p2J3

Soil & Tillage Research 101 (2008) 97100

2

Drainage class

Soil aeration

ten

ed b

rize

o-til

nven

ordi

n. The summary showed that no-till generally increased N2O emissions in

poorly-aerated soils but was neutral in soils with good and medium aeration. On average, soil N2O

emissions under no-till were 0.06 kg N ha1 lower, 0.12 kg N ha1 higher and 2.00 kg N ha1 higher than

Contents lists availab

Soil & Tillage

.e1. Introduction

No-till has been proposed to increase stocks of soil organicmatter and mitigate greenhouse gas emissions (Gregorich et al.,2005). However, denitrication is usually greater in soils under no-till than under conventional tillage as a result of higher bulkdensity and water content (Doran, 1980; Groffman, 1984; Arahet al., 1991; Palma et al., 1997). Denitrication is often the mainsource of N2O in agricultural soils and the benets of the adoptionof no-till on atmospheric CO2 sequestration could be offset byincreased N2O emissions (Six et al., 2002).

The impact of no-till on soil N2O emission is variable. Higher(Ball et al., 1999; Rochette et al., 2008) and lower (Chatskikh andOlesen, 2007; Gregorich et al., 2008) N2ON losses have beenmeasured in no-till compared to tilled soils. Predictions bymathematical models also indicated that the inuence of no-tillon N2O emissions could be either positive (Mummey et al., 1998; Liet al., 2005) or negative (Li et al., 1996). Six et al. (2004) concludedthat soil N2O emissions are increased under no-till but that thisimpact decreases with time. However, an explanation of the high

inter-site variability of the inuence of no-till on soil N2Oemissions is still lacking. In this study, we hypothesized thatadoption of no-till only increases N2O emissions in poorly-aeratedsoils.

2. Materials and methods

We summarized reports of eld N2O emissions from 25 studies(approximately 45 site-years of data) with same-site comparisonsof no-till and tilled soils. Soil aeration is closely related to watercontent (Linn and Doran, 1984). Therefore, each situation wasclassied under either good, medium or poor soil aerationclass based on soil drainage and precipitation during the growingseason. Soil aeration was estimated to be poor if drainage waspoor irrespective of precipitation. When not present in the citeddocument, information on drainage class for a given soil series wasobtained from soil survey publications. Situations with poordrainage and aeration were also mostly characterised by ne-textured soils under cool humid climates (Table 1). Soils with goodor medium drainage were assigned to a good or mediumaeration class depending if precipitation (including irrigation)during the growing season was 400 mm, respec-tively. At most sites characterized by a semi-arid climate,precipitation was

-till

illag

pe

ept

P (

P (

(10

(10

(10

(10

(10

P (

P (

P (

P (

s (2

+ R

P (

P (

P (

P (

(20

(15

ReseTable 1Cumulative eld N2O emissions and other ancillary parameters in tilled (T) and no

Aeration

status

Drainage Growing season

precipitationsa

(mm)

Soil texture Climate T

ty

(d

Good High 384 Loam Cool M

High 305 Loam Semi-arid M

Medium 271 Sandy cl. loam Semi-arid R

Medium 270 Sandy cl. loam Semi-arid R

Medium 320 Loam Semi-arid R

Medium 242 Clay loam Semi-arid R

Medium 291 Silt loam Semi-arid D

Mean 298

Medium ns 694 Volcanic ash Cool humid M

High 640 Sandy loam Cool humid M

High 622 Loam Cool humid M

High 429 Loamy sand Cool M

Medium 410 Loam Cool humid n

High 620 Loam Cool humid C

High 560 Loam Cool humid M

Medium 552 Clay loam Semi-arid + Ir. M

Medium 552 Clay loam Semi-arid + Ir. M

High 574 Loam Cool humid M

High 1200 Clay Sub-tropical D

High 1000 Clay loam Sub-tropical D

Mean 654

P. Rochette / Soil & Tillage98threshold above which soil water content can restrict aeration.When emission data were reported for several years in a givenstudy, all cumulative N2O emissions during the measurementperiod were averaged. Finally, to account for the skeweddistribution of soil N2O uxes, the mean cumulated N2O for eachsoil aeration class was estimated as the geometric mean of valuesreported for each tillage practice.

