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Korean Journal of Environmental Agriculture Korean J Environ Agric (2011) Online ISSN: 2233-4173 Vol. 30, No. 3, pp. 243-251 http://dx.doi.org/10.5338/kjea.2011.30.3.243 Print ISSN: 1225-3537 간척지논토양개량제로서석고처리가메탄배출량저감에미치는영향 임창현, 1 김상윤, 1 김필주 1,2* 1 경상대학교응용생명과학부 (BK 21 program), 2 경상대학교농업생명과학연구원 Effect of Gypsum Application on Reducing Methane (CH 4 ) Emission in a Reclaimed Coastal Paddy Soil Chang Hyun Lim, 1 Sang Yoon Kim, 1 and Pil Joo Kim 1,2* ( 1 Division of Applied Life Science (BK 21 Program), Gyeongsang National University, Jinju, 660-701, South Korea, 2 Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 660-701, South Korea) Received: 23 June 2011 / Accepted: 09 September 2011 c 2011 The Korean Society of Environmental Agriculture Abstract BACKGROUND: Gypsum(CaSO 4 ㆍ 2H 2 O) is known as an ideal amendment to improve soil quality of the reclaimed coastal land. Since gypsum has very high concentration of electron acceptor like SO 4 2-, its application might be effective on reducing CH 4 emission during rice cultivation, but its effect has not been studied well. METHODS AND RESULTS: The effect of gypsum on CH 4 emission and rice growth characteristics was studied by pot test, which was packed by reclaimed paddy soils collected from Galsa, Hadong, Gyeongnam province. Chemical-grade gypsum was applied in two soils having EC 2.25 and 9.48 ds/m at rates of 0, 0.5, 1.0 and 2.0%(wt/wt). CH 4 emission was characterized a week interval by closed chamber method during rice cultivation. CH 4 emission rate was significantly decreased with increasing salt accumulation and gypsum application levels. With increasing gypsum application, dissolved SO 4 2- concentration in the leachate water was significantly increased, which might have suppressed CH 4 production in soil. Total CH 4 flux was dramatically decreased with increasing gypsum application. In contrast, rice yield was * 교신저자 (Corresponding author), Phone: +82-55-772-1966; Fax: +82-55-772-1969; E-mail: pjkim@gnu.ac.kr These authors contributed equally to this work. increased with increasing