Effect of tillage practices on the soil carbon dioxide flux during fall and spring seasons in a Mediterranean Vertisol

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1 Journl of Soil Science nd Environmentl Mngement Vol. 2(11), pp , 29 Novemer, 2011 Aville online t ISSN Acdemic Journls Full Length Reserch Pper Effect of tillge prctices on the soil cron dioxide flux during fll nd spring sesons in Mediterrnen Vertisol R. Moussdek 1,2 *, R. Mret 1, R. Dhn 1, A. Douik 1, A. Verdoodt 2, E. Vn Rnst 2 nd M. Coreels 3 1 Institut Ntionl de l Recherche Agronomique, BP 415, Avenue l Victoire, 000, Rt, Morocco. 2 Deprtment of Geology nd Soil Science (WE13), Lortory of Soil Science, Ghent University, Krijgsln 281/S8, B-9000 Gent, Belgium. 3 Systèmes de Culture Annuels, Centre de Coopértion Interntionle en Recherche Agronomique pour le Développement (CIRAD), Frnce. Accepted 5 Octoer, 2011 In this study, we ssessed the effect of conventionl tillge (CT), reduced (RT) nd no tillge (NT) prctices on the soil CO 2 flux of Mediterrnen Vertisol in semi-rid Morocco. The mesurements focused on the short term (0 to 96 h) soil CO 2 fluxes mesured directly fter tillge during the fll nd spring period. Soil temperture, moisture nd soil strength were mesured congruently to study their effect on the soil CO 2 flux mgnitude. Immeditely fter fll tillge, the CT showed the highest CO 2 flux (4.9 g m -2 h -1 ); RT exhiited n intermedite vlue (2.1 g m -2 h -1 ) wheres the lowest flux (0.7 g m -2 h -1 ) ws reported under NT. After spring tillge, similr ut smller impcts of the tillge prctices on soil CO 2 flux were reported with fluxes rnging from 1.8 g CO 2 m -2 h -1 (CT) to less thn 0.1 g CO 2 m -2 h -1 (NT). Soil strength ws significntly correlted with soil CO 2 emission; wheres surfce soil temperture nd moisture were low correlted to the soil CO 2 flux. The intensity of rinfll events efore fll nd spring tillge prctices could explin the sesonl CO 2 flux trends. The findings promote conservtion tillge nd more specificlly no tillge prctices to reduce CO 2 losses within these Mediterrnen groecosystems. Key words: Tillge, CO 2 flux, sesonl vriility, Vertisol, semi-rid Morocco. INTRODUCTION The importnt role of CO 2 emissions from soils in the cron cycle hs (only) een clerly recognized for nerly decde (Schlesinger nd Andrews, 2000). Due to the lrge order of mgnitude, smll chnges in soil CO 2 flux cross lrge res cn produce gret effect on CO 2 tmospheric concentrtions (Ll, 2004). Soil plowing is principl cuse of CO 2 emission from croplnds leding to depletion of soil orgnic mtter *Corresponding uthor. E-mil: mouss.inr@gmil.com. Arevitions: CO 2, Cron dioxide; NT, no tillge; CT, conventionl tillge; RD, reduced tillge. content (Pustin et l., 1997; Six et l., 2002; Ll, 2004). Increse of soil CO 2 emission fter tillge ws reported y severl uthors from North Americ nd Europe (Reicosky nd Lindstrom, 1993; Ellert nd Jnzen, 1999). Additionlly, Reicosky et l. (1997) explined the increse in CO 2 flux immeditely fter tillge y physicl relese of CO 2 entrpped in soil pores from previous microil ctivity rther thn the chnges in microil ctivity t the time of tillge. The mgnitude of soil CO 2 flux, t tillge period, depends on the degree nd time of soil disturnce s well s on the soil conditions, siclly soil moisture nd temperture, (Prior et l., 2004; Alvro-Fuentes et l., 2007). Severl studies hve oserved sesonl CO 2 flux ptterns ssocited with fll or spring tillge nd some uthors hve reported

