Synergistic rhizosphere microbiome assembly in self-elevating ultra-high temperature compost-derived bioactive seedling substrates: Mechanistic insights and field applications for sustainable peat replacement

The widespread use of peat-based seedling substrates has led to increased carbon emissions and wetland degradation, highlighting the urgent need for sustainable bio-based alternatives. In this study, an independently developed self-elevating ultra-high temperature composting (sf-HTC) process (peak >80 °C) was employed to efficiently convert cattle manure, chicken manure, and straw into safe and sustainable bio-based seedling substrates. Within 28 days, this process reduced the bioavailability of heavy metals by 65 % and the abundance of antibiotic resistance genes (ARGs) by 74 %, thereby markedly improving ecological safety. Greenhouse and field experiments demonstrated that the substrate containing 40 % chicken manure (B40) increased seedling vigor by 228 % compared to commercial peat-based substrates, and enhanced fruit vitamin C, soluble sugar, lycopene, and capsaicin contents by 22 %, 34 %, 11.8 %, and 18.2 %, respectively. Mechanistic analysis revealed that the B40 substrate significantly increased the abundance of beneficial rhizosphere microorganisms such as Bacillus subtilis (by 257 %), and promoted the enrichment of Azospirillum and Nocardia (to 13 % and 10 %, respectively). In addition, soil alkaline phosphatase activity was elevated by 63 %. These changes were key drivers for enhanced plant growth, improved fruit nutritional quality, and reduced environmental risks. This technology provides a scientific basis for the high-value utilization of agricultural organic waste and the industrial application of bio-based seedling substrates, contributing to the advancement of green agriculture and ecological sustainability.