Nr

MGa

b

c

a

ARRAA

KGGHMMNS

1

tgnM(

0d

Agriculture, Ecosystems and Environment 138 (2010) 35–43

Contents lists available at ScienceDirect

Agriculture, Ecosystems and Environment

journa l homepage: www.e lsev ier .com/ locate /agee

itrous oxide and methane emission from a coarse-textured grassland soileceiving hog slurry

ario Tenutaa,∗, Manasah Mkhabelaa, Denis Tremorina,1, Luca Coppia,raham Phippsb, Don Flatena, Kim Ominskic

Department of Soil Science, University of Manitoba, Winnipeg, MB, Canada R3T 2N2Manitoba Water Stewardship, Winnipeg, MB, Canada R3J 3W3Department of Animal Science, University of Manitoba, Winnipeg, MB, Canada R3T 2N2

r t i c l e i n f o

rticle history:eceived 23 October 2009eceived in revised form 17 March 2010ccepted 19 March 2010vailable online 15 April 2010

eywords:rasslandreenhouse gasog slurryethaneoistureitrous oxideoil

a b s t r a c t

Methane (CH4) and nitrous oxide (N2O) are potent greenhouse gases (GHG) that contribute to globalwarming. The objectives of this study were to evaluate the impact of (i) timing of hog slurry applicationand (ii) a soil moisture gradient on CH4 and N2O emission from a coarse-textured, poorly drained, grass-land soil. A factorial design with three treatments and two replicates was utilized. Treatments were: (i)zero manure (Control), (ii) hog slurry applied as a split application in the fall and spring (Split), each at arate of 72 ± 8 kg plant available N ha−1, and (iii) a single application of hog slurry applied each spring at arate of 148 ± 20 kg available N ha−1 (Single). To achieve the second objective, two parallel transects eachwith 30 chambers placed 9 m apart along a soil moisture gradient were utilized.

Overall, CH4 and N2O emission from the manured treatments (Split and Single) were significantly higher(P < 0.001) compared to the Control. Over the 3 years, average CH4 emission from the Control, Split andSingle treatments were 2.1, 6.8 and 5.3 g C ha−1 d−1, while N2O emission were 0.2, 2.2 and 4.9 g N ha−1 d−1,respectively. Similarly, cumulative CH4 and N2O emission and the combined CO2 equivalents from themanured treatments were significantly higher (P ≤ 0.01) than from the Control. Over the 3 years, meancumulative CH4 emissions were 1.6, 3.5 and 2.7 kg C ha−1; cumulative N2O emission were 0.06, 0.4 and0.8 kg N ha−1; while cumulative CO2 equivalent was 74, 279 and 459 kg CO2 ha−1 for Control, Split and Sin-gle treatments, respectively. Nitrous oxide contributed more to CO2-equivalent emission for the manuretreatments with the ratio of N2O/CH4 CO2 equivalents being 0.7, 1.9 and 5 for the Control, Split and Sin-gle treatments, respectively. Soil water and NO3

− content were the main determinants of both the type−

and quantity of GHG emitted, i.e., saturated soils with low NO3 produced highest CH4, while drier soils

with high NO3− produced greatest N2O. Variation in height of the water table near the soil surface likely

resulted in the high variability observed in CH4 emissions between replicates and years for individualtreatments. These results suggest that: (i) split application of hog slurry to grassland has the potential toreduce emission of GHGs, in particular N2O, compared to applying all manure in spring, (ii) grassland soils

er tabn in

with seasonally high watwith hog slurry applicatio

. Introduction

In order to increase pasture productivity, many producers fer-ilize pastures with animal manure. This is especially true for

rass-based pastures, as there are no legumes to replenish lostitrogen (N) from the system (Bolan et al., 2004). In south-easternanitoba, some beef cattle pastures are fertilized with hog slurry

also called liquid hog manure). Unfortunately, manure applica-

∗ Corresponding author. Tel.: +1 204 474 7827; fax: +1 204 474 7642.E-mail address: tenutam@cc.umanitoba.ca (M. Tenuta).

1 Hytek Ltd., La Broquerie, MB, Canada R0A 0W0.

167-8809/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.agee.2010.03.014

les can be significant sources of CH4, and (iii) that CH4 emission increasesthis soil.

© 2010 Elsevier B.V. All rights reserved.

tion to grassland has the potential of increasing nitrous oxide(N2O) emission through enhanced denitrification and nitrification(Chadwick et al., 2000; Ellis et al., 1998; Granli and Bockman,1994). In addition, N in the manure has the potential of decreasingsoil methane (CH4) consumption, and the labile carbon (C) in themanure may stimulate CH4 production (Chadwick et al., 2000; Elliset al., 1998; Lessard et al., 1997). However, agricultural soils otherthan those for rice production are considered sinks for methane

because being aerobic is important to sustain crop growth.

Nitrous oxide and CH4 are potent greenhouse gases (GHG) impli-cated in global warming (IPCC, 2007), an important managementgoal to improve the sustainability of manure application to grass-land will be to decrease GHG emissions. An effective N2O abatement

3 tems a

swmtifdmtkttcsftbatNsamtafl

eit1s2ts2stappadfstt

tgmfta

2

2

Mtcim

6 M. Tenuta et al. / Agriculture, Ecosys

trategy would be to time manure application when it coincidesith plant uptake of N (Chadwick, 1997). Moreover, the environ-ental and plant factors that influence soil N2O production (soil

emperature, soil water content and crop growth) often change dur-ng the year (Rochette et al., 2004). In Manitoba, Canada, large hogarms (>300 animal units) are prohibited from applying manureuring the winter. Consequently, it is common practice to applyanure to grasslands once during the growing season, either in

he spring, summer or fall. Yet, in western Canada there is a lack ofnowledge regarding GHG emissions after application of hog slurryo grassland, and even less is known about hog manure appliedo coarse-textured soils prone to both dry and wet conditions. Inentral Canada (Quebec), Rochette et al. (2004) reported N2O emis-ions amounting to 1.74% and 2.7% of total hog slurry-applied Nrom single fall and spring applications, respectively. The poten-ial to decrease GHG emission from manure-fertilized grasslandsy applying manure at two different times of the year (i.e., splitpplication) has not been investigated. The use of split applicationhat provides the same total applied N has the potential to reduce2O emission compared to a single heavy application. This practice

hould reduce the possibility of a large flush of ammonium (NH4+)

nd nitrate (NO3−) in the soil. The application of manure in the fall

ay also reduce N2O emission, as soil conditions are cooler duringhis period. Cool soil conditions reduce the rate of both nitrificationnd denitrification. Christensen (1983) showed that N2O emissionrom manured grasslands were influenced by temperature in thatower temperatures in the fall corresponded to lower N2O emission.