2 Moussdek et l. 363 Tle 1. Selected soil properties t the strt of the experiment. Depth (cm) Cly (%) Silt (%) Snd (%) ph (1:1 H 2O) P 2O 5 (mg/kg) K 2O (mg/kg) Sept. Oct. Nov. Dec. Jn. Fe. Mr. Apr. My Jun. Jul. Aug. Month Figure 1. Long-term verge nd 2009 to 20 cropping seson vlues of rinfll nd temperture t the Merchouch reserch sttion. tht soil microclimte conditions during tillge events plyed n importnt role in CO 2 emission. Reicosky nd Lindstrom (1993) nd L Scl et l. (2001) reported tht the incresed CO 2 losses during fll tillge were due to higher degree of soil disturnce nd residue incorportion in soil. Similr findings hve een reported during spring tillge prctices (Reicosky et l., 1997; Ellert nd Jnzon, 1999; Prior et l., 2004). Other uthors did not detect n immedite shrp increse of soil CO 2 following spring tillge nd explined this y the impct of soil climte prmeters (soil moisture nd temperture) on soil respirtion during tillge (Hendrix et l., 1988). In the Mediterrnen region, the tilled soils re generlly chrcterized y reltively low soil moisture contents nd high tempertures. This reserch imed to ssess the soil cron flux under these climtic conditions of fll nd spring tillge. Hence, the specific ojectives of this study were (1) to quntify the sesonl, short (0 to 24 h) nd midterm (24 to 96 h) CO 2 flux fter fll nd spring tillge in response to contrsting tillge systems nd (2) to identify the soil properties tht my explin vritions in the soil respirtion. The otined results contriute to etter understnding of sesonl CO 2 fluxes in generl nd to define the optimum tillge opertions tht cn decrese soil CO 2 emission of Vertisols in the semi-rid Mediterrnen region. MATERIALS AND METHODS Loction, climte nd soil The experiment ws conducted t the Merchouch reserch sttion of the Ntionl Institute of Agriculturl Reserch (INRA), locted 60 km south of Rt (Ltitude N nd Longitude 6 43 W). The site is chrcterised y flt topogrphy nd is dominted y poorly drined Vertisols (Chromic Clcixererts) tht re slightly lkline nd hve low orgnic mtter contents ut dequte phosphorus (P) nd potssium (K) levels in the surfce horizons (Tle 1). The men long-term nnul precipittion nd temperture re 4 mm nd 23 C, respectively. Monthly verge precipittion nd temperture during the 2009 to 20 cropping seson s well s the long term (40-yer) verge vlues re shown in Figure 1. Dily temperture nd precipittion were mesured using utomted wether sttions nery the experiment. Experiment lyout nd tretments The study ws conducted on 1.5 h plot tht hs een under fllow nd disked in spring for weed control during 2 yers efore

3 364 J. Soil Sci. Environ. Mnge. strting the experimenttion in The lnd ws sudivided into 2 equl suplots of 0.75 h. The first suplot ws used for fll tillge prctices nd the second for spring tillge opertions. On 14 Novemer 2009, the first suplot ws divided into 12 smll plots (50 m) rrnged in rndomized complete lock design with 4 tretments, ech replicted 3 times. The tretments were (1) disk plough; nd (2) chisel s conventionl tillge; (3) tine hrrow s reduced tillge nd (4) no tillge. In spring (12 April, 20), the sme tillge