Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. n as 98 Nakic 1998; Sass, and ae n eaigro ise,te rnpr CH transport they tissues, root decaying and dates exu- root residues, crop through substrate methanogenic yr ugto iefed Rnebr ta. 92 Neue 1992; al., et (Rennenberg fields rice of budget O pee(ir ta. 99 asanadAlk,2000). Aulakh, and Wassmann 1999; al., et (Mitra sphere lnspa nipratrl nrgltn h CH the regulating in role important an play plants CH rwhsae flwadrc ( rice lowland of stages growth o1%o lblCH global of 15% to pdsse fitrellrarsae (aerenchyma), spaces CH active air an create they intercellular and of system oped 7 .SgeR. aio,W 31 USA 53711 WI Madison, Rd., Segoe (2005). S. 69:563–570 677 J. Am. Soc. © Sci. Soil in Published ([email protected]). author *Corresponding IA 2004. Ames, Mar. Drive, 21 Pammel Received 2150 50011. Lab., Olk, Tilth Kreuzeck- D.C. Soil National Germany. USDA-ARS, Garmisch-Partenkirchen, Karlsruhe, D-82467, 19, bahnstr. Research—Forschungszentrum Envi- Wassmann, Research-Atmospheric Climate R. ronmental and Punjab India. Meteorology Soils, Punjab, for of 141004, Institute Dep. Ludhiana Aulakh, M.S. Univ., Walter-Flex- Germany. Agricultural Bonn, Bonn, of D-53113 Univ. 3, (ZEFc), Str. Block, Cen- Research formerly, Seth Development India; Darbari 110003, for Delhi, Institute, ter New Resources Road, Lodhi and Place, Energy Habitat The Mitra, S. I role. a play to appear practices ment CH in differences less plain provided CH treatments into faster their field conversion organic enabling substances, better-aerated that amended the is the of stabilization explanation of chemical possible soils One in unknown. matter is trend this for associa- the common from CH the sampled of been opposes tion had which that treatments, soils field the better-aerated in greatest correlated was was production property that soil property no CH however, soil with II, sole Exp. In The (CEC). soils. capacity CH rice cumulative with five correlated CH the of was rates among I, Exp. differed In C. tion exudate root of conversion CH the to incorpora- than glucose-C residue soil of crop of conversion of degree The timing in tion. and varied rotation that crop treatments farmers’ through field five aeration four I) II) (Exp. (Exp. from collected and were fields that soils glucose rice and Philippine exudates to CH root of duration, addition 20-d following measured of was duction experiments crop incubation anaerobic and two properties In CH soil on of practices effects CH management the late-season of investigates factors study the laboratory about Little tissue. known root is autolysed else and exudates root of decomposition from 2 Ϫ olSineSceyo America of Society Science Soil lvtdCH Elevated rgtdlwadrc fields rice lowland rrigated motn CH important ewe oladamshr hog well-devel- a through atmosphere and soil between 1 4 rgeigo ehn rdcini ieSisb otEuae:Efcso Soil of Effects Exudates: Root by Soils Rice in Production Methane of Triggering Bcee n ee 93 n a otiue10 contribute may and 1993) Neue, and (Bachelet msinfo iefed agsfo 7t 2Tg 82 to 57 from ranges fields rice from emission 4 rdcinfo lcs n oteuae.Ised CH Instead, exudates. root and glucose from production 4 rdcinwt neoi odtos h xc reason exact The conditions. anaerobic with production 4 rdcini loe ol uigtereproductive the during soils flooded in production 4 olpoete ln periaeut oex- to inadequate appear alone properties Soil . 4 ore olwd.Etmtdannual Estimated worldwide. sources 4 rdcinfo oteuae;co manage- crop exudates; root from production ´ ABSTRACT enovic 4 4 msin Nu,19) Rice 1993). (Neue, emissions rz sativa Oryza rdcinfo iero exudates. root rice from production ´ 4 4 ta. 00.Te provide They 2000). al., et oiiigst nterhizo- the in site –oxidizing rdcinwscation-exchange was production .Mta .S uah .Wsmn,adD .Olk* C. D. and Wassmann, R. Aulakh, S. M. Mitra, S. 4 a . o36tmsgreater times 3.6 to 1.6 was r n ftemost the of one are rprisadCo Management Crop and Properties . sblee oresult to believed is L.) 4 rdcin This production. 4 produc- 4 4 and pro- 4 4 563 rdciegot stages. growth productive gmn rcie,ro xdtsadguoewere glucose and exudates root practices, agement h nlec fro xdtsadohrexogenous other and exudates CH root on substances of rice influence of the labeling pulse with through plants obtained was high exudates CH by Schu for evidence marked 1986; Direct al., stage 1989a). al., et growth (Holzapfel-Pschorn crop activity a root at and grow- Fisher, plants of and presence ing the Sass in solely 1991; occur al., they auto- because et 1997), and (Lindau exudates tissues root root lysed mi- rice to of attributed decomposition been crobial have rice of period Watanabe, reproductive and CH high Chidthaisong contrast, residues By 2000; 1997). crop