Carbon mineralization dynamics in soils amended with meat meals under laboratory conditions

Transcription

1 Aville online t Wste Mngement 28 (28) Cron minerliztion dynmics in soils mended with met mels under lortory conditions M.L. Cyuel,, T. Sinicco, F. Fornsier, M.A. Snchez-Monedero, C. Mondini, * CEBAS-CSIC, Cmpus Universitrio de Espinrdo, P.O. Box 164, 31 Espinrdo, Murci, Spin CRA-Istituto Sperimentle per l Nutrizione delle Pinte, sez. di Gorizi, vi Trieste 23, 3417 Gorizi, Itly Accepted 6 Septemer 27 Aville online 26 Novemer 27 Astrct Met nd one mel (MBM) is otined from the wstes produced during slughtering opertions. Its high concentrtion of N nd P mkes it interesting s n orgnic fertiliser ut its use in soil hs een rely studied previously. In this work four lortory experiments were performed to study the influence of different vriles (MBM composition, rte of ppliction, temperture of incution nd the type of soil) on C minerliztion dynmics of MBM in griculturl soils. The totl CO 2 C evolved (s % of dded C) fter 2 weeks rnged etween 1% nd 2%. The kinetics of minerliztion were rpid, with C evolved s CO 2 within the first 4 dys representing more thn 5% of totl C minerlized. A liner correltion ws found etween the rte of ppliction (dded-c) nd CO 2 C evolved (r 2 :.997; P <.1). A temperture coefficient (Q 1 ) ws used to ssess the difference in iologicl ctivity t 5 C intervls. Q 1, which rnged from 1. to 2.7 (25 h), ws higher for the lower temperture rnge (Q 1 (15 2 C) > Q 1 (2 25 C)) nd it ws found to e relted to the soil properties. Finlly, the minerliztion process ws found to e highly dependent upon the different soil fctors, lthough no simple liner correltion ws found etween minerliztion nd soil properties. Ó 27 Elsevier Ltd. All rights reserved. 1. Introduction Met nd one mel (MBM) is otined in met rendering plnts from the wstes produced during slughtering opertions. It hs een used for mny yers s n excellent source of protein in frm niml diet ut, since the ppernce of Bovine Spongiform Encephlopthy (BSE), the Europen legisltion hs nned the use of met wste for feeding nimls destined for humn consumption. This prohiition represents considerle wste prolem tht until now hs een minly tckled y incinertion processes (Cones et l., 25). Nevertheless, MBM contins high concentrtion of orgnic mtter nd considerle mount of N, P nd C, which mkes its inclusion s fertiliser ttrctive. In fct, the current Europen legisltion on orgnic frming (Council regultion (EEC) No. 292/ 91) considers MBM within the llowed fertilizers nd soil * Corresponding uthor. Tel.: ; fx: E-mil ddress: cludio.mondini@entecr.it (C. Mondini). conditioners (Annex II). There is still lck of knowledge out the implictions of their use in soil since limited reserch hs een done. In the literture, the few works evluting MBM s soil fertiliser report positive results. Bltt (1991) conducted field reserch compring severl orgnic mendments (mong them MBM) to minerl fertilizer nd found similr yields for wide rnge of horticulturl crops. More recently, Jeng et l. (24) found reltive efficiency of 8% when compring MBM to minerl N in cerel crops. MBM hs lso een shown to e io-control gent ginst the fungl wilt pthogen Verticillium dhlie (Tenut nd Lzrovits, 24). However, there is no informtion on MBM decomposition ptterns for specific soils nd climte. Decomposition results in the emission of cron into the tmosphere s cron dioxide, s well s the minerliztion of essentil nutrients. This informtion is vitl to develop effective mngement strtegies, since nutrient relese dynmics depends on the minerliztion rte of MBM orgnic compounds (minly proteins nd fts) X/$ - see front mtter Ó 27 Elsevier Ltd. All rights reserved. doi:1.116/j.wsmn