tretments were pplied in the second suplot using the sme experimentl design. The disk plough prctice consisted of tndem disk hrrow (John Deer type -215) operted t out 25 cm depth nd with width of 4 m. The disk ldes were spced t 22.8 cm nd hd rdius of 25 cm. The disk ngle ws djusted to out The chisel tretment operted t 20 cm nd consisted of 11 rigid shnks of 18 cm width nd spced 28 cm prt. The rigid tine hrrow consists of four rs. The hrrow ws tilling t less thn 15 cm soil depth with width of 1.8 m. In the lst tretment, the no-tillge plots were left undistured. The soil orgnic cron nd the mount of residues were the sme for the different tillge tretments. Soil CO 2 mesurement Soil CO 2 emission ws mesured using chmer system (ACE- Automted Soil CO 2 Exchnge System). Mesurements re typiclly mde y mesuring the rise in CO 2 concentrtions inside the chmer. The chmer utomticlly opens etween nlysis cycles llowing mient conditions to rech the soil. Soil CO 2 flux ws clculted from the difference in CO 2 concentrtions etween ir entering nd leving the chmer. The chmer hd cylindricl dimeter of 23 cm, covering soil surfce of 415 cm 2. To prevent CO 2 lekge to tmosphere, the chmer ws inserted 5 cm into the soil. The first flux reding ws tken 3 min fter the chmer ws instlled in order to void possile unrelistic vlues cused y the disturnce produced fter plcing the chmer into the soil (Pumpnen et l., 2004). In ech of the 12 smll plots, soil CO 2 flux ws mesured rndomely t 24 h efore nd immeditely fter tillge opertions with 24 h intervl (0, 24, 48 nd 96 h) in fll nd spring. To determine the cumultive CO 2 flux, trpezoidl function ws used (Alvro- Fuentes et l., 2007). Soil wter content nd soil temperture Soil temperture nd wter content were mesured t the sme times nd loctions when CO 2 emission ws mesured. A soil smple ws collected t the surfce horizon (0 to 5 cm) to determine the grvimetric soil wter content y oven drying t 5 C. Soil temperture ws mesured with hnd-held proe (ECT, decgon model) which ws inserted 5 cm into the soil ner the CO 2 chmer. Soil strength Immeditely fter tillge opertions, soil strength ws mesured throughout the topsoil 50 cm soil depth t rndomly locted points in ech of the tretments. Mesurements were done using Rimik CP- 20 cone penetrometer (se re 2 cm 2, ngle 60 ). The initil soil wter content ws determined y the grvimetric method in order to tke into ccount the effect of soil moisture on soil strength. Sttisticl nlysis The collected dt were sujected to sttisticl nlysis using SPSS. Since we re interessted in compring the tillge effect on CO 2 flux for ech seson nd ech time period, nlysis of vrince (ANOVA) ws used to study the difference etween tillge tretments nd lest significnt difference method (LSD) ws pplied for comprison of tretment mens. Correltions etween the soil CO 2 flux nd soil temperture, soil moisture nd soil strength were determined nd tested for their significnce using the Person correltion coefficient. RESULTS AND DISCUSSION ANOVA ws done, reconsidering ll fctors (seson, time nd tillge). The result of this nlysis showed tht there is very highly significnt difference (p<0.001) etween the two seson (fll, spring). Therefore, the susequent nlysis ws done seprtely for ech seson. Soil CO 2 emission in fll tillge Figure 2 shows tht oth the