Biochar mitigates dissolved organic carbon loss but does not affect dissolved organic nitrogen leaching loss caused by nitrogen deposition in Moso bamboo plantations

Abstract

Dissolved organic matter (DOM) is one of the most reactive and mobile components in terrestrial ecosystems. Frequent loss of DOM has a negative effect on the surrounding environment. Current abundant deposition of atmospheric nitrogen (N) could significantly influence DOM leaching, and biochar has been suggested to be applied for improving acidic soils However, it remains unclear whether biochar affects dissolved organic carbon (DOC) or dissolved organic nitrogen (DON) loss induced by N deposition in acidic soils. In this study, we observed the effects of biochar amendment (BC0: 0 t biochar ha−1, BC20: 20 t biochar ha−1, and BC40: 40 t biochar ha−1) on the leaching of soil DOC and DON in Moso bamboo plantations that received simulated N deposition (N30: 30 kg N ha−1 yr−1, N60: 60 kg N ha−1 yr−1, N90: 90 kg N ha−1 yr−1, and N-free) for 34 months. DOC loss showed a marked seasonal variation with the lowest loss occurring in spring and the largest loss in summer; no such trend was observed in DON loss. Nitrogen deposition generally increased DOC and DON leaching loss in all four seasons, except DOC leaching loss in spring. Biochar amendment significantly decreased DOC leaching loss in spring, autumn, and winter; however, there was no significant effect on DON. Biochar may therefore mitigate DOC and DON loss caused by N deposition. DOC loss mitigation was also greater than that for DON, especially in autumn. Biochar application is a potential approach to mitigate the DOC and DON leaching loss induced by increasing atmospheric N deposition in Moso bamboo plantations. Keywords: Dissolved organic matter, Biochar, Simulated leaching, Simulated nitrogen deposition, Phyllostachys edulis