gypsum application and then achieved maximum productivity at 1.0% gypsum application in two soils. CONCLUSION(s): Gypsum is a very good soil amendment to suppress CH 4 emission in reclaimed coastal paddy soils, and improve rice productivity and soil properties. The optimum application level of gypsum is assumed at ca. 1% to improve soil productivity with reducing effectively CH 4 emission during rice cultivation. Key Words: Calcium sulfate, CH 4 emission, Gypsum, Reclaimed soil 서론 메탄 (CH 4) 은이산화탄소 (CO 2) 와더불어주요한지구온난화가스로서, 지구전체온난화가스의약 20% 이상을차지하는것으로알려져있다 (IPCC, 2007). 메탄은약 10년이라는짧은대기잔존시간과약 1.7 ppmv의낮은대기중농도에도불구하고, 높은적외선흡수능때문에이산화탄소의약 23배에달하는지구온난화지수 (Global warming potential, GWP) 를가지고있다 (Blake and Rowland, 1988; Rodhe, 1990; Minami and Neue, 1994). 지구전체의메탄발생량은 515 Tg/year 로추정되고있으며습지와같은자연적인조건에서약 30%, 나머지약 70% 는논과같은인위적인요인에의하여발생되는것으로알려져있다. 전세계적으로벼논에서발생되는메탄은 20 150 Tg/year으로평균 60 Tg/year 이고, 메탄배출량의약 5 30% 를차지하는것으 243

244 LIM et al. 로알려지고있다 (Dickinson and Cicerone, 1986; Bronson and Moiser, 1991; Houghton et al., 1992). 세계적으로논의경지면적은인구증가에따른식량공급문제를해결을위해그규모가갈수록증가하고있는추세이다. IRRI(2009) 의조사에따르면벼가재배되고있는전세계논의면적은 1960년 120,138,000ha에서 2008년 155,711,000ha 로약 30% 가증가하였다. 국내에서는특히전체경작지중약 58% 이상이논으로이용되어지고있으나세계적인논면적증가의추세와는반대로국내의논면적은산업화와도로확장등으로시간이지날수록감소하고있다. 국내에서는 1960 년이후부터간척사업이활발하게진행되고있으며, 축소되어져가는농업용지의확충을위하여간척지내에대규모간척농경지를조성해오고있다 ( 한국농어촌공사보고서, 2009). 간척농경지는일반농경지와달리치환성칼리, 마그네슘, 나트륨함량이높은반면칼슘의함량이상대적으로낮아이온의불균형이존재하고, 염농도가상당히높아일반적으로높은 ph를가지고있어식물생육에매우불리한특징을가지고있다. 특히간척지논토양은경반층이형성되어용적밀도가높고공극률이낮으며, 경도가높아토양의물리적성질이매우불량하여, 벼생육및수량그리고미질등이저하되는것으로알려져있다 (Jung and Ryu, 2005). 간척지토양을개량할목적으로다양한종류의칼슘제재가사용되어지고있다. 석고 (CaSO 4) 는칼슘제재의일종으로다량의칼슘성분을함유하고있어이온불균형및토양의물리성을개량할뿐만아니라다량의황산염 (SO 2-4 ) 이함유되어있어간척지토양의높은 ph를저감시키는효과가높은것으로알려져있다. 석고시용은황환원균 (Sulfate reducer) 의활성증대로인하여메탄생성균 (Methanogens) 과동일한기질인 H 2 와 CH 3COOH를두고경쟁하기때문에메탄생성균의활성을낮추어메탄발생을크게저감시킬수있는것으로보고되고있다 (Hori et al., 1990; Ranjan et al., 2009). Ali 등 (2008) 은전자수용체를이용하여벼재배기간중전체메탄발생량을약 28% 까지저감할수있는것으로보고하였다. 따라서전자수용체인황산염을다량포함하고있는석고시용을통해간척지논토양에서메탄발생을크게저감시킬수있을것으로기대된다. 하지만현재간척농경지에서토양개량제로서석고처리가메탄발생량저감에미치는영향에관한연구는국내에서실시된바가없는실정이다. 따라서본연구는실제간척지논토양을대상으로석고의처리에따른메탄저감효과를평가하고이에따른토양개량효과를평가하고자하였다. 