

PotassiumPig manure can contain relatively high levelsof potassium (K). Most Manitoba soils withthe exception of sandy or peat soils arenaturally high in K. As a result, cropproductivity is not likely to benefit fromadditions of manure K.

Multiple applications of manure can increasethe amount of plant-available soil K. High

Table 5: Nutrient (kg/tonne) And Dry Matter (%) Content For Solid Finishing Pig Manure1 (Pre-phytase Use)

Parameter2Fresh Stockpiled3

Composted4

FreshComposted Stockpiled

Avg Min Max Avg Min Max Avg Min Max Avg Min Max

Total N 6.3 4.8 8.9 6.0 3.7 12.9 6.4 5.0 8.1 7.2 5.8 8.8

NH4-N 1.4 1.0 1.8 2.1 1.1 3.1 0.5 0.1 1.2 0.7 0.2 1.0

Total P2O5 6.5 5.0 9.9 5.5 3.4 8.8 9.2 7.6 10.5 8.6 6.4 9.9

Total K2O 8.8 6.0 15.1 9.0 6.8 13.2 10.4 8.9 12.0 10.8 9.0 14.2

Dry Matter 33.2 24.0 45.3 47.1 32.1 63.7 66.4 63.4 69.4 58.2 44.0 63.4

1 Values are on an as-is basis (i.e. untreated). See Appendix C for imperial units. SOURCE: Agriculture and Agri-Food Canada 2005. Results based on10 samples.

2 Total N refers to all forms of nitrogen in manure, but typically only includes ammonium N (NH4-N) and organic N. NH4-N is the inorganic, readilyavailable form of nitrogen in manure. Total P2O5 refers to all forms of phosphorus in manure expressed in the fertilizer equivalent (P content x 2.3).Total K2O refers to all forms of potassium in manure expressed in the fertilizer equivalent (K content x 1.2).

3 Maintained in a pile for approximately six months and minimally disturbed (i.e. not moved repeatedly or mixed).4 Carefully managed to maintain necessary moisture and temperature, resulting in the breakdown of manure to form a stable and uniform material.



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soil K can lead to increased uptake ofpotassium by forages, which can pose ahealth risk to dairy cows. High K levels indry cow diets elevate the risk of certainmetabolic disorders, such as milk fever. Ifhigh K levels in forage are a concern, tissuetesting should be used to ensure that theforage is of acceptable quality. In someinstances, it may be necessary to avoidmanure applications on those fieldsproducing low K forage for dry cows.

SulphurManure contains sulphur (S) in both organicand inorganic forms. As with other nutrients,the organic fraction must be broken down bysoil microorganisms before it is available tothe crop. The inorganic portion in thesulphate (SO4) form is readily available tothe crop. However, manure analysis typicallyprovides a result for total S only. Liquid pigmanure can be low in S relative to N. Thisshould be taken into account whenfertilizing crops such as canola that have arelatively high S requirement.

MicronutrientsMicronutrients, such as copper (Cu), zinc (Zn),cobalt (Co), boron (B) and other metals arefound naturally in soil as well as in bothmanure and some commercial fertilizers. Theyare required in small amounts for optimumcrop performance. Reduced crop performancecan result from either a deficiency or anexcess of micronutrients. Micronutrientconcentrations in manure often reflect thelevels of micronutrients in the feed. Unlessmicronutrients are being fed at high levels,the micronutrient contents of manure will notresult in a build up to toxic levels in the soil ifmanure is applied at rates to meet the N or Prequirements of the crop.

Pigs require Cu and Zn for normal growthand reproduction. These minerals areroutinely added at low levels to all pig diets.However, Cu and Zn concentrations aresometimes increased in pig feed since theseminerals have been shown to improvegrowth performance (Cu) and have somepharmacological effects (Zn) in young andgrowing pigs. Feed samples can be analyzedto verify the levels of these micronutrients inpig diets. Manure, soil and plant tissue testscan also be used to monitor micronutrientlevels if necessary.

SaltsManure and soil contain the salts ofammonium (NH4), calcium (Ca), magnesium(Mg), potassium (K), and sodium (Na). Whenmanure is applied to soil, varying amounts ofsalts are also applied. In areas of adequateprecipitation and drainage, salt accumulationsin soil are rare and crop production isunaffected. In areas with borderline salinesoils and low annual precipitation, manureapplications may elevate the soluble saltcontent of the soil above crop tolerance. Elevated soil salinity can hinder the ability ofa plant to absorb water from the soil. Inthese instances, salt levels in manure shouldbe minimized through dietary changes. Saltaccumulation in soil can also be monitoredwith soil testing. It is expressed as electricalconductivity (EC).

Weed seedsSome weed seeds in manure may retaintheir viability even after digestion bylivestock. Weed seeds can be effectivelydestroyed before they are fed to livestock byfeed grinding, rolling or other aggressivetreatment during the feed milling process.Weed seed viability can also be reduced byproper composting in which hightemperatures are maintained. Weed flushes

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following manure application may in fact becaused by an existing seed bank in the soilthat responds to the addition of readilyavailable nutrients.

MicroorganismsAs discussed in Section 3.6, livestock manurecontains a broad spectrum of microorganisms. Proper hygiene is required when handlinglivestock manure in order to reduce thetransmission of pathogens.

4.2 Manure and Soils

When manure is applied, the nutrients canundergo a number of transformations that mayaccelerate or delay their availability for cropuptake. The fate of the N in the manure is highlyvariable and is influenced by the forms of N in themanure, application techniques and timing, alongwith weather conditions. The availability of the Pin the manure depends on the forms of the P andits placement relative to the plant root system.

4.2.1 Manure nitrogen (N) after application

Manure N is affected by several processesafter it is applied. Some make N availablefor plant uptake, while others make it lessavailable to plants or even cause itspermanent loss. Application techniques thatconserve N maximize the fertility value ofthe manure and reduce the risk of N loss toair or water.

Mineralization The organic N in manure must go through adecomposition process known asmineralization – the conversion of organic Nto ammonium N. It can be slow and as aresult, the N is released throughout thegrowing season rather than being

immediately available following applicationas it is with commercial fertilizer. InManitoba, it is estimated that about 25 percent of the organic N in pig manure ismineralized and available to the next crop.The remainder becomes available duringsubsequent years at a significantlydecreased rate.

NitrificationAlthough nitrate is present at lowconcentrations in manure, manured soils cancontain significant amounts. This is becausethe ammonium from the manure isconverted to nitrate by soil microorganismsthrough the nitrification process.

VolatilizationThe ammonium N in manure can be lost tothe atmosphere as ammonia gas through thechemical process of volatilization. Nitrogenlosses through this process can occur duringstorage as well as during application.Volatilization losses during storage arehigher for open than enclosed structures andincrease with exposed surface area for openstructures. The amount of N lost throughvolatilization during application of manuredepends on the amount of ammonium in themanure, exposure of the manure to theatmosphere and weather conditions (Table6). The actual amount of ammoniumavailable to the crop is calculated bysubtracting the amount of ammoniaestimated to be lost by volatilization duringapplication, from the amount of ammoniumin the manure.