conventionl (chisel nd disk) nd reduced (hrrow) tillge prctices in the fll oth cused n immedite shrp increse in soil CO 2 flux within 24 h time. In contrst, the no-tillge prctice did not result in significnt chnge of the soil CO 2 flux. The chisel tillge showed the highest CO 2 fluxes (4.9 g m -2 h -1 ) followed y the disk tillge (3.9 g m -2 h -1 ). The reduced tillge (hrrow) exhiited intermedite vlues (2.1 g m -2 h -1 ) followed y the no-tillge tretment, which hd the lowest CO 2 flux (0.7 g m -2 h -1 ). The 4 treement were highly significntly different from ech other (p <0.001). These findings reflect the degree of soil disturnce tht the chisel nd disk tretments implemented. In fct, the disk nd chisel tretment resulted in more soil disturnce (Rper, 2002). 24 h fter tillge, the CO 2 flux hd lredy decresed to remin more or less constnt up to the end of the mesurements (Figure 2). The sme trend ws reported y Alvro-Fuentes et l. (2007) under semi-rid conditions in Spin, where the CO 2 flux immeditely otined fter fll tillge rnged etween 3 to 13 g m -2 h -1, while the no-tillge tretment hd lower CO 2 vlue (less thn 1 g m -2 h -1 ). Similrly, Reicosky et l. (1997) reported tht the mount of CO 2 emitted immeditely fter tillge ws proportionl to the degree of soil disturnce produced while no-tillge ws not inducing ny significnt CO 2 flux. Soil CO 2 emission in spring tillge The soil CO 2 emissions were lower in the spring tillge tretments compred to those oserved in the fll tillge opertions (Figure 3). CO 2 flux vlues rnged from 0.8 (hrrow) to 1.8 g m -2 h -1 (disk). The chisel tretment hd n intermedite vlue 1.4 g m -2 h -1. No significnt difference ws oserved etween the disk nd chisel tretments, ut the reduced tillge nd no-tillge

4 Moussdek et l (Fll) 5.0 d CO2 (gm -2 h -1 ) CO2 (g m -2 h-1 ) c Chisel Disk Hrrow NT h 0 h 24h 48h 96h h Hour efore nd fter tillge Figure 2. Soil CO 2 flux ssocited with fll tillge tretments (for the sme hour, tretments with the sme letter re not significntely differents, (LSD test, p<0.05) CO2 (gm -2 h -1 ) h Figure 3. Soil CO 2 flux ssocited with spring tillge tretments (for the sme hour, tretments with the sme letter re not significntely differents, (LSD test, p<0.05). tretments exhiited significntly lower CO 2 fluxes. Alvro-Fuentes et l. (2007) found similr trend in CO 2 fluxes tht rnged etween 0.1 nd 1.2 g m -2 h -1 immeditely fter no tillge nd conventionl spring tillge, respectively. Effect of soil temperture nd moisture content on the soil CO 2 flux Figure 4 shows tht the soil wter content (SWC) nd soil temperture (T) mesured t 24h time steps efore nd

5 366 J. Soil Sci. Environ. Mnge. A SWC (%) B -24h h 24h 48h 96h h Hour efore nd fter tillge (Fll) Chisel Disk Hrrow NT Temperture ( C) Air Temperture Soil Temperture (Fll) h h 00h 12h 24h 36h 48h 72h 96hh Hours efore nd fter tillge SWC (%) h 0 h 24 24h 48 48h 96 96hh Hour efore nd fter tillge (Spring) Chisel Disk Hrrow NT Temperture ( C) Air temperture Soil temperture (Spring) -24h -12h 00h 12 12h 24h 3636h 4848h 7272h96 h 96h Hours efore nd fter tillge Figure 4. Topsoil (0 to 5 cm) wter content (SWC) under different tillge tretments nd men soil (0 to 5 cm) nd ir temperture efore nd fter tillge during the () fll nd () spring. (*) mens the presence of significnt differences etween tretments.