3. Results and discussion

Most studies conducted in poorly-aerated soils had greater N2Oemissions under no-till than under conventional tillage while bothpositive and negative responses of emissions to no-till wereobserved on soils with good or medium aeration (Table 1).Cumulative emissions in poorly-aerated soils were greater underno-till in 6 out of 8 studies and differences were >2 kg N ha1 onfour occasions. In addition, the distribution of differences in N2Oemissions between tilled and no-till situations was skewedtowards positive values, indicating that the impact of no-till onN2O emissions can be exceptionally high at a few poorly-drainedlocations. In contrast, in soils with good and medium aeration,differences in emissions between tillage practices were small andequally distributed between positive and negative values. Onaverage, soil N2O emissions under no-till were 0.06 kg N ha

1

lower, 0.12 kg N ha1 higher and 2.00 kg N ha1 higher than undertilled soils with good, medium and poor aeration, respectively. The

Poor Poor 430 Clay loam Cool humid MP (

Poor 430 Clay loam Cool humid MP (

Poor 590 Loam Cool humid C (18

Poor 400 Heavy clay Cool humid MP (

Poore 377 Clay loam Cool humid MP (

Poor 680 Silty loam Cool humid MP (

Poor 574 Heavy clay Cool humid MP (

Poor 640 Heavy clay Cool humid MP (

Mean 515

a Including irrigation.b MP = moldboard plowing; R = rotovator; C = Chizel; RT = ridge tillage; D = disking;c Geometric mean.d Reduced tillage.e Gleysol.f Estimated using values in Fig. 3 of Ball et al. (1999).(NT) agricultural soils

eb

h)

Measurement

period (d yr1)Cumulated N2O emissions

(kg N2ON ha1)

Reference

NT T NTT

30) 365 1.32 0.80 0.52 Oorts et al., 2007

15) 365 0.25 0.31 0.06 Kessavalou et al. (1998)) 110 0.12 0.25 0.12 Malhi et al. (2006)) 130 0.34 0.40 0.06 Malhi and Lemke (2007)) 170 0.30 0.29 0.01 Lemke et al. (1999)

) 170 0.97 1.46 0.49 Lemke et al. (1999)) 365 0.38 0.38 0.0 Dusenbury et al. (2008)

239 0.39c 0.45c 0.06

25) 365 0.83d 0.27 0.56 Koga et al. (2004)

20) 215 1.11 0.99 0.12 Rochette et al. (2008)

ns) 365 1.32 1.20 0.12 Grandy et al. (2006)

20) 113 0.43 0.89 0.46 Chatskikh and Olesen(2007)

5) 6579 1.97 0.46 1.51 Baggs et al. (2003)

T 150 1.84 1.88 0.04 Jacinthe and Dick (1997)20) 180 1.00 1.34 0.34 Gregorich et al. (2008)ns) 365 1.19 1.51 0.32 Liu et al. (2005)ns) 365 0.99 1.29 0.30 Mosier et al. (2006)20) 225 2.10 1.80 0.30 Larouche (2006)

) 365 0.87 0.70 0.17 Jantilia et al. (2008)

) 180 0.31 0.35 0.04 Metay et al. (2007)247 1.02c 0.90c 0.12

arch 101 (2008) 97100ratio ofmean cumulative emissions fromno-till to tilled soils in thesame three aeration classes was 0.87, 1.13 and 1.50 (Fig. 1). Thissummary therefore suggests that the mean impact of no-till onN2O emissions is small inwell-aerated soils butmost often positiveon soils where aeration is restricted.

The response of N2O emissions to conversion from conventionaltillage to no-till was variable in all soil aeration classes butvariability was greatest in poorly-aerated soils (Table 1). Thegrouping of situations based on soil drainage class may explainpart of this variability. Soil drainage classes in soil classicationsystems do not necessarily reect the current drainage level butrather reect the conditions that prevailed during soil develop-ment. Especially, several poorly-drained agricultural soils arearticially drained and therefore have a better aeration status thanindicated by their drainage class. Also, the structure of surface soilwas shown to improve with time after conversion to no-till andthis evolution of soil properties likely impacts on N2O productionand emission (Six et al., 2004). Therefore, grouping soils withdifferent tillage history has likely contributed to increasevariability.

Increased emissions associated with poorly-aerated conditionsstrongly suggest that the additional N2O originates from enhanceddenitrication in no-till soils. Oxygen often limits denitrication inagricultural soils (Smith and Tiedje, 1979) and higher soil watercontent in no-till soils usually results in lower aeration and greaterdenitrication rates than in tilled soils (Doran, 1980; Groffman,

15) 215 3.35 3.82 0.47 Drury et al. (2006)15) 215 1.00 1.15 0.15 Kaharabata et al. (2003)) 365 7.74 7.58 0.16 Parkin and Kaspar (2006)

ns) 200 4.40 2.00 2.40 Burford et al. (1981)

20) 77 13.0f 3.80f 9.20 Ball et al. (1999)

25) 260 12.0 9.20 2.80 Choudhary et al. (2002)

20) 240 2.79 1.99 0.80 MacKenzie et al. (1997)

20) 215 32.7 13.3 19.34 Rochette et al. (2008)

223 5.97c 3.97c 2.00

ns = not specied.

