Soil & Water Res., X:X | DOI: 10.17221/71/2026-SWR

Effects of biochar‑based composite amendments on nitrogen migration and enzymatic activities in high‑nitrogen soilsOriginal Paper

Yu Chen1,2, Wenyin Zi1,2, Fangjing Wang1,2, Yan Zou1,2, Yunxue Li1,2, Jing Shi1,2
1 College of Resources and Environment, Yunnan Agricultural University, Kunming, Yunnan P.R. China
2 Key Laboratory for Improving Quality and Productivity of Arable Land of Yunnan Province, College of Resources and Environment, Yunnan Agricultural University, Kunming, Yunnan P.R. China

High nitrogen leaching from farmlands with excessive residual nitrogen in the Erhai Lake Basin, combined with a lack of effective in situ retention measures, threatens aquatic ecological security. Hence, efficient and regionally adaptable soil amendments are urgently needed. A pot experiment was conducted with cabbage grown in high-nitrogen soil from the western shore of Erhai Lake to evaluate biochar-based composite amendments. The composites consisted of biochar (corn straw, rice husk, or bamboo), bentonite, and humic acid at three ratios (1 : 1 : 1, 2 : 1 : 1, 3 : 1 : 1) and were applied at 2.5% and 5.0% (w/w). The optimal treatment was 5.0% corn straw biochar composite at a 3 : 1 : 1 ratio (coded CSB6). Compared to the unamended control, CSB6 significantly increased soil total N, NO3–-N, and NH4+-N by 79.19%, 167.44%, and 200.73%, and reduced leachate total N, NO3–-N, and NH4+-N by 48.8%, 44.9%, and 67.95%, respectively. Urease, leucine aminopeptidase, and peroxidase activities were significantly enhanced by 125.63%, 55.70%, and 262.24%. The enhanced N retention and reduced leaching were attributed to synergistic physical adsorption, cation immobilisation, and complexation-mediated slow release. This study elucidates the regulatory mechanisms and optimal formulation, providing theoretical and technical support for source control of agricultural non-point N pollution in high-nitrogen farmlands of plateau lake basins.

Keywords: bentonite; Erhai Lake basin; humic acid; nitrogen retention; non-point source pollution; soil enzyme activity

Received: June 5, 2026; Accepted: October 15, 2026; Prepublished online: November 2, 2026 

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