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1 Korean Journal of Environmental Agriculture Korean J Environ Agric (21) Vol. 29, No. 4, pp DOI : /KJEA Research Article Open Access 변곡점을이용한영농형태별토양인산유출잠재력평가 이슬비 1 이창훈 2 홍창오 3 이용복 4 김필주 4,5* 1 농촌진흥청국립농업과학원, 2 University of Illionis, 3 South Dakota State Univeristy, 4 경상대학교농업생명과학원, 5 경상대학교대학원 (BK 21 Program) 응용생명화학과 Evaluation of Phosphorus Release Potential in Arable land with Different Landuse by Phosphorus Threshold Seul Bi Lee 1, Chang Hoon Lee 2, Chang Oh Hong 3, Yong Bok Lee 4 and Pil Joo Kim 4,5 ( 1 National Academy of Agricultural Science, Rural Development Administration, 2 Department of Crop Sciences, University of Illlionis, 112 S. Goodwin Avenue, Urbana, IL 6181, USA, 3 Plant Science Department, South Dakota State University, 111 Rotunda Lane North, Brookings, SD 577, USA, 4 Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju, 66-71, South Korea, 5 Division of Applied Life Science, Graduate School (Brain Korea 21 Program), Gyeongsang National University Jinju, 66-71, South Korea) Received: 1 December 21 / Accepted: 21 December 21 c The Korean Society of Environmental Agriculture Abstract: Heavy application of fertilizer and manure in excess from the optimum requirement for crop growth can increase phosphorus (P) accumulation and P release potential in soils. In this study, the relationship between soil test P and extractable P was analysed to evaluate the P release potential of agricultural soils under different land-use. The paddy, upland, plastic film house(pfh) soils were sampled from Tongyoung and Changnyeong, and Daegok areas in Gyeongnam province, respectively. With respect to the P accumulation, available P contents in upland and PFH soils were 619 and 796 mg P 2 /kg, respectively indicating that different land-use types can greatly impact soil P accumulation. As soil available P was increased in the paddy soil, the content of extractable P also linearly increased without change point. Comparatively, P threshold were detected at 52 mg P 2 /kg in both upland and PFH soils, indicating that P release potential were higher in these land-use systems. For reducing P release from agricultural soils, management of optimum P content is needed in soils * 교신저자 (Corresponding author): P. J. Kim Tel: Fax: pjkim@gnu.ac.kr 공동제 1 저자 possessing high P release potential. Further, the change point value, if it is to be used as an environmental indicator, requires more detailed investigation to cover a wide range of soil characteristics. Key Words: Phosphorus accumulation, Phosphorus release, Threshold 서론 우리나라는 197년대이후화학비료와가축분뇨의사용량증가에따라농경지인산집적이심화되고있는실정이다 (Kim, 1996). 