Rese1984; Arah et al., 1991; Palma et al., 1997). Accordingly, Rochetteet al. (2008) observed that N2O emissions were increased in aheavy clay under no-till only when water-lled pore space (WFPS)was 0.6 m3 m3, the threshold above which denitrication isfavoured (Linn and Doran, 1984). In a well-drained gravely loam,WFPS remained below 0.6 m3 m3 and emissions were similar inno-till and moldboard plowed soils (Rochette et al., 2008). Wehypothesize that the inuence of soil aeration on the response ofN2O emissions to no-till (Table 1) is in part explained by the factthat, even though no-till increases soil density and water contentin most soils, WFPS values reach 0.6 m3 m3 more often in poorly-aerated soils than in well-aerated soils.

A relationship betweenN2O emissions and soil aeration suggeststhat disaggregating agricultural land into sub-categories based onsoil and climate characteristics may provide an opportunity forimproving our estimates of the response of soil N2O emission to no-till. Soil aeration level andwater content are highly variable in spaceand time. However, their mean value under given climaticconditions are closely related to soil texture. Strong relationshipswere found between particle size distribution and water content orair-lled porosity (da Sylva and Kay, 1997; Minasny et al., 1999).Accordingly, soil texture-related variables (sand or clay content)often correlate with N2O emissions from agricultural soils (Henaultet al., 1998; Corre et al., 1999; Chadwick et al., 1999; Bouwmanet al.,2002; Freibauer, 2003) and results summarized in Table 1 suggestthat soil texture and climate might also be used to estimate theresponse of soil N2O emissions to no-till.

Fig. 1. Mean ratio of cumulated N2O emissions from no-till (NT) to tilled (T) soilswith poor, medium and good aeration.

P. Rochette / Soil & Tillage4. Conclusions

Increases in soil organic matter content are often observedfollowing the adoption of no-till. For example, it was estimatedthat conversion of conventionally-tilled soils to no-till in Canadaresults in a mean gain of 60160 kg C ha1 yr1 during the rst20 yr following conversion (VandenBygaart et al., 2008). Inaddition to improve soil quality, this change in soil C stocks is asink for atmospheric CO2, the most abundant greenhouse gas. No-till is therefore often suggested as a mean for reducing netgreenhouse gas emissions from farms. In this study, we estimatedthat N2O emissions on poorly-aerated soils are on average2 kg N2ON ha

1 higher under no-till than under conventionaltillage. Considering that the global warming potential of 1 kg ofemitted N2ON ha

1 is equivalent to a loss in soil C ofapproximately 125 kg C ha1, we conclude that no-till mayincrease net greenhouse gas emissions from many poorly-drained(ne-textured) agricultural soils located in regions with a humidclimate.References

Arah, J.R.M., Smith, K.A., Crichton, I.J., Li, H.S., 1991. Nitrous oxide production anddenitrication in Scottish arable soils. J. Soil Sci. 42, 351367.

Baggs, E.M., Stevenson, M., Pihlatie, M., Regar, A., Cook, H., Cadisch, G., 2003. Nitrousoxide emissions following application of residues and fertiliser under zero andconventional tillage. Plant Soil 254, 361370.

Ball, B.C., Scott, A., Parker, J.P., 1999. Field N2O, CO2 and CH4 uxes in relation totillage, compaction and soil quality in Scotland. Soil Till. Res. 53, 2939.

Bouwman, A.F., Boumans, L.J.M., Batjes, N.H., 2002. Emissions of N2O and NO fromfertilized elds: summary of available data. Global Biogeochem. Cycl. 16 ,doi:10.1029/2001GB001811.

Burford, J.R., Dowdell, R.J., Crees, R., 1981. Emission of nitrous oxide to the atmo-sphere from direct-drilled and ploughed clay soils. J. Sci. Food Agric. 32, 219223.

Chadwick, D.R., Sneath, R.W., Phillips, V.R., Pain, B.F., 1999. AUK inventory of nitrousoxide emissions from farmed livestock. Atmos. Environ. 33, 33453354.

Chatskikh, D., Olesen, J.E., 2007. Soil tillage enhanced CO2 and N2O emissions fromloamy sand soil under spring barley. Soil Till. Res. 97, 518.