al., microbial incorporated et from (Wassmann freshly primarily of results decomposition climates, tropical in oainrltv osi flooding. soil incor- to residue relative crop of poration timing and crop rotation, The aboveground crop II). of residue, removal (Exp. in body three varied soil treatments of same four part the on were experiments that field four treatments (ii) management and I); crop (Exp. properties soil Philip- that intrinsic rice the in double-cropped from differed of soils fields farmers’ rice five lowland (i) of pines: sets two to added CH affect also properties soil in changes management-induced whether exists information qual- and of amount including properties soils, several rice lowland affect irrigated can crop crop of incorporation to time at residue relative aeration soil application and decomposition, fertilizer residue of timing conditions. crops, soil of range wider addi- a Yet, for 2001b). exudates CH al., root on et desirable Aulakh is information 2000; al., tional et al., (Wassmann et soils Lu some 1998; for studied been has tions ne otoldcniin osvrllwadrc soils rice lowland several to conditions controlled under rwhsae flwadrc,wihls 0t 0d 50 to 40 last which rice, lowland of stages growth rpriso CH on properties frc rpgot Aa ta. 00.Ytlimited Yet 2000). al., et (Abao growth crop rice of upy(ite l,19) hs aaeetpractices management These 1998). al., et (Witt supply r nw oatrCH alter to known are rprsde uigteeryadmdsao stages mid-season and early the during residues crop esrd odsigihteifune fitiscsoil intrinsic of influences the was distinguish production To methane measured. of triggering resulting the and t fsi rai atr irba ims,adN and biomass, microbial matter, organic soil of ity ieRsac Institute. Research Rice Abbreviations: nti td,ro xdtsadguoewr added were glucose and exudates root study, this In aaeetpatcssc srtto ihupland with rotation as such practices Management ehn omto uigteeryadmid-season and early the during formation Methane 14 E,cto xhnecpct;IR,International IRRI, capacity; exchange cation CEC, CO 2 Dnebr n ord 99,and 1999), Conrad, and (Dannenberg 4 4 rdcinfo hs fco man- crop of those from production rdcinudrcnrle condi- controlled under production 4 omto rmdecomposing from formation 4 lxsdrn h late-season the during fluxes 4 4 omto uigre- during formation omto rmroot from formation 4 rdcinfrom production ¨ zet tz Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. CH iefresicuigtoeo x.I etlzrrtswere rates Fertilizer I. Exp. lowland of tropical those of including all practice farmers of conventional rice decomposition the anaerobic “late” residues, in This sub- crop resulted the fallow. of and the transplanting of crop before end sequent d the 18 about at returned was tillage were incorporation during residues soil crop the aboveground to and yr, 5 previous h RI2si a ne ierc oaindrn the during rotation rice–rice a under was soil IRRI-2 The 6k ha P kg 26 aae ne tnadcliainpatcswt recom- with fertilizers. mineral practices were of I cultivation rates Exp. mended standard of fields under The fallow. managed 2-mo subsequent the during h avs fec rp loigtesraesi oair-dry to soil surface the allowing crop, each the before of shortly both drained harvest normally during (July–October). the are soil season fields rotation wet flooded this and Under in (January–April) grown season was dry lowland rice had double-cropped (Philippines) where fields of All rotation rice, Province 1). conventional (Table the Laguna radius in 15-km been about in of area located an across were farmers’ in that sampled were fields Pila) and Maligaya, (Bugallon, Famy, soils Luisiana, five soils), different to amendment glucose and olpoic olodr(SA oa ai eM HAalbePAalbeKCCCa Silt Clay CEC K Available P Available pH Mn Fe ratio C Total (USDA) order Soil province Soil ushdbe eoe rmti il fe h avs of harvest the after field this from removed been resi- had crop aboveground dues sampling, before rotation. years rice–rice several conventional During the rotations. under double-cropped was soil annual IRRI-1 in The were Rice fields Ban International All 1). Los the (Table (IRRI), of farm field Institute three research Research within the treatments on four from experiments sampled was soil clay al noprto Wt ta. 00.TeIR- olwas of soil IRRI-4 d The 60 2000). within al., the decomposed et field, were (Witt this residues incorporation In crop fallows. early the the of of most bulk throughout conditions lasted aerobic that under decomposing hence incorporation), RI4Lgn qadcEiqol1. 172. . . 90113. 