Soil water content influences the type and quantity of GHGmitted from the soil. Generally, higher soil moisture (up to approx-mately 60% water-filled pore space) increases N2O emission dueo enhanced nitrification and denitrification (Granli and Bockman,994). Further, very wet conditions can lead to anaerobic conditionsuitable for methanogenesis and CH4 production (Dunmola et al.,010). Variation in soil water conditions in a field is often relatedo topography, with lower-slope positions generally having higheroil water contents than higher-slope positions (Dunmola et al.,010). This can be due to collection of run-off water in the lower-lope positions, and the fact that water tables are generally closero the soil surface in this same position. Agricultural soils are gener-lly considered to be sinks for CH4 (Gregorich et al., 2005); however,oorly drained portions of fields (e.g., landscape depressions) areossible sources of CH4 during wet times of the year (Dunmola etl., 2010). To date, coarse-textured soils with a high water tableuring snow-melt and after heavy rainfall have not been examinedor CH4 and N2O emission. Since the type and quantity of GHG emis-ion is highly dependent on soil moisture conditions, it is importanto examine the influence of soil moisture gradient in determininghe pattern of GHG emission from such soils.

The objectives of this study, therefore, were to: (i) evaluatehe magnitude of CH4 and N2O emission from a coarse-textured,rassland soil having high spatial and temporal variability in soiloisture content and receiving a single spring or split (spring and

all) applications of hog slurry, and (ii) evaluate the impact of mois-ure gradient on GHG emission after application of hog slurry alongtransect of wet to dry soil.

. Materials and methods

.1. Site location and description

The University of Manitoba La Broquerie Pasture and Manure

anagement Project site, a 32-ha forage field located near the

own of La Broquerie, Manitoba, was used in the current study. Theoarse-textured soil at the site is classified as Class 3 m accord-ng to the Canada Land Inventory (CLI) Classification, which is

arginal for annual crop production due to low summer soil mois-

nd Environment 138 (2010) 35–43

ture (Hopkins, 1985). The soil series present are Berlo loamy finesand (70%) and Kergwenan loamy sand to gravel (30%) with the for-mer being a Gleyed Dark Gray Luvisol (FAO Gleyed Luvisol) and thelatter a Dark Gray Chernozem (FAO Greyzem) in the Canadian Sys-tem of Soil Classification (Hopkins, 1985). The topography was level(<2% slope). The forage was a mixture of grasses (Agropyron repens,Poa pratensis, Phleum pratense, Dactylis glomerata), legumes (Med-icago sativa, Lotus corniculatus, Trifolium spp.) and forbs (Wilson etal., 2010).

The field had not been fertilized since 2000, previous fertil-ization is uncertain. Soil properties (0–30 cm stone-free fraction)prior to start of the experiment (fall 2003) were pH (1:1 soil:water)7.9, electrical conductivity (1:1 soil:water) 0.1 mmhos cm−1, bulkdensity 1.59 Mg m−3, total organic carbon 13.0 g kg−1, calcium car-bonate equiv. 20.0 g kg−1, total nitrogen 1.0 g kg−1, extractableammonium-N 2.0 mg kg−1, nitrate-N 1.7 mg kg−1, sodium bicar-bonate extractable-P 10.8 mg kg−1, and stones (>2 mm) 28.3% oftotal soil mass. Drainage is very rapid and downward except whenthe water table is near the soil surface which occurs sometimes inspring following melt of a deep snowpack and less frequently insummer following successive days of heavy rain.

2.2. Experimental design and treatments

The experimental design was a factorial with three treat-ments and two replicates. The treatments were: (i) zeromanure (Control); (ii) hog slurry applied as a split applica-tion in the fall and in the spring (Split), each at a rate of72 ± 8 kg plant available N ha−1, and (iii) hog slurry applied eachspring at a rate of 148 ± 20 kg available N ha−1 (Single). The site area(32 ha) was divided into twelve paddocks, six of which were usedfor grazing and six were used for haying of the grass forage. The pad-docks used for haying were smaller, being 1.2 ha in size, whereasthe grazed paddocks were 8 ha for without manure and 4 ha for themanure treatments.

The hog slurry was obtained from the primary lagoon of aseries of three earthen manure lagoons of feeder barn oper-ations and had an average pH of 7.0 ± 0.3 and a dry mattercontent of 6.4 ± 3.3 g kg−1 and contained 0.5 ± 0.1% total N (freshweight), 0.3 ± 0.04% NH3-N (fresh weight), 1207 ± 637 mg P L−1,and 2142 ± 143 mg K L−1 over the study period. The slurry was sur-face applied by drag lines in fall 2003 and by splash-plate tankerin 2004 through 2006. Application rates were based on plant avail-able N content assuming a 25% volatilisation loss of ammonia N;the remaining ammonia N being all available and availability of25% of added organic-N in year of application (Prairie Provinces’Committee on Livestock Development and Manure Management,2006). The current study was part of a larger study that also evalu-ated forage yield and quality, cattle performance, and enteric CH4emissions (Wilson et al., 2010).

2.3. GHG measurements and analysis

Emission of greenhouse gases (N2O and CH4) and soil respiration(dark-chamber CO2 emission) were measured using vented, two-piece (collars and lids), polyvinyl chloride (PVC), static chambers(Hutchinson and Livingston, 1993). The collars measured 20.3 cmi.d. × 10 cm h. The aluminium insulated lids were 0.6 cm thick witha diameter of 23 cm. After manure application, six collars per plotwere inserted into the soil to a depth of approximately 3 cm. Collarswere left open to the atmosphere for the duration of the experi-

ment, except during forage harvesting, when they were removed.During gas sampling, lids were attached to the collars and 20 mLgas samples were collected through a rubber septum at regularintervals (0, 15, 30 and 45 min) using syringes (Becton-Dickinson,Franklin Lakes, NJ) and subsequently transferred to 12 mL pre-

M. Tenuta et al. / Agriculture, Ecosystems and Environment 138 (2010) 35–43 37

Table 1Mean monthly air temperature (temp) and total precipitation (precip) at the study site in 2004, 2005 and 2006 during the months of April through October and long-termaverage (1971–2000).a.