Choudhary, M.A., Akramkhanov, A., Saggar, S., 2002. Nitrous oxide emissions from aNew Zealand cropped soil: tillage effects, spatial and seasonal variability. Agric.Ecosyst. Environ. 93, 3343.

Corre, M.D., Pennock, D.J., Van Kessel, C., Elliot, D.K., 1999. Estimation of annualnitrous oxide emissions from a transitional grasslandforest region in Saskatch-ewan, Canada. Biogeochemistry 44, 2949.

da Sylva, A.P., Kay, B.D., 1997. Estimating the least limitingwater range of soils fromproperties and management. Soil Sci. Soc. Am. J. 61, 877883.

Doran, J.W., 1980. Soil microbial and biochemical changes associated with reducedtillage. Soil Sci. Soc. Am. J. 44, 765771.

Drury, C.F., Reynolds, W.D., Tan, C.S., Welacky, T.W., Calder, W., McLaughlin, N.B.,2006. Emissions of nitrous oxide and carbon dioxide: inuence of tillage typeand nitrogen placement depth. Soil Sci. Soc. Am. J. 70, 570581.

Dusenbury, M.P., Engel, R.E., Miller, P.R., Lemke, R.L., Wallander, R., 2008. Nitrousoxide emissions from a northern Great Plains soil as inuenced by nitrogenmanagement and cropping systems. J. Environ. Qual. 37, 542550.

Freibauer, A., 2003. Regionalized inventory of biogenic greenhouse gas emissionsfrom European agriculture. Europ. J. Agron. 19, 135160.

Grandy, A.S., Loecke, T.D., Parr, S., Robertson, G.P., 2006. Long-term trends in nitrousoxide emissions, soil nitrogen, and crop yields of till and no-till croppingsystems. J. Environ. Qual. 35, 14871495.

Gregorich, E.G., Rochette, P., St-Georges, P., McKim, U.F., Chan, C., 2008. Tillageeffects on N2O emissions from soils under corn and soybeans in eastern Canada.Can. J. Soil Sci. 88, 153161.

Gregorich, E.G., Rochette, P., VandenBygaart, A.J., Angers, D.A., 2005. Greenhousesgas contributions of agricultural soils and potential mitigation practices ineastern Canada. Soil Till. Res. 83, 5372.

Groffman, P.M., 1984. Nitrication and denitrication in conventional and no-tillage soils. Soil Sci. Soc. Am. J. 49, 329334.

Henault, C., Devis, X., Page, S., Justes, E., Reau, R., Germon, J.-C., 1998. Nitrous oxideemissions under different soil and land management conditions. Biol. Fertil.Soils 26, 199207.

Jacinthe, P., Dick, W.A., 1997. Soil management and nitrous oxide emissions fromcultivated elds in southern Ohio. Soil Till. Res. 41, 221235.

Jantilia, C.P., dos Santos, H.P., Urquiaga, S., Boddey, R.M., Alves, B.J.R., 2008. Fluxes ofnitrous oxide from soil under different crop rotations and tillage systems in thesouth of Brazil. Nutr. Cycl. Agroecosyst., doi:10.1007/s10705-008-9178-y.

Kaharabata, S.K., Drury, C.F., Priesack, E., Desjardins, R.L., McKenney, D.J., Tan, C.S.,Reynolds, W.D., 2003. Comparing measured and Expert-N predicted N2O emis-sions from conventional till and no till corn treatments. Nutr. Cycl. Agroecosyst.66, 107118.

Kessavalou, A., Mosier, A.R., Doran, J.W., Drijber, R.A., Lyon, D.J., Heinemeyer, O.,1998. Fluxes of carbon dioxide, nitrous oxide, and methane in grass sodand winter wheat-fallow tillage management. J. Environ. Qual. 27, 10941104.

Koga, N., Tsuruta, H., Sawamoto, T., Nishimura, S., Yagi, K., 2004. N2O emissionand CH4 uptake in arable elds managed under conventional and reducedtillage cropping systems in northern Japan. Global Biogeochem. Cycl. 18,111.

Larouche, F., 2006. Emissions de protoxyde dazote dans une rotation mais/sojatelles quinuencees par le travail du sol et la fertilisation azotee. M.Sc. Thesis,Laval University, Quebec city, Canada, 226 pp.

Lemke, R.L., Izaurralde, R.C., Nyborg, M., Solberg, E.D., 1999. Tillage and N sourceinuence soil-emitted nitrous oxide in the Alberta Parkland region. Can. J. SoilSci. 79, 1524.

