SoilUse and Management. Abstract. Keywords: Long-term experiment, P fertilizer, aggregates, soil nutrients, soil enzymes.

Transcription

1 SoilUse nd Mngement Soil Use nd Mngement, Mrh 217, 33, doi: /sum Chnges in soil ggregte-ssoited enzyme tivities nd nutrients under long-term hemil fertilizer pplitions in phosphorus-limited pddy soil W. T. LI 1,2,M.LIU 1,C.Y.JIANG 1,M.WU 1,X.F.CHEN 1,2,X.Y.MA 1,2 &Z.P.LI 1,2 1 Stte Key Lortory of Soil nd Sustinle Agriulture, Institute of Soil Siene, Chinese Ademy of Sienes, No. 71, Est Beijing Rod, P.O. Box 821, Nnjing 218, Chin, nd 2 University of Chinese Ademy of Sienes, Beijing 149, Chin Astrt Pddy soils in sutropil Chin re usully defiient in phosphorus (P) nd require regulr pplition of hemil fertilizers. This study evluted the effets of hemil fertilizers on the distriution of soil orgni ron (SOC), totl nitrogen (N) nd ville P, nd on the tivity of the ssoited enzymes in ulk soil nd ggregtes. Surfe soils ( 2 m) were olleted from 24- yr-old field experiment with five tretments: unfertilized ontrol (CK), N only (N), N nd potssium (NK), N nd P (NP), nd N, P nd K (NPK). Undistured ulk soils were seprted into >2, 1 2,.25 1, nd <.53 mm ggregte lsses using wet sieving. Results showed tht oth NPnd NPK-treted soils signifintly inresed men weight dimeter of ggregtes, SOC, ville P in ulk soil nd ggregtes, s ompred to CK. Most SOC nd totl N dhered to mro-ggregtes (>.25 mm), whih ounted for 64 81% of SOC nd 54 82% of totl N in ulk soil. The tivities of invertse nd id phosphtse in the 1 2 mm frtion were the highest under NPK tretment. The highest tivity of urese ws oserved in the <.53 mm frtion under NP tretment. Soil orgni ron nd ville P were mjor ontriutors to vrition of enzyme tivities t the ggregte sle. In onlusion, pplition of NP or NPK fertilizers promoted the formtion of soil ggregtes, nutrient ontents nd tivities of ssoited enzymes in P-limited pddy soils, nd thus enhned soil qulity. Keywords: Long-term experiment, P fertilizer, ggregtes, soil nutrients, soil enzymes Introdution Fertilizer mendment is key ftor to inrese rop prodution. Applition of nitrogen (N), phosphorus (P) nd potssium (K) in the form of hemil fertilizers inreses the vilility of nutrients to rops nd my lso influene soil qulity y hnging its physil nd hemil properties nd the ioproesses tht our within soil (Rkotoson et l., 215). These hnges re suseptile to the type of fertilizers, rop regimes nd soil fertility onditions (Zhong & Ci, 27; Jing et l., 211; Su et l., 215). Lemnowiz (213) proposed tht unlned minerl fertilizer pplition deresed soil nutrient ontents nd deteriorted soil sorption properties. Dou et l. (216) reported tht pplition of N nd NPK fertilizers did not signifintly Correspondene: Z. P. Li. E-mil: zhpli@isss..n Reeived Mrh 216; Revised Novemer 216; epted fter revision Novemer 216 inrese soil orgni ron (SOC) ontent. These studies were onduted minly on homogenized ulk smples, whih might verge out the lolized heterogeneities within soil mtrix. As mtter of ft, mny key miroil proesses our differentilly in sptilly segregted mirohitts. Thus, deep understnding of the influene of fertilizer pplition regimes on soil properties ould e hieved y investigting soil onditions t the ggregte sle. Soil prtiles (i.e. snd, silt nd ly) re ound together into ggregtes of different sizes y orgni nd inorgni mterils (Elliott, 1986; Peng et l., 215). Tisdll nd Odes (1982) oserved tht ggregtes of different size hd distint ementing gents. Odes (1984) identified polyshrides s the orgni olloids involved in inding ly into miro-ggregtes. Soil ggregte formtion nd stiliztion ws influened y fertilizer pplition regimes (Whlen & Chng, 22; Yu et l., 212). Mny experiments hve shown tht long-term omined pplition of orgni mnure nd hemil fertilizers 216 British Soiety of Soil Siene 25