Month 2004 2005 2006 Long-term average

Mean temp (◦C) Total precip (mm) Mean temp (◦C) Total precip (mm) Mean temp (◦C) Total precip (mm) Mean temp (◦C) Total precip (mm)

April 3.8 27 7.4 21 8.9 12 4.1 29May 7.8 137 10.4 110 11.9 23 11.9 59June 14.4 90 17.6 232 17.4 50 16.6 95July 18.2 85 19.9 68 21.3 42 19.1 80August 14.2 137 17.1 42 18.5 26 18.1 69September 15.1 89 14.4 19 12.8 94 12.1 60

, http

es(wu2esh(aa(LNoub

2

bagectdTwe6

2

lAaiamtwmft2tr

October 6.1 46 7.1 82

Mean 11.4 87 13.4 82

a Long-term (1971–2000) average data were obtained from Environment Canada

vacuated glass vials (Labco Exetainer, High Wycombe, UK). Gasamples were collected before noon to minimise the effect of highpeak) temperatures on gas emissions. Forage inside the collarsas clipped to approximately 3 cm before gas sampling to sim-late grazing, and to allow placement of lids on the collars. Two0 mL standard gas mixtures (N2O, CH4 and CO2) were placed intovacuated vials and handled in the same manner as the other gasamples to ensure handling and storage were consistent. Green-ouse gas concentrations were analysed using a gas chromatographGC) (Varian GP3800; Varian Canada, Mississauga, ON) fitted withn electron capture detector (ECD), flame ionization detector (FID),nd thermal conductivity detector (TCD) and automatic samplerCombi-PAL autosampler; CTC Analytics, Zwingen, Switzerland).aboratory prepared calibrants were prepared from dilution of pure2O, CH4 and CO2 gas (Welders Supplies, Winnipeg, MB). Analysisf a sample set was either repeated or the gas chromatograph col-mn reconditioned and calibration redone if check vials were offy more than 5% of the expected concentration.

.4. Transect study

Preliminary results in 2004 showed a strong relationshipetween soil moisture and GHG emissions. Consequently, in 2005transect study was conducted to determine how a soil moistureradient affects the type (N2O or CH4) and the amount of GHGsmitted following manure application to grassland. The study wasonducted on the Control and Single hayed plots of replicate 1 ashey were adjacent to each other and they had strong moisture gra-ients running from west (high moisture) to east (low moisture).wo parallel transects each with 30 chambers placed 9 m apart,ere established in the Control and Single plots. Greenhouse gas

missions was measured as previously described on 3 days; June 2,, and 13 (DOY 153, 157 and 164).

.5. Soil sampling and analysis

In the transect study, one soil core (5 cm i.d. × 5 cm h.) was col-ected 10 cm away from each collar position after gas sampling.ll other soil samples were collected weekly until the end of Junend after June, sampling was bi-weekly until the ground frozen late fall. Five soil samples were collected from a 2 m radiusrea around each collar position using a hand auger (2.5 cm i.d.)ixed and placed in a polyethylene bag. The soil samples were

hen stored on ice until transported to the laboratory, where theyere stored at −20 ◦C. Samples were then thawed and gravimetricoisture contents determined by drying 10 g sub-samples at 105 ◦C

or 24 h. The remainder of each sample was air-dried and passedhrough a 2 mm mesh screen. Sub-samples of 5 g were shaken with5 mL of 0.5 M K2SO4 for 30 min and the soil suspensions were cen-rifuged for 1.5 min at 1350 × g. A 15 mL aliquot of supernatant wasemoved, placed into scintillation vials and kept frozen until analy-

3.9 36 5.4 45

13.5 40 12.5 62

://www.climate.weatheroffice.ec.gc.ca/climate normals/stnselect e.html.

sis for NH4+, and NO3

− plus NO2- using a Technicon II Auto-analyser

(Technicon Instruments, Tarrytown, NY) following the method ofKeeney and Nelson (1982).

2.6. Meteorological and water table measurements

Rainfall at the site was monitored using a tipping bucket raingauge (Rain 110, Madgetech). During each gas sampling event, soiltemperature was measured at 2.5 cm beside each chamber and airtemperature was measured at 60 cm above ground using a Trace-able Longstem Thermometer (Fisher Scientific Canada, Nepean,ON). In addition, air temperature data were obtained from Stein-bach airport, located 12 km from the study site. Daily water tabledepth measurements were determined in a screened monitoringwell using a Telog WLS-31 data logger with pressure transducer(Telog Instruments Inc., Victor, NY).

2.7. Statistical analysis

Methane and N2O data as well as the combined CO2-equivalent(CO2-eq) emission of the two gases were subjected to analy-sis of variance (ANOVA) using Statistix 9 (Analytical Software,Tallahassee, FL). Differences among treatments were declared tobe significant at ˛ < 0.05. The CO2-eq emission was calculated usingglobal warming potential (GWP) factors (100 year mean) of 21 forCH4 and 310 for N2O from the Intergovernmental Panel on Cli-mate Change Second Assessment Report (as reported in IPCC, 2007).Equivalent CO2 emission is a useful, standardized metric for com-paring emission of different GHGs (IPCC, 2007). Data gaps betweengas sampling days were filled by linear interpolation (Pennock et al.,2006). Cumulative GHG emission was calculated by integrating thearithmetic mean of gas emission between sampling periods. Dueto high variability and violation of the normality and constant vari-ance assumptions, GHG data were log-transformed before analysis.Least square means/means were calculated and where appropri-ate, mean-separation was performed using Fisher’s least significantdifference (LSD) test. Spearman rank correlation analysis was per-formed to relate gas emissions to measured soil parameters usingdata in which both soil and gas samples were collected on the sameday. For the transect study, data collected on June 13 was used torelate GHG emissions to soil moisture.