특히, 밭과시설재배지토양의평균유효인산함량은 197년대각각 21 mg P 2/kg, 811 mg P 2/kg에서 2년대 584 mg P 2/kg, 1,72 mg P 2/kg 로크게증가하였다 (NIAST. 26). 농경지에집적된인산은표면유거, 지하용탈및침식과같은경로를통해유출되어수계에유입되며 (Pautler et al., 2), 수계에서부영양화를일으키는 dissolved P 농도는.1 mg P /L 으로알려져있다 (Sharpley et al., 1997). 농경지인산유출량은인산의집적량과고도의정의상관관계가있으며 (McDowell et al., 2), 특히유거수내인산 (dissolved reactive P, DRP) 의농도와토양유효인산분석방법 (soil test phosphorus, STP) 에따른함량과의상 343

2 344 이슬비 이창훈 홍창오 이용복, 김필주 관관계는일정한경향을가지고있었다. Pote et al.(1996) 는표면유거수내 DRP농도와 Mehlich-3 (r 2 =.72), Bray-I (r 2 =.75), Olsen (r 2 =.72), distilled water (r 2 =.82), iron oxide paper (r 2 =.82), ammonium oxalate (r 2 =.85), P sorption saturation (r 2 =.77) 사이에는직선관계식이있다고하였다. 그러나, Sibbesen et al. (1997) 는넓은분포범위의 STP 농도에따른인산유출량을분석하면, STP 농도가높은경우토양의인산고정자리가포화되기때문에 STP 농도와인산유출량은곡선형 (culvilinear) 관계를나타낸다고하였다. 즉, 일반적으로인산은토양에강하게흡착되지만토양의흡착용량을초과하면인산의유출량이급격하게증가하는데, 이때의 STP 농도를변곡점 (threshold) 이라고한다 (Addiscott and Thomas, 2). 따라서 STP의변곡점값은토양의인산유출잠재력을빠르고쉽게평가할수있는지표로활용할수있다. 지금까지우리나라의농경지인산관리방안에관한연구는작물의수량과품질향상측면에집중되어있다. 특히, 작물별적정유효인산함량기준은지속적농업생산을위한화학비료및가축분퇴비시용량결정에널리활용되고있다. 하지만, 수계오염에가장큰영향을미치는농경지로부터유출되는인산에관한연구는아직까지활발히이루어지지않고있는실정이다. 따라서우리나라농경지인산의합리적인관리를위한인산유출잠재력평가의필요성이대두되고있다. 본연구는논, 밭및시설재배지의인산유출변곡점을구명하여농경지로부터인산유출잠재력평가와합리적인농경지인산관리를위한기준설정에필요한기초자료로활용하고자한다. 재료및방법 본연구를위한토양시료는 28년 3월 ~ 6월까지경남통영과창녕으로부터논 1 곳, 밭 1 곳과경남진주의시설재배지 75 곳에서채취하여농경지이용형태에따른토양화학성분석에사용하였다. 토양시료를채취한논의주재배작물은벼이며, 밭은양파, 고구마, 옥수수, 참깨, 콩, 그리고시설재배지는토마토, 고추, 호박, 수박이었다. 토양 ph와 EC, 유기물함량, 치환성양이온 (K, Ca, Mg) 함량을농업과학기술원토양화학분석법 (NIAST, 2) 에준하여조사하였다. 토양의유효인산함량은 Lancaster 법으로분석하였으며간략히요약하면다음과같다. 실온에서건토 5g에 Lancaster 침출액 (ph 4.25) 을 2ml 가한후 1분간교반하여침출여과하여몰리브덴청법으로비색정량하였다 (NIAST, 2). 그리고 가용성인산은토양과침출액의비율을 1:5로하여실온에서 3분간침출하여침출액내인산의함량은몰리브덴청법으로비색정량하였다 (Murphy et al., 1962). 농경지이용형태에따른유효인산 (Lancaster) 함량과 인산함량사이의변곡점은변곡점보다큰부분과작은부분을구분하여구하였다 (McDowell et al., 21). 변곡점아래 : CaCl 2-P=m 1(STP)+c 변곡점위 : CaCl 2-P=m 1(STP)+m 2(STP-CP)+c 여기서, c: 절편, CP: 변곡점, m 1: 변곡점보다낮은직선의기울기, m 2: m 1 과변곡점다음직선기울기간의차이를나타낸다. 결과및고찰 농경지이용형태에따른토양의이화학적특성조사지역평균토양 ph는논, 밭, 시설재배지에서각각 5.74, 6.18, 6.71 이었으며 (Table 1), 조사지역의논의평균 ph는 2년대우리나라논토양평균값과비슷하며, 밭과시설재배지의평균값인 5.9와 6.3보다는다소높았다 (NIAST, 26). 그리고토양중염류집적정도를나타내는 EC 값은시설재배지, 밭, 논순으로나타났으며, 특히시설재배지 EC 값은 1.81 ds/m로논의.34 ds/m에비해약 5배가높은것으로확인되었다. 조사지역의평균유효인산함량은논, 밭, 시설재배지에서각각 86.4, 619, 796 mg P 2/kg 이었다. 논의경우벼재배를위한적정인산함량 8-12 mg P 2/kg 범위에포함되어과도한인산집적현상은나타나지않았다. 그러나밭과시설재배지는작물재배를위한적정유효인산함량 2~3 mg P 2/kg 과 5 Table 1. Chemical characteristics of soils used (n=1) (n=1) Land use ph EC O.M Av. P 2 CaCl 2-P Ex. Cation (cmol + (1:5) (ds/m) (g (mg (mg K Ca Mg Mean Range Mean Range PFH Mean (n=75) Range Note) PFH., plastic film house; O.M, organic matter; Av. P 2, available P 2; Ex.K, exchangeable K; Ex.Ca, exchangeable Ca; Ex.Mg, exchangeable Mg

3 변곡점을이용한영농형태별토양인산유출잠재력평가 345 mg P 2/kg 를크게초과하는것으로나타났다. 이와같이밭과시설재배지의인산이심하게집적되어있는것은가축분퇴비속에포함된인산함량을고려하지않은가축분퇴비와화학비료시비에의한것으로설명된다 (Koopmans., 27). 농경지이용형태에따른유효인산함량의분포패턴은 Figure 1에서보는바와같다. 논의경우조사농가의약 38 % 가유효인산함량 5 mg P 2/kg 이하로벼재배를위한적정함량보다낮은것으로나타났다. 그러나밭과시설재배지토양의유효인산함량은각각 9, 7% 가작물재배를위한적정함량보다높은것으로나타났다. 이와같은농경지토양유효인산함량의차이는화학비료와가축분퇴비시용량에크게영향을받는다. 조사지역의실제농가에서시비하는인산투입량을조사하기는어렵지만, 작물별표준시비량 (NIAST, 26) 을통해투입되는양분의양을간접적으로예측할수있다. 벼의경우표준시비량은 kg/ 1a (N-P 2-K 2O) 인데비해밭의주작목인양파의경우 (N-P 2-K 2O-가축분퇴비 ) kg/ 1a 이고, 시설재배지의주요작목인고추, 수박, 호박의표준시비량은각각 kg/1a, kg/1a, kg/ 1a 이다. 이를통해논에비해밭과시설재배지에많은양의인산질비료및퇴구비가투입되어토양인산축적에영향을준것으로판단된다. 그리고논에서 밭이나시설재배지보다인산함량이크게낮은또다른이유는토양이담수되어 ferric (Fe 3+ ) phosphate가 ferrous (Fe 2+ ) phosphate로환원되어불용성인산의용해도가증가되기때문이다 (Lindsay et al., 21). 농경지이용형태별토양 가용성인산과토양이화학성사이의상관관계를분석한결과는 Table 2와같다. 논, 밭및시설재배지에서 가용성인산은유효인산함량과고도의정의상관관계를나타냈다. 이러한결과는 Yoon et al. (1998) 의 4개밭토양에서유효인산함량과 가용성인산농도변화시험결과와일치하였다. 그리고토양내유기물함량과 가용성인산함량과도고도의정의상관관계를나타내었으며, 상관계수값은시설재배지, 밭, 논순으로높았다. Choi et al.(21) 은충남지역의딸기시설재배지의토양화학성조사에서가축분퇴비의시용량과토양유효인산함량이고도의정의상관을보인다고하였다. 따라서논보다밭과시설재배지에서유기물함량과 가용성인산함량과의상관계수값이높은것은가축분퇴비시용에의한인산집적량이높았기때문인것으로생각된다. 농경지이용형태에따른인산유출변곡점 Hesketh et al. (2) 는라이시메타의배출수중인산과토양중 CaCl 2 가용성인산함량과유사성이높기때문에 4 Plastic film house Observation (%) Fig. 1. Accumulation patterns of available phosphorus in paddy, upland and plastic film house soils in Gyeongnam province. Table 2. Relationship between CaCl 2 extractable P and chemical properties in soils with different land use based on linear regression Land use ph OM Available P 2 Ex. K Ex. Ca Ex. Mg (n=1).197*.224*.39** *.53 (n=1) **.697**.48** PFH (n=75) **.818**.21*.416**.225* Note) PFH., plastic film house; OM, organic matter; Ex. K, exchangeable K; Ex. Ca, exchangeable Ca; Ex. Mg, exchangeable Mg * and ** denote significance at 5.% and 1.%, respectively.

