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1 This rtil ppr in journl pulish y Elsvir. Th tth opy is furnish to th uthor for intrnl non-ommril rsrh n ution us, inluing for instrution t th uthors institution n shring with ollgus. Othr uss, inluing rproution n istriution, or slling or linsing opis, or posting to prsonl, institutionl or thir prty wsits r prohiit. In most ss uthors r prmitt to post thir vrsion of th rtil (.g. in Wor or Tx form) to thir prsonl wsit or institutionl rpository. Authors rquiring furthr informtion rgring Elsvir s rhiving n mnusript poliis r nourg to visit:

2 Author's prsonl opy Agriultur, Eosystms n Environmnt 139 (21) Contnts lists vill t SinDirt Agriultur, Eosystms n Environmnt journl hompg: Short ommunition Soil miroil tivity unr iffrnt grss spis: Unrgroun impts of ioful ropping Rihr L. Hny, Jms R. Kiniry, Mri-Vughn V. Johnson USDA-ARS, Grssln, Soil n Wtr Rsrh Lortory, 88 Est Blkln R., Tmpl, TX 7652, USA rtil info strt Artil history: Riv 12 July 21 Riv in rvis form 21 Sptmr 21 Apt 1 Otor 21 Avill onlin 29 Otor 21 Kywors: Bioful Cron minrliztion Nitrogn minrliztion Soil miroil iomss Soil orgni ron Wtr xtrtl orgni ron Miroil n plnt ommunitis intrt to trmin lol nutrint yling rts. As lns r onvrt to ionrgy rops, inluing orn n llulosi grsss, fous hs n on hngs in soil ron squstrtion. Littl ttntion hs n pi to impts of suh ln onvrsion on th tivity of lowgroun ommunitis. W hypothsiz tht in ition to ffting soil orgni ron (SOC), monoultur spis stlishmnts hv ppril ffts on miroil ommunity tivity, s vin y N n C minrliztion rts. W ompr soil miroil rspons in soils unr long-trm orn (Z mys L.) proution to soils unr 1-yr ol monoulturs of four wrm-sson prnnil grsss (swithgrss (Pnium virgtum L.), ostl rmugrss [Cynoon tylon (L) Prs.], siots grm [Boutlou urtipnul (Mihux) Torry] n ufflo grss [Boutlou tylois (Nutt.) Columus]). All ssy prnnil systms h highr SOC n wtr xtrtl orgni C (WEOC) thn th nnul orn systm. Howvr, of ll th prnnil grsss, swithgrss soils h th lowst SOC n WEOC vlus, n th lowst 28-y C n N minrliztion rts. This stuy inits tht soil miroil tivitis unr ufflogrss stns r mor tiv thn thos unr siots grm, swithgrss, ostl rmugrss, or orn. Pulish y Elsvir B.V. 1. Introution Thr is mpl vin for fks twn miroil soil ommunitis n plnt ommunitis (Win n Tilmn, 199; Hoi, 1992; Ehrnfl t l., 25). Miroil iomss funtion n pool siz r ontroll y soil C vilility, whih is trmin y plnt tissu qulity n quntity. Miroil C n N hv n link to ov groun nt primry proution. For xmpl, soil miroil iomss C (SMBC) unr tllgrss priri hs n msur t mor thn 5 tims grtr lvls n mks up muh lrgr portion of th soil orgni C pool (6.4% vs..2%) thn SMBC in shortgrss stpp soils (Zk t l., 1994). Aitionlly, N minrliztion rts hv n shown to snsitiv to plnt spis. Chnging plnt spis ovr hngs plnt littr proution qulity n quntity, ffting C n N pools n miroil iomss (Win n Tilmn, 199). Swithgrss (Pnium virgtum L.), ostl rmugrss [Cynoon tylon (L) Prs.], n orn (Z mys L.) hv ll n propos s potntil iomss sours for thnol s nrgy (MLughlin n Kszos, 25; Frrll t l., 26; Snrson n Alr, 