Inducing Inorganic Carbon Accrual in Subsoil through Biochar Application on Calcareous Topsoil

作者：Yang Wang, Stephen Joseph, Xiang Wang, Zhe Weng, David R. G. Mitchell, Mitchell Nancarrow, Sarasadat Taherymoosavi, Paul Munroe, Guitong Li, Qimei Lin, Qing Chen, Markus Flury, Annette Cowie, Olivier Husson, Lukas Van Zwieten, Yakov Kuzyakov, Johannes Lehmann, Baoguo Li, Jianying Shang · 发表于：Environmental Science & Technology · 年份：2023 · DOI：10.1021/acs.est.2c06419 · 被引用次数：72 · 研究领域：Soil Carbon and Nitrogen Dynamics、Peatlands and Wetlands Ecology、Clay minerals and soil interactions

Biochar amendments add persistent organic carbon to soil and can stabilize rhizodeposits and existing soil organic carbon (SOC), but effects of biochar on subsoil carbon stocks have been overlooked. We quantified changes in soil inorganic carbon (SIC) and SOC to 2 m depth 10 years after biochar application to calcareous soil. The total soil carbon (i.e., existing SOC, SIC, and biochar-C) increased by 71, 182, and 210% for B30, B60, and B90, respectively. Biochar application at 30, 60, and 90 t ha –1 rates significantly increased SIC by 10, 38, and 68 t ha –1, respectively, with accumulation mainly occurring in the subsoil (below 1 m). This huge increase of SIC (mainly CaCO 3 ) is ∼100 times larger than the inorganic carbon present in the added biochar (0.3, 0.6, or 0.9 t ha –1 ). The benzene polycarboxylic acid method showed that the biochar-amended soil contained more black carbon particles (6.8 times higher than control soil) in the depth of 1.4–1.6 m, which provided the direct quantitative evidence for biochar migration into subsoil after a decade. Spectral and energy spectrum analysis also showed an obvious biochar structure in the biochar-amended subsoil, accompanied by a Ca/Mg carbonate cluster, which provided further evidence for downward migration of biochar after a decade. To explain SIC accumulation in subsoil with biochar amendment, the interacting mechanisms are proposed: (1) biochar amendment significantly increases subsoil pH (0.3–0.5 units) 10 years after bioch...