4 346 이슬비 이창훈 홍창오 이용복, 김필주 - P (mg P kg -1 ) Y=.13X +.162, r=.388** Fig. 2. The relationship between Lancaster P and CaCl 2 extractable P in paddy soils. 가용성인산함량을유출가능한인산의값으로사용할수있다고하였다. 따라서본연구에서농경지이용형태별인산유출량은 CaCl 2 가용성인산함량으로표현하였다. 논토양에서인산유출량은유효인산의함량이증가할수록증가하였으며, 이들사이에는고도의정의상관관계를나타내었다 (Fig. 2). 그러나토양중인산의함량이인산흡착능력이상집적되어인산의유출량이급격히증가되는변곡점은나타나지않았다. 이러한이유는논토양은일반적으로 15일이상의담수조건에서벼재배가이루어지는데이때산화철의환원, 음이온의치환, 인산화합물의가수분해생성등에따른인산의유효화가증가되어인산이식물에흡수되거나유실되어토양의인산포화도가낮아진것이주원인으로해석된다 (Ponnamperuma, 1972). 밭과시설재배지에서인산유출변곡점은유효인산함량 52 mg P 2/kg에서나타났다 (Fig. 3). McDowell et al. (21) 은미국, 영국, 뉴질랜드의토양조사결과에서 Olsen P 나 Mehlich-3 P 가증가함에따라 CaCl 2 가용성인산함량이증가하며, Olsen P의경우 mg P/kg에서, Mechlich-3 P의경우 mg P/kg에서변곡점이나타났다고하였다. 외국의인산변곡점결과는주로토양의유효인산의함량을 Olsen P나 Mehlich-3 P로조사하여 Lancaster P 로조사한본연구결과와직접비교하기는어려울것으로판단되지만, 토양내유효인산의함량과 CaCl 2 가용성인산의함량과의관계는같은경향으로나타났다. 본시험결과로볼때밭과시설재배지의토양중유효인산의함량은 52 mg P 2/kg 이상일때그유출량이급격히증가한다는것을의미한다. 따라서밭과시설재배지에서주변수계의부영양화에최소영향을미치는적정유효인산함량관리범위는 52 mg P 2/kg 이하로판단된다. 그리고우리나라는국립농업과학원에서토양검정사업을통해전국대부분농경지에대한토양의이화학적특성이조사되어있기때문에인산유출변곡점을활용하여인산유출잠재력이높은지역을예측할수있을것으로판단된다. - P (mg P - P (mg P Plastic film house Fig. 3. The relationship between Lancaster P and CaCl 2 extractable P in soils from upland and plastic film house. 요약 우리나라농경지이용형태에따라서인산유출잠재력과합리적인농경지인산관리기준을설정하기위해서경남통영시, 창녕시및진주시의논, 밭, 시설재배지토양을각각 1, 1, 75 곳에서채취하여인산유출변곡점을분석하였다. 조사지역의논, 밭, 시설재배지의평균유효인산함량은각각 86, 619, 796 mg P 2/kg로농경지이용형태에따라토양의인산함량은큰차이를보였다. 논토양에서는유효인산함량이증가함에따라 함량도직선적으로증가하여변곡점이나타나지않았다. 반면밭과시설재배지에서는토양유효인산함량이약 52 mg P 2/kg에서 가용성인산함량이급격하게증가하는변곡점이확인되었다. 따라서밭과시설재배지에서주변수계로인산유출량을저감하기위해서는농경지유효인산함량을 52 mg P 2/kg 이하로관리하는것이바람직하다고판단된다. 감사의글 본연구는농촌진흥청어젠다프로그램 (PJ7816) 지원으로수행되었습니다.