재료및방법 조사대상토양선발본연구를위한공시토양으로경상남도하동군금성면갈사리 (34 57 17 E, 127 47 38 N) 에위치한갈사간척지의토양을선정하였다. 갈사간척지는경남하동군금성면가덕리, 갈사리, 고포리일대에위치한간척지로서, 총면적은약 Table 1. Chemical properties of reclaimed coastal paddy soils collected for pot test from Galsa, Hadong, Gyeongnam province Parameters Low salt High salt Mean SD Mean SD ph (1:5 with H 2O) 5.37 0.01 6.58 0.07 Electrical conductivity (ds/m) 2.25 0.07 9.48 0.05 Organic matter (g/kg) 20.4 0.35 14.3 0.37 Exchangeable cations (cmol + /kg) K 0.27 0.04 0.47 0.02 Ca 2.56 0.18 4.13 0.11 Mg 1.92 0.13 3.46 0.10 Na 1.55 0.16 6.62 0.34 Water soluble iron (mg/kg) 1.92 0.60 3.46 0.05 Water soluble sulfate (mg/kg) 275 2.14 392 2.30 Sodium adsorption ratio (SAR) 1.04 0.04 4.74 0.10 651ha로약 403ha가개답되어 1994년부터본격적으로답상태영농에이용되어져왔으며, 갈사간척지의평균적인토양이화학성은일반적인간척지논토양의특성과비슷하였다. 실험전갈사간척지 16개지점에서토양을채취하여토양의이화학적특성분석을실시하였다. 채취된간척지논토양에서석고처리에따른메탄발생저감효과를평가하기위하여분석한토양들을염농도에따라크게두가지로분류하였다. 저염도 (34 57 15 E, 127 47 47 N) 와고염도 (34 57 18 E, 127 47 42 N) 로나누어토양을선발하였으며, 이때선발된두지역의토양의이화학적특성은 Table 1과같다. 포트실험및처리방법간척농경지에서석고의처리에따른메탄발생특성과토양개량효과를조사하기위하여포트실험을실시하였다. 실험대상으로선정된저염도 (EC 2.25 ds/m) 와고염도토양 (EC 9.48 ds/m) 은채취후자연건조후사분 (<10mm) 한후벼재배를위한포트실험에사용되었다. 사분된토양 13.5 kg을 Wagner pot(1/2000a size) 25cm 높이까지가비중 1.2 g/cm 3 의조건으로충진하였다. 그리고지상부 10cm 토양 (5.4kg) 에분쇄볏짚 5 Mg/ha 비율로처리하였다. 토양개량제로서사용된공시재제는시약급석고 (CaSO 4 ㆍ2H 2O, 95%) 를이용하였으며, 처리량은지상부 10cm 토양무게의 0, 0.5, 1.0, 2.0%(wt/wt) 의비율로각각처리하였으며, 완전혼합후 3일간담수상태로안정화후실험에사용하였다. 농촌진흥청표준시비량을근거로하여이앙 1일전기비로질소 (N)-인산(P 2O 5)-가리 (K 2O) 를각각 50-45-40kg/ha로전층시비하였으며, 벼는조생종품종인오대벼 (Oryza sativa L.) 를공시작물로선택하여각포트당 3포기를손이앙하였다. 1차추비 ( 분얼비 ) 는이앙 2주후질소 (N) 20kg/ha를, 2차추비 ( 수비 ) 는이앙 2개월후 ( 출수 15일전 ) 에질소 (N) 와가리 (K 2O) 를각각 20, 17kg/ha를처리하였다 (RDA, 1999). 실

Effect of Gypsum Application on Reducing Methane (CH4) Emission in a Reclaimed Coastal Paddy Soil 245 험포트는무작위로배치되었으며, 모든처리구는 3반복으로하여실험을수행하였다. 생육기간동안약 5 7cm 높이로물수위를유지하였으며, 벼는이앙후 106일이경과된후수확하였다. 메탄가스채취및정량분석가스채취는벼재배기간동안일주일에 1회, 메탄발생량이가장많은오후 2 3시사이에실시하였다. 벼재배기간중벼를통해발생되는메탄가스는 Closed chamber method (Rolston, 1986) 를이용하여시료를채취하였으며, 원통형아크릴챔버내부에공기를혼합하기위해 64cm 2 (8cm 8cm) 사이즈의소형팬을설치하여시료의균질성을확보하였다. 메탄포집시간은 30분동안실시하였으며, 50ml 주사기를이용해채취하였다. 이때챔버내부와토양의온도를각각측정하였다. 