28). Siots grm [Boutlou urtipnul (Mihux) Torry] n ufflo grss [Boutlou tylois (Nutt.) Columus] proution potntils hv lso n ompr to swithgrss n Corrsponing uthor. Tl.: ; fx: E-mil rss: rik.hny@rs.us.gov (R.L. Hny). othr potntil iomss grsss (Roins, 21). It hs n suggst tht rpling row rops with prnnil grsss, n swithgrss in prtiulr, ltrs soil C iogohmil hrtristis, inluing lvting rts of C minrliztion, inrsing miroil iomss C n prntg of miroil iomss C in orgni C (M t l., 2). Inrsing nt primry proution typilly inrss SOC, ut inrsing omposition rts rs SOC (Wng n Hsih, 22). In prnnil grss systms mng for iomss proution, th mjority of th ovgroun iomss is hrvst, so C input ontriuting to SOC storg must primrily riv from root proution (Brnsy t l., 1998). Prnnil wrm-sson grsss tn to hv root iomss omprl to th nnul ovgroun iomss (MLughlin n Wlsh, 1998). Swithgrss n prou upwrs of fiv tims mor root iomss s ompr to orn (Zn t l., 1997; Tufkioglu t l., 23), so swithgrss ropping shoul yil to inrs SOC s ompr to orn ropping. Thr r vry fw stuis on soil N yling s rlt to iffrnt grss typs n thir ontriutions to SOC (Omono n Vyn, 26). In this mnusript, w trmin lowgroun impts ftr onvrting gronomilly mng ln to monoulturs of swithgrss, ostl rmugrss, ufflogrss, n si ots grm s ompr to orn. It is ssum tht onvrsion of ln to prnnil grsss ls to n inrs in nnul SOC squstrtion u to high low groun iomss proution (Lmus n Ll, 25). Thr is whol suit of othr nfits soil gins from improv SOC lvls, inluing improv wtr n /$ s front mttr. Pulish y Elsvir B.V. oi:1.116/j.g

3 Author's prsonl opy R.L. Hny t l. / Agriultur, Eosystms n Environmnt 139 (21) nutrint rtntion n rs rosion. Howvr, iomss quntity os not init SOC turn ovr rts. W hypothsiz tht th highr ovgroun iomss yiling spis (swithgrss n ostl rmugrss) woul hv highr low groun iomss, whih woul ontriut mor C to th soil, ontriuting to highr SOM lvls in th soil, whih shoul support mor SMB. 2. Mtrils n mthos 2.1. Fil sit n plnt spis All fil plots wr lot t th USDA-ARS Grssln, Soil n Wtr Rsrh Lortory in Tmpl, TX (31 4 N n W) on Houston Blk ly 55% ly, 35% silt n 1% sn (fin, smtiti, thrmi Ui Hplustrts). Th fous of this mnusript ws on miro mit ltrtions of SOM, WEOC, n N unr iffrnt monoultur rops. Thrfor, smpling pth ws limit to th uppr 1 m of th soil profil, whih is whr th mjority of SMB tivity ours. Smpling ourr in spring tim, whn soil moistur shoul hv n qut to support ssonlly mximum miroil iomss, limit y sustrt vilility. Soil smpls wr tkn from plots us in prvious xprimnts xmining ov-groun physiologil plnt funtion (Kiniry t l., 1999; Kiniry t l., 27). All grss plots wr stlish for t lst 1 yrs in fil historilly mng for row rops. Plots msur t lst 5 m 5 m. Tn surf soil smpls ( 1 m) wr ollt n homogniz from h of thr rplit plots for h trtmnt. All soil smpls wr ri for 24 h t 4 C n groun to pss 2-mm siv. Plnt spis monoulturs unr whih soil smpls wr ollt inlu siots grm, ufflo grss, swithgrss, n ostl rmugrss. A ultivt fil unr nnul orn wht (Tritium stivum L.) rottion srv s ontrol plot. Si ots grm is wrm-sson, ntiv, prnnil, mi-sussionl unh grss, olonizing