Available Ammonium N = Total Ammonium N x (100% - % Volatilization loss)



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ImmobilizationImmobilization is the conversion of inorganicN to organic N (i.e. the opposite ofmineralization). As soil microorganismsdecompose plant material and manure, theyuse the carbon (C) as a source of food. As Cis consumed, N is also consumed, making ittemporarily unavailable to plants. Therefore,when high C materials (such as straw andmanure with a lot of bedding) are added tosoil, the availability of N to the crop can bereduced or delayed. When thesemicroorganisms die, the nutrients theycontain are released back into the soil.

Nitrate LeachingNitrate is highly soluble in water. As watermoves down through the soil, such as aftersnowmelt or heavy rainfall, it can carrynitrate with it. Nitrate is more prone toleaching in coarse textured soils (e.g. sands)at times of the year when the crop is notactively growing and soil moisture levels arehigh. Nitrate and other dissolved forms ofnitrogen are also contributed to adjacentwater bodies through runoff both duringspring melt as well as during runoffassociated with rainfall events. Studies inManitoba have shown that runoff can be animportant source of nitrogen to surfacewaters where, along with phosphorus, it cancause large algal blooms.

DenitrificationSoils become anaerobic (lack oxygen) whensaturated or during periods of high microbialactivity. When soils are anaerobic, the soilbacteria can continue to breathe usingnitrate instead of oxygen. During thisprocess, nitrate is consumed and N gases(such as N2 and N2O) are released to theatmosphere. This process is calleddenitrification.

Crop Uptake and RemovalThe amount of N that the crop takes up fromthe soil largely depends on crop yield. Cropyield depends on crop type, agriculturalcapability of the soil, weather conditions andmanagement practices. The amount of Nremoved by the crop is also a function of theprotein content of the plant and the amountof plant material harvested from the field.

4.2.2 Manure phosphorus (P) after application

Although P is less dynamic in soil than N, itsmanagement in manure is challenging. MostManitoba soils are naturally deficient in plant-available P. Crops growing on low P soilsrequire fertilization to reach optimal yieldsand will benefit from a build up in soil P untilagronomic requirements are met. However,repeated applications can result in soil Plevels well above agronomic requirements. Inaddition to being a valuable crop nutrient, atelevated levels, P is a serious contaminant insurface water. For this reason, loss of P fromagricultural lands is of particular concern tosurface water quality.

MineralizationAs with N, mineralization of organic P toinorganic P takes place in the soil andcontributes to the supply of plant available P.

RetentionInorganic P tends to bind readily in bothalkaline and acidic soils to organic matter,calcium (Ca), magnesium (Mg), iron (Fe), andaluminum (Al). Fine textured soils (i.e. clays)are able to bind considerably more P thancoarse textured soils (i.e. sands).

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SolubilizationSoil does not have an unlimited capacity tobind P. Rising soil test P levels are oftenaccompanied by an increase in soluble P (Pdissolved in water). Soluble P can be easilytransported to surface water in runoff and itis more difficult to control than P transportedby soil erosion.

Crop Uptake and RemovalThe amount of P that the crop takes up fromthe soil largely depends on crop yield. Cropyield depends on the crop type, agriculturalcapability of the soil, weather conditions andmanagement practices of the producer. Theamount of P removed by the crop is also afunction of the P content of the plants andthe amount of plant material harvested fromthe field.

4.3 Using Manure as a Fertilizer

The most common way to take full advantage ofmanure as a resource on the farm is to use it asa fertilizer for crop production. Producers whouse manure as a fertilizer benefit economicallybecause they can replace expensive commercialsources of plant nutrients with the manurenutrients. Good nutrient management practicesalso minimize the risk to the environment frommanure nutrients. Following are the basic stepsto integrating manure into a farm’s nutrientmanagement program.

4.3.1 Test the soil

Soil sampling and analysis are the only wayto directly determine the plant-availablenutrient status of a field and to receive field-specific fertilizer recommendations. Thereare a number of soil sampling strategies thatmay be adopted, depending on site-specificconditions. Whichever strategy is employed

for a field, soils should be sampled at the 0to 15 centimetres (cm) (0 to 6 in) and 15 to60 cm (6 to 24 inch in) depths, andcomposite samples for each depth should bekept separate for analysis.

Although a variety of analytical packages areavailable, one that includes nitrate-N,exchangeable K, and available P should beselected. Nitrate-N should be determined onthe both the 0 to 15 cm and 15 to 60 cm (0 to6 in and 6 to 24 in) samples, whereasexchangeable K and available P only need tobe determined on the 0 to 15 cm samples. There are several analytical methods fordetermining available P, and results from eachcan be considerably different. The P2O5

fertilizer recommendations contained in theManitoba Soil Fertility Guide are based onsodium-bicarbonate extractable P or Olsen P. In areas where salinity (concentration ofsoluble salts) or sodicity (excess sodiumrelative to calcium and magnesium) is aconcern, electrical conductivity (EC) andsodium adsorption ratio (SAR), should beconsidered.

Qualified professionals should be consultedfor advice in selecting the most appropriatesampling strategy, analytical package andproper protocols for collecting, handling andshipping soil samples for laboratory analysis(see Appendix F).

Fertilizer recommendationsThe soil test report should also containrecommendations for any additional fertilizerthat is required. The amount of additionalnutrients required should be based on thesoil test results and a realistic crop yieldtarget provided by the producer. Realisticyield goals can be determined usingproducer experience and knowledge of theproductive capacity of soils on a given farm.



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4.3.2 Test the manure

Testing manure for each livestock operationand each application event is the best wayto estimate the nutrient content of manure.A manure analysis should be based on awell-mixed, representative sample. Manureis very heterogeneous and obtaining arepresentative sample can be very difficult.Sometimes, more than one sample isrequired to estimate the nutrientconcentration because the characteristics ofthe manure change (for example, duringpump-out of a liquid manure storagestructure).

It is ideal to know the nutrient content of themanure before application so thatapplication rates can be set to meet cropnutrient requirements. Receiving test resultsprior to manure application can bechallenging, particularly for liquid manure.This is because the manure storage structureis not typically agitated until just before andduring pump-out for application. One wayto address this concern is to have a databaseof historical manure test results for a givenoperation to use until recent test results canconfirm nutrient contents.

Manure samples should be analyzed by anaccredited laboratory on at least an annualbasis. More frequent manure analyses maybe required if the manure is applied atmultiple times during the year (such asspring and fall) or if management practicesare likely to create a change in the nutrientcontent of the manure. Rapid field test kitsfor liquid manure exist for estimating thereadily available portion of N, however, theresult of a field test should be verified bycomparing it to a laboratory analysis of thesame manure sample. Historical laboratorytest results for a given operation can be

used to assess the accuracy of recentlaboratory and field test results.