메탄가스는 GC(Shimadzu, GC-2010, Tokyo) 를이용하여측정하였으며, 이때 Packed Porapak NQ column (80-100mesh) 을이용하였으며검출기는 Flame ionization detector(fid) 를사용하여분석하였다. 이때분석조건은 column 80 C, injector 100 C, detector 110 C로설정하였으며, carrier gas로헬륨 (He) 을 burning gas로수소 (H 2) 를이용하였다. 재배기간중포트로부터배출되는메탄배출량은아래의식을이용하여계산하였다 (Rolston, 1986). F = ρ. V/A.Δc/Δt.273/T F: 단위시간당메탄배출량 (mg/m 2 /hr) ρ: 메탄가스의밀도 0.714(mg/cm 3 ) A: 챔버표면적 ( 가로 (m) 세로 (m):m 2 ) V: 챔버부피 (A h:m 3 ) Δc: 시료채취전후의농도차 (nl/cm 3 ) Δt: 시료채취시간 (hr) T: 273+ 측정시간중평균온도 ( o C). 재배기간중발생된총메탄발생량은 Singh 등 (1999) 이도입한식을이용하여도출하였다. 총메탄발생량 (Seasonal CH 4 flux) = in (R i x D i) Seasonal flux: 재배기간중발생된총메탄발생량 (CH 4 g/m 2 ) R i: i번째샘플링기간내일메탄발생량 (g/m 2 /day) D i: i번째기간내샘플링간격일수 n: 샘플링간격 토양및침출수의이화학적특성조사벼재배기간중에토양의산화환원전위 (Eh) 와온도변화를조사하였으며, 토양의산화환원전위는토양표면으로부터약 5cm 토양깊이에 Platinum electrode를설치하여 Eh meter(prn-41, DKK-TOA Corporation) 를이용하여측정하였다. 메탄채취일자와동일하게벼재배기간중포트를통해배출되는침출수의양을지속적으로모니터링하였으며, 15일간격으로수집된침출수의황산염함량을함께조사하였다. 이때 침출수중황산염함량변화는여과후 Ion Chromatography System(ICS-3000, Dionex) 를이용하여측정하였다. 시험전공시토양과수확후채취된토양은자연건조후사분 (<2mm) 하여이화학성분석에이용하였다. 토양의 ph 와 EC는토양과물을 1:5 비율로침출후 ph meter(orion 3 star, Thermo Electron Corporation) 와 EC meter (Orion 150A +, Thermo Electron Corporation) 로각각측정하였다. 치환성양이온은 1N NH 4OAc로침출후 ICP-OES (Inductively coupled plasma-optical emission spectrophotometer Perkin Elmer Model OPTIMA 4300DV, Shelton Connecticut USA) 를이용하여측정하였다. 토양내황산염함량은토양과물을 1:5의비율로침출후여과하여 Ion Chromatography System(ICS-3000, Dionex) 을이용하여측정하였다. 유기물은 Tyurin 법을이용하여측정하였다 (RDA, 1988). 토양용액중의 Ca 2+ 와 Mg 2+ 에대한농도비를이용하여 SAR(Sodium adsorption ratio) 을다음과같이계산하였다 (Sposito and Mattigod, 1997). 통계분석 통계분석은 SAS software(sas Institute Inc., 1995) 를이용하여실시하였으며최소유의차 (least significant difference, LSD) 를이용한 One-way ANOVA 방식으로각처리구간의평균값을비교하였다. 결과및고찰 석고처리에따른메탄발생저감효과저염도 (EC 2.25 ds/m) 와고염도의토양 (EC 9.48 ds/ m) 에서벼재배기간중메탄배출량변화를조사한결과 (Fig. 1), 대부분의메탄은벼생육초기인이앙후 13 55일사이에서집중적으로발생하는경향을나타내었다. 이앙후 48일경과후저염도와고염도토양에서각각 110.7과 57.9 mg/m 2 /hr 로가장높게메탄이발생되었다 (Fig. 1). 이는담수후메탄생성균에적합한극혐기조건 ( 토양산화환원전위 -200mV 이하 ) 이형성되고, 시용된유기물의분해로인하여메탄생성균의이용이가능한유기탄소함량이크게증가되었기때문으로판단된다 (Denier van der Gon et al., 1994; Yagi et al., 1994). 대부분의처리구에서이앙후 48일경과후염의농도와관계없이메탄발생은감소하는경향을나타내었다.