5 변곡점을이용한영농형태별토양인산유출잠재력평가 347 참고문헌 Addiscott, T. M., Thomas, D. 2. Tillage, mineralization and leaching: phosphate. Soil & Tillage Res. 53, Choi, M. T., Lee, J. I., Yun, Y. U., Lee, J. E., Lee, B. C., Yang, E. S., Lee, Y. H., 21. Relationship between fertilizer application level and soil chemical properties for strawberry cultivation under greenhouse in Chungnam province. Korean J. Soil Sci. Fert. 43(2), Hesketh, N., Brookes, P.C. 2. Development of an indicator for risk of phosphorus leaching. J. Environ. Qual. 29, Kim, Y. W., Impacts of fertilizer on agricultural environment and its countermeasure. pp '96 Symposium on Agricultural environment. The Korean Society of Environmental Agriculture. Koopmans, G. F., Chardon, W.J., McDowell, R.W., 27. Phosphorus movement and speciation in a sandy soil profile after long-term animal manure applications. J. Environ. Qual. 36, Lindsay, J. S., Qualls, G. Q., 21. Stability of phosphorus within a wetland soil following ferric chloride treatment to control eutrophication. Environ. Sci. Technol. 35, McDowell, R. W., Trudgill, S. T., 2. Variation of phosphorus loss from a small catchment in south Devon, U.K. Agric. Ecosys. Environ. 79, McDowell, R., Sharpley, A. N., 21. Approximating phosphorus release from soils to surface runoff and subsurface drainage. J. Environ. Qual. 3, Murphy, J., Riley, J. R., A modified single solution method for the determination of phosphate in natural waters. Anal. Chem. Acta. 27, Pautler, M. C., Sims. J. T., 2. Relationships between soil test phosphorus, soluble phosphorus, and phosphorus saturation in Delaware soils. Soil Sci. Soc. Am. J. 64, Ponnamperuma, F. N., Chemistry of waterlogged soils. Adv. Agron. 24, Pote, D. H., Daniel, T. C., Sharpley, A. N., Moore, P. A., Edwards, D. R., Nichols, D. J., Relating extractable soil phosphorus to phosphorus losses in runoff. J. Environ. Qual. 6, Sharpley, A. N., Rekolainen, Phosphorus in agriculture and its environmental implications. In: Phosphorus loss from soil to water, eds H Tunney OT Carton PC Brookes & AE Johnston. CAB International, Wallingford, pp Sibbesen, E., Sharpley, A. N., Setting and justifying upper critical limits for phosphorus in soils. pp In H. Tunney et al. (ed.) P loss from soil to water. CAB Int. Press, Oxon, England. Yoon, J. H., Jung, B. G., Kim, Y. H., Dependence of soluble phosphorus on extractable P and P sorptivity in upland soil. Korean J. Soil Sci. Fert. 31(3),

198 Korean Journal of Soil Science and Fertilizer Vol. 51, No. 3, 2018 Introduction 도시농업이란우리나라의 도시농업의육성및지원에관한법률 에의하면도시지역의생활공간을활용하여농작물을재배하는행위이며, 농촌진흥청에

198 Korean Journal of Soil Science and Fertilizer Vol. 51, No. 3, 2018 Introduction 도시농업이란우리나라의 도시농업의육성및지원에관한법률 에의하면도시지역의생활공간을활용하여농작물을재배하는행위이며, 농촌진흥청에 Korean J. Soil Sci. Fert. Vol.51, No.3, pp.197-203, 2018 Korean Journal of Soil Science and Fertilizer Article https://doi.org/10.7745/kjssf.2018.51.3.197 pissn : 0367-6315 eissn : 2288-2162 A Study of