Compost‐Based Organic Amendments and Synthetic Fertilisers Enhance Soil Health and Crop Yield Worldwide

ABSTRACT Fertiliser management is central to achieving sustainable increases in crop productivity while maintaining soil health. Yet, it remains unclear how chemical fertilisers, organic amendments (OAs), or their combination have comparable effects on soil health at a global scale. Here we synthesise 1657 observations from 204 published studies to assess the effects of compost (COM)‐based organic amendments, synthetic fertiliser (NPK), and their combination (COM + NPK; partial replacement) on crop yield and multiple soil health indicators. All treatments significantly increased yield, with the strongest increase under COM + NPK (62.6%), followed by COM (45.1%) and NPK (26.7%). Yield responses were crop‐dependent, with vegetables and legumes showing the largest benefits under organic‐based fertilisation (COM and COM + NPK). We found that COM + NPK most strongly improved soil health by increasing total carbon, nitrogen, and available nutrients, thereby enhancing organic matter retention and nutrient cycling. Moreover, COM alone produced the largest gains in soil organic carbon and microbial diversity, especially bacterial richness. In contrast, NPK had limited effects on total phosphorus, soil organic carbon and respiration. Together, our findings show that organic fertilisation strategies alone or combined with mineral fertilisers can simultaneously sustain yields and soil health, providing a practical route toward more resilient and sustainable agricultural systems worldwide.