246 LIM et al. 120 90 EC 2.25 ds/m CaSO 4 0% CaSO 4 0.5% CaSO 4 1.0% CaSO 4 2.0% 120 100 Y = 99.49e (-2.41X),R 2 = 0.999*** A 2.25 ds/m 80 CH 4 emission rate (mg/m 2 /hr) 60 30 0 120 90 EC 9.48 ds/m Seasonal CH 2 4 flux (g/m ) 60 40 20 120 100 B C Y = 60.50e (-4.39X),R 2 = 0.999*** C 9.48 ds/m 60 80 60 a 30 40 0 20 b c c 10 20 30 40 50 60 70 80 90 Days after transplanting 0 0.5 1.0 2.0 Gypsum application level (%) Fig. 1. Changes of CH 4 emission rates in the potted paddy soils amended with different levels of gypsum application. 벼재배기간중방출된총메탄발생량을조사한결과, 저염도토양에서는석고처리량을 0.5%, 1.0%, 2.0% 로각각증가시킴에따라석고무처리구 99.7g/m 2 대비 28.6(71.3%), 10.5(89.4%), 3.4(96.6%)g/m 2 으로까지메탄발생이감소되었고, 고염도토양에서는무처리구 60.5g/m 2 대비 6.7 (88.9%), 0.9(98.5%), 0.7(98.9%)g/m 2 까지메탄발생이감소되었다 (Fig. 2). 이러한석고처리에따른메탄저감효과는저염도토양에비하여고염도토양에서큰것으로나타났다. 유사한결과로서, Lindau 등 (1993) 은벼재배기간동안석고처리에따라총메탄발생을 29 46% 까지저감한것으로보고하였고, Denier Van der Gon 과 Neue(1994) 는 55 70% 까지총메탄발생량을감소시킬수있는것으로보고하였다. 특히석고의처리량이증가함에따라침출수내황산염의함량은크게증가하는경향이었으며, 석고처리량이가장높았던 2.0% 처리구에서침출수내황산염농도가가장높은수준에서오랫동안유지되었다. 오랜기간높은농도로유지되는황산염은결국토양내에서전자수용체로작용하여황환원균의활성은증가시키는반면메탄생성균의활성은감소시켜벼생육기간중메탄발생을저감시키는것으로판단되었다 (Van Breemen and Feijtel, 1990; Denier Van der Gon and Neue, 1994). 저염도토양에비해고염도토양에서황산염의농도가더욱높게나타났다. Marzzaco(1998) 는비활성염을가하였을경우이온성화합물의용해도는증가한다고보고하였다. 본연구에서도고염도토양내다량으로존재하는이온으로인해석고의용해도가크게증가되어더많은황산염이재배기간동안침출수내에존재할수있었던것으로평가된다. Fig. 2. Seasonal CH 4 fluxes in the potted paddy soils amended with different levels of gypsum application. (mg/kg) 2- Dissolved SO4 1800 1500 1200 900 600 300 1800 1500 1200 900 600 300 EC 2.25 ds/m EC 9.48dS/m Days after transplanting CaSO 4 0% 10 20 30 40 50 60 70 80 CaSO 4 0.5% CaSO 4 1.0% CaSO 4 2.0% Fig. 3. Changes of dissolved SO 2-4 in the percolated water from the potted paddy soils amended with different levels of gypsum application.