2 78 M.L. Cyuel et l. / Wste Mngement 28 (28) The rekdown of most orgnic compounds in soil is due to the decomposer microorgnisms nd cn e ffected y numer of soil fctors such s temperture, ph, redox, nd texture (Côté et l., 2; Khlil et l., 25; Crter nd Tiett, 26). The qulity of the dded orgnic mtter, such s C ORG /N T rtio, phenols, lignin or ft content, cn lso determine the ese with which energy nd nutrients re ccessed y the decomposer community (Sviozzi et l., 1993). The im of this study ws to exmine the influence of different vriles on the cron minerliztion dynmics of MBM in soil. We studied the effect of sustrte (MBM) qulity, rte of ppliction, incution temperture nd soil chrcteristics on the minerliztion dynmics nd the totl CO 2 relesed to the tmosphere. Hence, simple utomtic chromtogrphy system ws set up s the first step to design pproprite field mngement strtegies which cn improve soil productivity nd crop production, s well s help to reduce the tmospheric uild-up of cron dioxide. 2. Mterils nd methods 2.1. Met nd one mel (MBM) Six commercilly ville smples of MBM were selected for their incution with soil. Tle 1 presents their principl chemicl chrcteristics. The vriility of MBM s properties is due to their different compositions (they re otined from mixture of crcss trimmings, Tle 1 Min chemicl chrcteristics of met nd one mels (MBM) MBM C ORG N T C ORG / N T P Ashes Fts BV BV BV/SW n.d BV D-BV SW n.d. Concentrtions expressed on dry weight sis. BV: ovine; SW: swine; BV/SW: mixture ovine/swine; D-BV: deftted ovine. inedile offl, lipids nd ones from different nimls) nd to the production process itself (tempertures, seprtion methods).we used three ovine (BV1, BV2, BV3), deftted ovine (D-BV3), swine (SW) nd mixture of ovine/swine (BV/SW) MBMs. Before ppliction, the smples were ground to.5 mm to stndrdise the prticle size Soils Seven griculturl soils were smpled ( 2 cm depth), sieved to < 2 mm t field moisture content nd stored t 5 C. Their min properties re given in Tle 2. Before incution the soils were djusted to 4% of wter holding cpcity nd pre-conditioned y incution t 15, 2 or 25 C under eroic conditions for 7 dys Incution experiments MBM C minerliztion ws studied in four eroic incution experiments with soil; 5 g (dry weight sis) of the pre-conditioned soil smple nd the pproprite mount of MBM were thoroughly mixed nd introduced into seled 13 ml plstic ottles for their incution. A tretment without ddition of MBM (control) ws lso included for every experiment. Soil CO 2 emissions were mesured every 3 h for 1 14 dys with n utomted system for gs smpling nd nlysis (Section 2.4.2). The moisture levels in the ottles were checked dily y mesuring weight loss, nd deionised wter ws dded when necessry to mintin constnt moisture Incution with different MBMs S. Mrtino soil smples were incuted t 2 C fter ddition (4 kg N h 1 ) of five different commercil MBMs (Tle 1). The rte of MBM ppliction on soil ws clculted on n N sis nd thus, the dded-c rnged from 374 (D-BV3) to 481 (BV2) lg Cg 1 soil Incution with different ppliction rtes of MBM A smple of BV2 MBM ws dded t three different rtes (1, 2 nd 4 kg N h 1 ) to S. Mrtino soil smples nd incuted t 2 C. Tle 2 Min chrcteristics of soils used for incution Mngement Snd (%) Silt (%) Cly (%) ph CCO 3 Corg N T B C (lgg 1 ) S. Mrtino Arle Jumill Arle Gorizi Grsslnd Bueris Arle Lodi Grsslnd Ren Arle Riis Arle Concentrtions expressed on dry weight sis.