A basic manure analysis package shouldinclude total nitrogen (TKN), ammonium N,total P, total K, and dry matter content. Organic N is calculated by subtracting theammonium N from total N. In someinstances, micronutrient analyses may also bedesired.

Application rates are often based onestimated manure nutrient levels or bookvalues. Estimated values are not as reliableas multiple manure tests for an operationbecause manure nutrient levels vary widely. Inaccurate estimates will lead toapplication rates that are either lower orhigher than required.

4.3.3 Crop selection and rotation

Designing a crop rotation system that usesmanure as the nutrient source should be nodifferent than designing a crop rotationsystem using commercial fertilizer. However,since manure is handled and applieddifferently than commercial fertilizer, somemodifications may be necessary. The cropsincluded in the rotation should not only usethe nutrients from the manure as efficiently aspossible, but the overall rotation should havethe intensity and diversity to overcome otheragronomic challenges such as weeds, disease,insects, residue management, moisturemanagement and timing of field operations. Contact Manitoba Agriculture, Food and RuralInitiatives for information on crop selectionand rotation (or refer to ManitobaAgriculture, Food and Rural Initiative’s factsheet Crop Rotations and Timing of ManureApplication).

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Annual Crops and ForagesThe amount of nutrients, particularly N, usedby different crops varies widely. Grass-basedforage crops require much more N thanannual cereal crops. Legume-based foragecrops, such as alfalfa, can fix atmospheric Nand require little fertilizer N. Althoughalfalfa is capable of fixing N, it is alsocapable of utilizing large quantities of Nfrom soil, manure or commercial fertilizer. Assuch, it is a good recipient for manure.Alfalfa is also a deep-rooted plant, which iscapable of withdrawing nitrate-N that hasleached below the root zone of annual crops.

Forage crops offer other advantages tomanure management planning. In-seasonand split applications are more feasible onforage crops. High yielding forages alsohave the ability to remove more P thanmost annual crops. Silage crops offer asimilarly high P removal potential whenyields are high.

PasturePastures generally respond well to fertilizationby manure because their soil fertility istypically depleted after many years of grazing. Unlike forage fields that are mechanicallyharvested, most of the nutrients applied topastures will be re-deposited on the pastureby the livestock. Soil nutrient build-up shouldbe monitored when manure is used regularlyto fertilize pastures.

Fertilization of native or tame pastures, canaffect the relative dominance of differentforage species. Over time, species thatrespond well to applied nutrients tend tobecome dominant after manure application. Species that thrive under low fertilityconditions tend to become less dominantafter manure application. Although forageyield may increase with manure application,

the potential shift in species on pastureshould be considered when planning whereto apply manure.

Consideration should be given to providing aperiod of time between manure applicationand subsequent grazing so that the standcan make use of the applied nutrients. Thispractice will ensure a stronger regrowth ofthe pasture forages and minimize the risk ofnutrient loss to the environment. Delayinggrazing following broadcast application ofmanure is also suggested as a preventivemeasure against transmission of potentiallypathogenic organisms that may be presentin livestock manure. A rest period providesthe opportunity for natural environmentalfactors to inactivate potential pathogens. Aminimum 30-day rest period isrecommended before livestock arereintroduced to pastures on which manurehas been broadcast applied. Certainapplication techniques or othercircumstances may allow shorter restperiods. Manitoba Agriculture, Food andRural Initiatives can provide advice on thisissue. Application of manure from aparticular livestock species onto a pasturethat will be grazed by a different livestockspecies may be another effective way tointerrupt the chain of infection frompathogens to livestock. Livestock shouldnever be present on the pasture whilemanure is being applied.

Fallow landApplying manure to fallow land is not arecommended practice for environmentalreasons, and is prohibited before August 15unless prior approval has been obtainedfrom Manitoba Conservation. The absenceof a growing crop in the year of applicationmeans manure nutrients will not be utilizeduntil the following growing season and



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increases the risk of nutrient loss from thefield. Accumulation of nutrients in a fallowfield, particularly nitrate-N, is likely to beaccelerated as nutrients from manure andthe soil are released through microbialactivity. The build-up of soil nitrate-N mayexceed the N requirements of the next crop.Soil sampling for N to a depth of 1.2 m (4 ft),either in the fall of the fallow year or thenext spring, is recommended when applyingmanure to fallow land. Deeper samplingmay detect leached nitrate-N that can betaken into account in crop selection andfuture manure management planning.

Under the Livestock Manure and MoralitiesManagement Regulation, manure can onlybe applied to land as a fertilizer and theland must be cropped no later than thefollowing growing season.

4.3.4 How to calculate the manure application rate

Manure application rate calculations arebased on fertilizer recommendations. Thesefertilizer recommendations should be basedon soil test results for nitrate-N and P and arealistic target yield for the crop to be grown. The target yields should be appropriate forthe region, productive capacity of the soil andthe producer’s management practices. Cropinsurance data and historical yield records forthe operation provide guidance forestablishing target yields. AgricultureCapability ratings, which are based on naturalsoil and landscape characteristics, can be usedto identify the severity and kind of limitationsto crop production for a given field. ManitobaAgriculture, Food and Rural Initiatives may becontacted for information on agriculturecapability ratings. If the target yield chosen is

not realized, soil nutrient levels should bemonitored and future target yields should beadjusted accordingly.

The soil test report should provide fertilizerrecommendations. When necessary, theManitoba Soil Fertility Guide can alsoprovide nutrient recommendations based onsoil test values. In some situations,estimates of crop nutrient removals fromappropriate published sources may also beuseful when determining target manureapplication rates.

Nitrogen based application ratesManure application rates are based on thesoil analyses and fertilizerrecommendations, manure analyses, timingand method of application and weatherconditions. Traditionally, manureapplication rates have been based on N. For all crops except legumes, the rate ofmanure application has been based on theamount of fertilizer N required to achieve atarget yield. Since legumes can fix theirown N and do not require additionalfertilizer, manure application rates forlegumes have been based on the potentialN removal of the crop (Table 6).

The N requirements of a crop can be providedby manure N. However, not all of the N in themanure will be available to the crop in thefirst year after application. Therefore, theavailable N in the manure must be calculated.

The manure test report provides results fortotal N (TKN) and ammonium N. Organic Nis calculated from the manure test report asthe difference between total N andammonium N.

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Organic N = Total N – Ammonium N

Nitrogen availability is estimated for both theinorganic (ammonium) and organic forms. Allof the ammonium is available to the crop,however, it is also highly susceptible tovolatilization losses as ammonia gas. Theactual amount of ammonium N available isthe amount remaining after volatilization:

Available Ammonium N = Total Ammonium N x (100% – % Volatilization Loss)

Volatilization loss estimates are provided inTable 7.

Two factors are considered when estimatingvolatilization loss: weather conditions atthe time of application and method ofapplication. Generally, volatilization lossesare expected to be greater under warmerand dryer conditions (e.g. summer) andlower under cooler and wetter conditions(e.g. early spring or late fall). Volatilizationlosses also increase with prolongedexposure of manure on the soil surface.Therefore, injection of liquid manure, orrapid incorporation following broadcastapplication, should minimize loss ofammonia to the atmosphere.

Table 6: Crop Removal Rates For N And P2O51

Crop2 Example Target Yield3

Average Nutrient Uptake Rate4 Average Nutrient Removal Rate5

N P2O5 N P2O5

Spring Wheat 2.69 t/ha 35.2 kg/t 13.4 kg/t 25.1 kg/t 9.8 kg/t

Winter Wheat 3.36 t/ha 22.5 kg/t 10.2 kg/t 17.4 kg/t 8.5 kg/t

Barley 4.30 t/ha 29.0 kg/t 11.7 kg/t 20.3 kg/t 8.8 kg/t

Oats 3.81 t/ha 31.5 kg/t 12.1 kg/t 18.3 kg/t 7.7 kg/t

Rye 3.45 t/ha 29.9 kg/t 15.0 kg/t 19.0 kg/t 8.1 kg/t

Grain Corn 6.27 t/ha 27.4 kg/t 11.3 kg/t 17.4 kg/t 7.9 kg/t

Canola 1.96 t/ha 63.9 kg/t 29.5 kg/t 38.7 kg/t 20.8 kg/t

Flax 1.50 t/ha 52.0 kg/t 14.8 kg/t 38.1 kg/t 11.6 kg/t

Sunflowers 1.68 t/ha 49.8 kg/t 17.0 kg/t 35.7 kg/t 10.7 kg/t

Alfalfa 11.2 t/ha N/A6 N/A 29.0 kg/t 6.9 kg/t

Grass 6.7 t/ha N/A N/A 17.1 kg/t 5.0 kg/t

Corn Silage 11.2 t/ha N/A N/A 15.6 kg/t 6.4 kg/t

Barley Silage 10.1 t/ha N/A N/A 17.2 kg/t 5.9 kg/t

1 Adapted from Nutrient Uptake and Removal by Field Crops, Western Canada, 2001. Compiled by the Canadian Fertilizer Institute.2 As bushel weights can vary considerably among some crop varieties, values other than those presented here may need to be chosen to

better reflect a given cropping scenario.3 Example target yields for Manitoba. Site specific and actual yields for any parcel of land will depend on the agricultural capability of the

land, climate and the producer’s management practices.4 Total nutrient taken up by the crop5 Nutrient removed in the harvested portion of the crop6 Not applicable



37

Organic N must be mineralized before it canbe used by the crop. The proportion oforganic N in manure that is estimated to beavailable to the following crop is 25 per cent:

Available Organic N = 25 per cent Organic N

For solid manure that contains considerableamounts of straw or other bedding materials,less than 25 per cent of the organic N maybe available in the first year following asingle application. As soil microorganismsconsume the carbon (C) from the beddingmaterials, they tie up N from the manureand/or soil that would otherwise beavailable to the crop. Solid manure, thatcontains a lot of bedding, returns asignificant amount of carbon to the soil.Application of this type of manure may resultin temporary immobilization of N, reducingplant-availability. Repeated applications ofsolid manure, however, may result in a build-up of soil N that becomes available to cropsgrown in subsequent years.

The C:N ratio of the manure may provideinformation on how much N will be availableto the crop in the year following application.

Research has indicated that manures with C:N ratios higher than 15:1 are not likely torelease N very quickly to the crop in the yearfollowing application. In these cases, lessthan 25 per cent of the organic N will beavailable in the first year. Eventually most ofthe additional N will be released and thismust be taken into account, preferablythrough a soils test, when calculating thesoil requirement for N in subsequent years.

The estimated total available N isdetermined by adding the available organicand inorganic fractions:

Total Available N = Ammonium N x (100% – % Volatilization loss) + 0.25 Organic N

Phosphorus based application rates

Unlike commercial fertilizer, manure nutrientsare usually not in balance with the nutrientrequirements of the crop. Manure applicationrates are based on the most limiting nutrientfor crop production, which is most frequentlyN. Although P is usually found in manure insmaller quantities than N, crops requiresignificantly less P than N to reach optimumyields. It is therefore common for more P to

Table 7: Volatilization Losses (%)1

Method of Application Cool Wet Cool Dry Warm Wet Warm Dry Average

Injected 0 0 0 0 0

Incorporated within 1 day 10 15 25 50 25





Not Incorporated 40 50 75 90 64

IrrigatedAbove+ 10%

Above+ 10%

Above+ 10%

Above+ 10%

Above+ 10%

Applied to Standing Crop 25 25 40 50 35

1MARC 2005. Manitoba Agriculture, Food and Rural Initiatives.

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be applied than the crop can remove whenapplication rates are based on N. This resultsin a build-up of soil test P.

This nutrient imbalance is magnified whenmanure is applied using a practice that doesnot conserve N for crop use and, instead,exposes the N to greater loss from the field. For example, broadcast application of manurewithout incorporation leads to increased lossof N through volatilization. To compensatefor this fact, the manure application rate mustbe increased to ensure that the N demand ofthe crop is satisfied. A higher manureapplication rate leads to a higher applicationof manure P and a more rapid rise in soil P. The same situation also arises with annualapplications of manure having a low availableN content (common with solid manure).

As soil test P levels increase, soluble P alsoincreases. Soluble P is more mobile in waterand can threaten surface water quality if itmoves from the field to a watercourse.Controlling the build-up of soil test P willreduce the formation of soluble P. This canbe achieved by reducing the P in manure orby basing manure application rates on P.

As soil test P builds, the requirement foradditional fertilizer P decreases, often to onlystarter P levels. The fertilizer recommendationfor P can be found on the soil test report. Fertilizer P is expressed as P2O5:

P x 2.3 = P2O5

It is often not feasible to apply manure at thetypically low rates recommended in soil testreports to meet crop P requirements. Whenmanure is applied based on P, the targetapplication rate should be based on the crop-specific removal rate for P, expressed as P2O5

(Table 6). In order to slow the build up of soil

test P, at moderate to high soil test P levels(60 to 119 ppm Olsen P), the manure P2O5

application rate should not exceed two timesthe crop P2O5 removal rate:

At 60 to 119 ppm Olsen PManure P2O5 Application Rate 2 x Crop Removal P2O5

When soil test P values are very high (120 to179 ppm Olsen P), manure P2O5 applicationrates should not exceed the total amount ofP2O5 that the crop can remove. This willprevent further build-up of soil test P.

At 120 to 179 ppm Olsen PManure P2O5 Application Rate 1 x Crop Removal P2O5

Manure should not be applied to soils thatalready have excessive levels of soil test P(>180 ppm Olsen P). These soils should becropped to bring down soil test P levelsbefore additional manure is applied. If anapplication rate based on P2O5 removal is stillprohibitive, it may be necessary to applymanure once at a rate that is equivalent tomultiple years of P2O5 removal (e.g. totalremoval by crops that will be grown overseveral years). After this single application,no additional manure is applied during thatmulti-year period; therefore, other nutrientrequirements are met using syntheticfertilizer or other sources (e.g. N fixation bylegumes).