8 360 360 390 580 360 550 580 520 37.2 37.7 37.6 38.2 580 540 1.1 210 260 420 0.9 1.1 660 0.6 690 290 44.2 18.7 570 31.1 290 24.2 29.0 15.0 32.0 9.4 56.8 0.4 0.2 0.3 0.1 6.9 6.4 6.8 0.1 6.7 62.0 11.0 1.3 0.7 1.8 0.9 4.1 0.7 27.4 3.4 20.5 7.5 25.7 6.1 11.7 17.3 11.4 6.2 – 4.3 14.2 1.6 0.5 – 16.0 6.9 16.4 1.5 11.3 0.9 12.6 12.4 Epiaquoll Aquandic 0.2 12.6 16.7 11.5 Epiaquoll Aquandic 43.3 Epiaquoll Aquandic 14.8 45.5 14.9 Epiaquoll 6.5 10.1 Aquandic Laguna Laguna Haplaquoll 11.8 Andaqueptic 18.1 10.6 IRRI-4 Laguna IRRI-3 Laguna Tropaquept 24.3 IRRI-2 Vertic Laguna IRRI-1 Endoquerts Troporthent Ustic Aquic Laguna Ecija Nueva Pila Haplaquoll Maligaya Typic Laguna Famy Pangasinan Luisiana Bugallon solution exudate the in acids organic Individual (2001a). al. II. and I Experiments in used soils the and of properties maize Selected yr, 5 1. Table previous soil the flooded in During grown season. ( rice wet by maize the followed a during season under dry was the but during IRRI-3 as field mays same the from (“early” harvest after wk a 3 under to also 2 was within residues soil crop incorporated sampling, IRRI-3 to were previous The yr 5 IRRI-1. For rotation. for rice–rice as same the ha N kg crop, 120 crop: subsequent each to applied the were rates for tilizer fer- preparation Recommended probably was practices. management field was in standard the following soil when flooded surface fallow, and the dry of tilled the end the in until roots largely delayed crop the decompo- of harvest, after sition done was tillage no Because crop. each 564 nEp tigrn fCH of (triggering I Exp. In nEp I(feto rpmngmn ntetigrn of triggering the on management crop of (effect II Exp. In 4 rdcinb oteuae n lcs) h Maahas the glucose), and exudates root by production .–iertto,weemiewsgoni eae soil aerated in grown was maize where rotation, L.)–rice Ϫ hlpieCNAtv Active Active C/N Philippine AEIL N METHODS AND MATERIALS 1 olcinadAayi fSoils of Analysis and Collection a uepopae,ad5 gha kg K 50 and superphosphate), (as 4 rdcinb otexudate root by production ˜ s aua Philippines Laguna, os, OLSI O.A.J,VL 9 AC–PI 2005 MARCH–APRIL 69, VOL. J., AM. SOC. SCI. SOIL gkg Ϫ Ϫ Ϫ 1 1 1 a urea), (as a KCl). (as Zea x.II Exp. x.I Exp. gkg Kha ouin nefrdwt hs nlss fe ,teCaSO the h, 2 After organic analyses. soil these and the with of C interfered representative solution, solution more en- while also total solutions, It nutrient for acids; 2001a). analyses al., et subsequent (Aulakh abled medium with water compared deionized exudation root a solution, of soil rates the realistic more approximated enabling that environment osmotic an mte u ahrc rprcie 6k ha P kg 26 received crop rice was each fertilizer N but of omitted application treatments, the IRRI-4 In and incorporation. early IRRI-3 via incorporated were residues rice ahpatwspae naPCtb otiig50m of mL 500 containing tube PVC a in placed 0.01 was plant each eermvdfo h otdsi n h otsse of system root the and soil potted the from removed were nlzr,NaHCO analyzer), analyses. all for used of were replicates composite Three each performed. were experiments incubation h usmlswr trdi akesa 25 at darkness in a stored analyses. and were further screen, all subsamples 2-mm for The a drawn was through subsample of was sieved representative soil composite and composite a Each air-dried, was together plots. mixed, replicate soil mixed three IRRI and from Each field taken soil composite. the corings core one of three make a middle field, to the with farmer’s near each collected taken For rice were were diam. season Samples 8-cm wet of the 1998. of sampler October harvest after in layer crop surface 15-cm to 0- imaeaeetatbeK(ra rti iityo Agricul- of Ministry Britain (Great K acetate-extractable nium olwtrsure Peh 95,adpril ie(a,1965). (Day, size 1:1 particle in and pH 1965), Britain 1981), (Peech, (Great Food, slurries soil/water CEC and Fisheries, 1959), Agriculture, Kumada, of and Ministry (Asami active Mn dithionite-extractable and 1981), Fe Food, and Fisheries, ture, n I n thdacnetaino . oa rai L I C Exp. organic both total g in 1.2 soils of concentration the a to had it added and was II, was exudates and it root solu- Then of final debris. This tion freeze-drying. cell through mL microbial 600 to and concentrated detritus root remove yNlo n omr 19)admdfe yAlk et Aulakh by modified and (1996) Sommers and described procedure Nelson digestion by wet the through determined as 0.45- a and paper filter What- solution through 42 successively exudate filtered No. was combined man L) (15 the plants and all from removed, was solution the plants were intact following Briefly, exudates 2001b). stage (2001a, al. Root growth soil et Aulakh initiation (2001a). of potted procedure panicle al. flooded the et in at Aulakh collected greenhouse by the described in as grown were IR72 Ϫ 1 h ol eeaaye o oa atmtdcombustion (automated C total for analyzed were soils The o l iefedtetet,si a ape rmthe from sampled was soil treatments, field nine all For hryrc lnso h ihyedn eiwr