3 M.L. Cyuel et l. / Wste Mngement 28 (28) Incution t different tempertures A smple of BV3 MBM ws pplied (4 kg N h 1 )to S. Mrtino nd Ren soil smples nd incuted t three different mesophilic tempertures (15, 2 nd 25 C) Incution with different soils A smple of BV/SW MBM ws pplied (2 kg N h 1 ) to seven pre-conditioned griculturl soils (Tle 2) nd incuted t 2 C Anlyticl methods Cumultive extr CO 2 -C C mx C mx / Chemicl nlyses Totl nitrogen (N T ) nd orgnic cron (C ORG ) were determined y utomtic elementl micronlysis (NA 15 Crlo Er Instruments); ph ws determined in 1:1 (w:v) wter extrct using glss electrode. The sh concentrtion ws nlysed y loss on ignition t 55 C for 2 h. Soil microil iomss C (B C ) ws determined y the fumigtion-extrction method (Vnce et l., 1987) CO 2 evolution nlyses CO 2 evolution ws determined y mens of n utomted system for continuous gs smpling nd nlysis. The system siclly opertes s n open chmer system in which the plstic ottles contining the soil smple re continuously erted t constnt flow rte y mens of n ir pump. At regulr time, single ottle is mde closed chmer for selected period (usully in the rnge 1 6 min) y mens of two vlves. The gs concentrtion in the chmer is utomticlly mesured t the eginning nd the end of this ccumultion period y gs chromtogrph specificlly fitted for gs mesurements (Vrin, CP23) nd the difference etween the finl nd initil mesurements provides the rte of gs production for the selected time intervl. The system cn operte with up to 16 smples nd llows the mesurements of the evolution rte of greenhouse gses over regulr periods of time (usully every 1 4 h) Tretment of dt All results re expressed on n oven-dry sis (15 C, 24 h) nd represent the men of three replictes. SPSS 12. progrm for Windows ws used to sttisticlly nlyse the dt. Considering tht the kinetics of C minerliztion my result from the comined effect of mny fctors, multivrile liner regression nlysis ws used to identify MBM nd soil properties ffecting minerliztion dynmics Extr CO 2 C The extr CO 2 C ws clculted sutrcting the mount evolved during the incution of control smples (tretments without MBM) from the mount of CO 2 C evolved during the incution of mended soil. It is ssumed tht this difference represents the mount of CO 2 C evolved t 1/2 from the soil tht is cused y the MBM ddition nd is referred to in the text s extr CO 2 C Minerliztion kinetic model Sigm Plot 2 (SPSS Inc. Sigm Plot for Windows) ws used to fit the cumultive extr CO 2 C curves to the following eqution: C mx CO 2 CðtÞ ¼ ð1þ 1 þðt=t 1=2 Þ k where t represents time of incution. Three kinetic prmeters were determined: the rte constnt (k) representing the slope of the curve, the mximum cumultive respirtion level (C mx ) nd the hlf-life time (t 1/2 ) tht represents the time necessry to rech hlf of the mximum minerliztion (Fig. 1) Temperture coefficient (Q 1 ) Temperture coefficient ws clculted ccording to the eqution: Q 1 ¼ðA 2 =A 1 Þ 1=ðT 2 T 1 Þ ð2þ where A 2 nd A 1 re the cumultive mounts of CO 2 C produced t two oserved tempertures T 2 nd T 1 (Kirschum, 1995). 3. Results nd discussion time (t) Fig. 1. Logistic response curve with kinetic prmeters C mx nd t 1/ Incution with different MBMs Fig. 2 shows the respirtion rte curves (lg CO 2 Ckg 1 soil h 1 ) of soil smples fter the ddition of five different MBMs. Although ll MBMs followed similr minerliztion ptterns, noticele differences were oserved etween the smples. The ddition of MBM cused, fter short lg-phse, n exponentil increse in the soil respirtion rte, reflecting the growth of microorgnisms due to C sustrte nd nutrients vilility. The mximum rte of CO 2 production occurred etween 24 h (SW) nd 48 h (BV2) fter the MBM ppliction. This

