SOC Turnover and Lime-CO₂ Evolution during Liming of an Acid Andisol and Ultisol

Abstract

Agricultural liming contributes significantly to atmospheric CO₂ emission from soils but data on magnitude of lime- contributed CO₂ in a wide range of acid soils are still few. Data on lime-contributed CO₂ and SOC turnover for global acid soils are needed to estimate the potential contribution of agricultural liming to atmospheric CO₂. Using Ca¹³CO₃ (¹³C 99%) as lime and tracer, here we separated lime-contributed and SOC-originated CO₂ evolution in an acidic Kuroboku 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-CO₂ was 76.84% (Kuroboku Andisol) and 66.36% (Kunigami Mahji Ultisol) of overall CO₂ emission after 36 days. There was increased SOC turnover in all limed soils, confirming 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 12C 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 CO₂ emission from acid soils during agricultural liming. Liming can influence the size of CO₂ evolution 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.