Peat-Free Growing Media for Tropical Agroforestry Seedlings: A Systematic Review and Predictive Substrate-Quality Framework with Supplementary Multilevel Meta-Analysis

Purpose The successful establishment of perennial species in agroforestry systems depends critically on nursery-phase conditions, yet evidence on alternative growing media remains fragmented across species, crop groups, and experimental contexts. This study synthesized evidence on peat-reduced and alternative nursery substrates to identify recurrent substrate systems and physicochemical conditions associated with high performance in tropical perennial seedlings relevant to agroforestry. Methods We conducted a PRISMA-guided systematic review and quantitative synthesis integrating treatment-level Composite Performance Index (CPI) values, physicochemical modelling, empirical quality-control windows, and a supplementary log response ratio (lnRR) meta-analytic layer. The deduplicated evidence base comprised 84 eligible studies distributed across the tropical belt. Results Coir/cocopeat-based mixes showed the strongest recurrent integrated-performance signal, with the highest median CPI (0.569) and the greatest proportion of treatments above the 70th percentile threshold (51.3%). Vermicompost-based mixes, agroindustrial residues, and selected biochar-amended media also performed well. Bulk density showed the strongest negative association with CPI (standardized β = −0.339), whereas nitrogen, total organic carbon, cation exchange capacity, and phosphorus were positively associated with performance. pH and electrical conductivity showed nonlinear responses, with peak performance at intermediate values. Conclusions High-performing tropical nursery media were defined less by a single ingredient than by a coherent physicochemical profile. The resulting framework provides evidence-based guidance for designing regionally adapted, peat-reduced growing media for perennial planting material used in agroforestry systems.