3. Results and discussion

3.1. Meteorological conditions and water table levels

Mean monthly temperatures and total precipitation during thegrowing season (April through October) in 2004 through 2006 areshown in Table 1. Average air temperature was approximately 1 ◦Cbelow normal in 2004 and 1 ◦C above normal in 2005 and 2006.Meanwhile, growing season precipitation was 40% and 32% above

38 M. Tenuta et al. / Agriculture, Ecosystems and Environment 138 (2010) 35–43

F le moa el.

n2Mttnp(

3

7tdhCmtsHa

3

3

ciottCtgit22(ccgrcrZma6

ig. 1. Depth to water table (m) in 2004, 2005 and 2006 at the study site. Water tabmalfunctioning pressure transducer. The dashed line indicates the soil surface lev

ormal in 2004 and 2005, respectively, and 33% below normal in006. In the 2004 growing season, precipitation was greatest inay and August, while in 2005 it was greatest in June when 2.4

imes higher than average rainfall was received. In 2006, precipita-ion was below normal during all months. As a result of the belowormal precipitation in 2006, the water table was much lower com-ared to 2004 and 2005, which had comparable water table levelsFig. 1).

.2. Soil inorganic N status

Soil NH4+ levels in the manured treatments were highest (up to

6 mg N kg−1 dry soil) 1–3 weeks following slurry application andhereafter declined to Control levels of approximately 10 mg kg−1

ry soil (data not shown). Similar to NH4+, soil NO3

− levels wereigher (up to 60 mg N kg−1 dry soil) in the manured plots than in theontrol plots in which NO3

− concentrations remained at approxi-ately 5 mg N kg−1 dry soil. In general, soil NO3

− concentrations inhe manured plots increased as soil NH4

+ concentrations decreased,uggesting that nitrification was converting soil NH4

+ to NO3−.

owever, some of the NH4+ was probably taken up by the grass

nd also lost through ammonia volatilisation.

.3. CH4 and N2O daily and cumulative emissions

.3.1. MethaneMethane emissions were highly variable for within plots, repli-

ates and years for individual treatments. In general, CH4 emissionsncreased following hog slurry application reaching a maximumn day of the year (DOY) 156 in 2004 and DOY 194 in 2005 andhereafter declined (Fig. 2). Methane emissions from the manuredreatments (Split and Single) was much higher than those from theontrol treatment, particularly in 2004 and 2005. In 2004 and 2005,he Split treatment averaged 5.9 and 17 g C ha−1 d−1, while the Sin-le treatment averaged 6.6 and 11.6 g C ha−1 d−1, respectively. Its important to note that only one replicate mainly contributedo the emission of CH4 from the manure treatments in 2004 and005. The Control averaged 0.06 and 7.2 g C ha−1 d−1 in 2004 and005, respectively. In 2006, CH4 emissions from all treatmentsincluding the manured treatments) were negative indicating CH4onsumption (uptake), which was presumably caused by the drieronditions (Table 1). Emission from the Control, Split and Sin-le treatments were on average −1.0, −2.5 and −2.4 g C ha−1 d−1,espectively. An increase in CH4 emission soon after manure appli-ation, albeit of shorter duration, has also been observed by other

esearchers (Chadwick et al., 2000; Dittert et al., 2005). In Newealand, Sherlock et al. (2002) reported that CH4 emissions com-enced at a rate of 39 g C ha−1 d−1 immediately after hog slurry

pplication to a pasture plot and decreased to 10 g C ha−1 d−1 withinh, and then continued at a low rate for 7 d. In contrast to the

nitoring started on 20 February 2004 (DOY 51). The breaks in 2006 were caused by

short-duration CH4 emission measured in the above-mentionedstudies, the longer-lasting CH4 emission observed in the currentstudy indicate CH4 production by the soil rather than volatilisation(degassing) of dissolved CH4 from the slurry after application tosoil.

When averaged over the 3 years of the study, cumulative CH4emission from the Split and Single treatments were similar to eachother and significantly (P ≤ 0.01) higher than those from the Control(Table 2). On average, cumulative CH4 emissions from the Con-trol, Split and Single treatments were 1.6, 3.5 and 2.7 kg C ha−1,respectively. As such, emissions from Split and Single treatmentswere 1.9 kg C ha−1 and 1.1 kg C ha−1 greater than that of the Con-trol, respectively. Sherlock et al. (2002) reported that a hog slurrytreated plot produced a net CH4 emission of 1.1 kg CH4-C ha−1 after90 d of gas measurement. Hernandez-Ramirez et al. (2009) foundthat manured soils were net CH4 emitters of 0.16–0.33 kg CH4-C ha−1 yr−1. Soils are generally regarded as a sink for CH4; however,when fertilized with N, the consumption rates can decrease (vanAmstel and Swart, 1994; Lessard et al., 1997). In addition, manure isa source of readily available C, and when applied it has the potentialto increase the availability of soil C; an increase in the availability ofsoil C can enhance CH4 emission from a saturated soil environment(Sylvia et al., 1998), with the latter most likely operative in thisstudy. Manure application may also cause an increase in soil CH4emission by reducing the redox potential of the soil or by increasingO2 consumption by heterotrophic organisms (Lessard et al., 1997)and plant roots. The high CH4 emissions in 2004 and 2005 couldalso have been a result of the high water table (Fig. 2) during these2 years (Dunmola et al., 2010; Windsor et al., 1992; Heyer et al.,2002). Methane produced below the water table forms gas bub-bles under the water table, and once the water table drops, CH4escapes via open soil pores (Heyer et al., 2002). The results of thecurrent study clearly indicate that grassland soils with a water tablenear the soil surface can be a significant source of CH4 without hogslurry application and even a greater source having received hogslurry. This is supported by the fact that in 2004 and 2005, bothwet years with a high water table, cumulative CH4 emissions werepositive, while in 2006, a dry year with a low water table, cumu-lative CH4 emissions from all treatments were negative, indicatingthat the soil was a sink for CH4 during that year. According to vanden Pol-van Dasselaar et al. (1998), a rise in soil moisture contentmay decrease net atmospheric CH4 uptake, due to increased CH4production as a result of a higher proportion of anaerobic sites.

