The incorporation of amendments is a commonly employed strategy to enhance the effectiveness of phytostabilization in remediating mine tailings. Although the remediation effectiveness of organic phosphate fertilizer (P), manure (M), and biochar (B) as individual amendments for heavy metal pollution has been extensively investigated, yet, the effectiveness of combined amendments for mine tailings remains unknown. The objective of this study is to assess the potential effectiveness of the co-application of P, M, and B in remediating Pb-Zn mine tailings by examining the alterations of chemical and biological properties. In this study, the mine tailings were amended with single and combined P, M, and B at a dosage of 5 % (w/w) followed by a two-month pot trial involving the seeding of ryegrass (Lolium perenne L.). In comparison to the control, all amendments effectively elevated the levels of organic matter, total nitrogen, and total phosphorus in the mine tailings while reducing diethylenetriamine-pentaacetic acid (DTPA)-extractable Pb, Cd, and As; Zn did not show significant changes except in combined treatment with P + M + B (i.e. PMB combination). The combined amendment treatments, particularly PMB, resulted in a substantial enhancement in both microbial biomass and the activities of alkaline phosphatase, urease, invertase, and dehydrogenase. Moreover, the combined amendments facilitated ryegrass growth while concurrently mitigating heavy metal uptake. Pearson's correlation analysis demonstrated a positive association between biological properties of the mine tailings (microbial biomass, enzyme activities, and ryegrass biomass) and nutritional levels while showing a negative correlation with DTPA-extractable heavy metals. Principal component analysis revealed that the addition of PMB exhibited superior efficacy in remediating mine tailings. Overall, our findings suggest that the application of PMB shows promise for in-situ remediation of Pb-Zn mine tailings; however, further research is required to validate these findings under field conditions.

The intensive management of double-cropping rice systems relies on high inputs of fertilizer and labor to sustain high yields. However, this leads to substantial reactive nitrogen (Nr) losses and severe environmental degradation. Although both enhanced-efficiency nitrogen fertilizers (EENFs) and deep placement are recognized for mitigating specific Nr loss pathways within individual seasons, robust field evidence for their combined, cross-seasonal efficacy across multiple loss pathways remains scarce. This study assessed the integrated agronomic, environmental, and economic performance of deep-placed EENFs in a double-rice cropping system. The EENFs included stabilized urea (SU) and controlled-release urea (CRU). Nitrogen release patterns differed significantly between fertilizers: SU showed strong season-dependent dynamics, while CRU provided a stable, consistent supply across both early and late rice seasons, achieving superior synchronization with crop nitrogen demand. Crucially, deep placement was indispensable for reducing environmental risks. The integrated strategy of deep-placing CRU (CRUD) facilitated a “spatiotemporal dual regulation” of nitrogen, spatially mitigating surface losses via deep placement and temporally synchronizing nutrient release with crop demand via the controlled-release mechanism. Compared with conventional surface-applied urea, CRUD significantly enhanced grain yield (16.1% and 17.5%), increased nitrogen recovery efficiency (41.5% and 67.4%), reduced total N losses (42.3% and 31.3%), and improved net economic benefits (35.0% and 30.9%) in early and late rice, respectively. It provides a concrete, actionable solution for advancing sustainable intensification in double-cropping rice systems, contributing directly to Sustainable Development Goals (SDGs).