istur rs typilly ftr ufflo grss pprs (Osorn n Alln, 1949). Bufflogrss, wrm-sson ntiv prnnil so-forming short grss, is o-ominnt in th limx ommunity of th shortgrss priri, n is ommon in mix-grss priri n ostl priri of Txs n Louisin; though limx spis, ufflo grss stlishs uring th rly to mi-stg sonry sussionl stgs n prsists (Ju, 1974; Anlt t l., 1987). Both ufflogrss n siots grm fvor fintxtur soils (Ju, 1974). Swithgrss is wrm-sson, ntiv, prnnil unhgrss pt to tll grss priri of Cntrl n North Amri (Prrish n Fik, 25). Costl rmugrss is n rly sussionl spis, wrm-sson, mtt forming grss ntiv to Afri, ut ommon throughout th US, prtiulrly in sutropil rs Cron minrliztion On hunr grms of homogniz soil wr wigh out of ir-ri smpls. Soils wr rwtt to pproximtly 5% wtr-fill por sp to stimult miroil tivity n inut t 25 ± 1 C in th rk. Soils wr inut iniviully in gs-tight, stril 1-l glss jrs with vil ontining 1 ml of 1. M KOH to trp volv CO 2 n vil of wtr to mintin humiity. Dstrutiv soil smpling ourr t 1, 1, 14, n 28 ys. Alkli trps wr rmov/rpl t ys 1, 3, 1, 14, n 28. Unrt lkli in th KOH trps following pripittion of CO 3 with BCl 2 ws titrt with 1. M HCl to trmin CO 2 -C volution (Anrson, 1982) Nitrogn minrliztion Dstrutivly hrvst soils wr msur for nt nitrogn (N) minrliztion (mg N kg 1 y 1 ) ovr th inution prio, trmin s th iffrn twn initil wtr-xtrtl soil inorgni N onntrtions (NH 4 + -N+NO 2 -N+NO 3 -N) of noninut soil smpls from soil N xtrt ftr 28 ys of inution. Inorgni N ws xtrt from 4-g soil susmpls using 4 ml of 2. M KCl. Smpls wr shkn for 3 min on riprol shkr, filtr n th xtrts nlyz for NH 4 -N n NO 2 - plus NO 3 -N using n OI Anlytil rpi flow nlyzr for NH 4 -N, n NO 3 -N. Th sum of th ov N forms ws signt inorgni N Soil ron nlysis Four grms su-smpls wr wigh into 5-ml plsti ntrifug tus. Forty millilitrs of ioniz wtr ws to h tu, shkn for 3 min n ntrifug for 5 min t 35 rpm. Th xtrts wr filtr through Whtmn 2V filtr ppr n nlyz for wtr xtrtl orgni C (WEOC) on Tlyn-Tkmr Phonix 8 Cron nlyzr. Aitionlly, 2-g susmpls wr nlyz on Lo C nlyzr for totl soil orgni C (SOC) Soil miroil iomss C n N A fumigtion-inution mtho (Jnkinson n Powlson, 1976) ws us to trmin soil miroil iomss ron (SMBC). For h trtmnt, 4-g soil smpl ws rwtt n inut t 25 C for 5 ys prior to ing xpos to lohol-fr CHCl 3 vpor for 24 h. Following vution n rmovl of vpors, th soil ws inut in th rk in 1-l gs-tight glss ontinrs for 1 ys t 25 C. Cron ioxi volv uring th 1-y inution prio following fumigtion ws trpp in 1. M KOH n trmin s sri prviously. Th quntity of volv CO 2 - C ws ivi y n ffiiny ftor of.41 to lult miroil iomss C (Vorony n Pul, 1984). Soil miroil iomss nitrogn (SMBN) ws trmin on th sm smpls, y nlyzing soil NH 4 -N onntrtions of fumigt smpls following th 1-y inution prio minus initil NH 4 -N prior to fumigtion, ivi y n ffiiny ftor of.41 (Crtr n Rnni, 1982). Extrtion n nlysis of NH 4 -N ws omplish s prviously sri. Sttistis wr nlyz using SigmStt vr 3.5 n inlu on-wy ANOVA Holm Sik mtho (P <.5). 