4 71 M.L. Cyuel et l. / Wste Mngement 28 (28) CO 2 -C (μg kg -1 h -1 ) Cumultive extr CO 2 -C evolved (% C dded) difference my e due to the comintion of severl MBM chrcteristics, minly the vilility of wter-solule sustnces, generlly considered to e the most esily ssimille compounds. The mximum rte of respirtion underwent noteworthy differences etween MBMs nd rnged etween 54 nd 88 lg CO 2 C kg 1 soil h 1. The different mounts of dded C do not totlly explin such differences. In fct, considering the CO 2 evolution per grm of dded C, it rnged etween 1.42 (BV3) nd 1.98 (BV1) mg CO 2 Cg 1 dded-c h 1. After this mximum, the respirtion rte strted to drop, keeping respirtion plteu for 2 3 dys efore decresing to the se level. This plteu could e explined y sustrte/nutrients limittion or the formtion of toxic inhiitory sustnces tht determine short trnsitory limittion in microil ctivity. This phenomenon hs een previously descried y other uthors. Foster et l. (198) oserved decrese in respirtion rte fter the ddition of N to N-limited forest soil nd ttriuted this fct to toxic effect of the dded N. The rte of minerliztion ws high, with C evolved s CO 2 within the first 4 dys representing more thn 5% of totl C minerlized. The decomposition process ws very rpid in comprison to other more complex residues such s chicken mnure nd crop residues (Khlil et l., 25), frmyrd mnure, rice strw (Sviozzi et l., BV1 BV2 BV3 D-BV3 SW CONTROL Fig. 2. Respirtion rte () nd cumultive extr CO 2 C evolution () during the decomposition of five different MBM (ppliction rte 4 kg N h 1 ) in S. Mrtino soil (2 C). 1993), nd composts from different wstes (Bernl et l., 1998) tht contin plnt structurl components more resistnt to microil ttck nd which rek down more slowly. In order to normlize respirtion dt for the different mounts of C pplied with MBM, in Fig. 2 the cumultive extr CO 2 C evolution ws represented s % of dded C. The totl extr CO 2 C evolved fter 2 weeks rnged etween 1% nd 2%. Compring these results with other previous C minerliztion studies, they re in the rnge of poultry mnure (16%) or pig slurry (19%) ccording to 2-dy incution study (22 C) performed y Levi-Minzi et l. (199). Beloso et l. (1993) found minerliztion of out 27% of dded-c for urn refuse compost fter 3 weeks of incution. Jones (1999) studied the minerliztion of mixture of C-lelled mino cids in different soils nd found production of CO 2 -etween 1% nd 25% of totl dded-c t 18 C. Moreover, Thuriès et l. (21) studied the C minerliztion of 17 different orgnic mterils nd found wide rnge of percentges of minerliztion etween 1% (compost) nd 9% (guno). A common pproch to nlyse the minerliztion dt of orgnic mterils is the fitting to mthemticl models to estimte the prmeters tht descrie the dynmics of the process. First order or comined first-zero order exponentil equtions re the kinetic models most used in literture to descrie C-minerliztion (Blet-Chrudeu et l., 199; Sviozzi et l., 1993; Bernl et l., 1998; Henriksen nd Brelnd, 22). However, in this study, cumultive extr CO 2 C dt, expressed s % of dded-c, fitted est typicl sigmoidl growth model (Hnstr nd Doelmn, 1985; Demetz nd Insm, 1999) nd were djusted to logistic eqution (prmeters shown in Tle 3). The mximum cumultive respirtion level (C mx ) rnged from 11.7% (D-BV3) to 22.4% of dded-c (BV1). The hlf-life time (t 1/2 ), tht represents the time necessry to degrde hlf of the potentilly minerlizle C, ws very short (68 92 h). The results found in this work gree with previous studies on mino cids decomposition in soil. Jones (1999) found tht it ws extremely rpid, with typicl hlf-lives eing in the region of 1 12 h depending on soil type nd environmentl conditions. In nother work, Jones nd Shnnon (1999) estimted the men hlf-life of mixture of 15 mino cids in different soils nd concluded it ws etween 4.3 nd 19.6 h depending on the soil smple. In Tle 3 Prmeters estimted ccording to the logistic model (Eq. (1)) for the C-minerliztion of the different MBMs dded to S. Mrtino soil t 2 C (P <.1) MBM k C mx (%) t 1/2 (min) F BV BV BV D-BV SW