2 26 W. T. Li et l. inreses the men weight dimeter of soil ggregtes, wheres the effets of hemil fertilizer re smll (Wng et l., 211; Liu et l., 213). Pddy soils in sutropil Chin, whih re derived from quternry red ly, re generlly defiient in ville nutrients, prtiulrly N nd P (Li et l., 2; Zhong & Ci, 27). Wng et l. (211) found tht pplition of hemil fertilizers in reddish pddy soil inresed the ontents of totl nd ville P in ll sizes of wter-stle ggregtes, while hd little effet on totl C nd N ontents. Zhong & Ci (27) found tht SOC umultion ws limited in soils defiient in N nd P nutrients, ut the pplition of P fertilizer n inrese growth of rops nd susequent SOC umultion in the soils. However, there is still gp in the informtion urrently ville out responses of ggregte-ssoited C nd N to sustined fertilizer N nd P pplitions. Extrellulr enzymes tlyse most of the hemil retions within soil, suh s minerliztion of orgni C, N nd P from soil orgni mtter (SOM) (Wring et l., 214). Mesured enzyme tivities reflet the strength nd diretion of vrious iohemil proesses in soils, whih n e used to evlute miroil nutrient demnds nd to formulte n eosystem response index tht reflets environmentl hnges (Wng et l., 215). There re two mjor forms of extrellulr enzymes in soil: free enzymes, whih n e swiftly dentured, degrded or irreversily inhiited, nd those inorported into humi mterils (Burns, 1986) tht n umulte nd stilize in soil (Busto & Perez-Mteos, 2). The speifi distriution of extrellulr enzymes within the soil mtrix (Ali et l., 215) hs reeived gret del of ttention. Mrx et l. (25) elieved tht the distriution of enzyme tivities within the ggregtes depended on the enzyme type: rohydrses predominted in the orser frtions, while phosphtse nd leuine minopeptidse were predominnt in the ly-size frtions. Zhng et l. (215) reported tht id phosphtse showed the highest tivity in the.1 2 lm rnge, while - gluosidse nd minopeptidse exhiited the highest tivities in the 63 2 lm rnge. However, Liu et l. (213) oserved tht enzyme tivities were higher in mroggregtes thn in miro-ggregtes. The distriutions of vrious enzymes in ggregtes re vrile nd these ptterns re influened y fertilizer pplition (Liu et l., 213; Zhng et l., 215). Yu et l. (212) suggested tht ompost pplition signifintly lowered the speifi tivities of invertse (tivity per unit orgni C) in mro-ggregtes nd the silt + ly frtion, nd this effet ws more pronouned thn the ddition of fertilizer NPK. Liu et l. (213) found tht long-term pplition of orgni mnure with hemil fertilizer signifintly inresed invertse, urese nd id phosphomonoesterse tivities within different ggregte frtions. The influene of fertilizers on the distriution of enzyme tivities in wter-stle ggregtes ws miguous nd needs further elortion. A long-term experiment ws set up in pddy field, whih ws formerly unultivted, to evlute the effets of fertilizer pplition on soil fertility. The ojetives of this study were to (i) mesure soil nutrients nd enzyme tivities in ulk soil nd ggregte size frtions, nd (ii) explore the reltive influene of soil nutrients nd soil frtions on soil enzyme tivities t the ggregte sle. The findings provide sound sis for rtionl pplition of fertilizers to ensure sustinle rop prodution. Mterils nd methods Study site nd smpling A long-term field experiment ws initited in 199 t the Yingtn Ntionl Agroeosystem Field Experiment Sttion ( N, E) in Yujing County of Jingxi Provine, Chin. The site hs sutropil monsoon limte with men nnul rinfll of 1795 mm nd men nnul temperture of 17.6 C. The ropping system is douleropping rie (Oryz stiv L.) (i.e. erly nd lte seson rie). Plnting dte is from erly April to the end of Otoer, nd the rest period is fllow. The soil is derived from quternry red ly nd initilly hd the following physiohemil properties of surfe soil ( 2 m): ph, 4.5; orgni mtter, 5.7 g/kg; totl N,.43 g/kg; totl P,.65 g/kg; totl K, 13.4 g/kg; lkli-hydrolysle N, 9.2 mg/kg; ville P, 5.6 mg/kg ( vlue typil of P- limited pddy soils); ville K, 15.9 mg/kg; nd ly (<1 lm), 38%. The experiment hd five tretments: nitrogen lone (N), nitrogen together with either phosphorus (NP) or potssium (NK), NPK nd unfertilized ontrol (CK). The experiment ws lid out in rndomized omplete lok design with three replitions. Nitrogen ws pplied