Li, C., Frolking, S., Butterbach-Bahl, K., 2005. Carbon sequestration in arable soils islikely to increase nitrous oxide emissions, offsetting reductions in climateradiative forcing. Clim. Change 72, 321328.

Li, C., Narayanan, V., Harriss, R., 1996. Model estimates of nitrous oxide emissionsfrom agricultural lands in the United States. Global Biogeochem. Cycl. 10, 297306.

Linn, D.M., Doran, J.W., 1984. Aerobic and anaerobicmicrobial populations in no-tilland plowed soils. Soil Sci. Soc. Am. J. 48, 794799.

Liu, X.J., Mosier, A.R., Halvorson, A.D., Zhang, F.S., 2005. Tillage and nitrogen

arch 101 (2008) 97100 99application effects on nitrous and nitric oxide emissions from irrigated cornelds. Plant Soil 276, 235249.

MacKenzie, A.F., Fan, M.X., Cadrin, F., 1997. Nitrous oxide emission as affected bytillage, cornsoybeanalfalfa rotations and nitrogen fertilization. Can. J. Soil Sci.77, 145152.

Malhi, S.S., Lemke, R.L., Wang, Z., Chhabra, B., 2006. Tillage, nitrogen and cropresidue effects on crop yield, nutrient uptake, soil quality, and greenhouse gasemissions. Soil Till. Res. 90, 171183.

Malhi, S.S., Lemke, R.L., 2007. Tillage, crop residue and N fertilizer effects on cropyield, nutrient uptake, soil quality and nitrous oxide gas emissions in a second4-yr rotation cycle. Soil Till. Res. 96, 269283.

Metay, A., Oliver, R., Scopel, E., Douzet, J.-M., AlvesMoreira, J.A.,Maraux, F., Feigl, B.J.,Feller, C., 2007. N2O and CH4 emissions from soils under conventional and no-till management practices in Goiania (Cerrados, Brazil). Geoderma 141, 7888.

Minasny, B., McBratney, A.B., Bristow, K.L., 1999. Comparison of differentapproaches to the development of pedotransfer functions for water-retentioncurves. Geoderma 93, 225253.

Mosier, A.R., Halvorson, A.D., Reule, C., Liu, X., 2006. Net global warming potentialand greenhouse gas intensity in irrigated cropping systems in northeasternColorado. J. Environ. Qual. 35, 15841598.

Mummey, D.L., Smith, J.L., Bluhm, G., 1998. Assessment of alternative soil manage-ment practices on N2O emissions from US agriculture. Agric. Ecosyst. Environ.70, 7987.

Oorts, K., Merckx, R., Grehan, E., Labreuche, J., Nicolardot, B., 2007. Determinants ofannual uxes of CO2 and N2O in long-term no-tillage and conventional tillagesystems in northern France. Soil Till. Res. 95, 133148.

Palma, R.M., Rimolo, M., Saubidet, M.I., Conti, M.E., 1997. Inuence of tillage systemon denitrication in maize-cropped soils. Biol. Fertil. Soils 25, 142146.

Parkin, T.B., Kaspar, T.C., 2006. Nitrous oxide emissions from cornsoybean systemsin the midwest. J. Environ. Qual. 35, 14961506.

Rochette, P., Angers, D.A., Chantigny, M.H., Bertrand, N., 2008. N2O emissionsrespond differently to no-till in a loam and a heavy clay soil. Soil Sci. Soc.Am. J. 72, 13631369.

Six, J., Feller, C., Denef, K., Ogle, S.M., de Moraes Sa, J.C., Albrecht, A., 2002. Soilorganic matter, biota and aggregation in temperate and tropical soilseffects ofno-tillage. Agronomie 22, 755775.

Six, J., Ogle, S.M., Breidt, F.J., Conant, R.T., Mosier, A.R., Paustian, K., 2004.The potential to mitigate global warming with no-tillage management is onlyrealized when practised in the long term. Global Change Biol. 10, 155160.

Smith, M.S., Tiedje, J.M., 1979. Phases of denitrication following oxygen depletionin soil. Soil Biol. Biochem. 11, 261267.

VandenBygaart, A.J., McConkey, B.G., Angers, D.A., Smith, W., de Gooijer, H., Ben-tham, M., Martin, T., 2008, in press. Soil carbon change factors for the CanadianAgriculture National Greenhouse Gas Inventory. Can. J. Soil Sci.

P. Rochette / Soil & Tillage Research 101 (2008) 97100100

No-till only increases N2O emissions in poorly-aerated soilsIntroductionMaterials and methodsResults and discussionConclusionsReferences