Effect of Gypsum Application on Reducing Methane (CH4) Emission in a Reclaimed Coastal Paddy Soil 247 Eh value (mv) 200 100 0-100 -200 200 100 0-100 -200 EC 2.25 ds/m EC 9.48 10 ds/m 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 Days after transplanting CaSO 4 0% CaSO 4 0.5% CaSO 4 1.0% CaSO 4 2.0% Fig. 4. Changes of soil Eh values in the potted paddy soils amended with different levels of gypsum application. 벼재배기간중토양의산화환원전위 (Eh) 를조사한결과고농도와저농도전체토양에서유사한변화양상을보였으며, 특히담수이후급격하게감소하는경향을나타내었다. 벼재배기간중에는 -200mV 이하를유지하였다가배수후급격하게증가하는경향을보였다 (Fig. 4). Takai(1961) 와 Garica 등 (2000) 은메탄은극한혐기상태 ( 토양산화환원전위 -200mV 이하 ) 에서제한적으로메탄생성균에의한유기물의분해과정으로부터생성되는것으로보고하고있다. 무처리구에서산화환원전위는가장급격하게감소하였으나석고처리구에서산화환원전위는무처리구에비하여다소느리게감소하는경향을나타내었다. 특히석고처리량이가장높았던 2.0% 처리구에서가장느린감소를나타내었다. 이는석고투입을통한황산염투입의증가가토양의산화환원전위를느리게감소시킨원인으로판단되며, 석고처리에따른느린산화환원전위의감소가메탄생성을저감시킨것으로평가된다. 석고처리에따른최대평균배출속도는저염도와고염도토양석고 2.0% 처리구에서각각 2.02 10-5 과 1.27 10-5 cm/ sec로무처리에비하여전체토양에서약 5배의배출량증가를보여, 석고처리가토양의배수성을개선시킨것으로평가되었다. 이전연구에따르면, 소석회, 석고, 탄산석회, 생고등의석회질제재의시용은간척지토양의투수성을개선시켰으며, 그중석고의투수성개량효과가가장우수한것으로보고하였다 ( 농촌진흥청보고서, 2002). 간척지논에서석고와같은토양개량제의시용은배수조건개선을통한토양내용존산소공급증가로인하여메탄발생저감에다소기여한것으로평가된다. 벼수확후석고처리에따른토양의이화학적특성을살펴본결과 (Table 2) 석고처리에따라토양의 ph는유의적으로감소하는경향을보였다. 이는간척지와같은높은 ph를가진토양에석고를시용할경우토양의 ph를적절하게낮춤으로서충분하게토양개량의효과가클것으로판단된다. 또한석고처리에따라치환성칼슘의함량은유의적으로증가하는것을확인할수있었다. 따라서간척농경지의낮은칼슘함량과이온의불균형을개량할수있을것으로판단된다. 또한석고처리에따라고염도와저염도처리구전체에서작물에악영향을끼치는치환성나트륨이온함량과 SAR값이감소하는것을확인할수있었다 (Table 2). 과량의석고처리시치환성나트륨이온과 SAR값의감소효과는큰유의적인차이를나타내지않았는데, 이는석고의낮은용해도때문인것으로평가된다. 석고의처리로인한칼슘의공급효과는간척지논토양의물리성을개선할수있을것으로판단되며, 이를통하여간접적으로메탄발생저감에영향을줄수있을것으로평가된다. Mean water percolation rates (cm/sec) 2.5e-5 2.0e-5 1.5e-5 1.0e-5 5.0e-6 EC 2.25 ds/m EC 9.48 ds/m 석고처리에따른간척농경지의토양개량효과저ㆍ고염도의토양에서석고를처리함에따라일평균침출량이증가하는것을확인하였다 (Fig. 5). 저ㆍ고염도의토양에서석고무처리구에서평균침출속도는 4.05 10-6 과 1.78 10-6 cm/sec로약 2배이상의침출량차이를보여고염도토양의물리성과배수성이불량함을확인할수있었다. 0% 0.5% 1.0% 2.0% Gypsum application level (%) Fig. 5. Mean water percolation rates in the potted paddy soils amended with different levels of gypsum application.