5 M.L. Cyuel et l. / Wste Mngement 28 (28) this study, since MBM ws minly mixture of proteins nd lipids, the reltive greter complexity of the orgnic mtter required longer time nd greter vriety of enzymes to rek down peptides nd triglycerides onds. Therefore, the rte of degrdtion will depend on the proportion of esily degrdle proteins (lumin, hemogloin) to other more complex firous proteins such s collgen nd kertin tht re the min proteins of connective tissue in nimls. The C ORG /N T rtio of orgnic sustrtes hs een frequently used s convenient tool for predicting their rte of decomposition. However, in this work since the C ORG / N T rtios of different MBM were quite similr (rnge: ), it is likely tht other fctors hd greter effect on MBM decomposition rte. Thus, significnt multiple liner regressions were found for C mx (r 2 =.956; P <.5) nd t 1/2 (r 2 =.997; P <.1) considering s independent vriles C ORG nd lipid concentrtion Incution with different rtes of MBM A soil incution experiment with BV2 MBM ws performed to estimte the effect of the dose of ppliction on the rte of minerliztion of orgnic cron. The ppliction dose rnge ws 1, 2 nd 4 kg N h 1 tht ws equivlent to 12, 24 nd 48 kg MBM h 1, respectively. Fig. 3 shows respirtion rtes nd cumultive extr CO 2 C curves. The cumultive extr CO 2 C evolved incresed linerly with the mount of cron dded up to 4 kg N h 1 (r 2 :.997; P <.1). According to these results, the MBM doses of ppliction ssyed in this work hd no effect on the C use efficiency y the soil microil iomss nd consequently they did not influence the uild-up of C in soil. Also Levi-Minzi et l. (199) reported liner correltion etween CO 2 C evolved nd mount of dded-c (ppliction rtes:.5%, 1.% nd 2.% dry mtter) Incution t different tempertures Temperture cn directly ffect metolic processes. In soils with mesophilic microil popultion, n pproximte increse of 1 C is normlly ssocited with douling of ctivity (Dvidson nd Jnssens, 26). Fig. 4 shows CO 2 respirtion rte fter the ppliction of BV3 MBM (4 kg N h 1 ) t three mesophilic tempertures (15, 2 nd 25 C) in S. Mrtino nd Ren soils. The peks were significntly delyed with decresing temperture. The mximum respirtion rte ws chieved fter 2 nd 19 h of incution t 25 C, 3 nd 38 h t 2 C nd 6 nd 57 h t 15 C in S. Mrtino nd Ren soils, respectively. A decrese in temperture ws ssocited s well with reduction of the mximum respirtion rte nd widening of the pek. Fig. 4 shows the cumultive extr CO 2 C curves (right side xis) t every temperture for oth soils. A 5 C increse in temperture cused sttisticlly significnt (P <.1) CO 2 -C (μg kg -1 min -1 ) Cumultive extr CO2-C evolved (μg g -1 ) control 1 kg N H -1 2 kg N H -1 4 kg N H Fig. 3. Respirtion rte () nd cumultive extr CO 2 C () during the decomposition of BV2 MBM t three different rtes (1, 2 nd 4 kg N h 1 ) in S. Mrtino soil (2 C). increse in cumultive extr CO 2 C (% of dded-c) in S. Mrtino soil in oth temperture intervls (C mx : 12.4 ±.1% (15 C), 13.1 ±.1% (2 C) nd 14.8 ±.% (25 C)). Nevertheless, for Ren soil, there ws remrkle increse for the (15 2 C) intervl, ut it ws not significnt for the (2 25 C) rnge (C mx : 11.2 ±.1% (15 C), 16.7 ±.1% (2 C) nd 16.7 ±.1% (25 C)). These results suggest tht microil decomposition is more efficient t lower tempertures (15 C) since less C is emitted s CO 2, s reported y Crter nd Tiett (26). A temperture coefficient (Q 1 ) ws used to sses the difference in iologicl ctivity t 5 C intervls during incution (Fig. 5). Q 1, defined s the increse in cumultive CO 2 for every 1 C, ws not constnt vlue ut vried with time. Q 1 reched the mximum vlue t 36 h (15 2 C) nd 24 h (2 25 C) for oth mended soils, corresponding with the time when higher respirtion rtes were oserved. The mximum vlues recorded for Q 1 were 1.9 in S. Mrtino soil nd 1.7 in Ren soil for the (15 2 C) intervl, while 2.7 nd 5. were the mximum vlues for the (2 25 C) intervl. The fluctution of Q 1 with time demonstrtes tht the influence of temperture is greter with higher microil ctivity nd therefore tht soil respirtion response to chnges in temperture is relted to the effect of temperture on the ctivity of decomposer microorgnisms.