cultivar semidwarf high-yielding the of plants rice Thirty M Ϫ 1 . CaSO soil/H 1:1 4 ·2H 2 Omgkg 2 .Ti ouinpoie h otclswith cells root the provided solution This O. usrt Preparation Substrate 3 etatbeP(le ta. 94,ammo- 1954), al., et (Olsen P –extractable Ϫ 1 cmol ␮ ebaefle to filter membrane m c kg Ϫ 1 Ϫ Њ 1 ni the until C n 0kg 50 and gkg Ϫ 1 Ϫ 1 4 Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. CH oueo CH of volume he usrt treatments substrate three fhasae() Wtemlclrwih fCH of weight molecular the L MW mol (L (L), day headspace per of headspace vessel the in d where equation: following 60 the were using puted temperatures detector and 150 and column The m gas. 2 carrier mesh, (100/200 Porapak column a and N detector ionization flame a with equipped (2002a). graph al. et Mitra by provided were CH procedure septum of a through determination removed were for vessel each of headspace and the d, 13 d, 7 d, incubation 3 CH an d, for N before 2 with sampled hours d, be 1 Twenty-four would h, spiking. vessel 12 after h, 6 d h, 20 2 measured was tion the N spiking, 30 with at after de-aerated reincubated in Immediately were resulting 1:2. suspensions vessel, of soil ratio incubation soil/water an glu- final into of a exudates solutions of root final mL the or 20 or cose adding (control) by water deionized imposed either were control) unamended and solution. glucose or exudate root the with to CH period background this the during stages. measure sampled periodically growth was crop air late-season Headspace under of occur representative would of methanogenesis conditions addition ensuing subsequent and that substrates so soils C the of air- grinding the and following drying conditions anaerobic redox of equilibrium reestablishment their the 30 attained at had d (E soils 70 potential the for time pre-incubated which and by capped were vessels the as were inlet suspensions an soil min The and N (2002a). a with outlet al. with de-aerated gas et sealed Mitra a by was with described beaker mL each equipped 20 Each beakers, stopper with bar. glass rubber soil spoutless magnetic air-dried 100-mL a of in containing g water 20 deionized mixing of by prepared were 6.8. of pH a had solutions final both that so solution total buffer 0.025 g with diluted (1.2 were solution solution exudate exudate L root C final organic the as concentration m glucose stock 3.47 A concentration 2000). al., of et solution (Lu studies CH previous for in used C been organic exogenous of source 1960). anthrone al., the et by (Brink determined was assay solution colorimetric con- (1986) exudate carbohydrate the Pratz Total of (2001a). and al. tent Badoud et Aulakh of by protocol modified as the by measured were ehn rdcinrt gCH (g rate production Methane nbt x.IadI,guoewscniee h standard the considered was glucose II, and I Exp. both In ehn ocnrto a eemndo a chromato- gas a on determined was concentration Methane exudates, root (glucose, treatments substrate d, 70 After soils (nine vessels incubation 81 experiments, both For 4 Ϫ Ϫ tec apigtm,tilct -Lgssmlsof samples gas 1-mL triplicate time, sampling each At . (d 1 1 ), hl h upnin eesirdsmlaeul.Then simultaneously. stirred were suspensions the while 2 c a t20m min mL 250 at gas c W Њ /d ,rsetvl.TeCH The respectively. C, /d esrmn fMtaeProduction Methane of Measurement s t t )[( h r egto ol() n Vtemolecular the MV and (g), soil of weight dry the Ϫ ersnstecag ntecnetaino CH of concentration the in change the represents H 1 aus hslnt fpenuainensured preincubation of length This values. ) .Teguoesokslto n h nta root initial the and solution stock glucose The ). 4 V t30 at hs Њ .Frbt x.IadI,diyCH daily II, and I Exp. both For C. ϫ 2 a o i tafo aeo 0 mL 300 of rate flow a at min 3 for gas Њ MW)/( 2.8Lmol L (24.88 C Ϫ 4 ute eal ntesampling the on details Further . 1 ϫ o i ormv accumulated remove to min 3 for 4 W rdcinrt eoespiking before rate production he aoaoyreplications) laboratory three ϫ s IR TA. RGEIGMTAEPOUTO NRC SOILS RICE IN PRODUCTION METHANE TRIGGERING AL.: ET MITRA M ϫ 4 4 0m ..,wt N with i.d.), mm 20 rdcin twsflushed was it production, rdcinrt a com- was rate production a iue otesm C same the to diluted was V][1] MV)] Ϫ Ϫ 4 1 ). 