3. Rsults 3.1. Cron minrliztion Cron minrliztion ws nhn y prnnil grss monoultur stlishmnt s ompr to th ontrol orn monoultur (Fig. 1). On y 1, th highst C minrliztion rts wr osrv unr ufflogrss (168.4 ± 3.6; mn ± on stnr vition) follow y siots grm (129.1 ± 7.7), rmugrss (99.3 ± 6.2), swithgrss (85.8 ± 3.4) n orn (55.6 ± 2.3). Th sm rltionships twn plnt spis n C minrliztion rts wr osrv t y 1 n y 28 of th inution xprimnt, with h spis sprting out from h othr (P <.5) Nitrogn minrliztion Nitrogn minrliztion ws nhn y prnnil grss monoultur stlishmnt s ompr to th ontrol orn monoultur (Fig. 2). N minrliztion rts follow th sm pttrn s C minrliztion rts. Th highst N minrliztion rts wr

4 Author's prsonl opy 756 R.L. Hny t l. / Agriultur, Eosystms n Environmnt 139 (21) CO 2 (4.6%), swithgrss (3.9%) n orn (1.8%). SOC vlus unr ll fiv grsss wr signifintly iffrnt from h othr (P <.5), s wr wtr xtrtl orgni C (WEOC) vlus, whih follow th sm orr (Fig. 3). C minrliz mg C kg -1 soil CO Siots Bufflo Swith Brmu Control Fig. 1. Mn ron minrliztion rts unr th fiv ssy spis. Eh spis C minrliztion rt ws sttistilly iffrnt from th othrs using onwy ANOVA Holm Sik mtho (P <.5). Error rs r on stnr vition. Lttrs of th sm r not signifintly iffrnt t (P <.5) Soil miroil iomss C n N All prnnil grss trtmnts support signifintly mor SMBC n SMBN thn th orn trtmnt. Soil miroil iomss C n N wr oth highst unr ufflogrss (SMBC 1983 ± 128) (SMBN 244 ± 22) though ths vlus wr not sttistilly highr thn thos osrv unr siots grm (1827 ± 226) (237 ± 17) (Fig. 4). Swithgrss (195 ± 174) (161 ± 12) n ostl rmugrss (13 ± 211) (178 ± 11) lso group out togthr s supporting th lowst SMBC n SMBN of th prnnil grsss. Corn support signifintly lss SMBC n SMBN (73 ± 42) (129 ± 2) thn th prnnil spis. 4. Disussion High C minrliztion rts signify high soil miroil tivity. Of th four prnnil spis ssy, swithgrss h th lowst C minrliztion rt, signifying tht it sustin th lst tiv soil miroil tivity of ny of th four prnnil grsss. Nitrogn minrliztion is mor snsitiv soil msurmnt thn SMB in trms of monstrting N minrliztion/immoiliztion (Figs. 2 n 4). Th SMB C:N rtio ws lowst for th ontrol orn fil, whih woul pritly rsult in th grtst lvls of N minrliztion ourring unr orn. How- 12 osrv unr ufflogrss (2.7 ± 1.6), follow y siots grm (17.9 ± 2.2), rmugrss (13.3 ± 1.4), n swithgrss (7.6 ± 1.). Corn tully show immoiliztion of N rthr thn minrliztion ( 1.9 ± 1.9) Soil ron nlysis Soil orgni C mg g -1 soil 8 4 Soil orgni C (SOC) ws highst unr ufflo grss (vrging 7.5%), follow y siots grm (6.1%), ostl rmugrss y N minrliztion mg N kg -1 soil Wtr xtrtl orgni C mg C kg -1 soil Siots Bufflo Swith Brmu Control Fig. 2. Nitrogn minrliztion rts unr th fiv ssy spis. Error rs signify on stnr vition. Eh spis N minrliztion rt ws sttistilly iffrnt (P <.5) from th othrs using on-wy ANOVA Holm Sik mtho with th xption of siots n ufflo, whih group togthr. Lttrs of th sm r not signifintly iffrnt t (P <.5). Siots Bufflo Swith Brmu Control Fig. 3. SOC n WEOC follow th sm orr. Vlus in soil unr h monoultur wr signifintly iffrnt from on nothr using on-wy ANOVA Holm Sik mtho (P <.5). Error rs r on stnr vition. Lttrs of th sm r not signifintly iffrnt t (P <.5).

