Renewal effects of multi-source organic solid waste compost on soil organic matter continuum

Conventional agriculture relies heavily on nitrogen-based chemical fertilizer (CF) to facilitate agricultural productivity, which contributes little to soil organic carbon and leads to ecosystem degradation. Compost, which is rich in active microorganisms and microbial residues, contributes to enhanced environmental sustainability by improving soil nutrient availability, stimulating microbial activity, promoting carbon sequestration, and reducing reliance on CF. Soil organic matter (SOM) plays a pivotal role in sustaining agricultural productivity, regulating ecosystem functions, and mitigating climate change. Compost has been proven to increase the content of SOM and modulate the microbial community. The ecological value of compost is primarily determined by its biochemical properties, with the heterogeneity and complexity of organic constituents across various organic solid waste (OSW) sources contributing to the distinct biochemical profiles of compost products. However, composts derived from different OSW are often treated as generic products. The systematic mechanisms by which compost derived from multisource OSW replenishes SOM remain insufficiently understood, limiting the development of precision composting technologies and targeted soil management strategies. Therefore, developing a deeper understanding of how composts derived from various types of biowaste contribute to the renewal of SOM and its ecological functions is essential for guiding scientific fertilization strategies aimed at improving soil quality—which we refer to as a “soil demand-oriented, compost quality-based utilization strategy”. The conceptual understanding of SOM has evolved through humification theory, the theory of selective preservation, and the continuum model. The proposed microbial carbon pump theory has further improved our understanding of the dynamic changes in SOM. Microorganisms regulate the balance between the priming effect and the burial effect of SOM through dual metabolic pathways: extracellular modification and intracellular turnover. On the basis of the SOM continuum model, this study systematically elucidated how multisource OSW composts alter SOM by reshaping molecular composition, microbial dynamics, and functional site renewal. The first process involves molecular composition renewal, whereby compost modulates the levels of labile compounds, such as lipids, and recalcitrant substances, such as phenolic compounds, in the soil, thereby reconstructing the SOM continuum through molecular weight fractionation. The second process is microbial community regulation, where compost enhances the complexity of fungal–bacterial interaction networks, activates aromatic carbon-degrading functional bacteria, and alters microbial carbon pump efficiency and the molecular assembly mechanisms of SOM. The third process is functional molecular site renewal, in which compost changes the abundance, chemical forms, and spatial configuration of redox and proton complexation sites in SOM; thus, regulating π–π conjugation systems and electron cloud density, ultimately affecting soil biogeochemical cycles. Future research should comprehensively assess the effects of multisource OSW compost on the molecular composition, structure, function, and assembly mechanisms of SOM from an organic matter continuum perspective, as well as their temperature responses. Molecular weight is an intrinsic characteristic of SOM and plays a significant role in influencing its biogeochemical cycling. The integration of molecular fractionation dialysis with mass spectrometry analysis is crucial for elucidating the effects of compost application on the molecular composition and functional properties of SOM across a broad range of molecular weights. By integrating molecular dynamics simulations with molecular structure modeling, this approach enables the analysis of functional characteristic changes induced by structural variations in SOM at the molecular level, thereby providing a theoretical foundation and predictive tools for guiding the utilization of compost soil and forecasting improvements in compost quality. In particular, quantifying the molecular dynamics and stability thresholds of the SOM continuum under long-term, multisource OSW compost application with the microbial carbon pump as the core is necessary to provide a basis for evaluating the carbon sequestration potential of different types of compost and matching soil demands.

传统农业高度依赖氮肥化肥（nitrogen-based chemical fertilizer, CF）以提升农业生产效率，但其对土壤有机碳（soil organic carbon）的贡献微乎其微，且会导致生态系统退化。堆肥富含活性微生物与微生物残体，可通过提升土壤养分有效性、激活微生物活性、促进碳固存以及降低对氮肥化肥的依赖，推动环境可持续发展。土壤有机质（soil organic matter, SOM）在维持农业生产效率、调节生态系统功能以及减缓气候变化方面发挥着关键作用。已有研究证实，堆肥可提升土壤有机质含量，并调控微生物群落结构。堆肥的生态价值主要由其生化特性决定，而不同有机固体废物（organic solid waste, OSW）来源的有机组分具有异质性与复杂性，这造就堆肥产品各具独特生化特征。然而，来自不同有机固体废物的堆肥常被视为通用产品。多源有机固体废物堆肥补充土壤有机质的系统性机制仍未得到充分阐明，这限制了精准堆肥技术与针对性土壤管理策略的发展。因此，深入解析不同类型生物废弃物堆肥如何促进土壤有机质更新及其生态功能，对于指导旨在改善土壤质量的科学施肥策略至关重要——我们将该策略称为"以土壤需求为导向、基于堆肥品质的利用策略"。学界对土壤有机质的概念认知历经腐殖化理论、选择性保存理论与连续体模型的发展演变，而微生物碳泵理论的提出进一步深化了我们对土壤有机质动态变化的理解。微生物通过双重代谢途径——胞外修饰与胞内周转——调控土壤有机质的激发效应与埋藏效应之间的平衡。基于土壤有机质连续体模型，本研究系统阐明了多源有机固体废物堆肥如何通过重塑分子组成、微生物动态与功能位点更新来改变土壤有机质。其一为分子组成更新：堆肥可调控土壤中脂质等易变化合物与酚类化合物等难降解物质的含量，进而通过分子量分级重构土壤有机质连续体。其二为微生物群落调控：堆肥可提升真菌-细菌互作网络的复杂性，激活降解芳香碳的功能菌，并改变微生物碳泵效率与土壤有机质的分子组装机制。其三为功能分子位点更新：堆肥可改变土壤有机质中氧化还原与质子络合位点的丰度、化学形态与空间构型，进而调控π-π共轭体系与电子云密度，最终影响土壤生物地球化学循环。未来研究应从有机质连续体视角，全面评估多源有机固体废物堆肥对土壤有机质的分子组成、结构、功能与组装机制及其温度响应的影响。分子量是土壤有机质的固有特性，对其生物地球化学循环具有重要影响。将分子分级透析与质谱分析相结合，对于阐明堆肥施用对不同分子量范围土壤有机质的分子组成与功能特性的影响至关重要。通过整合分子动力学模拟与分子结构建模，该方法可实现从分子层面分析土壤有机质结构变异诱导的功能特性变化，从而为指导堆肥的土壤利用以及预测堆肥品质提升提供理论基础与预测工具。尤为重要的是，以微生物碳泵为核心，量化长期施用多源有机固体废物堆肥条件下土壤有机质连续体的分子动态与稳定性阈值，可为评估不同类型堆肥的碳固存潜力以及匹配土壤需求提供依据。