s ure (115 kg N/ h); P ws dded s lium mgnesium phosphte (68 kg P 2 O 5 /h); nd K ws pplied s potssium hloride (42 kg K 2 O/h) in eh growing seson. Fertilizers P nd K were pplied s sl dressing, while fertilizer N ws pplied t 61.3 kg N/h s sl dressing nd t 53.7 kg N/h s top dressing. After the lte rie hrvest in Novemer 214, ulk soil smples were olleted from the surfe lyer ( 2 m), nd eh smple onsisted of five intt ores tken t rndom from eh plot. The smples were pled in selle plsti oxes nd trnsported to the lortory. Sreening of wter-stle ggregtes The moist soil were gently sieved through 1-mm sieve nd then ir-dried t room temperture. Three 1 g susmples were wet-sieved y hnd following the proedure desried 216 British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

3 Distriution of nutrients nd enzymes in red soil 27 Tle 1 Chrteriztion of ontents (g/kg), men weight dimeter (MWD, mm) nd geometri men dimeter (GMD, mm) of wter-stle ggregtes mong different fertilizer tretments Aggregte tegory (prtile size, mm) CK N NK NP NPK > d d < Men weight dimeter Geometri men dimeter Vlues re mens SE, n = 3. Different lowerse letters within row indite signifint (P <.5) differene mong tretments. CK, N, NK, NP nd NPK tretments represent unfertilized ontrol nd fertilizer pplition with N, with N nd K, with N nd P, nd with N, P nd K, respetively. Tle 2 The effets of fertilizer P on nutrient ontent nd enzyme tivities in ggregte size frtion of the soils Fertilizer tretments Aggregte frtion Fertilizer tretments 9 ggregte frtion Prmeter F P F P F P Soil orgni ron Totl nitrogen C:N rtio Aville phosphorus Invertse tivity Urese tivity Aid phosphtse tivity y Elliott (1986). Eh susmple ws sumersed in deionized wter on 2-mm sreen for 1 min prior to wet sieving. Soil smples were wet-sieved under wter y gently moving the sieve 3 m vertilly 5 times over period of 2 min through wter ontined in shllow pn. The soil remining on the 2-mm sieve ws olleted nd ir-dried t room temperture. The slurry omprising the frtion <2 mm nd wter ws poured through 1-mm sieve, nd then the sieving proess ws repeted. We otined prtiles of sizes 1 2 mm,.25 1 mm nd mm following the sme sieving proedure. The lst frtion (less thn.53 mm, omprised of silt nd ly prtiles) settled to the ottom of the wter olumn y grvity sedimenttion. After denting the superntnts, the preipitte ws olleted nd ir-dried t room temperture. Wter-stle ggregtes lrger thn.25 mm in dimeter were defined s mroggregtes nd those smller thn.25 mm were lssified s miro-ggregtes. After wet sieving, ll ggregtes were irdried t room temperture for 1 week nd then olleted for ssying soil orgni C, totl N, ville P nd enzyme tivities. The men weight dimeter (MWD) nd the geometri men dimeter (GMD) of the soil ggregtes were used to represent the wter stility of ggregtes. They were lulted s follows (Kemper & Rosenu, 1986): MWD ¼ Xn i¼1 x i w i where x i is the men dimeter (mm) nd w i is the weight proportion of the i size frtion, nd P n i¼1 GMD ¼ exp w i ln x P i n i¼1 w ð2þ i where w i is the weight of ggregtes in the i size frtion (g) nd ln x i is the nturl logrithm of the men dimeter of the i size frtion. Soil hemil nlysis The ontents of soil orgni ron (SOC) nd totl nitrogen (N) were determined y using the Tyurin method nd semimiro-kjeldhl method, respetively (Lu, 1999). Aville phosphorus (P) ws extrted with.5 M NHCO 3 nd determined y the Mo-S olorimetry method (Lu, 1999). ð1þ 216 British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