248 LIM et al. Table 2. Chemical properties of soils amended with different levels of gypsum application at rice harvesting stage EC levels (ds/m) 2.25 9.48 Gypsum application (%) Parameters 0 0.5 1.0 2.0 LSD 0.05 ph(1:5, H 2O) 4.40 4.09 3.90 3.74 0.51 Organic matter (g/kg) 25.2 25.4 25.0 25.6 2.1 Electrical conductivity (ds/m) 1.97 4.63 5.12 6.87 1.48 Exchangeable cation (cmol + /kg) K 0.21 0.22 0.21 0.23 0.04 Ca 1.99 4.81 5.11 6.81 0.91 Mg 0.89 0.65 0.40 0.39 0.17 Na 0.16 0.15 0.11 0.13 0.11 Water soluble SO 2-4 (mg/kg) 459 624 789 978 192.6 Sodium adsorption ratio (SAR) 0.42 0.29 0.21 0.22 0.13 ph(1:5, H 2O) 5.72 5.50 5.28 4.88 0.62 Organic matter (g/kg) 18.2 18.9 17.9 18.5 1.8 Electrical conductivity (ds/m) 1.67 3.03 3.32 6.36 2.51 Exchangeable cation (cmol + /kg) K 0.40 0.35 0.34 0.33 0.09 Ca 3.27 5.28 6.53 10.4 3.02 Mg 1.82 1.08 0.82 0.38 0.20 Na 0.65 0.15 0.14 0.15 0.23 Water soluble SO 2-4 (mg/kg) 471 741 843 1179 224.3 Sodium adsorption ratio (SAR) 1.29 0.27 0.23 0.20 0.27 벼생육및수량특성석고처리에따른벼수량변화및구성요소는 Fig. 6 과 Table 3에나타내었다. 벼수량은석고처리를 1.0% 수준까지증가시킴에따라저염도토양에서는무처리구 5.3Mg/ha에비하여최대 6.0Mg/ha(13.2%) 까지수량이증가하였으며, 고염도토양에서는무처리구 2.3Mg/ha에비하여최대 3.2Mg/ha(39.1%) 까지수량이증수되는것으로조사되었다. 저염도와고염도두토양에서 2차방정식을이용하여최대수량을추정한결과, 두토양에서석고처리량을각각 0.76% ( 저염도, Y= 5.2+ 2.3X-1.6X 2, R 2 =0.993 *** ) 와 0.84%( 고염도, Y= 2.2+2.0X-1.2X 2, R 2 =0.927 *** ) 까지처리하였을때가장높은수량을얻을수있는것으로평가되었다. 석고처리량을저염도토양에서 0.76%, 고염도토양에서 0.84% 이상처리시수량은각각감소하는경향을나타내었다. 과량의석고처리로인한증가된황산염은독성을유발시킬수있으며, 이로인하여수량이감소한것으로평가된다. 수량구성요소인분얼, 천립중, 등숙율과수당입수또한석고처리에따라증가되는경향을나타내었으며, 수량변화와동일한경향을나타내었다. 따라서간척지와같이염이집적된토양에서석고의처리는수량증수와벼의생육개선효과가충분할것으로평가된다. Grain yield (Mg/ha) 7 6 5 4 3 2 1 EC 2.25 ds/m, Y=5.2+2.3X-1.6X 2,R 2 =0.993 *** EC 9.48 ds/m, Y=2.2+2.0X-1.2X 2,R 2 =0.927 *** A a A a A a 0.0 0.5 1.0 1.5 2.0 Gypsum application level (%, wt/wt) Fig. 6. Grain yield in the potted paddy soils amended with different levels of gypsum application. B b

Effect of Gypsum Application on Reducing Methane (CH4) Emission in a Reclaimed Coastal Paddy Soil 249 Table 3. Effect of gypsum application levels on rice plant growth and yield properties in reclaimed paddy soil packed pots at the harvesting stage EC levels (ds/m) 2.25 9.48 Gypsum application (%) Parameters 0 0.5 1.0 2.0 LSD 0.05 Tiller number per hill 13 15 17 13 2.9 Plant height (cm) 95 98 98 84 10.9 Shoot biomass (g/hill) 83 83 101 47 18.4 Panicle number per hill 12 14 16 11 2.5 Number of grains per panicle 97 97 106 68 18.2 Ripened grains (%) 71 71 83 65 13.5 1000 grain weight (g) 24.9 26.4 26.6 24.5 2.2 Straw yield (Mg/ha) 5.9 5.9 5.9 2.9 1.8 Total biomass (Mg/ha) 11.1 11.7 11.9 6.4 1.9 Tiller number per hill 11 12 13 8 1.2 Plant height (cm) 76 78 84 71 