Table 8a and 8b are worksheets forcalculating N or P-based manure applicationrates (see appendix C for imperial version).



39

Table 8a: Manure Application Rate Calculation Worksheet1 Based On Liquid Manure

Field I.D.:________________ Crop: ____________________ Target Yield: __________________

Step 1. Target Nutrient Rate Units [2]

Nitrogen (based on soil test recommendation) (A) 90 kg/ha

Phosphorus (as P2O5): 2x Crop Removal (B1) 60 kg/ha


Other: (B3) kg/ha

Step 2. Manure Test Data

Total Nitrogen (C) 3.1 kg/m3

Ammonium Nitrogen (D) 1.9 kg/m3

Organic Nitrogen = (C) - (D) (E) 1.2 kg/m3

Phosphorus (F) 1.0 kg/m3

P2O5 = (F) x 2.3 (G) 2.3 kg/m3

Step 3. Amount of manure nitrogen available to crop:

Application method Incorporated within 1 day

Volatilization losses due to application method (Table 6) (H) 25%

Ammonium nitrogen available = (D) x [100-(H)]% = 1.9 x 0.75 = 1.4 (I) 1.4 kg/m3

Organic nitrogen available to the next crop = (E) x 0.25 = 1.2 x 0.25 = 0.3 (J) 0.3 kg/m3

Total available N = (I) + (J) = 1.4 + 0.3 = 1.7 (K) 1.7 kg/m3

Total available N in spring = (K) x 100% = 1.7 x 1.0 = 1.7 (L) 1.7 kg/m3

Total Available N in fall = (K) x 83% = 1.7 x 0.83 = 1.4 (M) 1.4 kg/m3

Step 4. Application rate based on N requirements:

Spring N-based Application Rate = (A) ÷ (L) = 90 ÷ 1.7 = 52.9 orFall N-based Application Rate = (A) ÷ (M) = 90 ÷ 1.4 = 64.3

(N) 64.3 m3/ha

Amount of P2O5 applied = (G) x (N) = 2.3 x 64.3 = 147.9 (O) 147.9 kg/ha

P2O5 balance3 (using 1x crop removal) = (O) - (B2) = 147.9 - 30 = 117.9 (P) +117.9 kg/ha

Step 5. Applicaton rate based on P removal:

2x crop removal P-based Application Rate2 = (B1) ÷ (G) = 60 ÷ 2.3 = 26.1 or1x crop removal P-based Application Rate2 = (B2) ÷ (G) = 30 ÷ 2.3 = 13.0

(Q) 26.1 m3/ha

Amount of available N applied in spring = (L) x (Q) = 1.7 x 26.1 = 44.4 orAmount of available N applied in fall = (M) x (Q) = 1.4 x 26.1 = 36.5

(R) 36.5 kg/ha

N balance5 (N applied - N recomended) = (R) - (A) = 36.5 - 90 = -53.5 (S) -53.5 kg/ha

Step 6. Compare N Rate (N) with P rate (Q):

If soil test P is low to moderate (<60 ppm), apply manure at N rate (N) 64 m3/ha

If soil test P is high )> 60 ppm), apply manure at P rate (Q)[6] 26 m3/ha

1 See Appendix C for imperial units and a blank template worksheet.2 1 kg/m3 = 1 kg/ 1000 L3 A positive value indicates that more P2O5 will be applied than the crop will remove (1x crop removal) when manure is applied based on N. A

negative value indicates that less P2O5 will be applied than the crop will remove (1x crop removal) and the rate should be compared to the soiltest recommendation to determine if the crop requirement for P will be met.

4 When soil test phosphorus (STP) is low to moderate, manure can be applied based on N. When STP is high, a P-based application rate can beused up to 2X the crop removal of P2O5. At very high to excessive STP, no more than 1X crop removal of P2O5 should be applied.

5 Positive value indicates N application rate is above soil test recommendation when manure is applied based on P2O5. Negative value indicates Napplication rate is below soil test recommendation and supplemental commercial fertilizer is required to meet crop requirements.

6 If annual applications are too low, multi-year application rates and rotation of fields should be considered.

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Table 8b: Manure Application Rate Calculation Worksheet1 Based On Solid Manure

Field I.D.:________________ Crop: ____________________ Target Yield: __________________

Step 1. Target Nutrient Rate Units [2]

Nitrogen (based on soil test recommendation) (A) 90 kg/ha



Other: (B3) kg/ha

Step 2. Manure Test Data

Total Nitrogen (C) 6.0 kg/t

Ammonium Nitrogen (D) 2.1 kg/t

Organic Nitrogen = (C) - (D) (E) 3.9 kg/t

Phosphorus (F) 2.4 kg/t

P2O5 = (F) x 2.3 (G) 5.5 kg/t

Step 3. Amount of manure nitrogen available to crop:

Application method Incorporated within 1 day

Volatilization losses due to application method (Table 6) (H) 25%

Ammonium nitrogen available = (D) x [100-(H)]% = 2.1 x 0.75 = 1.6 (I) 1.6 kg/t

Organic nitrogen available to the next crop = (E) x 0.25 = 3.9 x 0.25 = 1.0 (J) 1.0 kg/t

Total available N = (I) + (J) = 1.6 + 1.0 = 2.6 (K) 2.6 kg/t

Total available N in spring = (K) x 100% = 2.6 x 1.0 = 2.6 (L) 2.6 kg/t

Total Available N in fall = (K) x 83% = 2.6 x 0.83 = 2.2 (M) 2.2 kg/t

Step 4. Application rate based on N requirements:

Spring N-based Application Rate = (A) ÷ (L) = 90 ÷ 2.6 = 34.6 orFall N-based Application Rate = (A) ÷ (M) = 90 ÷ 2.2 = 40.9

(N) 34.6 t/ha

Amount of P2O5 applied = (G) x (N) = 5.5 x 34.6 = 190.3 (O) 190.3 kg/ha

P2O5 balance3 (using 1x crop removal) = (O) - (B2) = 190.3 - 30 = 160.3 (P) +160.3 kg/ha

Step 5. Applicaton rate based on P removal:

2x crop removal P-based Application Rate2 = (B1) ÷ (G) = 60 ÷ 5.5 = 10.9 or1x crop removal P-based Application Rate2 = (B2) ÷ (G) = 30 ÷ 5.5 = 5.5

(Q) 10.9 t/ha

Amount of available N applied in spring = (L) x (Q) = 2.6 x 10.9 = 28.3 orAmount of available N applied in fall = (M) x (Q) = 2.2 x 10.9 = 23.9

(R) 28.3 kg/ha

N balance5 (N applied - N recomended) = (R) - (A) = 28.3 - 90 = -61.7 (S) -61.7 kg/ha

Step 6. Compare N Rate (N) with P rate (Q):

If soil test P is low to moderate (<60 ppm), apply manure at N rate (N) 35 t/ha

If soil test P is high )> 60 ppm), apply manure at P rate (Q)[6] 11 t/ha1 See Appendix C for imperial units and a blank template worksheet.2 1 tonne = 1000 kg3 A positive value indicates that more P2O5 will be applied than the crop will remove (1x crop removal) when manure is applied based on N. A

negative value indicates that less P2O5 will be applied than the crop will remove (1x crop removal) and the rate should be compared to the soiltest recommendation to determine if the crop requirement for P will be met.