4 28 W. T. Li et l. Aville P (mg/kg) N ontent (g/kg) C ontent (g/kg) () () () Bulk soil >2 mm 1 2 mm.25 1 mm mm <.53 mm CK N NK NP NPK Figure 1 Soil nutrient ontents in ulk soil nd ggregte sizes mong different tretments. All vlues re mens SE, n = 3. Brs with the sme letter do not differ signifintly t P <.5. CK, N, NK, NP nd NPK tretments represent unfertilized ontrol nd fertilizer pplition with N, with N nd K, with N nd P, nd with N, P nd K, respetively. The perentge of SOC nd totl N in eh size lss in the ulk soil ws lulted s follows: The perentge of SOC, TN in ggregte ¼ i p i where i is SOC, totl N ontent in i ggregte (g/kg), p i is the perentge of i ggregte (%), nd is the SOC, totl N ontent in ulk soil. Mesurement of soil enzyme tivity The ulk soil smples nd wter-stle ggregtes were sieved through 2-mm sreen for determintion of enzyme tivities. Invertse tivity ws determined following Gun (1986): 3 g ir-dried smple ws inuted with 15 ml of 8% (w/v) surose solution, 5 ml phosphte uffer (ph 5.5) nd.5 ml toluene for 24 h t 37 C in the drk. Immeditely fter inution, the soil suspension ws filtered nd 2 ml filtrte ws used to mesure the mount of gluose produed using 3,5-dinitrosliyli id olorimetry method. The tivity of invertse ws expressed in lg gluose/g/h. The prinipl funtion of urese is hydrolysis of ure to CO 2 nd NH 3. Urese tivity ws mesured ording to ð3þ the method of Gun (1986). In this proedure, 5 g ir-dried smple ws inuted with 1 ml of 1% (w/v) ure solution, 2 ml itrte uffer (ph 6.7) nd 1 ml toluene for 24 h t 37 C in the drk. Immeditely fter inution, the soil suspension ws filtered nd 3 ml filtrte ws used to mesure the onentrtion of mmonium ion using indophenol-lue olorimetry method. The tivity of urese ws expressed in lg NH 3 -N/g/h. Aid phosphtse minerlizes P from orgni P esters. Aid phosphtse tivity ws determined following the method of Gun (1986): 4 g ir-dried soil ws inuted with 2 ml of.5% (w/v) disodium phenyl phosphte nd 1 ml toluene for 24 h t 37 C in the drk. Immeditely fter inution, the soil suspension ws filtered nd 3 ml filtrte ws used to mesure the mount of phenol relesed using disodium phenyl phosphte olorimetry method. The tivity of id phosphtse ws expressed in lg phenol/g/h. Dt nlysis Anlyses of vrine were performed using SPSS ver. 16. for Windows (SPSS, In., Chigo, Illinois, USA), nd the Fisher s lest signifint differenes (LSD, P =.5) test under two-wy ANOVA ws used for determining whether 216 British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

5 Distriution of nutrients nd enzymes in red soil 29 Figure 2 Contriutions of wter-stle ggregtes to soil orgni ron nd totl nitrogen. All vlues re mens SE, n = 3. Brs with the sme letter do not differ signifintly t P <.5. CK, N, NK, NP nd NPK tretments represent unfertilized ontrol nd fertilizer pplition with N, with N nd K, with N nd P, nd with N, P nd K, respetively. Contriution rtes of wter-stle ggregtes in soil orgni C (%) Contriution rtes of wter-stle ggregtes in totl N (%) () () >2 mm 1 2 mm.25 1 mm CK N NK NP NPK mm <.53 mm the differenes mong soil ggregte frtions nd fertilizer tretments were signifint. Aggregted oosted tree (ABT) nlysis ws used for evluting the reltive importne of soil nutrients nd size of soil ggregtes to the soil enzymes, whih ws performed using the gmplus pkge in R softwre (ver ) (De th, 27). Results Soil ggregtes distriution The reovery rtios of soil ggregtes in the proess of wet sieving of smples from CK, N, NK, NP nd NPK tretments were 94.8, 95.8, 95.2, 96.3 nd 96.1%, respetively. The predominnt size frtions in ll tretments were lrge mro-ggregtes (>2 mm) nd smll mro-ggregtes (.25 1 mm), whih together ounted for 61% of the ulk soil on verge y weight (Tle 1). Compred with CK, the frtions of mro-ggregte (>.25 mm) in NP nd NPK tretments were inresed y 25 nd 26%, respetively. The MWD vlues in NPK-treted soil smples were 45, 21 nd 51% higher thn those in CK, N nd NK tretments, respetively, wheres the orresponding vlues for GMD were 77, 34 nd 73%, respetively. Both the prmeters (MWD nd GMD) in the NP tretment were lso signifintly higher thn those in the CK, N nd NK tretments, ut were not signifintly different mong the tretments without P (Tle 1). These results suggested oth NP nd NPK tretments inresed MWD nd GMD of wter-stle ggregtes nd the proportion of mro-ggregtes, ut deresed the perentge of miro-ggregtes. Distriution of soil C, N nd P in wter-stle ggregtes Averging ross ll tretments, the reovery rtes of C nd N were 99 nd 95%, respetively. Both the frtion nd fertilizer pplition influened the ontents of SOC, totl N nd ville