1 4 g M d rdcin si has it as production, Ϫ 2 Ϫ KH 1 a o i and min 3 for gas 1 ), old soil 2 V PO hs h volume the 4 Ϫ –Na 1 ) 4 produc- 2 ϭ 4 2 sthe as HPO 1 g (16 Њ C, ϫ 4 4 hspeicbto a iia ewe h unamended the CH between of For similar amount was methanogens. pre-incubation total this to the soils, available five been all initially substrates had all on- of that five depletion indicating the 1a), for (Fig. treatment soils control farm the in ceased had tion soils. IRRI the the dominated of P four clay available in while separate of soils, size on-farm soil levels five major high the was had Silt II) K. I) and (Exp. (Exp. soils comparison, By soils IRRI K. and the on-farm P available Most in low Pila. relatively were alkaline mildly Luisiana acidic and strongly varied the for Mn except and acidic values mildly pH Fe were Soil active 1). (Table and respectively II, eight-fold, and and six- I Exp. in used soils rprsde Wsmn ta. 98.O h olprop- soil the Of been 1998). al., has et (Wassmann as residues properties, crop soil CH for intrinsic previously shown CH by on influenced exudates is root of effect stimulating had soils and production. three glucose of other both levels the for intermediate and soil treatments, Famy soils exudate the five root in the that soil Bugallon of double the four that was in production in double methane Total treatment least 2b). exudate at (Fig. was root the treatment of glucose the of tion root soils. the all in for than the treatment treatment glucose exudate in CH the soil in the faster Bugallon creased and the began for treatment, decrease steepest glucose the was decrease and soils; of soonest among pattern considerably CH The of varied rate considerably. daily decreased the spiking had of d 12 within Famy rates. lowest and the treatments, among exudates had both Pila root for and and rate firs production glucose the highest the During the four-fold. had to soil Bugallon two- h by 24 varied after example it CH for soils; of five root the among rate following considerably The than addition. addition exudate glucose following CH root faster of that rate the (2001b) d, 8 al. next CH to et con- contribute 1c), Aulakh can (Fig. of exudates exudates finding root or the 1b) firming spik- (Fig. after glucose hours within of soils ing all in increasing began root tion or glucose of 2a). were addition (Fig. that exudates subsequent vessels to incubation those dedicated and vessels control enadaon fCH pat- of in variation amount the and management, crop tern and use land of xeietI rgeigo CH of Triggering I: Experiment yteedo h 0dpeicbto,CH pre-incubation, 70-d the of end the By nine the among four-fold varied content C soil Total uuaieCH Cumulative CH of production increased This CH of rate the pre-incubation, 70-d the After eas l iesishdrltvl iia histories similar relatively had soils five all Because otEuaeadGuoeAedetto Amendment Glucose and Exudate Root EUT N DISCUSSION AND RESULTS 4 olProperties Soil ifrn Soils Different rdcindrn h 0dincuba- 20-d the during production 4 rdcini l ol remained soils all in production 4 4 rdcinfo incorporated from production rdcinsget htthe that suggests production 4 rdcin uigthe During production. 4 rdcinrt de- rate production 4 4 rdcinvaried production 4 rdcinby Production rdcdduring produced 4 a transient; was 4 4 production production 4 4 t4dthe produc- produc- 565 Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. nmne soil. unamended rislse nTbe1 oee,ol E a signifi- was CEC ( only however, correlated 1, cantly Table in listed erties fMtae l 20a 02)frCH for 2002b) (2002a, al. et results treatment. Mitra the with of exudate consistent root positive, the was association for This only then and duction, i.1 al ae fCH of rates Daily 1. Fig. 566 ftesmlnsfo o2 fe pkn istgah)are graphs) (inset spiking after h 24 to CH 0 from those Units Vertical samplings replicates. to shown). the laboratory identical three (not of of were treatments errors From treatment exudate standard exudates. represent control root root bars and the rice glucose in (c) the trends and of d, glucose 70 (b) to with 0 d 70 following to incubation at 20-d corresponded spiking a that during d and 20 incubation, post-spiking additional the an during plus treatment pre-incubation control 70-d unamended a the (a) for fields farmers’ five 4 g –1 old soil Ϫ 1 . P 4 rdcinfrlwadrc ol ae from taken soils rice lowland for production Ͻ .5 ihcmltv CH cumulative with 0.05) OLSI O.A.J,VL 9 AC–PI 2005 MARCH–APRIL 69, VOL. J., AM. SOC. SCI. SOIL 4 rdcinfrom production 4 pro- ␮ g raigsapywti or fe pkn iheither with spiking after hours within sharply creasing oeol lgtyi RI3adIR- Fg ) Cumu- 3). and (Fig. IRRI-4 CH soils and lative IRRI-2 IRRI-3 in and slightly IRRI-1 only rose the in negligible mained CH oigsiigadpa rdcinrahda modest at reached production fol- peak response and delayed spiking a lowing with produc- subdued, the residues, was crop increase all tion of or de- roots anaerobic of with composition treatments de- rice–rice the to IRRI-1 IRRI-2, For appeared and 3). (Fig. that practices management manner crop a on pend in but treatments, field CH of rate exu- root or glucose 4a). with d (Fig. 70 dates at amendment desig- for samples those nated and treatment control the between CH Total 2. Fig. eoi eopsto fco eius h ne of onset the the residues, IRRI-4, crop and