How Climate, Soil Conditions, and Biochar Characteristics Influence Crop Yield, Nitrogen and Phosphorus Fertilizer Productivity, and Economic Returns Across Cereals and Legumes: A Global Meta–Analysis

Biochar application is widely proposed to improve crop yield and fertilizer productivity, yet its performance varies across climatic, soil, and management contexts. This global meta–analysis study of about 705 database entries retrieved from 93 studies analyzed responses across climatic classification, biochar feedstock and properties, soil properties, fertilizer and co–application regimes, and experimental types. Overall, biochar responded at 33%, 34%, and 32% for yield, PFPN, and PFPP. The strongest response occurred at the tropical, humid agro–ecological zone under moderate temperature regimes. Wood-derived biochar with lower pyrolysis temperatures (<400 °C), combined with moderate soil carbon content and nitrogen, produced a greater improvement. Organic + biochar co–applied fertilizer application rates of ≤50 kg N ha–1 and 50–100 kg P2O5 ha–1 increased the response, while excessive fertilizer rates (>200 kg ha) showed reduced response. Economic benefit analysis also showed the average overall highest maximum yield at ≤40–80 t ha–1 biochar rates demonstrating simultaneous improvement in yield and fertilizer productivity under appropriate management.