3.3.2. Nitrous oxide

Similar to CH4, N2O emissions was highly variable both within

plots and between replicates. Nitrous oxide emissions in the Splitand Single treatments, increased following hog slurry application,reached a maximum a few days after application, and then declinedto levels similar to the Control. This is in agreement with previous

M. Tenuta et al. / Agriculture, Ecosystems and Environment 138 (2010) 35–43 39

F treat( anure

sh2o

TCg

f

ig. 2. Mean daily CH4 emissions (g C ha−1 d−1) for Control, Split and Single manuresome bars are smaller than symbols). Hanging bars on Split and Single represent m

tudies, which reported that N2O emissions increased followingog slurry application (Chadwick et al., 2000; Mkhabela et al., 2008,009; Sherlock et al., 2002; Smith et al., 2008). In all the 3 yearsf the study, emissions from the Control were on average lower

able 2umulative emissions of nitrous oxide, methane and their combined carbon dioxide equirassland.

Treatment 2004 2005

Rep 1 Rep 2 Rep 1

Methane (g C ha−1)Control −62 52 9896Split −40 1038 19,319Single 1743 −221 16,452

Nitrous oxide (g N ha−1)Control −36 65 156Split 135 513 490Single 589 1663 1158

Carbon dioxide equivalent (kg CO2 ha−1)c

Control −19 33 353Split 65 279 780Single 336 804 1025

a Means followed by the same letter for the same gas are not significantly different at Pb Difference between manured and Control treatments.c Carbon dioxide equivalent (kg CO2 ha−1) was calculated by converting g N-N2O or C-C

actors (100 years mean) of 310 or 21 for N2O or CH4, respectively, and summing them.

ments in 2004 through 2006. Vertical bars represent +1 standard error of the meanapplication days on replicate 1 (open bars) and replicate 2 (closed bars).

than those from both the Split and Single treatments. However,emissions from the Single treatment were higher than those fromthe Split, particularly in 2004 and 2005. Emissions from the Con-trol were on average 0.13, 0.61, and 0.25 g N ha−1 d−1 in 2004, 2005

valent from each plot in 2004, 2005 and 2006 following application of hog slurry to

2006 Meana SEM Net lossb

Rep 2 Rep 1 Rep 2

P < 0.016 −227 −169 1583b 1148 –

1374 −479 −275 3490a 2322 1907−745 −300 −479 2742a 2593 1159

P < 0.001102 32 42 60c 13 –695 264 135 372b 68 312853 230 218 785a 237 725

P < 0.00150 9 16 74b 33 –

377 115 58 279a 80 205395 104 93 459a 131 385

≤ 0.05 using the LSD test.

H4 ha−1 to respective kg N2O or CH4 and then applying Global Warming Potential

40 M. Tenuta et al. / Agriculture, Ecosystems and Environment 138 (2010) 35–43

F treat( anure

atttwt

s(ta7tserora(ortS2

ig. 3. Mean daily N2O emissions (g N ha−1 d−1) for Control, Split and Single manuresome bars are smaller than symbols). Hanging bars on Split and Single represent m

nd 2006, respectively. At the same time, emissions from the Splitreatment was 2.36, 2.91 and 1.24 g N ha−1 d−1, while those fromhe Single treatment were 7.63, 5.43 and 1.48 g N ha−1 d−1. Dueo the drier conditions in 2006 (Table 1), average N2O emissionsere much lower than in 2004 and 2005, especially in the manured

reatments (Fig. 3).Averaged over the 3 years of the study, cumulative N2O emis-

ions were significantly different (P < 0.001) among the treatmentsTable 2). Total N2O emissions from the Single treatment werehe highest at 785 g N ha−1, followed by the Split at 372 g N ha−1

nd then the Control at 60 g N ha−1, giving net N2O emissions of25 and 312 g N ha−1 for the Single and Split treatments, respec-ively. The net emissions accounted for 0.51% and 0.29% of totallurry N applied for Single and Split treatments, respectively. Inxperiments that lasted 21 days, Mkhabela et al. (2008, 2009)ecorded cumulative N2O emission ranging from 0.003% to 1.52%f total surface-applied hog slurry N, while Smith et al. (2008)ecorded N2O emission ranging from 0.0008% to 0.23% of surface-pplied hog slurry N over the same period. Similarly, Petersen1999) reported cumulative N2O emission between 0.14 and 0.64%

f total N applied over a 6–8 weeks measurement period. Otheresearchers, however, have reported higher cumulative emissionshan those observed in our study. Over a 90-d measurement period,herlock et al. (2002) recorded total N2O emission equivalent to.1% of hog slurry-applied N. Similarly, Chadwick et al. (2000)

ments in 2004 through 2006. Vertical bars represent +1 standard error of the meanapplication days on replicate 1 (open bars) and replicate 2 (closed bars).

recorded cumulative N2O losses ranging from 0.12 to 0.97% of totalN applied as hog or dairy slurries during experiments that lasted24 d, while Rochette et al. (2004) recorded total N2O losses amount-ing to 1.7% and 2.7% of total hog slurry-applied N in the fall andspring, respectively. Nonetheless, results of the current study sug-gest that N2O emissions can be minimised significantly by adoptingsplit application of manure where half of the required manure isapplied in fall and the other half in spring. In the USA, Hernandez-Ramirez et al. (2009), reported that fall manure application reducedN2O emissions compared to spring manure application. Rochette etal. (2004) reported similar findings in Quebec and attributed thisto cooler and wet conditions in the fall, which reduced nitrifica-tion and subsequently reduced denitrification and N2O emission.Cool soil temperatures reduce both nitrification and denitrifica-tion activity (Haynes, 1986; Aulakh et al., 1992) and also reduceN2O emission (Christensen, 1983). A concern with fall applicationof hog slurry is possible increased indirect N2O emissions fromammonia volatilisation and over-winter leaching of NO3

−. How-ever, Wilson et al. (2010) reported similar performance for forageproductivity at the site between the Split and Single manure treat-

ments that does not indicate greater loss of applied hog slurry Nwith Split treatment. Standing forage biomass, crude protein con-centration of forage, dry matter intake by grazing animals and crudeprotein intake to be similar for the manure treatments applied topaddocks having backgrounding steers. Rather, animal productiv-

M. Tenuta et al. / Agriculture, Ecosystems and Environment 138 (2010) 35–43 41

Table 3Spearman rank correlation coefficient (r) values for the relationship between greenhouse gas (GHG) emissions and measured soil parameters.