of with IRRI-3 decomposition respectively, For aerobic treatments, rice–maize d. and 16 rice–rice about after levels CH xeietI:Efc fCo aaeeton Management Crop of Effect II: Experiment roso he aoaoyreplicates. laboratory three of standard represent errors bars Vertical with treatment. compared control exudates unamended root the or glucose incuba- with 20-d a spiking during following (b) tion and pre-incubation, 70-d a during (a) fields olwn pkn ihguoeo oteuae,the exudates, root or glucose with spiking Following of rate the period, pre-incubation 70-d the During 4 4 h rgeigo CH of Triggering the omto nteuaeddcnrltetetre- treatment control unamended the in formation rdcinwsmr ioos t aebgnin- began rate Its vigorous. more was production 4 4 rdcindrn hspro ifrdlittle differed period this during production rdcinicesdi ol rmalfour all from soils in increased production 4 rdcinfrfv iesistknfo farmers’ from taken soils rice five for production xdtsadGlucose and Exudates 4 rdcinb Root by Production Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. b,idctn htCH that indicating 4b), ae elaoetoeahee nIR- n RI2 nsisfo l orfedtetet,cmltv CH cumulative treatments, field four all from soils In at IRRI-2. (glucose) and d IRRI-1 in 12 achieved or those exudates) above (root well rates d 8 after reached n lcs ramnsfloe h re IRRI-1 order the followed IRRI-2 treatments glucose and aaeettetet uigti 0dpro Fg ,a. 2000). al., (Bachoon Everglades Florida four the all from 3, from soils (Fig. soils period wetland 20-d for this during negligible of treatments management was lack to vessels due control unamended the in established production Methane be replication. field cannot significance cal CH incubation, 20-d the of remainder the For hnfrIR- n RI2 uuaieCH Cumulative IRRI-2. and IRRI-1 for IRRI-3 for than amount larger a by decreased tion indrn h 0dpro o ohtero xdt huhguoeadro xdtswr de tthe at added were exudates root and glucose though exudate root the both for period 20-d the during tion oteuae rguoe n ekpouto a orsisrfetddfeecsi h ovrino the of conversion the in differences reflected soils four was production peak and glucose, or exudates root CH of rates Daily 3. Fig. ftrelbrtr elcts brvain:DI aso nuain A,dy fe spiking. after days DAS, incubation; of days DOI, Abbreviations: replicates. laboratory three of uiga7- r-nuainpu nadtoa 0dta orsoddt h otsiigicbto.Gah o aho h ormanagement four the of each rates is for production Graphs IRRI-4 shows incubation. residues. treatment post-spiking control crop the unamended to all the corresponded of that for decomposition d graph CH rice 20 aerobic The depict additional double-cropped residues. with an is treatments crop rice plus IRRI-2 all pre-incubation double-cropped roots. of 70-d is crop a decomposition of IRRI-3 during aerobic decomposition with residues. anaerobic rotation crop and rice-maize all residues a of crop decomposition aboveground anaerobic of removal with with rice double-cropped is oto.Uiso h apig rm0t 4hatrsiig(ne rps are graphs) (inset spiking after h 24 to 0 from samplings the of Units control. Ͻ IRRI-3 Յ 4 4 RI4(i.4) lhuhsait-I rvossuis lcs mnmn nacdCH enhanced amendment glucose studies, previous In statisti- although 4b), (Fig. IRRI-4 rdcindrn h 0dicbto olwn pkn ihguoeo oteuae oprdt h unamended the to compared exudates root or glucose with spiking following incubation 20-d the during production rdcinfrlwadrc ol ae rmfu rpmngmn ramnso h RIrsac am IRRI-1 farm. research IRRI the on treatments management crop four from taken soils rice lowland for production 4 rdcinatrsiigi these in spiking after production IR TA. RGEIGMTAEPOUTO NRC SOILS RICE IN PRODUCTION METHANE TRIGGERING AL.: ET MITRA n IRRI-4 and 4 4 produc- produc- Ͻ n oe,19)adtoPiipn iesis(uet (Lu soils rice Philippine two and 1992) Jones, and two in amendment acetate with compared production glucose the for incubation 20-d the during production iial nEp ,ternews16 o27fl,al- 2.7-fold, to 1.6- was exudates. range root the for I, that Exp. 3.6-fold in to Similarly 2.9- was treatment aert f1. of rate same mne lcs n oteuae oCH to exudates root and glucose amended h ossetyhge rdcino CH of production higher consistently The ␮ gCH 4 g –1 2gCkg old soil Ϫ 1 etclbr ersn tnaderrors standard represent bars Vertical . Ϫ 1 oli ohexperiments. both in soil 4 . 4 rmglu- from 567 4 4 Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. pkdwt oteuae.Slaelvl rae than greater levels Sulfate 105 to exudates. 