6 Moussdek et l. 367 Tle 2. Person s correltion coefficients etween soil CO 2 flux nd soil wter content nd soil temperture in fll nd spring tillge. Vrile CO 2 flux (Fll) CO 2 flux (Spring) r p r p SWC T SWC - soil wter content t (0-5 cm); T - soil temperture t (0-5 cm). fter the tillge pplied in fll nd spring. For ll tretments, soil moisture decresed slightly fter tillge events in fll nd spring ut no significnt difference ws oserved etween tillge tretments in oth sesons. Mret (2002) reported tht the soil moisture decrese fter tillge is due to high soil wter evportion in this semi-rid re. Also, soil surfce (0 to 5 cm) temperture (T) ws not significntly ffected y tillge prctices nd no significnt differences were oserved etween tretments t fll nd spring. Severl uthors reported similr insignificnt effects of tillge opertions on soil temperture nd moisture in similr semi-rid conditions (Alvro-Fuentes et l. 2007). Soil CO 2 flux oserved in fll nd spring period were not correlted to soil wter content (SWC) nor to temperture (T) mesured t 0 to 5 cm topsoil lyer (Tle 2). The sence of significnt correltion etween T nd SWC nd CO 2 flux my e relted to the fct tht those prmeters were ssessed t surfce horizon (0 to 5 cm) only, wheres soil tillge opertions were ffecting the deeper soil horizons. Soil strength The influence of tillge prctices on soil strength mesured one hour fter tillge is shown in Figure 5. The cone index (C.I.) vried with tretments nd depths.the C.I. t 0 to cm depth ws significntly higher under notillge compred to the other tretments. This is explined y the immedite effect of soil disturnce under those tillge tretments compred to the no till plots. However, t depth more thn cm, no sttisticlly significnt differences in C.I. were found etween reduced nd no tillge. The chisel nd disk tretments exhiited the sme trends in oth fll nd spring. Soil strength of the topsoil (15 cm) ws significntly negtively correlted with the soil CO 2 flux during fll nd spring periods (Tle 3). At 20 to 30 cm depth, the correltion ws not sttisticlly significnt, ut clerly showed negtive trend. As C.I. is used s indictor for soil disturnce (Crter et l., 2007), our results showed tht soil CO 2 flux is correlted to the degree of soil disturnce ner the soil surfce. Cumultive CO 2 emission during fll nd spring tillge Figure 6 indictes the cumultive soil CO 2 emissions using simple trpezoidl integrtion function from 0 to 96 h fter tillge in ll tretments during the fll nd spring periods. In fll period, no significnt difference in cumultive CO 2 loss ws oserved etween the chisel nd disk tillge (out 155 g m -2 ). The reduced tillge (hrrow) exhiited intermedite vlues (4 g m -2 ) followed y the no-tillge tretment, which hd the lowest CO 2 flux (56 g m -2 h -1 ). The sme trend ws oserved in spring period. In fct, no significnt difference in cumultive CO 2 loss ws oserved etween the chisel nd disk tillge (43 g m -2 ). The reduced tillge (hrrow) exhiited intermedite vlues (24 g m -2 ) followed y the no-tillge tretment, which hd the lowest CO 2 flux (6 g m -2 h -1 ). From Figure 6, we conclude tht the cumultive CO 2 higher during fll period compred to spring period. This difference in sesonl CO 2 fluxes losses during spring nd fll cn e explined y the greter uild-up of CO 2 in the soil t the time of fll tillge due to microil rekdown of esy decomposle orgnic sustrtes (Prior et l., 2004). Also, the soil CO 2 reservoir t the time of spring tillge is expected to e lower due to winter losses ttriutle to oth microil respirtion nd physicl displcement of soil CO 2 s result of regulr rinfll (Hrper et l., 2005). In fct, in our cse study, efore fll period (Septemer nd Octoer 2009) only 40 mm rinfll occurred in contrst with 300 mm rinfll tht occurred efore spring period (from Jnury to Mrch 20) (Figure 1). Conclusion This reserch demonstrtes tht soil disturnce increses CO 2 flux immeditely fter tillge of semi-rid Vertisol. Yet, the mgnitude of the CO 2 flux chnges through the yer, with fll tillge exhiiting much higher CO 2 emissions thn spring tillge. The soil CO 2 flux under no tillge ws lower thn other tretments during fll nd spring periods. The tillge-induced flush CO 2 ws ttriuted most proly to the soil disturnce, therey reducing soil strength nd promoting CO 2 diffusion. These findings promote the use of no tillge prctices to

7 368 J. Soil Sci. Environ. Mnge. Depth (cm) Cone Index (C.I.) in KP * * * * (Spring) Chisel Disk Hrrow NT Figure 5. Soil strength (C.I) mesured 1 h fter tillge under different tretments, during fll nd spring period. At ech depth, (*) mens the presence of significnt differences etween tretments. Tle 3. Person s correltion coefficients etween soil CO 2 flux nd soil cone index per depth in fll nd spring tillge. Vrile CO 2 flux (Fll) CO 2 flux (Spring) r p r p C.I. (0- cm) C.I. (-20 cm) C.I. (20-30 cm) C.I. soil cone index.

