The in-field burning of sugarcane leaf residues presents a major environmental and health burden in Thailand. In this study, sugarcane leaves were converted into a biochar-based slow release phosphorus (P) fertilizer via pyrolysis at 600 °C, and the influence of pre- and post-pyrolysis treatment on the P loading and release was investigated. The sugarcane leaves were pre-treated with an alkaline (diammonium phosphate, DAP) or an acidic P source (phosphoric acid, PA), with or without addition of MgO. Additionally, the biochar was post-treated with DAP to increase the P loading. Extraction of P in DI water and 2% formic acid were used as indicators for potential slow release. The microporous biochars had a specific surface area of 69–333 m² g⁻¹ and pre-treatment resulted in a P content of 34–82 g kg⁻¹. When MgO was included in the pre-treatment, XRD analysis confirmed formation of crystalline Mg₂P₂O₇, irrespective of the P source. This Mg₂P₂O₇ was responsible for slow P release in DI water over 240 h via a dissolution-controlled process. Post-treatment with DAP increased the P loading to 156 g kg⁻¹ in the form of water-soluble monoammonium phosphate (MAP), which did not contribute to slow release. The tunable P release via combinations of pre- and post-pyrolysis treatment makes these engineered biochars attractive as P sources for crops and presents an attractive solution to mitigate in-field sugarcane residue burning.

甘蔗叶残留物的田间燃烧是泰国的主要环境和健康负担。在这项研究中，甘蔗叶在 600 °C 下通过热解转化为基于生物炭的缓释磷 (P) 肥料，并研究了热解前后处理对 P 加载和释放的影响。甘蔗叶用碱性（磷酸二铵，DAP）或酸性磷源（磷酸，PA）预处理，添加或不添加 MgO。此外，生物炭用 DAP 进行后处理以增加 P 负载。在去离子水中提取 P 和 2% 甲酸被用作潜在缓释的指标。微孔生物炭的比表面积为 69–333 m ²  g ^-1预处理导致 P 含量为 34–82 g kg ^-1。当预处理中包含 MgO 时，XRD 分析证实了结晶 Mg ₂ P ₂ O _{7 的形成}，而与 P 源无关。这种 Mg ₂ P ₂ O ₇是通过溶解控制过程在 240 小时内在去离子水中缓慢释放 P 的原因。用 DAP 后处理将 P 负载增加到 156 g kg ^-1以水溶性磷酸一铵 (MAP) 的形式存在，这对缓释没有贡献。通过热解前和热解后处理组合的可调磷释放使这些工程生物炭作为作物的磷源具有吸引力，并提供了一种有吸引力的解决方案，以减轻田间甘蔗残渣燃烧。