60 root with spiked M evdt etrrss irba erdto under degradation microbial resist ob- better been have to acids Com- organic served 2). simple (Table glucose, acid with lactic pared and citric, succinic, tartaric, fCcmons nldn rai cd uha malic, as such acids organic variety including a compounds, contain C exudates of root whereas easily contains C, Glucose degradable quality. substrate to incubation due 20-d likely the is during exudates root from than cose eodpsil as ftegetrCH greater the of cause possible Schu second 1979; (Tate, conditions flooded h lcs ramn a h ih(prxmtl 0.12 (approximately high the was treatment glucose the oa rai 1.2 detected Not m 1.74 0.4 0.7 detected Not m m 1.21 12.06 Concentration C organic Total carbohydrates Total acids organic Total acid Lactic acid Citric acid Succinic acid Tartaric acid Malic Compound was that solution exudate root final the of Composition 2. Table CH Total 4. Fig. 568 uft ocnrto nteslto ftesoils the of solution the in concentration sulfate ) gmn ramnso h RIfr a uiga7- pre-incuba- 70-d a during (a) farm IRRI the on treatments agement xdtswr olce ttepnceiiito rwhstage growth plants. initiation root rice panicle The the the pre-incubation. of at 70-d collected after were samples exudates soil the to added replicates. laboratory three of errors repre- standard bars Vertical sent 3. Fig. in treatment. explained control are unamended treatments Management the with compared glucose exudates with spiking root following or incubation 20-d a during (b) and tion, ␮ M 4 a tmlt uft eues hc sup- which reducers, sulfate stimulate can rdcinfrrc ol ae rmfu rpman- crop four from taken soils rice for production ¨ ze l,18b.A 1989b). al., et tz OLSI O.A.J,VL 9 AC–PI 2005 MARCH–APRIL 69, VOL. J., AM. SOC. SCI. SOIL 4 rdcinin production 0gCL 5gCL 5gCL M M M Ϫ Ϫ Ϫ 1 1 1 rdcdsbtaeCaedd(ue l,20) indi- 2000), al., et (Lu methane-C amended of produced/substrate-C ratios molar the as calculated efficiencies, 00,btw i o bev hsefc.Transformation effect. this observe not did we but 2000), te tde DlnegadJgr 99 ue al., et Lu 1989; Jager, and (Dalenberg studies other u h / aisfrIR- n RI4d o suggest IRRI-2, not do CH and IRRI-4 IRRI-1 and that IRRI-3 for for ratios available C/N not the but was N soil Total fEp n a oascainwt CH with soils association the no among had 14.8 and to I 10.1 The Exp. from IRRI-2. of varied and ratio IRRI-1 abundant C/N in more than soil was IRRI-4 1997) and al., IRRI-3 et in Gaunt 2002; al., et (Ito ovre oCH to converted plcto fNfriie,a etlzrwsapplied soil was measured fertilizer Commonly IRRI-2. N and as IRRI-1 to fertilizer, solely N of application fCH methano- of association promote general the that oppose they conditions Specifically, genesis. soil under- the current our of with standing consistent established. not residues are be soil), results (IRRI-4 cannot These rice residues significance rice either statistical and although maize of or treatments soil) decomposition the (IRRI-3 from aerobic soils in with occurred incubation 20-d n lcs nterptnilfrCH for potential their in glucose study, exudates this and root in between used difference soils intrinsic same an the suggesting of some to added when ihtedge fsi eaindrn rvoscrop previous during CH aeration greatest soil The of management. degree the with ologncmte,ta s o / ratio. C/N low a is, that matter, organic soil oge l 19)o nrae CH increased of (1999) al. et Chidthai- by association song the to communication). contrary rice– are personal findings the Scow, Our with M. compared (K. rotation rotation decomposition, maize rice–rice aerobic of the with (ii) decomposition and compared anaerobic ester residues (i) methyl crop with acid in treatments found fatty were field by the subpopulations anaerobic determined of more analysis: as subpopulations soils microbial IRRI in trends contradict oteuae naslaefe ouinadsilfound CH still and less solution provided sulfate-free they a collected however, in (2000), exudates al. et root Lu 1983). Klug, and ley (Lov- competition substrate through methanogens press ennso irognssta e f h otexu- root the off fed cellular that microorganisms and associ- of exudates been remnants Root yet methanogenesis. not with have ated that processes other involve CH CH to 2000). glucose al., occurs of et that conversion efficiency stoichiometric 50% only the with indicated exceeds be value would this matter when organic decompo- Accelerated native C. of amended sition of 28% CH most at of was quantity the that cated CH soils a as IRRI of four thought commonly the Fe, among Active CH of varied rates different distinctly scarcely their despite it I, Exp. CH with associated for explanation an indicate CH not did 1) (Table properties eopsto fntv ologncmte noCH into matter organic soil native of decomposition h eret hc oteuae n lcs were glucose and exudates root which to degree The ec h oiieascaino olarto with aeration soil of association positive the Hence mnmn fognccmonsaclrtdthe accelerated compounds organic of Amendment 4 4 rdcinfo oteuae n lcs must glucose and exudates root from production rnsi x.I.Atog E a positively was CEC Although II. Exp. in trends 4 rdcinwt neoi olcniin.They conditions. soil anaerobic with production 4 rdcinwsascae ihmr labile more with associated was production 4 a oiieyascae nEp II Exp. in associated positively was 4 rdcinfo oteuae in exudates root from production 4 rdcinta i glucose did than production 4 Ceovdi hsstudy this in evolved –C 4 rdcindrn the during production 4 4 rdcinwith production production. 