P mrkedly (P <.5), nd their intertion hd signifint effet on the ron to nitrogen (C/N) rtio (Tle 2). Compred to CK, the NPK tretment inresed SOC onentrtions signifintly in three wter-stle ggregte (WSA) size lsses y 24% in the >2 mm lss, 28% in the 1 2 mm lss nd 32% in the.25 1 mm lss (Figure 1). Compred to N nd NK tretments, the NPK tretment inresed the onentrtions of SOC in ll five size lsses y 9 26% nd 4 19%, respetively, nd NP tretment did the sme y 14 27% nd 8 2%, respetively (Figure 1). Compred to CK, the NK, NP nd NPK tretments signifintly inresed the onentrtions of totl N in the 1 2 mm ggregte frtion (Figure 1), wheres the signifint differenes in C/N mong the five tretments were oserved only in the mm ggregte frtion. Totl N onentrtions in ulk soil nd in the >2 mm,.25 1 mm, mm nd <.53 mm ggregtes showed no signifint differenes mong the tretments. 216 British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

6 3 W. T. Li et l. Invertse tivity (µg gluose/g soil/h) Urese tivity (µg NH 3 -N/g soil/h) Aid phosphtse tivity (µg phenol/g soil/h) () () () Bulk soil >2 mm 1 2 mm.25 1 mm CK N NK NP NPK mm <.53 mm Figure 3 Enzyme tivity mong different ggregtes under different tretments. All vlues re mens SE, n = 3. Brs with the sme letter do not differ signifintly t P <.5. CK, N, NK, NP nd NPK tretments represent unfertilized ontrol nd fertilizer pplition with N, with N nd K, with N nd P, nd with N, P nd K, respetively. Aville P in ulk soil nd in ll WSA showed similr pttern: it ws higher in NP nd NPK tretments thn in CK, N nd NK tretments (Figure 1). The NPK tretment inresed the onentrtion of ville P signifintly ompred to the CK y 2.1 times in ulk soil, 4 times in the >2 mm tegory, 4.4 times in the 1 2 mm tegory, 4.7 times in the.25 1 mm tegory, 4.8 times in the mm tegory nd 4.2 times in the <.53 mm tegory. Compred to the N nd NK tretments, the NPK tretment inresed the ville P onentrtions in the five ggregte sizes y times nd times, respetively; the NP tretment inresed ville P y times nd times, respetively. Fertilizers lso ffeted the ontents of SOC nd totl N in WSA to ulk soil (Figure 2): CK, N nd NK tretments hd the highest proportions of SOC nd N in the.25 1 mm frtion, nd NP nd NPK tretments hd the highest SOC nd N proportions in the >2 mm frtion. Most soil C nd N were in the mro-ggregtes (>.25 mm), whih ounted for 64 81% of soil C nd 54 82% of soil N. Enzyme tivities mong ggregtes The tivities of the three enzymes showed different ptterns in the five ggregte sizes (Figure 3). Both soil ggregte frtion nd fertilizer tretment ffeted soil enzyme tivity, ut their intertion hd mrked effet only on urese tivity (P =.842 for invertse nd P =.412 for id phosphtse) (Tle 2). Invertse tivity in ulk soil nd WSA (exept for the >2 mm frtion) ws higher in NP nd NPK tretments thn in CK, N nd NK tretments, nd generlly ws higher in NPK thn in NP tretment (Figure 3). Overll, pplition of NP or NPK fertilizers resulted in higher invertse tivity. Compred to the CK, fertilizer tretments inresed urese tivity in ulk soil nd WSA y %. Generlly urese 216 British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

7 Distriution of nutrients nd enzymes in red soil 31 () () () SOC AP TN FC AP SOC FC TN AP SOC TN FC C:N C:N Invertse Urese C:N Aid phosphtse Reltive influene (%) Figure 4 Reltive importne of extrted preditors for soil enzymes y ggregted oosted tree model. SOC, soil orgni ron; AP, ville phosphorus; TN, totl nitrogen; FC, ggregte frtions ontent; nd C:N, rtio of SOC to TN. tivity in P tretments ws higher thn tht in no P tretments. Compring the vrious ggregte frtions, urese tivity ws the highest in the <.53 mm ggregte (Figure 3). Compred to the CK, NPK tretment inresed id phosphtse tivity in ulk soil nd ll WSA y 46 73%. However, no signifint id phosphtse tivity differenes were oserved mong the NK, NP nd CK tretments (Figure 3). Enzyme tivity in WSA ws relted to soil nutrients nd the distriution of WSA. Aggregted oosted tree nlysis identified the reltive importne of different nutrients to enzymes: SOC