CH4 N2O CO2 NO3− NH4

+ Soil moisture

N2O −0.03NS

CO2 0.05NS

0.41(0.0001)

NO3− −0.24

(0.0001)0.42(0.0001)

0.27(0.0001)

NH4+ −0.03

NS0.16(0.0001)

0.10(0.0004)

0.38(0.0001)

Soil moisture 0.45(0.0001)

−0.14(0.0001)

−0.04NS

−0.32(0.0001)

−0.15(0.0001)

01)

V

iwhgaNmb

ssW

Ft

Soil temperature 0.05NS

0.16(0.0001)

0.64(0.00

alues in parentheses are P-values. NS: not significant (P > 0.05).

ty was increased with Split rather than Single manure treatmentith the number of grazing days (sum of number of steers grazinga−1 d−1 for a 84 day grazing season) being greater for Split (340razing days) than Full (308 grazing days) treatment. Other studiest the site are currently examining the occurrence of leaching ofO3

− and the site. Preliminary examination of the results indicatesinimal leaching with either manure treatment and no difference

etween Split and Single Manure treatments (unpublished).Our monitoring of N2O emissions began after thawing of soil in

pring. It is unlikely that substantial emission were missed, thusignificantly affecting the estimates of cumulative N2O emission.

agner-Riddle and Thurtell (1998) did not observe N2O thaw emis-

ig. 4. Mean daily N2O emissions (g N ha−1 d−1) and CH4 emissions (g C ha−1 d−1) for the tro wet (right).

0.17(0.0001)

−0.10(0.0004)

−0.21(0.0001)

sions for permanent grass (P. pratensis) as NO3− concentrations

were less than 2.5 mg N kg−1. In our study, the concentrations ofNO3

− post-thaw to a 5 cm depth were similar for manure and Con-trol treatments with all treatments being less than 2.5 mg N kg−1

(data not presented).When N2O and CH4 emissions were combined to estimate a

CO2-eq emission, the Split and Single treatments averaged acrossthe 3 years of the study, were statistically similar but significantly

higher (P < 0.001) than the Control (Table 2). Nitrous oxide wasthe more important of the two GHGs in that lower N2O emissionresulted in lower levels of CO2-eq emissions. Averaged over the3 years of the study, N2O contributed approximately 90% of the

ansect study. Chambers (30) are arranged along a moisture gradient from dry (left)

42 M. Tenuta et al. / Agriculture, Ecosystems and Environment 138 (2010) 35–43

mber

tefi

3e

wc(lmsttCmrwhelotiN1

3

eboNo

Fig. 5. Gravimetric moisture content and soil NO3− for the 30 cha

otal CO2-eq emissions produced by the manured treatments. Thismphasises the importance of reducing N2O emissions followingeld-application of manure.

.4. Relationship between measured soil variables and gasmissions

Correlations between measured soil variables and gas emissionsere weak, as indicated by the low Spearman rank correlation

oefficient (r) values; however, some were statistically significantTable 3). Nitrous oxide emission was strongly positively corre-ated to soil NO3

− concentration and negatively correlated to soiloisture. Negative correlation for soil moisture and N2O emis-

ions indicates that either the nitrification process as a source ofhe gas was inhibited at higher moisture contents and/or deni-rification went to completion with the reduction of N2O to N2.onversely, CH4 emissions was strongly positively correlated to soiloisture and negatively correlated to soil NO3

− concentration. Thisesult indicates that higher soil NO3

− favoured N2O production,hile higher soil moisture favoured CH4 production. Followingog slurry application to a pasture field in New Zealand, Sherlockt al. (2002) observed that N2O emissions were positively corre-ated to soil NO3

− and concluded that most of the N2O emittedriginated from NO3

−. In addition, N2O emissions were also posi-ively correlated to soil temperature and soil respiration, probablyndicating an increase in microbial (dinitrifiers) activity. Generally

2O emissions increase with temperature (Granli and Bockman,994).

.5. Transect study

A gradient in soil moisture had an impact on both CH4 and N2O

missions during all sampling dates. A distinct pattern in the distri-ution of the two gases along transects was evident. The majorityf N2O was produced mainly in the drier areas with higher soilO3

−, while the majority of CH4 was produced in the wetter areasf transects (Figs. 4 and 5). This pattern was observed in both the

positions of the transect study on 2 June 2005 and 13 June 2005.

Single and Control transects. Correlation analysis showed that CH4emissions were positively correlated to soil moisture (R2 = 0.40,P < 0.0001), supporting the above observation. Meanwhile, N2Oemissions generally increased as soil moisture increased up toapproximately 40–50% gravimetic moisture and above declined toslightly negative values (data not shown). Our results are consis-tent with Dunmola et al. (2010), who found that up-slope cultivatedareas emitted only N2O, while depression areas of higher mois-ture content emitted both N2O and CH4, and while wetter riparianzones emitted only CH4. Methanogens are highly sensitive to O2concentration, so that populations only thrive in areas that arewet (anaerobic) most of the time (Topp and Pattey, 1997). On thecontrary, Ambus (1998), Reiners et al. (1998), and Velthof et al.(1996, 2000) recorded larger N2O emissions at lower-slope posi-tions than at higher-slope positions. The lower N2O emissions fromthe saturated (anaerobic) areas in the current study was likelydue to inhibition of nitrification and/or complete reduction of N2Oto N2 during denitrification (Arah and Smith, 1990; Weier et al.,1993; Sylvia et al., 1998). This is consistent with the coincidenceof higher NO3

− concentrations and N2O emissions for the driestthan the wettest positions of the transect. Results of this transectstudy showed a gradient in soil moisture across study plots couldexplain the variation in emissions of N2O and CH4. Further, theresults imply that perennial grass systems when saturated due topoor drainage and or high water table can be a source and not asink of CH4, especially when manured.