8 Moussdek et l. 369 Figure 6. Cumultive CO 2 flux during the first 96h following fll nd spring tillge opertions (tretments with the sme letter re not significntly different from ech other, LSD (p < 0.05). reduce CO 2 losses in this semi-rid region, contiuting to the mitigtion of green house gses nd consequently reducing the negtif impct of climte chnge. REFERENCES Alvro-Fuentes J, Cntero-Mrtınez C, Lopez MV (2007). Soil cron dioxide fluxes following tillge in semirid Mediterrnen groecosystems. Soil Tillge. Res. 96: Crter EA, Aust WM, Burger JA (2007). Soil strength response of select soil disturnce clsses on wet pine flt in South Crolin. Forest. Ecol. Mng., 247: Ellert BH, Jnzen HH (1999). Short-term influence of tillge on CO 2 fluxes from semi-rid soil on the Cndin Priries. Soil Tillge Res., 50: Hrper CW, Blir JM, Fy PA, Knpp AK, Crlisle JD (2005). Soil moisture decresed slightly fter tillge events. Glo. Chnge Biol., 11: Hendrix PF, Hn CR, Groffmn PM (1988). Soil respirtion in conventionl nd no tillge groecosystems under different winter cover crop rottions. Soil Tillge Res. 12: Ll R (2004). Soil cron sequestrtion to mitigte climte chnge. Geoderm. 123: L Scl N, Lopes A, Mrques J Jr, Pereir GT (2001). Cron dioxide emissions fter ppliction of tillge systems for drkred Ltosol in southern Brzil. Soil Tillge Res. 62: Mret R (2002). Whet yield nd wter use efficiency under contrsting residue nd tillge mngement systems in semirid re of Morocco. Exp. Agric., 38: Pustin OA, Jnzen HH, Ll R, Smith P, Tin G, Tiessen H, Vn Noordwijk M, Woomer PL (1997). Agriculturl soils s sink to mitigte CO 2 emissions, Soil Use Mnge., 13: Prior SA, Rper RL, Runion GB (2004). Effect of implement on soil CO 2 efflux: fll vs. spring tillge. Trns. ASAE, 47: Pumpnen J, Kolri P, lvesniemi H, Minkkinen K, Vesl T, Niinistö S, Lohil A, Lrmol T, Morero M, Pihltie M, Jnssens I, Yuste JC, Grünzweig JM, Reth S, Suke JA, Kutsch KW, Ostreng G, Ziegler W, Anthoni P, Lindroth A, Hri P (2004). Comprison of different chmer techniques for mesuring soil CO 2 efflux. Agron. For. Meteorol., 123: Rper RL (2002). The influence of implement type, tillge depth, nd tillge timing on residue uril. Trns. ASAE. 45: Reicosky DC, Lindstrom MJ (1993). Fll tillge method: effect on shortterm cron dioxide flux from soil. Agron. J., 85: Reicosky DC, Dugs WA, Torert HA (1997). Tillge-induced soil cron dioxide loss from different cropping systems. Soil Tillge Res., 41: Schlesinger WH, Andrews JA (2000). Soil respirtion nd the glol cron cycle. Biogeochemistry, 48: Six J, Connt RT, Pul EA (2002). Stiliztion mechnisms of soil orgnic mtter: implictions for C-sturtion of soils: Review. Plnt Soil, 241: