Combined application of rice husk biochar and fly ash improved the yield of lowland rice

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1 CSIRO PUBLISHING Soil Reserch Comined ppliction of rice husk iochr nd fly sh improved the yield of lowlnd rice Sushmit Mund A,E, A. K. Nyk A, P. N. Mishr A, P. Bhttchryy A, Sngit Mohnty A, Anjni Kumr A, Upendr Kumr A, M. J. Big B, Rhul Tripthi A, Mohmmd Shhid A, Totn Adk C, nd V. Ksturi Thilgm A,D A Crop Production Division, ICAR-Ntionl Rice Reserch Institute, Cuttck, Indi B Crop Physiology nd Biochemistry Division, ICAR-Ntionl Rice Reserch Institute, Cuttck, Indi C Crop Protection Division, ICAR-Ntionl Rice Reserch Institute, Cuttck, Indi D ICAR-Indin Institute of Soil nd Wter Conservtion, Reserch Centre, Ooty, Indi E Corresponding uthor. Emil: sustot@gmil.com; sushmit.mund@icr.gov.in Astrct. The effects of rice husk iochr (BC) nd col fly sh (FA) on growth nd yield of rice nd soil properties were investigted in lowlnd rice soil. All growth prmeters nd yield were positively influenced y the integrted ppliction of BC, FA nd chemicl fertilisers compred with sole ppliction of chemicl fertilisers. Yield increse ws 16.4% when BC+FA ws pplied together with 5% of the recommended dose of nitrogen (N) compred with the recommended dose of N, phosphorus nd potssium (NPK). Post-hrvest soil nlysis suggested tht BC nd FA oth ct s supplier, s well s reservoir of nutrients. Accumultion of hevy metls in soil nd plnt prts fter hrvest ws elow the toxicity threshold for plnts nd humns. There ws lso no significnt chnge in microil popultion compred with the initil soil. Therefore, comined ppliction of BC nd FA supplemented with chemicl fertilisers could e recommended to improve soil fertility nd crop productivity without ffecting the soil qulity. Additionl keywords: fertilisers, hevy metls, microes, nutrients, rice husk. Received 12 Octoer 215, ccepted 2 Novemer 215, pulished online 3 June 216 Introduction Utilistion of griculturl nd industril wstes is worldwide concern. Among the different gro-wstes, 116 million tonnes of rice husk is produced nnully y more thn 75 countries (FAO 22). Rice husk constitutes vlule resource, ut due to lck of proper residue mngement prctices its potentil is often underutilised leding to negtive environmentl consequences. Except for limited use in power genertion, rice husk wste cuses serious environmentl prolems. Burning rice husk wste on open fields is thought to e one of the mjor contriutors to greenhouse gs emissions. Recycling of this gro-wste for nutrient mngement in soil my e considered s n lterntive option to urning. Biochr (BC), highly stle orgnic mteril, produced through pyrolysis of woody mterils, griculturl wstes, green wste nd niml mnures is reported to hve pronounced effects on soil physico-chemicl (Cross nd Sohi 211) nd iologicl properties (Lehmnn et l. 211). Significnt increses in plnt growth nd reduction in greenhouse gs emissions from soil hs een reported (Chn et l. 27). Previous studies hve shown tht soil properties re gretly ffected y the rte of BC ppliction nd more pronounced effects re recorded with higher rtes of ppliction (Asi et l. 29). Furthermore, informtion on the use of BC ppliction Journl compiltion CSIRO 216 in rice crops nd its effect on soil properties is limited. Therefore, optimistion of BC ppliction rtes for rice cultivtion is importnt not only to chieve higher crop yields ut lso for its effect on soil properties. Fly sh (FA), n inorgnic y-product of col comustion, is produced in therml power plnts nd its disposl nd mngement is mjor environmentl chllenge. Fly sh contins mny elements (clcium, mgnesium, iron, zinc, molydenum, sulfur nd selenium) tht cn e source of nutrients to plnts (Kesh et l. 23) ut contins only trces of cron (C) nd nitrogen (N). Ameliorting soil with FA improves soil physicl properties (wter holding cpcity, soil plsticity, soil texture, ulk density nd crust formtion). Thus, it cn e considered s potentil soil mendment. The effect of FA is determined primrily y chemicl composition nd the rte of ppliction. Appliction of high quntities of FA is thought to increse solule slts nd hevy metl content in soils nd this ppers to e the most serious constrint. As FA hs limited C, if comined with BC, it my improve nd restore the fertility of tropicl soil leding to incresed crop productivity. Therefore, the ojective of the present study ws to investigte the potentil of rice husk BC to improve rice yield when pplied lone or in comintion with fertiliser nd FA.

2 B Soil Reserch S. Mund et l. Mterils nd methods Rw mterils Rice husk ws collected from rice mill in the suur of Cuttck, Odish, Indi (2.38N, E). The husk ws pyrolysed t 38C for 6 h to otin stle BC (to e clssified under pyrogenic cronceous mteril, PCM). Fly sh ws collected from the FA dykes of the Arti Steel Plnt, Athgrh, Odish, Indi. The FA ws stilised t 528C for 24 h to kill off pthogens nd dried t room temperture for 1 week. Biochr nd FA were ground to pss through 2-mm nd 4-mm sieve, respectively, to otin homogeneous smples for mixing with the soil. Physicl nd chemicl nlyses To understnd the surfce morphology of rice husk BC nd col FA, smples were exmined using scnning electron microscopy (SEM). SEM nlysis ws performed using Zeiss EVOMA1 scnning electron microscope, operting t 2 kv. The moisture nd sh content ws determined ccording to stndrd methods NREL/TP nd NREL/TP , respectively. Soil smples were dried in n oven t 158C for 24 h to determine moisture content. For the determintion of sh content in BC, smples were heted t C for 4 h. Moisture nd sh content were clculted grvimetriclly fter ttining constnt weight. The ph nd electricl conductivity (EC) were mesured with deionised wter 1 : 2 W/V for BC nd 1 : 2.5 W/V for soil nd FA. Ction exchnge cpcity (CEC) ws determined using 1 N mmonium cette. Totl C, N nd hydrogen (H) contents were mesured using n orgnic elementl nlyser (Thermo Scientific, Flsh 2). The oxygen (O) percentge in BC ws estimted using the following eqution: O% = 1% -(C% + H % + N% + sh%) (Brewer et l. 211). Hevy metls (P, Cd, Cu, Cr) were determined y tomic sorption spectrophotometry (AAS; Perkin Elmer 21, Germny). Biochr smples were extrcted y the dicid method (nitric cid perchloric cid) (Amcher 1996) for nlysing hevy metls. The vilility of metls in soil is strongly influenced y the quntity nd qulity of orgnic mtter. Therefore, DTPA-extrctle hevy metls were extrcted from 1 g soil with 2 ml of extrcting solution (.5 M DTPA,.1 M CCl 2 nd.1 M tetrethylmmonium djusted to ph 7.3), following the Lindsy-Norwell procedure (Lindsy nd Norwell 1978). Orgnic cron (OC) in soil nd FA ws determined using the Wlkley-Blck method (Nelson nd Sommers 1996). Soil smples were nlysed for OC, ph, EC, N, P, K, micronutrients (Fe, Mn, Zn) nd hevy metl (Cu, P, Cr, Cd) content efore plnting nd fter hrvest. Experimentl detils A pot experiment ws conducted to study the effect of rice husk BC in comintion with fertilisers nd FA on rice growth nd yield. A ulk soil (Aeric Endoquept) smple ( 15 cm) ws collected from the experimentl frm t the Ntionl Rice Reserch Institute in Cuttck (2.488N, E) nd ws irdried, ground, nd pssed through 2. mm sieve. Nine kg of processed soil ws plced in plstic pots with n inside dimeter of 25 cm. The quntities of NPK (12 : 6:6 kg h 1 NPK), BC (1%) nd FA (3%) were clculted on weight sis nd mixed with dry soil efore plcing in the pots. The ddition of nutrients through BC nd FA ws not tken into ccount when considering the equivlent nutrient level. The properties of the experimentl soil, BC nd FA used in this experiment re presented in Tle 1. Tretments consisted of the recommended dose of fertilisers, RDF (T2); ppliction of BC plus RDF (T3); ppliction of BC plus FA without RDF (T4). Becuse FA contined ~.5% P nd 2% K, tretment of FA + BC with 5% N (5%N+BC+ FA) ws included to ssess the comined effect of BC nd FA with only 5% of the recommended dose of N without P nd K ppliction (T5). A control soil with no mendments (T1) ws included for comprison. The experiment ws conducted for two consecutive sesons (July to Novemer 212 nd Jnury to April 213) nd ll dt presented re the men vlues of the two sesons. A totl of four replictions of the five tretments were undertken in ech yer of the experiment. Twenty-five-dy old rice seedlings (vr. Swrn) were trnsplnted to these pots. Full P, K nd 5% N ws pplied slly t the time of trnsplnt nd the remining mount of N ws pplied in two split tretments, t mximum tillering nd pnicle initition. Wter depth (4 5 cm) ws mintined throughout the rice growth stge except 1 week efore hrvest. The plnts were hrvested fter reching physiologicl mturity. Plnt growth prmeters nd yield Plnt height, numer of tillers, rte of photosynthesis, chlorophyll (chl ) nd chlorophyll (chl ) were recorded t mximum tillering stge (6 dys fter trnsplnt, DAT) to study the effect of tretments during the vegettive growth phse. Chlorophyll concentrtion ws determined following Tle 1. Chemicl, physicl nd iologicl properties of soil, iochr nd fly sh used for the experiment Property Soil Biochr Fly sh ph EC (ds m 1 ) CEC (meqn 1 g of soil 1 ) Totl C (%) Totl N (%).5.32 Trces C/N rtio H% 4.3 O% H/C rtio.12 Moisture content (%).9 Ash content (%) 2.6 DTPA extrctle metls (mg kg 1 ) Fe Zn Mn Cu P Cr Cd Microil count (log CFU g 1 ) Bcteril count 7.1 Actinomycetes count 5.9 Fungl count 2.68

3 Rice husk nd fly sh utilistion in griculture Soil Reserch C the procedure of Porr (22). Chopped fresh lef tissue of.1 g ws trnsferred to cpped mesuring tue contining 25 ml of 8% cetone nd kept inside refrigertor t 48C for 48 h. Mesurements were mde using spectrophotometer (SICAN 231; Doule Bem Spectrophotometer, USA) t wvelength of 663 nm nd 645 nm to clculte chlorophyll nd chlorophyll content, respectively. Photosynthetic rte (Pn rte), stomtl conductnce, tmospheric CO 2 concentrtion (C ) nd intercellulr CO 2 concentrtion (C i ) were mesured with portle, infrred gs nlyser (IRGA, Li-Cor-64, Li-Cor, Lincoln, Nersk, USA). All mesurements were recorded from the top of three rndomly selected tillers under mient conditions from 9 to 11 h t mximum tillering stge (Psk et l. 212). Oservtions on plnt height, numer of pnicles nd pnicle weight per pot were recorded in ech tretment t hrvest. The hrvested smples were sun-dried, weighed nd recorded s totl iomss. Grin yield ws djusted to moisture concentrtion of 14% of fresh weight. Grin moisture concentrtion ws mesured with digitl moisture meter (DMC-7, Seeduro, Chicgo, IL, USA). experimentl soil. Both BC nd FA were lkline with ph 8.7 nd 7.8, respectively, while the soil ph ws 6.8. The EC of FA ws similr to tht of the soil (Tle 1). The hevy metl content of BC followed the order Fe > Mn > Zn > Cd > Cu > P > Cr wheres in FA the order ws Fe > Mn > Zn > Cu > P > Cr > Cd. Fly sh hd sustntilly greter contents of Cu (4.5 ppm), P (2.44 ppm), Cr (.79 ppm), nd Cd (.48 ppm) (Nyk et l. 214) thn the experimentl soil nd BC. This my e due to the oxides, lumin silicte, sulfides nd chlorides present in the FA, which ct s hevy metl crriers (Dnielowsk 26). The cteril, ctinomycetes nd fungl count of the experimentl soil were 7.1, 5.9 nd 2.68 log CFU g 1, respectively. The SEM imges of BC showed highly porous structure (Fig. 1). The irregulr shpe nd rough surfce of FA ws lso clerly visile (Fig. 2) indicting high degree of porosity. Porosity increses with the increse in surfce roughness nd decreses with the increse in its fineness (Sinsiri et l. 21). Anlysis of plnt smples The N content of plnt mterils ws estimted using modified Kjeldhl method, P ws determined using spectrophotometer nd K ws determined y flme photometry fter cid digestion using HF cid decomposition method (Chpmn nd Prtt 1961). Micronutrients (Fe, Mn, Zn) nd hevy metls (Cu, Cd, Cr nd P) were mesured in strw nd grin with AAS (Perkin Elmer- 21, Germny) fter cid digestion with HNO 3 /HClO 4 (4 : 1 V/V) (Amcher 1996). Enumertion of microil popultion Cultivle microorgnisms were enumerted using the memrne filtrtion method. Seril dilutions of soil suspensions were filtered through 47 mm memrne with.45 mm porosity (Knowles nd Brrquio 1994). Plte Count Agr nd Actinomycetes Isoltion Agr cultures were incuted t 38C for 48 h nd 7 dys, respectively, for enumertion of heterotrophic cteri nd ctinomycetes. Rose Bengl- Chlormphenicol cultures were incuted t 228C for 7 dys for enumertion of fungi. Dt from triplictes were expressed s log colony forming units (CFU) g 1 dry soil (oven-dried soil sis). 2 µm EHT = 2. kv Signl A = SE1 WD = 9.5 mm Mg = 811 X 2.93e-5 mr Dte :3 Jn 215 Time :16:54:49 Fig. 1. Scnning electron microscope imge of rice husk iochr otined y pyrolysis t 38C for 6 h. A highly complex porous structure is clerly visile. Sttisticl nlysis Significnt differences of the men mong the tretments were sttisticlly nlysed y one wy ANOVA (t P.5) using SAS softwre pckge 9.2 (SAS Institute 21). Results nd discussion Chrcteristion of initil soil, iochr nd fly sh The soil used in this study hd totl C nd N contents of.52% nd.5%, respectively, with C : N rtio of 1.4. Totl C, totl N nd C : N rtio of the rice husk BC were 47% (to e clssified under PCM),.32% nd 146.8, respectively. In ddition to this, BC lso contined significnt mount of Fe, Zn nd Mn. The ph nd EC of BC were higher thn the 3 µm EHT = 2. kv Signl A = SE1 WD = 8. mm Mg = 6.9 K X 4.6e-5 mr Dte :3 Jn 215 Time :15:43:53 Fig. 2. Scnning electron microscope imge of col fly sh. The irregulr shpe nd rough surfce is clerly visile.

4 D Soil Reserch S. Mund et l. Post-hrvest physico-chemicl nd microil properties of soil The eneficil effects of rice husk BC nd FA ddition on crop production re determined y chnges in soil chrcteristics nd nutrient vilility (Chn et l. 27). Aville N, P nd K content in soil fter hrvest were found to differ significntly (P <.5) etween the tretments (Fig. 3). The highest ville N (139.5 kg h 1 ) nd K (168 kg h 1 ) were found in T3 (RDF + BC). Some reserchers oserved high N residue in soil mended with BC suggesting BC ddition might e regulting N loss from the system s studies showed BC mendment significntly decresed N 2 O emission from pddy soils (Zhng et l. 21; Liu et l. 212). In ddition to this, minerlistion of BC in soil possily led to the relese of N t lter stge of crop growth. Phosphorus content ws 85% higher in T4 (15.5 kg h 1 ) compred with the control (8.4 kg h 1 ). The liming effect of BC nd FA contriuted to P vilility in soil (DeLuc et l. 29; Vn Zwieten et l. 21). Fly sh ddition lso decresed P loss from soil y converting the lile wter solule-p to dsored-p, which my induce slow relese mechnisms mking P ville for longer. DeLuc et l. (29) cited three possile mechnisms through which BC my directly or indirectly influence P vilility in soil. BC could ct s direct source of solule P slts nd exchngele P, modifier of soil ph nd meliortor of P complexing metls (Al 3+,Fe 3+,2+,C 2+ ), or promote microil ctivity nd P minerlistion. The soil ville K incresed significntly (P <.5) in response to ppliction of BC nd FA compred with the control tretment. The increse in soil K in T3 ws ~6% over RDF. Comined ppliction of BC+FA (T4) incresed soil K y 6.7%. Similr evidence of n increse in ville K ws reported y Mjor et l. (21). The concentrtion of hevy metls in soil fter crop hrvest were well within permissile limits for soil (Dennemn nd Roerse 199). There ws no significnt chnge in Fe, Mn, Zn, Cu nd P content in the soil due to the ppliction of the vrious tretments (Tle 2). Despite higher initil hevy metl (Mn, Zn, Cu nd P) contents, when FA ws pplied in comintion with BC there ws no significnt increse in hevy metl content in the soil. The BC nd FA used in the study hd very high degree of porosity. A structured cron mtrix of BC with high degree of porosity nd extensive surfce re my ct s surfce sorent, plying n importnt role in controlling hevy metl vilility in the soil (Msto Aville N nd K (kg h 1 ) c c c c c c c Aville P (kg h 1 ) T1 T2 T3 T4 T5 Tretments N K P Fig. 3. Aville N, P nd K (kg h 1 ) in soil. Tle 2. Hevy metl content in soil s influenced y tretment Mens followed y the sme letter re not sttisticlly significnt using Tukey s honest significnt difference t P.5. NS, Not significnt Tretments Fe Mn Zn Cu P Cd Cr Initil soil After hrvest T c.8 T c.12 T T T Tukey s HSD t 5% NS NS NS NS NS.98.69

5 Rice husk nd fly sh utilistion in griculture Soil Reserch E et l. 213). However, soils treted with FA (T4 nd T5) recorded higher Cd content thn the other tretments. This my e due to the presence of the oxide form of the metl which is solule in wter nd redily ville. At hrvest, soil ph showed significnt chnges for the different tretments (Tle 3). The highest ph (7.14) ws recorded in T4 (BC+FA) followed y 6.82 in T5 (BC+FA+ 5% N). The soil ph recorded in RDF (T2) ws 6.4. Similr oservtions were reported y Steiner et l. (27). Higher concentrtions of lkline metl oxides (C 2+,Mg 2+, nd K + ) nd decresed concentrtion of solule soil Al 3+ in BC were reported to explin such n effect. Fly sh contins sustntil mounts of silicte minerls tht rect with hydrogen ions (H + ) leding to neutrlistion through formtion of silicic cid (Msto et l. 213). Mohptr nd Knungo (1997) explined tht s the silicte minerl surfce ecomes more nd more negtively chrged, H + will e concentrted close to the surfce, forming the counter-ion lyer nd OH- will tend to form diffuse doule lyer resulting in n increse in ph. The incresed ph cn lso improve CEC, io-ville P nd se ctions in soil (Mjor et l. 21). The ph chnge (DpH) ws most negtive in T3 which supports the present elief tht dsored nions render surfce more negtive. This ws sustntited y n increse in CEC from n initil soil vlue of 25 meq 1 g 1 of soil to 3.6 meq 1 g 1 t hrvest. Comined ppliction of BC +FA significntly incresed EC (Tle 3) nd the gretest EC (1.3 ds m 1 ) ws recorded in T5 followed y 1.26 ds m 1 in T4. High solule slt concentrtions in BC or FA might hve contriuted for increse in soil EC. Addition of BC lone nd in comintion with FA significntly incresed the OC from.42% in RDF to.5% nd.52% t T3 (RDF+BC) nd T5 (5% N+BC+FA), respectively. The increse in soil C content is result of the greter initil C content in the BC. In the comined tretment, FA might hve helped to stilise the BC cron in soil through formtion of orgno-minerl complexes. Surfce hydrophoic nd hydrophilic interctions of BC nd FA occur through direct electrosttic interctions, H onding, ction ridging, nd lignd exchnge rections in the hydrophilic zone (Yriv nd Cross 22). Bcteril, ctinomycetes nd fungl counts were significntly higher in T3 fter hrvest. The generl improvement in the soil properties (ph, nutrients) due to BC or FA mendment would hve contriuted to the increse in soil microil popultion. This is consistent with the findings of Lehmnn et l They reported tht BC treted soils showed n increse in microil popultion due to the improvement of physicl nd chemicl chrcteristics of the soil. Steiner et l. (27) oserved positive correltion etween microil iomss nd soil ph in n cid Xnthic Ferrlsol of Brzil fter BC pplictions. Comined ppliction of BC nd FA tretments with or without chemicl fertiliser (T4 nd T5) recorded significntly lower cteril, ctinomycetes nd fungl counts fter hrvest of the crop. A decrese in the cteri count with incresing FA quntities ws oserved y Kuchrski et l. (26) in soils with n ot crop. They lso reported tht fungl count showed negtive reltionship to n increse in FA content. Vllini et l. (1999) oserved tht FA promoted cteril nd ctinomycetes counts when dded to soil with lingo-cellulosic residuls in greenhouse study, wheres no positive response ws recorded when FA ws pplied lone. Yeledhlli et l.(27), reported n increse in the totl cteri count nd ctinomycetes, ut decresed the numer of fungi with FA ppliction. Effect on plnt growth nd photosynthesis Significnt effects of BC nd FA on rice growth ws oserved (Tle 4). Appliction of 5% N together with BC nd FA (T5) produced the highest numer of tillers per plnt followed y T3 (BC+RDF), while the control tretment recorded the lowest numer of tillers. The significntly greter numer of tillers in the BC nd FA treted pots confirmed the findings of Chn et l. (27) who showed tht the ppliction of rice husk BC to soil could increse the numer of rice tillers compred with the control soil. The increse in tillering oserved in these pots is most likely due to the extr nutrients ville to plnts (Zhng et l. 213) s result of incresed wter holding cpcity with the ppliction of BC nd FA. The complex porous structure of BC nd FA used in the study is responsile for the very high porosity nd high wter holding cpcity of the soil. Chn et l. (27) reported improved physicl properties of soils, such s incresed soil ggregtion, fter BC ppliction resulting in n incresed nutrient plnt supply. Photosynthetic rte (Pn rte) rnged from 14 to 19 mmols CO 2 m 2 sec 1 nd followed the order of T5 > T3 > T4 > T2 > T1. Biochr soil mendment led to modest improvement of lef Pn rte. This is ssocited with oth incresed lef N nd soil Tle 3. Effect of physico-chemicl nd microil properties of soil fter hrvest Mens followed y the sme letter re not sttisticlly significnt using Tukey s honest significnt difference t P.5. NS, Not significnt Tretment Soil ph DpH CEC (meq 1 g soil 1 ) EC (ds m 1 ) OC fter hrvest (g kg 1 ) Bcteril count (log CFU g 1 ) Actinomycetes count (log CFU g 1 ) Fungl count (log CFU g 1 ) Initil soil After hrvest T1 6.48cd c 7.5c T2 6.41d c 7.12c 5.43c 3.54 T3 6.63c T c 2.d T c d 2.3c Tukey s HSD t 5% NS

6 F Soil Reserch S. Mund et l. ville N. Stomtl conductnce showed similr trend. The fertilistion in ddition to comined BC nd FA ppliction hd positive effect on gs exchnge vriles such s Pn rte, stomtl conductnce nd intercellulr CO 2 concentrtion (C i ). Similr results were otined y Alurquerque et l. (213). Mximum stomtl conductnce, C i nd C i /C were recorded in T3 (RDF+BC) indicting enhnced vegettive growth due to the tretment (Tle 4). Chl concentrtion, Chl concentrtion nd Chl / rtio in leves rnged from 1.6 to 1.8,.6 to.7 nd 2.2 to 2.6, respectively. However, the effect of tretment ws not sttisticlly significnt. Other studies showed contrdictory results with respect to the effect of BC ppliction on chlorophyll content. Reserch work suggests positive response (Noguer et l. 212) to BC ppliction. They ttriuted this to higher N uptke ided y etter soil physicl properties fter BC ppliction. Wheres, Asi et l. (29) oserved tht BC ppliction reduced chlorophyll concentrtion in rice leves. A possile explntion could e relted to decrese in soil N vilility due to the high C : N rtio of BC, nd lile C nd soil microil ctivity re likely to increse, leding to immoilistion of N. Yield nd yield prmeter A significnt effect of tretment ws recorded on yield nd yield prmeters (Fig. 4). Numer of grins per pnicle ws gretest (133) in T3 (RDF+BC) followed y T2 (RDF) nd T5 (5%N +BC+FA). The tretments without ny chemicl fertilisers (T1, T4) resulted in lower numer of grins. In T4 (BC+FA), grin yield increse ws ~38% more thn the control soil. This increse ws lower thn tht in other tretments: 46% increse in T2, 65% increse in T3 nd 71% increse in T5 compred with the control soil. These results re in greement with other reserchers (Chn et l. 27; Vn Zwieten et l. 21) who found little response of crop yield nd nutrient sttus to the sole use of BC, which is likely due to its cron-rich nture ut nutrient poor mteril. Therefore, most studies hve shown the eneficil effects of BC ddition on crop production re most evident when it is comined with minerl fertilisers (Asi et l. 29; Chn et l. 27; Lehmnn et l. 23; Vn Zwieten et l. 21). In this study, even 5% N (no P nd K) ppliction in ddition to BC nd FA produced similr yield to tht of 1% RDF. This indictes tht, in ddition to enhncing soil orgnic C, mendment with rice husk BC nd col FA would potentilly reduce N fertiliser use. Srngi et l. (21) reported tht rice plnts responded positively to FA mendment with no visul symptoms ttriutle to either toxicity or deficiency of nutrients. Zhng et l. (21) reported tht ppliction of 4 t h 1 of whet strw BC incresed yield y 14% compred with N fertilistion. Zhng et l. (213) suggested tht the increse in grin yield ws minly ttriutle to high soil CEC nd nitrte retention. Peng et l. (211) suggested tht Tle 4. Tiller numer, Pn rte, Chl content, Chl content, Chl / rtio, stomtl conductnce, Ci nd Ci/C rtio t mximum tillering stge Ci, Intercellulr CO 2 concentrtion; C, tmospheric CO 2 concentrtion; Pn rte, rte of photosynthesis. Mens followed y the sme letter re not sttisticlly significnt using Tukey s honest significnt difference t P.5. NS, Not significnt Tretments No. of tillers plnt 1 Chl (mg g 1 of fresh wt) Chl (mg g 1 of fresh wt) Chl / rtio Pn rte (mmols CO 2 m 2 sec 1 ) Stomtl conductnce (mol H 2 Om 2 s 1 ) Ci (mmol CO 2 mol 1 ) Ci/C T1 9d T2 12c T T4 11c T Tukey s HSD t 5% 1.6 NS NS NS Grin yield, strw yield nd pnicle numer c T1 T2 T3 T4 T5 2 Tretments Numer of pnicles/pot Grin yield (g)/pot Strw yield (g)/pot Numer of gins/pnicle Numer of grins per pnicle Fig. 4. Numer of pnicles per plnt, numer of grins per pnicle, grin nd strw yield s influenced y tretment.

7 Rice husk nd fly sh utilistion in griculture Soil Reserch G ph neutrlistion could hve cused n increse in yield, ecuse nutrients ecome more ville t neutrl ph. Nutrient uptke nd hevy metl ccumultion in plnts Appliction of rice husk BC nd FA ffected nutrient uptke (Fig. 5). Nitrogen, P nd K uptke in plnts rnged from 34 to mg N pot 1, 35 to 73.8 mg P pot 1 nd 184 to 34.2 mg K pot 1. The highest N uptke (511.5 mg pot 1 ) ws recorded in T5 followed y T3 (496.7 mg pot 1 ) nd T2 (447.6 mg pot 1 ). T3 nd T5 resulted in the highest uptke of N, P nd K. This ws possily due to etter root growth, enhnced nutrient supply nd conducive physicl environment creted y the ddition of BC or FA or comintion of oth which fcilitted incresed sorption of N, P nd K. Tretments T3, T4, nd T5 recorded considerly higher P nd K uptke compred with the control tretment. DeLuc et l. (29) indicted tht BC cts s direct source of solule P slts nd meliortor of P complexing metls (Al 3+, Fe 3+, 2+, C 2+ ), therey incresing the vilility of minerlised P to plnts. The Fe, Mn, Zn, Cu, nd Cd contents in grin were less thn those in strw. Led nd Cr recorded higher concentrtions in grin thn in strw (Tles 5 nd 6). Hevy metl concentrtion in grins vried mong the tretments ut no trend ws evident. Iron concentrtion rnged from 1.6 ppm to 12.9 ppm, Mn N nd K uptke (mg pot 1 ) d c c P uptke (mg pot 1 ) T1 T2 T3 T4 T5 Tretments N K P Fig. 5. Nutrient uptke (grin + strw) s influenced y tretments. Tle 5. Hevy metl concentrtion in grin s influenced y tretment Mens followed y the sme letter re not sttisticlly significnt using Tukey s honest significnt difference t P.5. NS, Not significnt Tretment Fe (ppm) Mn (ppm) Zn (ppm) Cu (ppm) P (ppm) Cd (ppm) Cr (ppm) T1 1.6d T2 1.8c T T4 1.6e T Tukey s HSD t 5% NS.3 NS Tle 6. Hevy metl concentrtion in strw s influenced y tretment Mens followed y the sme letter re not sttisticlly significnt using Tukey s honest significnt difference t P.5. NS, Not significnt Tretment Fe (ppm) Mn (ppm) Zn (ppm) Cu (ppm) P (ppm) Cd (ppm) Cr (ppm) T c.1 T c.4 T T T Tukey s HSD t 5% NS NS NS NS NS