9.2 Shoot biomass (g/hill) 29 40 43 24 16.4 Panicle number per hill 9 10 12 8 1.2 Number of grains per panicle 75 87 91 60 14.8 Ripened grains (%) 46.0 55.7 58.8 33.4 9.9 1000 grain weight (g) 20.3 21.2 21.8 19.4 1.6 Straw yield (Mg/ha) 2.0 2.9 2.9 1.7 2.4 Total biomass (Mg/ha) 4.1 5.5 6.1 3.0 2.9 메탄발생에관련된요인분석본연구에서토양의화학성, 벼의생육특성및수량구성요소와메탄발생간의상관관계를조사한결과 (Table 4), 식물체의생육및수량에비해토양의화학적인특성이더욱높은상관관계를가지는것으로조사되었다. 특히고염도와저염도토양에서전기전도도, 치환성칼슘, 수용성황산염의함 량은고도의부의상관관계가있는것으로평가되었다. Lindau 등 (1993) 은메탄발생과황산염의함량은높은역의상관관계가성립하는것으로보고하였으며, 본연구에서도동일하게황산염과메탄발생은고도의역의상관관계가성립되는것으로조사되었다. Table 4. Correlation between seasonal CH 4 flux, soil properties, plant growth and yield components at the harvesting stage (n=12) EC levels (ds/m) Parameters Correlation coefficient (r) ph 0.543 Electrical conductivity -0.872 *** 2.25 Soil properties Organic matter -0.268 Exchangeable K -0.359 Exchangeable Ca -0.927 *** Exchangeable Mg 0.488 Exchangeable Na 0.486 Water soluble SO 4 2- -0.789 **

250 LIM et al. 2.25 Growth and yield components Soil properties Tiller number per hill -0.406 Plant height 0.126 Shoot biomass 0.233 Panicle number per hill -0.240 Number of grains per panicle 0.344 Ripened grains -0.046 1000 grain weight -0.284 Grain yield 0.162 Straw yield 0.395 Total biomass 0.353 ph 0.515 Electrical conductivity -0.570 * Organic matter -0.199 Exchangeable K 0.538 Exchangeable Ca -0.656 * Exchangeable Mg 0.487 Exchangeable Na 0.451 Water soluble SO 2-4 -0.727 ** 9.48 Tiller number per hill -0.269 Plant height -0.111 Shoot biomass -0.310 Panicle number per hill -0.287 Growth and yield Number of grains per panicle -0.114 components Ripened grains -0.102 1000 grain weight -0.207 Grain yield -0.114 Straw yield -0.205 Total biomass -0.188 Note) Asterisks (*, ** and ***) denote significant at 5%, 1% and 0.1% levels, respectively 요약 간척지논토양에서석고의처리는염의농도에관계없이고염도와저염도전체토양에서무처리대비 71.3 98.9% 까지메탄발생을저감할수있었다. 석고처리에따른황산염을증가는전자수용체, 즉황산염이온의양증대에따른전자의활성저하와황환원균의활성증가가메탄발생을저감시키는가장큰요인인것으로판단된다. 간척지논에석고를시용할경우부족한칼슘의공급효과를통하여토양의물리성및배수개선을통하여메탄발생감소에영향을줄수있었다. 또한석고의시용은간척지토양의높은 ph와높은나트륨이온을효과적으로저감할수있어식물생육및수량에긍정적인영향을주었으며, 물리성개선을통하여메탄발생을저감시킬수있었다. 간척지토양에서석고의시용은벼수량을 13.2 39.1% 까지증수효과가있었으나, 과량처리시오히려생산성을감 소시켰다. 결론적으로간척지에서토양개량을위해사용되어지는석고는토양의물리ㆍ화학성을개선할뿐만아니라메탄발생을효과적으로저감할수있는우수한토양개량제로서평가되었다. 감사의글 This research was conducted with subsidies for a research professor under study year system of Gyeongsang University in 2009 (KRF2008013F00003) and supported by Rural Development Administration, Republic of Korea (PJ0067842011). Sang Yoon Kim was supported by scholarships from the BK21 program of Ministry of Education and Human Resources Development, Korea.

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