ounted for 39% of the interprettion rtio of invertse, whih ws higher thn other ftors; however, ville P ounted for the highest interprettion rtios of urese nd id phosphtse, whih were 32 nd 35%, respetively (Figure 4). Disussion Over the 24-yr period, pplitions of NP or NPK fertilizer to phosphorus-limited soils promoted the formtion of wterstle mro-ggregtes. Soil orgni mtter (SOM) hs een reognized s mjor ontriutor to the formtion nd stile of ggregtes (Elliott, 1986; Mjumder & Kuzykov, 21; Yu et l., 212). An dequte supply of P for rop growth inresed the mount of rop residues, whih ounted for out 15% of the totl iomss returned to the soil (Li, 1999; Shng et l., 214), therey promoting the formtion nd stility of soil ggregtes. Thus, the tretments of NP or NPK inresed SOM ontent indiretly nd enhned the formtion nd stility of the ggregtes. Miro-ggregtes re ound together y SOM to form mro-ggregtes, nd C nd N onentrtions inrese with inrese in the size of ggregtes (Elliott, 1986). In the present study, the highest onentrtions of SOC nd totl N were in the 1 2 mm frtion nd the lowest were in the mm frtion. This result ws different from n erlier report tht SOC nd totl N ontents were lowest in the <.53 mm frtion (Liu et l., 213). Compred with other types of soil, the higher the silt nd ly ontents in red soil, the higher the speifi surfe re nd tion exhnge pity nd therefore the higher in nutrient ontents of soil ggregtes (Mgwu & Piolo, 199). In reddish pddy soils, ompred with the mm frtion, the inrese in SOC nd totl N onentrtion in the <.53 mm ould e due to the higher ontent of ly, whih hs strong ility to ind with orgni mtter (Sh et l., 211). Applition of phosphorus fertilizer inresed ville P ontent in ulk soil nd ggregtes. The onentrtion of ville P in ulk soil ws signifintly higher thn tht in ggregte frtions. During the wet sieving proess, the desorption of P into wter my redue P onentrtions in the solid phse (Adesodun et l., 25). We expeted tht the distriution of ville P in ll ggregtes hd onsistent trend euse the sme proess ws pplied for ll the ggregte frtions. Thus, it is pproprite to indite soil P sttus y investigting the distriution of ville P in ll wter-stle ggregtes. In the present study, NP nd NPK tretments enhned soil enzyme tivities signifintly in ulk soil nd WSA. Su et l. (215) proposed tht the effet of N fertilizer on miroil funtionl genes ws mitigted y the pplition of P fertilizer in the P-limited pddy soil. P defiieny hs known to e ritil onstrint to the iohemil proesses in red soils, nd pplition of P fertilizer n stimulte the funtioning of miroil ommunities (Zhong & Ci, 27) s well s the development of roots nd the seretion of enzymes. Applition of P in the P-limited pddy soil promotes the enzyme tivities in the ioproess ourring in ggregte frtions. 216 British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

8 32 W. T. Li et l. Invertse nd id phosphtse tivities were generlly higher in mro-ggregtes (1 2 mm) thn in miroggregtes (<.53 mm), whih ws similr to the findings of Liu et l. (213). The distriution pttern of soil enzyme in ggregtes ws similr to tht of SOC nd TN. Lgomrsino et l. (212) elieved tht orgni C vilility drove the proess of toli tivity. It is elieved tive miroes exrete more enzymes to use the newly introdued nd more lile C in growth, therey inresing enzyme tivities in mro-ggregtes (Gregorih et l., 1996). Unlike the distriution of invertse nd id phosphtse, urese tivity ws predominntly higher in miro-ggregtes (<.53 mm). This result differed from previous reports (Liu et l., 213; Zhng et l., 215). Urese might e ound preferly with ly prtiles; therefore, its highest tivity ws in the <.53 mm (Kndeler et l., 1999). The speifi distriution of enzyme tivities my rely not only on the lotions of miroil ommunity nd their sustrtes ut lso on the preferentil dsorption sites (Gregorih et l., 1996; Kndeler et l., 1999). Among mny ftors, soil orgni ron ounted for the lrgest interprettion rtio for invertse proly euse invertse ws diretly involved in the degrdtion of orgni mtter. In