6 712 M.L. Cyuel et l. / Wste Mngement 28 (28) Sn Mrtino Ren CO2-C (μg kg-1min-1) Cumultive extr CO 2 -C (% dded C) MBM 15 C MBM 2 C MBM 25 C control 15 C control 2 C control 25 C cumultive 15 C cumultive 2 C cumultive 25 C Fig. 4. Respirtion rte () nd cumultive extr CO 2 C logistic model fitting () of BV3 MBM (4 kg N h 1 ) in S. Mrtino nd Ren soils t three different tempertures (15, 2 nd 25 C). Q 1, ws lwys significntly higher (P <.1) for the lower temperture rnge (Q 1 (15 2 C)) > (Q 1 (2 25 C)) in oth mended soil smples nd ws found to e ssocited to the specific soil chrcteristics. Hence, Q 1 ws higher in Ren thn in S. Mrtino soil in the (15 2 C) intervl, ut lower in the (2 25 C) one. This fct my reflect tht Ren soil is colonized y microil community tht requires lower energy for ctolism. This remrkle fct hs een previously oserved in other studies. For instnce, Kirschum (1995), who quntified rtes of response using Q 1 reltionship, found it ws inversely relted to temperture. He concluded tht soils from colder climtes re more sensitive to increses in temperture. Likewise, Lloyd nd Tylor (1994) reported tht soil respirtion rte ws more sensitive to fluctutions in temperture for res where soil tempertures were low. On the other hnd, Blet-Chrudeu et l. (199), studying the effect of temperture on soils under different mngement prctices, reported tht soils under ntive grss underwent higher respirtion increse for lower tempertures thn soils under whet or grpes, while when the temperture ws eyond 19 C, soils under grss prcticlly did not incresed their respirtion rte. They pointed out tht microil iomss ws less dpted to thermophilic conditions under grss, due to soil lower tempertures ecuse of the lck of crop cover. In our study oth soils corresponded to rle soils under rottion crops so the differences cnnot e explined in terms of mngement. Possily they re simply due to the dpttion of the microil iomss to the different physico-chemicl chrcteristics of the soil.

7 M.L. Cyuel et l. / Wste Mngement 28 (28) Q 1 Q Incution with different soils Q 1 (15-2ºC) Q 1 (2-25ºC) Fig. 5. Dynmics of temperture coefficient (Q 1 ) of cumultive CO 2 C evolution in S. Mrtino () nd Ren () soils. Fig. 6 shows the outstnding differences oserved in minerliztion dynmics depending on the soil used for incution. For ll smples, the mount of dded-c ws 287 lg Cg 1 soil, nd the mximum extr cumultive CO 2 C rnged etween 11.5% (Ren) nd 3.3% (Lodi) of dded-c (dt not shown). No simple liner correltion ws found etween soil properties nd minerliztion prmeters, which demonstrtes tht the MBM decomposition is complex process depending on mny interrelted physico-chemicl nd iologicl soil fctors. These results re in greement with previous findings y Jones nd Shnnon (1999), who investigting mino cids minerliztion in different soils concluded tht the decomposition of mino cids cron ws due to microil ctivity nd tht the minerliztion kinetics were soil-type dependent. In fct, multivrile liner regression ws found for the MBM hlf-life time (t 1/2 ) depending on soil ph, snd concentrtion nd microil iomss (r 2 =.97; P <.1). The hlf-life time represents, in some wy, the MBM minerliztion rte. The higher it is, the lower the minerliztion rte. Thus, in our work t 1/2 ws directly correlted with ph nd inversely with snd concentrtion nd microil iomss (B C ). The interreltionships mong severl soil properties (orgnic C, totl N, snd, cly, ph, etc.) my ffect the vilility of the sustrte to decomposer communities s well s their own ctivity, influencing the minerliztion rte nd extent. Soil ph hs often een considered s mjor fctor controlling C turnover in soil. It is possile tht the minerliztion of MBM nd the relese of NH 3 hve slightly incresed the ph in the most cid soils which could improve the conditions for microil growth. ph lso influences the dsorption of proteins to minerl surfces since it modifies electrosttic interctions etween chrged soil surfces nd dissocited nionic functionl groups of the proteins. Furthermore, ph hs direct influence on the response of extrcellulr enzymes to complex Cumultive extr CO 2 -C (μg g -1 ) Lodi Gorizi S.Mrtino Riis Bueris Jumill Ren Fig. 6. Cumultive extr CO 2 C evolved during the decomposition of BV/SW MBM (2 kg N h 1 ) in seven different griculturl soils t 2 C.

