Soil–plant-microbial evidence for the available phosphorus generation and utilization of Ca/Mg salts conditioned hydrochar from sewage sludge

作者：Qian Zhao, Wei Guo, Yuhan Zhu, Dongyue Li, Xiaohui Liu, Minda Yu, Dongyang Li, Xiang Gao, Xi–Shi Tai, Jun Li · 发表于：Carbon Research · 年份：2025 · DOI：10.1007/s44246-025-00228-2 · 被引用次数：4 · 研究领域：Phosphorus and nutrient management、Adsorption and biosorption for pollutant removal

Abstract Metal salts-modified sewage sludge (SS) biochar is increasingly used in agricultural soil remediation, although its effects on available phosphorus (P) species, plant growth and microbial communities remain unclear. This study prepared CaO, CaCl 2 , MgO and MgCl 2 -modified hydrochars derived from SS at 260 °C for 2 h. Then the available P characteristics of the hydrochars and their effects on the growth of Vigna radiata (mung bean) and soil microorganisms were comprehensively evaluated by chemical extraction, pot experiments and the diffusive gradients in thin-films (DGT) technique. Results indicated that Ca-based hydrochars contained more slow-release apatite P (AP) compounds (e.g., Ca 5 (PO 4 ) 3 OH, Ca 5 (PO 4 ) 3 Cl and Ca 2 PO 4 Cl), with a 48.6%–86.3% increase in AP content compared to the control at 260 °C. In contrast, Mg-based hydrochars were richer in easy-release AP compounds (e.g., Mg 3 (PO 4 ) 2 and Ca 3 Mg 3 (PO 4 ) 4 ), with a lower AP increase of 0–50.7%. Compared with Ca salts modified hydrochars, Mg-modified hydrochars (especially MgO) were more effective for the promotion of rapid growth, chlorophyll synthesis and photosynthesis in V. radiata plants, resulting in more P accumulation within mung beans, which was consistent with the P release results obtained by DGT. The addition of Ca-modified hydrochars promoted the enrichment of bacterial communities such as Skermanella and RB41 , which was helpful for improving the mineralization and circulation...