4 When soil test phosphorus (STP) is low to moderate, manure can be applied based on N. When STP is high, a P-based application rate can beused up to 2X the crop removal of P2O5. At very high to excessive STP, no more than 1X crop removal of P2O5 should be applied.

5 Positive value indicates N application rate is above soil test recommendation when manure is applied based on P2O5. Negative value indicates Napplication rate is below soil test recommendation and supplemental commercial fertilizer is required to meet crop requirements.

6 If annual applications are too low, multi-year application rates and rotation of fields should be considered.



41

4.3.5 Calibrate field equipment to deliver target rate

Calibration refers to the combination ofsettings needed to deliver manure at aparticular rate. The calculation of manureapplication rates is of little value if theequipment is not properly calibrated todeliver the required application rate. Detailson how to calibrate manure applicationequipment can be found in the Tri-ProvincialManure Application and Use Guidelines(Manitoba Version, 2004).

Solid, semi-solid and liquid manureapplication systems can discharge manure atvarious rates, depending on factors such asspeed of travel, flow meter setting, width ofapplication or other parameters. Wheneverpossible, data from the manufacturer shouldbe used to calibrate application equipment.

4.3.6 Record keeping

Every livestock operation should keep trackof soil and manure test results, manureapplication rates, application methods,application dates, crop rotations and yields,and any other relevant information for eachfield that receives manure.

Maintaining detailed records on an ongoingbasis is an essential part of proper manurenutrient management. Complete sets ofhistorical soil and manure test results, cropperformance, weather conditions andmanagement practices can help producersmake sound decisions and document propermanagement of land and fertilizer resourceson the farm. For instance, soil test resultscan be used to track nutrient levels over timeand detect build-up in the soil before itbecomes excessive. A manure test databasefor a particular operation can be used to

determine more accurate manure applicationrates, confirm the accuracy of a singlemanure test and indicate changes inmanagement that have affected thecomposition of the manure. Documentingweather conditions during and after manureapplication may help explain the fate ofmanure nutrients (e.g. loss from the field oruptake by the crop). Cropping informationcan indicate any adverse effects of manureapplication (e.g. compaction leading todepressed growth), as well as the suitabilityof soils for manure application (i.e.consistently high yields and quality on moreproductive land, consistently low yields andquality on less productive land).

4.4 Benefits of Using Manure as a Fertilizer

The costs of handling and applying manure arehigh when compared on an equivalent weightbasis with commercial, inorganic fertilizers.However, proper periodic applications can alsoresult in substantial long-term improvements inthe physical and chemical characteristics of thesoil. Manure should be viewed as a resource tobe properly managed, rather than as a wasterequiring disposal.

The direct economic benefits of livestock manuremanagement rest in its ability to replacecommercial fertilizers as a source of plantnutrients. The manure nutrients, particularly Nand P, will reduce or replace the need foradditional synthetic fertilizer, thereby reducingfertilizer purchasing costs.

Caution should be exercised not to over-applymanure. In addition to increasing environmentalrisks, excessive applications of manure can havea negative impact on crops by causing excessivevegetative growth, lodging, and/or delayedmaturity. Applying manure nutrients in excess of

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crop requirements also represents a missedopportunity for putting those nutrients to use onother fields where a crop response is likely to beobserved.

4.5 Environmental Health Concerns

Manure is a valuable source of nutrients andorganic matter that can replace or reduce theneed for synthetic fertilizer and improve soilquality. However, there are risks associated withusing manure that must be minimized throughproper management.

4.5.1 Odour

The potential relationship between odoursand health is addressed in detail in Section5. This section also provides managementoptions to address odour concerns whenapplying manure in close proximity toneighbours.

4.5.2 Nitrate contamination of drinking water

Groundwater may contain nitrate fromnatural sources (e.g. peat bogs), commercialfertilizers, domestic sewage systems ormanure. Nitrate is very soluble in water andcan be easily leached in soils with goodinternal drainage (e.g. sandy soils) whenmoisture levels are high. Nitrate thatleaches below the crop rooting zone mayeventually reach groundwater, which mayserve as a drinking water source.

The guideline maximum acceptableconcentration of nitrate in drinking water,set by Health Canada, is 10 milligrams perlitre (mg/L) nitrate-N (or 45 mg/L nitrate). Below 10 mg/L, nitrate does not appear to

cause health problems. Above this level,there may be heath concerns, particularlyfor infants less than one year of age andpregnant women. For infants, ingestion ofnitrate may result in a shortage of oxygenin the blood, which manifests itself in abluish colouration of the skin and mouth.This condition is called methemoglobinemiaor “blue-baby syndrome”. In pregnantwomen, the presence of nitrate may causea lack of oxygen for the fetus. Thepossibility of blue-baby syndrome is entirelypreventable by avoiding the consumptionof water high in nitrates.

Although adults have a higher tolerance fornitrates, some studies suggest an associationbetween nitrates in drinking water and thedevelopment of stomach cancer. For adults,food is generally the main source of ingestednitrate unless drinking water contains elevatedconcentrations. A link between drinking waterhigh in nitrates and gastric cancer has beenobserved in some studies, however, otherstudies have not supported this associationand, to date, no firm conclusions aboutdrinking water high in nitrates causing gastriccancer have been made.

As there are many potential sources forelevated nitrate levels in private drinkingwater wells, it is advisable to have the watertested regularly. This is particularlyimportant if members of the householdinclude pregnant women or infants. Yourregional Manitoba Water Stewardship officecan be contacted for advice on how to haveyour drinking water tested.

Managing manure to reduce the risk of nitrate contamination of groundwater

Careless or improper storage, excessive Napplications, as well as improperly protected



43

well casings may result in groundwatercontamination. The best preventivemeasures consist of ensuring that N sources,whether manure or commercial fertilizer, arestored properly and applied at rates thatmatch plant requirements.

Although nitrate-N levels are very low inmanure, the organic-N and ammonium-Ncan be converted to nitrate-N when manureis applied to soil. Heavy or repeatedapplications of manure can result in a build-up of N in the soil. All fields that are toreceive manure should be tested for residualnitrate-N so that the appropriate manureapplication rate can be targeted. Fields thathave received heavy or repeated applicationsof manure, or have supported low crop yieldsand quality, may have adequate N to supplycrop needs and may not be suitable foradditional applications. Those fields thatrequire additional N should only receiveenough manure to meet the crop’s Nrequirement.