8 714 M.L. Cyuel et l. / Wste Mngement 28 (28) nutrient inputs in soil. On the other hnd, the high cronte content in the soils with the highest ph could lso hve influenced the minerliztion in these soils. As reported y Beloso et l. (1993), crontes re le to protect the fresh orgnic mtter ginst microil ttck through the formtion of CCO 3 film round these mterils, thus preventing their minerliztion. The soil texture lso seems to e n importnt fctor in the MBM minerliztion process. Thus, prticulrly high t 1/2 ws found for the Bueris soil (lmost twofold in reltion to the other soils), indicting tht the MBM minerliztion rte ws the slowest in this soil. This fct seems to e linked to its peculir texturl chrcteristics with very high concentrtion of cly nd little snd. The influence of soil texture on C minerliztion hs een widely studied. Indeed severl uthors hve previously reported greter minerliztion rtes in soils with higher snd contents for different orgnic mterils (Côté et l., 2; Khlil et l., 25). Generlly, high cly content in soil limits microil ctivity due to sorption of the decomposition sustrte onto minerl prticles nd incorportion into soil ggregtes (Khlil et l., 25). Specificlly, the dsorption of mino cids nd proteins on soil frctions hs een widely investigted. Brtlett nd Doner (1988) found tht dsorption of lysine to minerl surfces in soil suppressed its decomposition. In more recent rticle, Chevllier et l. (23) investigted the ility of soil clys to protect proteins from iodegrdtion nd demonstrted tht proteins were unville for microorgnisms when dsored to cly. This fct could hve importnt implictions for the sequestering of C in griculturl soils since ddition of protein-rich wstes could contriute to their sorption into minerl frctions tht could comprise significnt frction in the soil C pool remining stle for long time. 4. Conclusion Results gthered in this work showed the importnce of environmentl fctors nd soil properties on C minerliztion of MBM in soils. The origin nd nture of MBM lso influenced the rte of iodegrdtion nd the reltive mount of dded C tht ws relesed to the tmosphere. The MBM ppliction rte ws linerly correlted with the cumultive extr CO 2 C evolved nd therefore, the rtes of ppliction used in this work would not ffect the C use efficiency y microorgnisms. Temperture incution ffected not only the rte of minerliztion, ut lso the totl minerlized C. The influence of temperture on MBM minerliztion ws higher for lower temperture intervls nd depended on the soil chrcteristics. The incution of MBM with different soils reveled remrkle differences in the minerliztion rtes nd extents. Our results support the hypothesis tht the decomposition of MBM is soil specific nd lrgely relted to the soil iochemicl nd texturl chrcteristics. Moreover this work shows tht lortory studies cn e useful tool to fcilitte soil mngement strtegies since they llow previous evlution of the effect of mny vriles on the C minerliztion dynmics nd therefore on the nutrients supply nd the soil C sequestrtion. Acknowledgement Specil thnks to Fundción Sénec (Agenci Regionl de Cienci y Tecnologí. Región de Murci) for finncing the postdoctorl Grnt 2534/PD/5. Thnks to ILSA Sp. for providing MBM smples. References Brtlett, J.R., Doner, H.E., Decomposition of lysine nd leucine in soil ggregtes: dsorption nd comprtmentliztion. 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