ddition, ville P ounted for higher interprettion for urese nd phosphtse. Aording to previous studies, there is positive orreltion etween the tivity of id phosphtse nd ville P (Ydv & Trfdr, 21; Lemnowiz, 213; Piotrowsk-Dlugosz & Wilzewski, 214). P defiieny n stimulte plnt root nd miroorgnism to serete id phosphtse (Zhong & Ci, 27). Nutrient vilility nd sptil distriution ffet miroil growth nd enzyme synthesis (Allison, 25). In this study, pplitions of NP or NPK fertilizer improved soil struture nd inresed the ontent of SOC nd ville P, therey promoting the growth of miroorgnisms nd enzyme synthesis. Conlusions Long-term fertilizer pplition strongly influened the distriution of nutrients nd enzyme tivities in WSA. Soil nutrient ontents nd enzyme (invertse nd id phosphtse) tivities were the highest in mro-ggregtes. The ontents of SOC nd AP were key ontriutors to the vritions of enzyme tivities. The NP nd NPK tretments improved soil physil struture nd enhned the soil nutrient ontents nd enzyme tivities in ulk soil nd ggregte frtions. Thus, omined pplition of N nd P or N, P nd K fertilizers on P-limited pddy soil enhnes soil qulity. Aknowledgements This study ws finnilly supported y the Ntionl Nturl Siene Foundtion of Chin (grnt No ), the Ntionl Bsi Reserh Progrm of Chin (grnt No. 213CB12741) nd the Nturl Siene Foundtion of Jingsu Provine, Chin (BK213144). We thnk the nonymous reviewers nd editors for their helpful omments on the mnusript. Referenes Adesodun, J.K., Mgwu, J.S.C. & Oti, N. 25. Distriution of ron, nitrogen nd phosphorus in wter-stle ggregtes of n orgni wste mended Ultisol in southern Nigeri. Bioresoure Tehnology, 96, Ali, R.S., Ingwersen, J., Demyn, M.S., Funkuin, Y.N., Wizemnn, H.D., Kndeler, E. & Poll, C Modelling in situ tivities of enzymes s tool to explin sesonl vrition of soil respirtion from gro-eosystems. Soil Biology nd Biohemistry, 81, Allison, S.D. 25. Cheters, diffusion nd nutrients onstrin deomposition y miroil enzymes in sptilly strutured environments. Eology Letters, 8, Burns, R Intertion of enzymes with soil minerl nd orgni olloids. In: Intertions of soil minerls with nturl orgnis nd miroes (eds P.M. Hung & M. Shnitzer), pp SSSA, Mdison, WI. Busto, M.D. & Perez-Mteos, M. 2. Chrteriztion of et-dgluosidse extrted from soil frtions. Europen Journl of Soil Siene, 51, De th, G. 27. Boosted trees for eologil modeling nd predition. Eology, 88, Dou, X.L., He, P., Zhu, P. & Zhou, W Soil orgni ron dynmis under long-term fertiliztion in lk soil of Chin: evidene from stle C isotopes. Sientifi Reports, 6, Elliott, E.T Aggregte struture nd ron, nitrogen, nd phosphorus in ntive nd ultivted soils. Soil Siene Soiety of Ameri Journl, 5, Gregorih, E.G., Monrel, C.M., Shnitzer, M. & Shulten, H.R Trnsformtion of plnt residues into soil orgni mtter: hemil hrteriztion of plnt tissue, isolted soil frtions, nd whole soils. Soil Siene, 161, Gun, S.Y Methodology of soil enzyme mesurement. In: Methods of soil enzymology (eds S.Y. Gun), pp Chin Agriulturl Press, Beijing, Chin. Jing, X., Hu, Y., Bedell, J.H., Xie, D. & Wright, A.L Soil orgni ron nd nutrient ontent in ggregte-size frtions of sutropil rie soil under vrile tillge. Soil Use nd Mngement, 27, Kndeler, E., Stemmer, M. & Klimnek, E.M Response of soil miroil iomss, urese nd xylnse within prtile size frtions to long-term soil mngement. Soil Biology & Biohemistry, 31, Kemper, W.D. & Rosenu, R.C Aggregte stility nd size distriution. In: Methods of soil nlysis, Prt 1. Physil nd minerlogil methods, Agronomy Monogrph (eds A. Klute), pp Amerin Soiety of Agronomy nd Soil Siene Soiety of Ameri, Mdison, WI. Lgomrsino, A., Grego, S. & Kndeler, E Soil orgni ron distriution drives miroil tivity nd funtionl diversity in prtile nd ggregte-size frtions. Pedoiologi, 55, British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33