5 Author's prsonl opy R.L. Hny t l. / Agriultur, Eosystms n Environmnt 139 (21) Soil miroil iomss C mg C kg -1 soil Soil miroil iomss N mg N kg -1 soil Siots Bufflo Swith Brmu Control Fig. 4. Soil miroil iomss C n N unr th vrious prnnil grsss n orn (ontrol). SMB C n SMB N follow th sm pttrn, with siots grm n ufflogrss grouping togthr, swithgrss n ostl rmugrss grouping togthr, n orn (ontrol) s th signifintly lowst SMB C n SMB N using on-wy ANOVA Holm Sik mtho (P <.5). Error rs init on stnr vition. Lttrs of th sm r not signifintly iffrnt t (P <.5). vr, th miros in th ultivt orn soils wr N limit, s vin y th ngtiv 28-y N minrliztion t, whih show N immoiliztion inst. Th prnnil grss with th lowst soil N minrliztion rt ws swithgrss. This fining is in kping with stuis tht monstrt soils plnt with lt sussionl grsss hv lowr N minrliztion rts thn rlir srl spis (Win n Tilmn, 199). Msur SOC unr orn ultivtion ws lowr thn SOC in ll priri spis monoulturs. Th orn plot ing onvntionlly plow monstrts th strk iffrn twn stlish prnnil grsss n nnul ultivtion on C squstrtion. Soil isturn ssoit with orn ultivtion inrss th rt of omposition, lowring SOC (Grny n Rortson, 27). Also, prnnil grsss introu mor ron to th soil thn os orn (Anrson-Tixir t l., 29). Our prnnil grss plots prou minimum of twi th SOC s i th orn fils. Swithgrss prou 3 tims th orgni C s th orn fil. This is in kping with othr work xmining swithgrss n othr lrg iomss prouing prnnil grss SOC (Corr t l., 1999; Anrson-Tixir t l., 29). A novl fining in this stuy is tht th SOC unr th ufflogrss n siots grm monoulturs ws nrly twi wht it ws unr swithgrss. Thrfor, lthough swithgrss my provi mor soil C storg thn os orn in th uppr 1 m of soil, th lowr iomss ufflogrss n siots grm outprform swithgrss in trms of SOC in this zon. This is surprising, onsiring tht stuis hv shown swithgrss n prou mor thn twi th root iomss of siots grm (Sott, 1998). This stuy ws limit to th rs of th soil profil whr miros r most tiv ( 1 m). Rsrhrs intrst in SOC, WEOC, n N minrliztion n C minrliztion rts throughout th soil profil shoul onsir msuring similr proprtis t pr pths. Dpr rooting prnnil grsss my mov C pr into th soil, storing C in lotions not ssy hrin. Both N minrliztion n C minrliztion hv n monstrt t pths of up to 7 m (Ajw t l., 1998). In this xprimnt, SOC sprt trtmnts ttr thn WEOC. Howvr, WEOC my mor nvironmntlly snsitiv pool thn SOC givn th shr mgnitu of sl. Th rng in WEOC is 5 2 mg C kg 1 soil whrs SOC is mg C g 1 soil, WEOC ing thr orrs of mgnitu smllr. WEOC vlus signify miroil tivity lvls, s WEOC is th C from th SOC pool tht is sily minrlizl (Hong t l., 26; Wng t l., 23). Swithgrss, th only lt-sussionl