Open Journal of Soil Science, 2011, 1, 49-53 doi:10.4236/ojss.2011.12007 Published Online September 2011 (http://www.SciRP.org/journal/ojss) Copyright © 2011 SciRes. OJSS 49 SOC Turnover and Lime-CO 2 Evolution during Liming of an Acid Andisol and Ultisol Wilfredo A. Dumale Jr. 1,2* , Tsuyoshi Miyazaki 2 , Kenta Hirai 2 , Taku Nishimura 2 1 Department of Plant Science, Nueva Vizcaya State University, Bayombong, Nueva Vizcaya, Philippines; 2 Department of Biological and Environmental Engineering, University of Tokyo, Tokyo, Japan. Email: * dumalewajr@soil.en.a.u-tokyo.ac.jp; dumalewajr@nvsu.edu.ph Received June 15 th , 2011; revised July 24 th , 2011; accepted August 10 th , 2011 ABSTRACT Agricultural liming contributes significantly to atmospheric CO 2 emission from soils but data on magnitude of lime- contributed CO 2 in a wide range of acid soils are still few. Data on lime-contributed CO 2 and SOC turnover for global acid soils are needed to estimate the potential contribution of agricultural liming to atmospheric CO 2 . Using Ca 13 CO 3 ( 13 C 99%) as lime and tracer, here we separated lime-contributed and SOC-originated CO 2 evolution in an acidic Ku- roboku Andisol from Tanashi, Tokyo Prefecture (35˚44′ N, 139˚32′ E) and Kunigami Mahji Ultisol of Nakijin, Okinawa Prefecture, Japan (26˚38′ N, 127˚58′ E). On the average, lime-CO 2 was 76.84% (Kuroboku Andisol) and 66.36% (Ku- nigami Mahji Ultisol) of overall CO 2 emission after 36 days. There was increased SOC turnover in all limed soils, con- firming priming effect (PE) of liming. The calculated PE of lime (Kuroboku Andisol, 51.97% - 114.95%; Kunigami Mahji Ultisol, 10.13% - 35.61%) was entirely 12 C turnover of stable soil organic carbon (SOC) since SMBC, a labile SOC pool, was suppressed by liming in our experiment. Our results confirmed that mineralization of lime-carbonates is the major source of CO 2 emission from acid soils during agricultural liming. Liming can influence the size of CO 2 evo- lution from agricultural ecosystems considering global extent of acid soils and current volume of lime utilization. We propose the inclusion of liming in simulating carbon dynamics in agricultural ecosystems. Keywords: Agricultural Liming, Soil Organic Carbon, SOC Turnover, Andisol, Ultisol 1. Introduction Agricultural liming has increased with agricultural inten- sification and periodic use has become necessary to counteract acidification of cultivated soils [1,2] brought by inorganic fertilization, cultivation of N-fixing crops, and crop removal. The chemical liberation of CO 2 from lime has been recognized to contribute significantly to the CO 2 emissions from agricultural soils [3,4]. However, the default methodology of the Intergovernmental Panel for Climate Change that assumes that all carbon in ap- plied lime dissolve as CO 2 [5] tends to overestimate lime contribution to atmospheric CO 2 . This is challenged by several authors [6,7]. Biological theory suggests that the dissolution of carbonate minerals can act as either a net source or sink for CO 2 [6], depending whether the reac- tion occurs with either strong acids or carbonic acid. The dissolved “soil CO 2 ”, from root and microbial respiration exists in equilibrium with the weak acid H 2 CO 3 . Soil CO 2 reacts with the lime involving dolomite as an example:   2 2 3 2 3 2 CaMg CO 2H CO Ca Mg 4HCO       This case is a sink for soil CO 2 since the reaction pro- duces two moles of CO 2 -equivalent ( 2 ) for every mole of gaseous CO 2 taken up. Most of the dissolution of carbonate minerals in moderately acid, neutral and alka- line soils can be pointed to carbonic acid weathering. This is the major natural process of limestone weathering and the primary source of alkalinity of most surface and groundwaters [8]. If, however, H + comes in contact with the 3 2HCO  HCO  , it will be consumed and CO 2 will be pro- duced [6]. During nitrification of 4 to 3 NH  NO  , strong acids such as HNO 3 may be present, and the dissolution of carbonate minerals acts as a CO 2 source:   3 3 2 2 2 3 2 2 CaMg CO 4HNO Ca Mg 4NO 2CO 2H O.          This reaction becomes important at pH < 5 and greatly enhances the dissolution rate of lime [9]. Experimental data is still insufficient to reliably estimate how much of the applied lime is released as CO 2 to the atmosphere [5], and its effect to the soil organic carbon (SOC) pools. 3  .