Ideally, manure should be applied so that N isavailable to the crop at the appropriate timeand in the required amount. While spring, in-season or split applications may be the mostdesirable in this respect, fall applications maybe more practical in areas where spring soilconditions limit opportunities for manureapplication, or in cases of limited manurestorage capacity. Extra care should be takenwhen applying manure at times that increasethe length of time during which nitrateleaching may occur.

Although the risk is low for many ofManitoba’s agricultural soils and aquifers,manure applications, like commercial fertilizers, must always be properly managed to minimize the risk of contaminating groundwater.

Additional information on N managementcan be found in the Manitoba Agriculture,Food and Rural Initiatives fact sheetsNitrogen Dynamics, Retrieval Strategies forDeep Leached Nitrates and Manure NitrogenLosses and Prevention.

4.5.3 Sensitive groundwater areas

In some areas, soil and groundwaterconditions are more sensitive to agriculturalpractices, specifically the application ofeither inorganic or organic (manure) Nfertilizers. The degree of sensitivity of anaquifer to contamination depends on manyfactors. These may include the depth to theaquifer, the type of aquifer, the properties ofoverburden material overlying the aquifer(soil, subsoil, and parent materialcomposition and structure), the type ofvegetation at the soil surface, and whetherthe area is located within a recharge source. Where very permeable soils, such as coarsesands or gravels, immediately overlay anaquifer or where the overburden above anaquifer is shallow, nutrients applied to thesoil surface may leach rapidly downwardbeyond crop rooting depths and eventuallyreach the aquifer. Since these areas tend tobe excessively well drained, crop productivityis often relatively low and plant uptake ofnutrients tends to be limited.

4.5.4 Nutrient loss to surface water

Nitrogen and phosphorus are the twoprimary manure nutrients of concern withrespect to surface water quality. Excessnutrients in water result in eutrophicationand have been associated with fish kills.

Nitrogen – Manure contains N asammonium (NH4) which is toxic to aquatic

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life and can convert to the more toxicammonia (NH3) form. The greatest risk ofammonium from manure entering surfacewater is through direct runoff or erosionsoon after application.

Phosphorus – Eutrophication is theenrichment of water bodies by nutrients –both N and P. Phosphorus, however, is thenutrient that most commonly limits plantgrowth in fresh water bodies. Excess Pentering water can result in increasedproduction of algae and other aquatic plants,affecting water quality and the diversity oforganisms present. During winter, theincreased algae and aquatic plants decayand may deplete the oxygen supply in thewater, potentially causing fish kill. At highconcentrations of P in fresh water, blue-green algae can flourish and can releasetoxins that can harm wildlife, livestock, andhumans if they drink the water.

Managing manure to reduce the risk of surface water contamination

Manure nutrients can contaminate surfacewater if manure enters surface water directlyor through runoff or soil erosion from landsthat receive manure. Liquid manureapplication rates should not exceed the abilityof the soil to absorb the manure. Heavy-textured soils, such as clay soils, have muchslower infiltration rates than light texturedsoils. Manure application rates on these soilsshould avoid ponding or runoff. Reducedapplication rates may also be necessary onsloping lands and manure should not beapplied when heavy rain is in the forecast. Tillage and cropping practices that reduce soilerosion should also be adopted.

4.5.5 Pathogen transfer to surface water or groundwater

Livestock manure contains bacteria, viruses,protozoa and parasites, some of which maybe pathogenic (cause disease) in humans.Such organisms in manure may enter surfacewater if manure leaves the field throughrunoff or erosion or if manure is accidentallyspilled or intentionally discharged intosurface water. Although the soil tends to actas a natural filter that protects groundwaterfrom contamination by pathogens, there maybe a risk of micro-organisms moving throughthe soil profile to groundwater under certainconditions, such as the presence of coarselytextured surficial material, shallow watertable, fractured bedrock or poorlyconstructed wells.

Manure applications must always be properly managed to minimize the risk of contaminating surface and groundwater. The risk of watercontamination from pathogens will bereduced when the setbacks listed in Table 9and Table 10 are maintained. Communityhealth risks from pathogens are furtherreduced when the precautions in Section 3.6are followed.



45

4.5.6 Setback requirements for livestock manure application on land adjacent to surface water or a surface watercourse

To reduce the risk of runoff contaminatedwith manure entering drinking water wells,wells should be located and constructed toprotect water quality over the long-term(See Section 6.3).

Setbacks from application on land adjacentto surface water or a surface watercourse

reduces the risk of runoff contaminated withmanure entering water. The effectiveness ofthe setbacks depends on such factors as itswidth, soil and landscape conditions and theintensity and duration of rainfall. To reducethe risk of overland flow entering sinkholes,springs or wells, the area immediatelyaround these features should be sown topermanent cover. Table 9 provides setbackrequirements for livestock manureapplication on land adjacent to surfacewater or a surface watercourse.

Table 9. Setback Requirements For Livestock Manure Application On Land Adjacent To Surface Water Or A Surface Watercourse1 (m)

Surface Water orSurface Watercourse

Feature

Manure Application

Method

Manure Application Setback Width with

Permanently Vegetated Buffer Width

Manure Application

Setback Width with no

Permanently Vegetated Buffer

Lakes

Injection or low-levelapplication followed byimmediate incorporation

15 m setback, consistingof 15 m permanentlyvegetated buffer

20 m setback

High-level broadcast orlow-level applicationwithout incorporation

30 m setback, including15 m permanentlyvegetated buffer

35 m setback

Rivers, creeks and largeunbermed drains, designated asan Order 3 or greater drain on aplan of Manitoba WaterStewardship, Planning andCoordination, that showsdesignations of drains

Injection or low-levelapplication followed byimmediate incorporation

3 m setback, consistingof 3 m permanentlyvegetated buffer

8 m setback

High-level broadcast orlow-level applicationwithout incorporation

10 m setback, including3 m permanentlyvegetated buffer

15 m setback

All other types of surface wateror surface watercourses

No manure application allowed

1 See Appendix C for imperial units.

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Topography should be considered whenapplying manure. As the slope increases,the chance that manure may run off alsoincreases. Therefore, added caution andmanagement is needed when applyingmanure to sloping lands, particularlysteeply sloping land (six per cent orgreater). Soil management practices thatreduce runoff and soil erosion should bepracticed on lands fertilized with manure. Susceptible areas could be avoided duringapplication. Crop or residue cover shouldbe maintained to provide protection againsterosion. In some instances, a grassedbuffer strip may be required.

