Short-term effects of rice straw biochar on sorption, emission,and transformation of soil NH4+-N 2017-11-27

Fan Yang & Xinde Cao & Bin Gao & Ling Zhao & Feiyue Li

Abstract Although previous work has explored and reported the influence of biochar on the fate and transformation of soil nitrogen (N), the governing mechanisms are still unclear. In this study, an incubation experiment was first conducted to investigate the overall fate of NH₄⁺-N in two soils: Gleyi- Stagnic Anthrosols (pH=6.31) and Argi-Udic Ferrosols (pH= 5.05) amended with rice straw biochar. In addition, batch sorption experiments were designed to explore the potential mechanisms of NH₄⁺-N transformation in biochar-amended soils. Results showed that the KCl extractable NH₄⁺-N concentrations in the amended Anthrosols and Ferrosols decreased by 9–35 and 5–22 %, respectively, compared to the unamended soils, but limited nitrification of NH₄⁺-N into NO₃⁻-N was observed in both soils. In Anthrosols, biochar increased NH₄⁺-N sorption, but it decreased N biotransformation (mineralization, nitrification, and assimilation) into NO₃⁻-N. It implies that the chemical sorption is a dominant process in the biochar-amended soil. As for Ferrosols, biochar seemed to have less effect on either NH₄⁺ sorption or biotransformation. Biochar addition promoted NH₃ emission in both soils due to the elevated pH, but the overall amount of the N emission losses were negligible.