8 H Soil Reserch S. Mund et l. from 12.3 to 16 ppm, Zn from 17.3 to 22.7, Cu from 1.8 to 2.1 ppm nd Cd from.119 to.147 ppm. Led nd Cr content in grin ws not ffected y the ppliction of fertilisers, BC or FA (Tle 5). Iron, Mn, Zn, Cu nd P concentrtion in strw (Tle 6) did not differ significntly etween tretments. The BC nd FA used in the study oth hd irregulr nd rough surfces indicting high porosity. Previous studies reported low uptke of hevy metls y plnts mended with BC nd ttriuted this to the high degree of porosity nd extensive surfce re of BC which my ct s surfce sorent inhiiting uptke (Msto et l. 213). Biochr plus FA (T4) nd 5%N +BC+FA (T5) oth hd high Cd concentrtions which could e result of the very high ppliction rte of FA used in this study. Conclusion Beneficil effects of BC nd FA on soil properties nd crop yield ws exhiited in comintion with chemicl fertilisers. Improved soil properties in terms of ph, OC, CEC, EC nd ville NPK were oserved with BC nd FA ppliction. In this study, even 5% N ppliction with BC nd FA produced similr yield s tht of 1% RDF. This indictes there is further opportunity to decrese the use of N fertilisers. Overll, utilistion of rice husk BC is potentil opportunity for crop residue mngement nd the use of col FA for gronomic purposes provides potentil option for its ginful disposl. Acknowledgement We express our thnks to the Director, ICAR-Ntionl Rice Reserch Institute, Cuttck, Indi, for ll finncil nd technicl support. References Alurquerque JA, Slzr P, Brrón V, Torrent J, del Crmen del Cmpillo M, Gllrdo A, Villr R (213) Enhnced whet yield y iochr ddition under different minerl fertiliztion levels. Agronomy for Sustinle Development 33, doi:1.17/s Amcher MC (1996) Nickel, cdmium, nd led. In Method of soil nlysis, Prt 3: Chemicl methods. (Eds DL Sprks, AL Pge, PA Helmke, RA Leoppert, PN Soltnpour, MA Tti, CT Johnston, ME Sumner) pp (Soil Science Society of Americ: Mdison, WI, USA) Asi H, Smson BK, Stephn HM, Songyikhngsuthor K, Homm K, Kiyono Y, Inoue Y, Shiriw T, Horie T (29) Biochr mendment techniques for uplnd rice production in Northern Los 1. Soil physicl properties, lef SPAD nd grin yield. Field Crops Reserch 111, doi:1.116/j.fcr Brewer CE, Unger R, Schmidt-Rohr K, Brown RC (211) Criteri to select iochrs for field studies sed on iochr chemicl properties. BioEnergy Reserch 4, doi:1.17/s Chn KY, Vn Zwieten L, Meszros I, Downie A, Joseph S (27) Agronomic vlues of green wste iochr s soil mendment. Austrlin Journl of Soil Reserch 45, doi:1.171/sr719 Chpmn HD, Prtt PF (1961) Method for nlysis of soil, plnts nd wters. (University of Cliforni: CA, USA) Cross A, Sohi SP (211) The priming potentil of iochr products in reltion to lile cron contents nd soil orgnic mtter sttus. Soil Biology & Biochemistry 43, doi:1.116/j.soilio Dnielowsk DS (26) Hevy metls in fly sh from col-fired power sttion in Polnd. Polish Journl of Environmentl Studies 15, DeLuc TH, McKenzie MD, Gundle MJ (29) Biochr effects on soil nutrient trnsformtions. In Biochr for environmentl mngement: science nd technology. (Eds J Lehmnn, S Joseph) pp (Erthscn: London) Dennemn PRJ, Roerse JG (199) Eco-toxicologicl risk ssessment s se for development of soil qulity criteri. The NPO report. (Ntionl Agency for the Environmentl Protection: Copenhgen) FAO (22) Sttisticl dtse. Aville t: Kesh S, Klr N, Shrm SK, Chudhry A (23) Fly sh incorportion effects on soil chrcteristics, growth nd yield of whet. Asi Pcific Journl of Environmentl Development 4, Knowles R, Brrquio WL (1994) Free living dinitrogen-fixing cteri. In Methods of soil nlysis. Prt 2: Microiologicl nd iochemicl properties. 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