4 4 4 suppressant production. production. 4 (Lu 4 in Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. a idn.A n osbeepaainfrorrsls ai atrsc hti rvddls hmclstabiliza- chemical less provided soils it that such soil in matter ganic that matter speculate We organic residues. treatments soil crop aerated of better young the decomposition from that results, our speculate for explanation we chemi- possible involves one As which binding. matter, de- cal organic some soil to the incorporated into likely gree were glucose and dates on rai atrta omdudrtemr an- more the the under formed did that than matter root remnants organic the cellular young with and bonds glucose, chemical exudates, weaker or fewer formed rmtdb oainwt padmieo yaerobic by or been maize upland had with conditions rotation soil sampled by treatments Aerobic promoted field experiment. the this in for aeration soil of degree Exp. In CH experiments. to both II, related for closely property not soil were intrinsic any they but soils, among varied CH of Rates amendment. glucose following CH to led II. Exp. of conditions soils field IRRI-4 and anaerobic IRRI-3 more the with under compared been had generally CH that the of explain rates cannot higher aeration CH soil addi- as control likely exudates, that are factors there soil aeration tional measured soil commonly Besides in properties. differences perceptible of on practices and management exudates CH previous root the of with effects the consistent observed be from would stabilization formed Such glucose. were rem- microbial that and exudates nants root the strongly stabi- more conceivably lize could II Exp. of treatments anaerobic 1990). (Malcolm, soils anaerobic accu- in commonly in- mulate 1997) compounds and al., phenolic et 1993) and Noguchi al., compounds, 1985; Ding, et and (Chen (Ceccanti organic organic of plant stabilization of chemi- cal promoted decomposition conditions Anaerobic controlled under 2004). materials al., N et soil (Schmidt- organic rice Rohr practiced triple-cropped was soil decomposition a anaerobic of in where residues binding lignin covalent phenolic by for di- by evidence provided Analysis rect spectroscopy rice. resonance magnetic double-cropped nuclear under N crop and inhibited of residues decomposition the anaerobic with under associated mineralization phe- was of compounds accumulation nolic an Simultaneously, pro- double- rice. with cropped compared were rotation maize–rice benefits the by with vided Similar than residues decomposition. crop anaerobic of decomposition aerobic immobilized with and total both N in-season of matter organic rotation, organic rice young IRRI-4 from double-cropped mineralization and the IRRI-3 ex- the For field for soils. the sampled in was cycling that N periment studied who (2002), Cassman short-term for IRRI-4 and IRRI-3 CH available in remained methanogens glucose-C to or exudate-C root Consequently more IRRI-2. and IRRI-1 of conditions aerobic hsseuaini ae nterslso l and Olk of results the on based is speculation This eopsto fro xdtsi umre soils submerged in exudates root of Decomposition the from soils in matter organic phenolic-rich Hence 4 4 production. rdcinfo oteuae ept h lack the despite exudates root from production 4 rdcinwspstvl soitdwt the with associated positively was production 4 rdcin lhuha lwrrt than rate slower a at although production, CONCLUSIONS 4 rdcini h ol fEp I Exp. of soils the in production IR TA. RGEIGMTAEPOUTO NRC SOILS RICE IN PRODUCTION METHANE TRIGGERING AL.: ET MITRA 15 etlzrwsgreater was fertilizer N 4 rdcinfo root from production IR- n IRR and (IRRI-3 4 production I-4) ino h mne usacsadealdterfaster CH their into enabled and conversion substances amended the of or- tion soil young of nature chemical the changed aeration aebr,JW,adG ae.18.Piigefc fsm organic some of effect Priming 1989. Jager. G. and J.W., Dalenberg, i treatments. bic anneg . n .Cna.19.Efc frc lnso methane on plants rice of Effect 1999. Conrad. R. and S., Dannenberg, ahlt . n ..Nu.19.Mtaeeisosfo wetland from emissions Methane 1993. Neue. H.U. and D., Bachelet, uah .. .Wsmn,C un,J ruwee,adH Ren- H. and Kreuzwieser, J. Bueno, C. Wassmann, R. free M.S., determining Aulakh, for method new A 1959. Kumada. K. and T., Asami, 2000. Singh. U. and Wassmann, R. Bronson, K.F. 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