9 Distriution of nutrients nd enzymes in red soil 33 Lemnowiz, J Minerl fertilistion s ftor determining seleted sorption properties of soil ginst the tivity of phosphtses. Plnt Soil nd Environment, 59, Li, Z.P The utiliztion nd development strtegies of orgni mteril in ultivted lnd of red soil regions. Soil nd Environmentl Sienes, 8, (in Chinese). Li, Z.P., Cheng, L.L. & Lin, X.X. 2. Aumultion of orgni mtter in infertile red soils nd its eologil importne. Pedosphere, 1, Liu, Y.R., Li, X., Shen, Q.R. & Xu, Y.C Enzyme tivity in wter-stle soil ggregtes s ffeted y long-term pplition of orgni mnure nd hemil fertiliser. Pedosphere, 23, Lu, R.K Methodology of soil nutrients ssy. In: Anlytil methods for soil nd griulturl hemistry (eds R.K. Lu), pp Chin Agriulturl Sienteh Press, Beijing, Chin. Mjumder, B. & Kuzykov, Y. 21. Effet of fertiliztion on deomposition of C-14 lelled plnt residues nd their inorportion into soil ggregtes. Soil nd Tillge Reserh, 19, Mrx, M.C., Kndeler, E., Wood, M., Wermter, N. & Jrvis, S.C. 25. Exploring the enzymti lndspe: distriution nd kinetis of hydrolyti enzymes in soil prtile-size frtions. Soil Biology nd Biohemistry, 37, Mgwu, J.S.C. & Piolo, A Cron, nitrogen nd phosphorus onentrtion in ggregtes of orgni wste-mended soils. Biologil Wstes, 31, Odes, J.M Soil orgni-mtter nd struturl stility mehnisms nd implitions for mngement. Plnt nd Soil, 76, Peng, X., Yn, X., Zhou, H., Zhng, Y.Z. & Sun, H Assessing the ontriutions of sesquioxides nd soil orgni mtter to ggregtion in n Ultisol under long-term fertiliztion. Soil nd Tillge Reserh, 146, Piotrowsk-Dlugosz, A. & Wilzewski, E Soil phosphtse tivity nd phosphorus ontent s influened y th rops ultivted s green mnure. Polish Journl of Environmentl Studies, 23, Rkotoson, T., Six, L., Rzfimnntso, M.P., Rehriso, L. & Smolders, E Effets of orgni mtter ddition on phosphorus vilility to flooded nd nonflooded rie in P-defiient tropil soil: greenhouse study. Soil Use nd Mngement, 31, Sh, D., Kukl, S.S. & Shrm, S Lnduse impts on SOC frtions nd ggregte stility in typi ustohrepts of Northwest Indi. Plnt nd Soil, 339, Shng, Q.Y., Ling, N., Feng, X.M., Yng, X.X., Wu, P.P., Zou, J.W., Shen, Q.R. & Guo, S.W Soil fertility nd its signifine to rop produtivity nd sustinility in typil groeosystem: summry of long-term fertilizer experiments in Chin. Plnt nd Soil, 381, Su, J.Q., Ding, L.J., Xue, K., Yo, H.Y., Quensen, J., Bi, S.J., Wei, W.X., Wu, J.S., Zhou, J.Z., Tiedje, J.M. & Zhu, Y.G Long-term lned fertiliztion inreses the soil miroil funtionl diversity in phosphorus-limited pddy soil. Moleulr Eology, 24, Tisdll, J.M. & Odes, J.M Orgni-Mtter nd Wter-Stle Aggregtes in Soils. Journl of Soil Siene, 33, Wng, W., Chen, W.C., Wng, K.R., Xie, X.L., Yin, C.M. & Chen, A.L Effets of long-term fertiliztion on the distriution of ron, nitrogen nd phosphorus in wter-stle ggregtes in pddy soil. Agriulturl Sienes in Chin, 1, Wng, R.Z., Dorodnikov, M., Yng, S., Zhng, Y.Y., Filley, T.R., Turo, R.F., Zhng, Y.G., Xu, Z.W., Li, H. & Jing, Y Responses of enzymti tivities within soil ggregtes to 9-yer nitrogen nd wter ddition in semi-rid grsslnd. Soil Biology nd Biohemistry, 81, Wring, B.G., Weintru, S.R. & Sinsugh, R.L Eoenzymti stoihiometry of miroil nutrient quisition in tropil soils. Biogeohemistry, 117, Whlen, J.K. & Chng, C. 22. Mroggregte hrteristis in ultivted soils fter 25 nnul mnure pplitions. Soil Siene Soiety of Ameri Journl, 66, Ydv, R.S. & Trfdr, J.C. 21. Influene of orgni nd inorgni phosphorus supply on the mximum seretion of id phosphtse y plnts. Biology nd Fertility of Soils, 34, Yu, H.Y., Ding, W.X., Luo, J.F., Donnison, A. & Zhng, J.B Long-term effet of ompost nd inorgni fertilizer on tivities of ron-yle enzymes in ggregtes of n intensively ultivted sndy lom. Soil Use nd Mngement, 28, Zhng, Q., Zhou, W., Ling, G.Q., Sun, J.W., Wng, X.B. & He, P Distriution of soil nutrients, extrellulr enzyme tivities nd miroil ommunities ross prtile-size frtions in longterm fertilizer experiment. Applied Soil Eology, 94, Zhong, W.H. & Ci, Z.C. 27. Long-term effets of inorgni fertilizers on miroil iomss nd ommunity funtionl diversity in pddy soil derived from quternry red ly. Applied Soil Eology, 36, British Soiety of Soil Siene, Soil Use nd Mngement, 33, 25 33