spis in our stuy, prou mor iomss thn ny of th othr trtmnt spis (Kiniry t l., 1999). In 1995 n 1997, mn siots grm yils wr 4 11 g m 2 whil swithgrss yils wr 23 4 g m 2. In 1998, 1999, n 2, mn yils wr 312 g m 2 for siots grm, 1182 g m 2 for swithgrss, 325 g m 2 for ufflogrss, n 618gm 2 for ostl rmugrss. On th mro-sl, Zk t l. (1994) foun lt sussionl osystms ovgroun nt primry proution to signifintly rlt to oth lil orgni C pools in th soil n miroil iomss. Tilmn n Win (1991) foun lt sussionl grss spis ru soil N low vlus mintin y rly n mi-sussionl grss spis. Contrry to wht on woul hv prit s on Zk t l. s (1994) finings, soil unr our swithgrss, th highst ovgroun iomss prour in our stuy, h lowr soil N minrliztion rts n lowr SOC thn th othr prnnil grsss. This xprimnt i not rss th mhnisms of plnt-soil fks rsponsil for th hng in C n N ynmis vin y this work. For xmpl, it is possil tht iffrnt spis, with sustntilly iffrnt growth forms n iomss yils, my ltr soil ggrgtion pttrns. Howvr, prvious stuis foun no fft on soil ggrgt-siz istriution rlt to monoulturs of six grsss, inluing siots grm n swithgrss (Sott, 1998). As lrg rs of th US r onvrt to swithgrss, orn, n ostl rmugrss for ioful proution, oftn t th xpns of ntiv ommunitis (hrin rprsnt y ufflogrss n siots grm), thr will ltrtions of th N n C yls in th soils. Long trm C n N ynmi stuis r n s ths onvrsions ontinu. This stuy is n importnt slin stuy, whih will usful for futur squntil smpling, whih will provi rsrhrs with furthr t n insight into th soil nutrint n miroil ynmis unr this iomss for nrgy proution systms. Rfrns Ajw, H.A., Ri, C.W., Sotomyor, D., Cron n nitrogn minrliztion in tllgrss priri n griulturl soil profils. Soil Si. So. Am. J. 62, Anlt, W.F., Ki, J.G., Knowlton, F.F., Dn, C., Vrition in oyot its ssoit with sson n sussionl hngs in vgttion. J. Willif Mng. 51, Anrson, J.P.E., Soil rspirtion. In: Pg, A.L., t l. (Es.), Mthos of Soil Anlysis. Prt 2. Agron. Monogr., 2n. ASA n SSSA, Mison, WI, pp Anrson-Tixir, K.J., Dvis, S.C., Mstrs, M.D., Dlui, E.H., 29. Chngs in soil orgni ron unr ioful rops. Glo. Chng Biol. Bionrgy 1, Brnsy, D.I., MLughlin, S.B., Prrish, D.J., A rviw of ron n nitrogn imlns in swithgrss grown for nrgy. Biomss Bionrgy 14, Crtr, M.R., Rnni, D.A., Chngs in soil qulity unr zro tillg frming systms: istriution of miroil iomss n minrlizl C n N potntils. Cn. J. Soil Si. 62, Corr, M.D., Shnl, R.R., Shffr, J.A., Evlution of soil orgni ron unr forsts, ool-sson n wrm-sson grsss in th northstrn US. Soil Biol. Biohm. 31, Ehrnfl, J.G., Rvit, B., Elgrsm, K., 25. Fk in th plnt-soil systm. Annu. Rv. Environ. Rsour 3,

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