4.5.7 Greenhouse gas emissions

Greenhouse gases are compounds in the airthat increase the amount of the sun’s energythat is trapped on the earth, resulting inrising atmospheric temperatures. This isknown as the greenhouse effect. Carbondioxide (CO2), methane (CH4) and nitrousoxide (N2O) are the three greenhouse gaseslinked to agriculture. Manure application isa source of CO2 and N2O. Carbon dioxide isgenerated by the burning of fossil fuels to

manufacture commercial fertilizer andoperate manure application equipment. It isalso produced when soil is tilled toincorporate surface application of manurebecause the tillage results in the breakdownof soil organic matter. Denitrificationproduces N2O which is a potent greenhousegas. Denitrification is most common insaturated soils where microorganisms areforced to use nitrate to respire becauseoxygen is unavailable.

Beneficial management practices thatreduce greenhouse gases from theapplication of manure often have otherenvironmental or economic benefits. Carbon dioxide emissions from applicationof manure can be reduced by minimizingthe number of equipment passes in the fieldwhich burns less fossil fuel. This can bedone by injecting manure to eliminate theneed for an additional pass to incorporatethe manure or by scheduling tillageoperations to coincide with incorporation ofsurface applied manure so that additionaltillage passes are avoided. Maximizing theN value of the manure reduces the need topurchase additional synthetic N fertilizer,

Table 10: Required1 Distances From Watercourses, Sinkholes, Springs, Wells And Recommended Distances From Residential Property Lines For Applying Manure Between November 10 And April 10 2 (m)

Slope

Application Method

Surface Applied and Irrigation

No incorporation Incorporation within 48 hours Injection

less than 4% 150 N/A N/A

4 – less than 6% 300 N/A N/A

6 – less than 12% 450 N/A N/A

Greater than 12% Prohibited Prohibited Prohibited1 Refer to the Livestock Manure and Mortalities Management Regulation – Appendix B.2 See Appendix C for imperial units.



47

the manufacturing of which generates CO2 . As well, maximizing crop uptake of manureN will reduce the amount of nitrateremaining in the soil at times of the year(such as early spring) when the risk ofleaching or denitrification is high. This canbe achieved through optimal timing ofmanure applications (as close to cropgrowth as possible) at rates that closelytarget crop requirements.

4.6 Regulations on Manure Application

The Livestock Manure and MortalitiesManagement Regulation (Appendix B) containsthe environmental laws specific to manuremanagement.

4.6.1 General rules regarding pollution of water

It is illegal to allow manure to enter surfaceor groundwater. Section 11 of the LivestockManure and Mortalities ManagementRegulation requires that no person shallhandle, use or dispose of livestock manure,or store manure in an agricultural operation,in such a manner that it is discharged orotherwise released into surface orgroundwater.

4.6.2 Prohibition on winter application

Applying manure in the winter is not arecommended practice because manure cannot infiltrate into frozen soil and thus ismore susceptible to runoff and entry intosurface watercourses. Furthermore, winterapplication of manure is the least desirabletime to apply manure to land because morenutrients in the manure will be lost due to

volatilization and spring runoff thanapplications at any other time of the year.However, where over-winter storage capacityis inadequate, winter application of manuremay be necessary.

Under Section 14 of the Livestock Manure andMortalities Management Regulation, alllivestock operations are prohibited fromapplication of livestock manure fromNovember 10 until April 10, unless they areexempted by regulation. Existing livestockoperations (defined as those in existence priorto March 30, 2004) with fewer than 300animal units of any one type of livestock areexempt from the prohibition unless they havebeen ordered to cease winter applicationbecause it is causing unacceptableenvironmental risk. Existing operationsbetween 300 and 399 animal units in sizehave until November 10, 2010 to comply withthe prohibition. Existing producers with 400or more animal units are currently required tocomply with the prohibition on winterapplication. New producers must complywith the prohibition on winter application assoon as their operations are established. Upon approval by Manitoba Conservation,emergency situations may warrant exceptionsto the prohibition on winter application.

Livestock operations that are exempt from theprohibition of winter manure application mustmeet minimum setback distance requirementsfrom sensitive areas as set out in theLivestock Manure and MortalitiesManagement Regulation. The required wintersetback distances from watercourses,sinkholes, springs, wells and therecommended setback distances fromresidential property lines are provided in Table10. Winter application on land with slopesgreater than 12 per cent is not permitted.

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If manure must be applied in the winter,stubble fields with adequate trash cover orperennial forage fields should be used.Surface cover reduces runoff volumes. Fieldswith limited access should receive manurefirst, leaving nearer fields for later whenaccess is more difficult due to snow orthawing conditions.

4.6.3 Registering manure management plans

Section 13 of the Livestock Manure andMortalities Management Regulation(Appendix B) requires that all livestockoperations, 300 animal units or greater in size,register a Manure Management Plan annually. The deadline for submission is February 10 forspring applications and July 10 for fallapplications. Alternatively, for a $100 fee, theoperator may submit a manure managementplan up to 14 days prior to application ofmanure. See Appendix G for the ManureManagement Plan registration form orcontact Manitoba Conservation.

Manitoba Agriculture, Food and RuralInitiatives has developed a computer softwareprogram that calculates manure applicationrates. The Manure Application Rate Calculator(MARC 2005) facilitates the preparation ofmanure management plans for all livestockoperation types. It supports easy recordkeeping of nutrient management informationon a field-by-field basis. The software isprogrammed to fill in the manuremanagement information directly on theManure Management Plan registration formrequired by Manitoba Conservation. Alternately, persons who wish to electronicallyfile a Manure Management Plan may do sousing the MMP Filer program available onManitoba Conservation’s website.

Those who prepare and certify manuremanagement plans on behalf of livestockproducers must have successfully completed

a manure management planning courseacceptable to the director of ManitobaConservation and must be a member in goodstanding of the Manitoba Institute ofAgrologists or hold the designation ofCertified Crop Advisor under theinternational Certified Crop Advisor programof the American Society of Agronomy.

4.6.4 Soil nitrate-N limits

To reduce the risk of nitrate contamination ofgroundwater, for those lands receivingmanure, the Livestock Manure and MortalitiesManagement Regulation (Appendix B) setsenforceable limits on the amount of residualsoil nitrate-N and the amount of nitrate-Nthat can be present in the soil at any point intime. The soil nitrate-N limits apply to the top60 cm (24 in) of soil and vary depending onthe agricultural capability rating of the soil. Nitrates in excess of these values may besubject to enforcement action by ManitobaConservation.

To ensure soil nitrate-N limits are notexceeded, the rate of manure applicationshould not exceed the additional N requiredto achieve a realistic crop yield. The rateshould consider the residual soil nitrate-Nand the N content of the manure.

4.7 Training and Licencing of Manure Applicators

Changes to The Pesticides and Fertilizers ControlAct were assented to in 2002. These changes willrequire commercial applicators that apply manurefrom large (300 animal units or greater)operations off-farm to be formally trained,certified and licenced. The training requirementswill be established by regulation and will covernutrient management, environmental issuesassociated with the application of manure,equipment calibration, spills and liability issues.

Documents

SECTION 4 Application of Manure - Province of …...should be based on crop nutrient requirements or removals. The goals of using livestock manure as a fertilizer should be to: ®maximize