4. Conclusions

Application of hog slurry increased CH4 and N2O emissions, aswell as, their combined CO2-equivalent emission. Compared to Sin-gle application in spring, Split application of manure decreased

GHG emissions, in particular N2O. This result implies that GHGemissions can be reduced by adopting split application of manure(applying half of the required manure during the fall and the otherhalf during spring), compared to applying all manure in spring. Soilmoisture and NO3

− concentration were the main determinants of

tems a

blwhothopmsCtwbcm

A

gISCPSsAApEpNf

R

A

A

A

A

B

C

C

C

D

D

E

M. Tenuta et al. / Agriculture, Ecosys

oth the type and quantity of GHG emitted; saturated soils withow NO3

− produced the greatest CH4 emissions, while drier soilsith high NO3

− produced the largest N2O emissions. This studyas shown that seasonally saturated grassland soils can be a sourcef CH4 to the atmosphere. When manured, perennial grass fieldshat are partially saturated due to localized poor drainage and/origh water table can further be a significant source and not a sinkf CH4. However, CH4 emissions were highly variable for withinlots, replicates and years for individual treatments because of soiloisture. The relative importance of N2O and CH4 to GHG emis-

ions was dependent upon treatment with the N2O/CH4 ratio ofO2 equivalents being 0.7, 1.9 and 5 for the Control, Split and Singlereatments, respectively. The findings of this study are importanthen considering GHG budgets from agricultural systems as grass-

ased pasture and hay systems situated in poorly drained areasomprise a considerable portion of agricultural land in Canada andany other countries.

cknowledgements

This study was funded by: Canada’s Greenhouse Gas Miti-ation Fund, Manitoba Conservation’s Sustainable Developmentnnovations Fund, the Canada Research Chair Program in Appliedoil Ecology (MT), the Natural Sciences and Engineering Researchouncil (NSERC) of Canada Discovery Grant Program (MT), NSERCost-graduate Scholarship Program (DT), the Manitoba Graduatecholarship Program (LC), Manitoba Pork Council, Manitoba Live-tock Manure Management Initiative, Manitoba Cattle Producersssociation, Beef Council Research of Canada and Manitoba Ruraldaptation Council. In-kind contribution of field equipment wasrovided by Hytek Ltd., Palmlite Electric Motors, Southeast Farmquipment, and Enns Brothers Equipment. The technical assistancerovided by Trevor Fraser, Tobin Harrison, Steven Laurie, Emilieovara, Peter Petrash, Jordan Ramm, and Siobhan Stewart is grate-

ully appreciated.

eferences

mbus, P., 1998. Nitrous oxide production by denitrification and nitrification intemperate forest, grassland and agricultural soils. Eur. J. Soil Sci. 49, 495–502.

nalytical Software, 2008. Statistix 9 User’s Manual. Analytical Software, Tallahas-see, FL.

rah, J.R., Smith, K.A., 1990. Factors influencing the fraction of the gaseous productsof soil denitrification evolved to the atmosphere as nitrous oxide. In: Bouwman,A.F. (Ed.), Soils and the Greenhouse Effect. John Wiley and Sons Ltd., Hoboken,NJ, pp. 475–480.

ulakh, M.S., Doran, J.W., Mosier, A.R., 1992. Soil denitrification – significance, mea-surement, and effects on management. In: Stewart, B.A. (Ed.), Advances in SoilScience. Springer-Verlag, New York, NY, pp. 1–57.

olan, N.S., Saggar, S., Luo, J., Bhandral, R., Singh, J., 2004. Gaseous emission ofnitrogen from grazed pastures: processes, measurements and modelling, envi-ronmental implications, and mitigation. Adv. Agron. 84, 37–120.

hadwick, D.R., 1997. Nitrous oxide and ammonia emission from grassland follow-ing applications of slurry: potential abatement practices. In: Jarvis, S.C., Pain, B.F.(Eds.), Gaseous Nitrogen Emission from Grassland. CAB International, Walling-ford, UK, pp. 257–264.

hadwick, D.R., Pain, B.F., Brookman, S.K.E., 2000. Nitrous oxide and methane emis-sion following applications of animal manures to grassland. J. Environ. Qual. 29,277–287.

hristensen, S., 1983. Nitrous oxide emission from a soil under permanent grass:seasonal and diurnal fluctuations as influenced by manuring and fertilization.Soil Biol. Biochem. 15, 531–536.

ittert, K., Lampe, C., Gasche, R., Butterbach-Bahl, K., Wachendorf, M., Papen, H.,Sattelmacher, B., Taube, F., 2005. Short-term effects of single or combinedapplication of mineral N fertilizer and cattle slurry on the fluxes of radia-tively active trace gases from grassland soil. Soil Biol. Biochem. 37, 1664–1674.

unmola, A.S., Tenuta, M., Moulin, A.P., Yapa, P., Lobb, D.A., 2010. Pattern of green-house gas emission from a Prairie Pothole agricultural landscape in Manitoba,Canada. Can. J. Soil Sci. (in press).

llis, S., Yamulki, S., Dixon, E., Harrison, R., Jarvis, S.C., 1998. Denitrification and N2Oemission from a UK pasture soil following the early spring application of cattleslurry and mineral fertilizer. Plant Soil 202, 15–25.

nd Environment 138 (2010) 35–43 43

Granli, T., Bockman, O.C., 1994. Nitrogen oxide from agriculture. Norway J. Agri. Sci.12, 7–127.

Gregorich, E.G., Rochette, P., VandenBygaart, A.J., Angers, D.A., 2005. Greenhouse gascontributions of agricultural soils and potential mitigation practices in EasternCanada. Soil Till. Res. 83, 53–72.

Haynes, R.J., 1986. Nitrification. In: Kozlowski, T.T. (Ed.), Mineral Nitrogen in thePlant–Soil System. Academic Press, Inc., Orlando, FL, pp. 127–165.

Hernandez-Ramirez, G., Brouder, S.M., Smith, D.R., Van Scoyoc, G.E., 2009. Green-house gas fluxes in an Eastern corn belt soil: weather, nitrogen source, androtation. J. Environ. Qual. 38, 841–854.

Heyer, J., Berger, U., Kuzin, I.L., Yakovlev, O.N., 2002. Methane emission from dif-ferent ecosystem structures of the subarctic tundra in Western Siberia duringmidsummer and during the thawing period. Tellus 54B, 231–249.

Hopkins, L.A., 1985. Soils of the Rural Municipalities of Ste Anne and la Broquerie,and Part of the Local Government District of Stuartburn. Report No. D49. Canada-Manitoba Soil Survey. Winnipeg, MB.

Hutchinson, G.L., Livingston, G.P., 1993. Use of chamber systems to measure tracegas fluxes. In: Harper, L.A., et al. (Eds.), Agro-Ecosystem Effect on RadiativelyImportant Trace Gases and Climate Change. Agronomy Society of America Spec.Publ, Madison, WI, pp. 63–78.

Inter-governmental Panel on Climate Change (IPCC), 2007. Climate Change 2007:Synthesis Report. Contribution of Working Groups I, II and III to the FourthAssessment Report of the IPCC, Geneva, Switzerland, 104 pp.

Keeney, D.R., D.W. Nelson, 1982. Nitrogen-inorganic forms. In Methods of soil anal-ysis, chemical and microbial processes. A.L. Page (ed.). Agron. Series no. 9. SoilScience Society of America, Madison, WI, pp. 643–709.

Lessard, R., Rochette, P., Gregorich, E.G., Desjardins, R.L., Pattey, E., 1997. CH4 fluxesfrom a soil amended with dairy cattle manure and ammonium nitrate. Can. J.Soil Sci. 77, 179–186.

Mkhabela, M.S., Gordon, R., Burton, D., Madani, A., Hart, W., 2008. Nitrous oxideproduction and soil mineral nitrogen status following application of hog slurryand inorganic fertilisers to acidic grassland soils. Can. J. Soil Sci. 88, 145–151.

Mkhabela, M.S., Gordon, R., Burton, D., Smith, E., Madani, A., 2009. The impact ofmanagement practices and meteorological conditions on ammonia and nitrousoxide emission following application of hog slurry to forage grass in Nova Scotia.Agric. Ecosyst. Environ. 130, 41–49.

Pennock, D.J., Yates, T.T., Braidek, J.T., 2006. Towards optimum sampling for regional-scale N2O emission monitoring in Canada. Can. J. Soil Sci. 86, 441–450.

Petersen, S.O., 1999. Nitrous oxide emissions from manure and in- organic fertilizersapplied to spring barley. J. Environ. Qual. 28, 1610–1618.

Prairie Provinces’ Committee on Livestock Development and Manure Management,2006. Tri-provincial Manure Application and Use Guidelines, Manitoba Edition.Alberta, Food and Rural Development, Saskatchewan Agriculture, and RuralRevitalization, and Manitoba Agriculture, Food and Rural Initiatives. Availableonline http://www.gov.mb.ca/agriculture/livestock/beef/pdf/baa08s01a.pdf(accessed March 17, 2010).

Reiners, W.A., Keller, M., Gerow, K.G., 1998. Estimating rainy season nitrous oxideand methane fluxes across forest and pasture landscapes in Costa Rica. WaterAir Soil Pollut. 105, 117–130.

Rochette, P., Angers, D.A., Chantigny, M.H., Bertrand, N., Cote, D., 2004. Carbon diox-ide and nitrous oxide emission following fall and spring applications of pig slurryto an agricultural soil. Soil Sci. Soc. Am. J. 68, 1410–1420.

Sherlock, R.R., Sommer, S.G., Khan, R.Z., Wood, W.C., Guertal, F.E., Freney, J.R., Daw-son, C.O., Cameron, C.K., 2002. Ammonia, methane and nitrous oxide from pigslurry applied to a pasture in New Zealand. J. Environ. Qual. 31, 1491–1501.

Smith, E., Gordon, R., Bourque, C., Campbell, A., 2008. Management strategiesto simultaneously reduce ammonia, nitrous oxide and odour emission fromsurface-applied swine manure. Can. J. Soil Sci. 87, 469–477.

Sylvia, D.M., Fuhrmann, J.J., Hartel, P.G., Zuberer, D.A., 1998. Principles and Applica-tions of Soil Microbiology. Prentice Hall Publishers, Upper Saddle River, NJ, 293pp.

Topp, E., Pattey, E., 1997. Soils as sources and sinks for atmospheric methane. Can.J. Soil Sci. 77, 167–178.

van Amstel, A.R., Swart, R.J., 1994. Methane and nitrous oxide emission: an intro-duction. Fert. Res. 37, 213–225.

van den Pol-van Dasselaar, A., van Beusichem, M.L., Oenema, O., 1998. Effects of soilmoisture content and temperature on methane uptake by grasslands on sandysoils. Plant Soil 204, 213–222.

Velthof, G.L., Jarvis, S.C., Stein, A., Allen, A.G., Oenema, O., 1996. Spatial variabilityof nitrous oxide fluxes in mown and grazed grasslands on a poorly drained claysoil. Soil Biol. Biochem. 28, 1215–1225.

Velthof, G.L., van Groenigen, G., Gebauer, G., Pietrzak, S., Jarvis, S.C., Pinto, M., Corre,W., Oenema, O., 2000. Temporal stability of spatial patterns of nitrous oxidefluxes from sloping grassland. J. Environ. Qual. 29, 1397–1407.

Wagner-Riddle, C., Thurtell, G.W., 1998. Nitrous oxide emission from agriculturalfields during winter and spring thaw as affected by management practices. Nutr.Cycl. Agroecosyst. 52, 151–163.

Weier, K.L., Doran, J.W., Power, J.F., Walters, D.T., 1993. Denitrification and the dini-trogen/nitrous oxide ratio as affected by soil water, available carbon and nitrate.Soil Sci. Soc. Am. J. 57, 66–72.

Wilson, C., Undi, M., Tenuta, M., Wittenberg, K.M., Flaten, D., Krause, D.O., Entz, M.H.,Holley, R., Ominski, K.H., 2010. Pasture productivity, cattle productivity andmetabolic status following fertilization of a grassland with liquid hog manure:a three year study. Can. J. Anim. Sci. (in press).

Windsor, J., Moore, T.R., Roulet, N.T., 1992. Episodic fluxes of methane from subarcticfens. Can. J. Soil Sci. 72, 441–452.