Optimizing organic manure substitution in orchards: Meta-analysis reveals gains in productivity, fruit quality, and soil health and reduced nitrogen losses

The strategy of substituting organic manure for chemical fertilizer (SMCF) is a critical agricultural practice that influences orchard productivity, nitrogen (N) losses, and soil health. However, the effects of the SMCF strategy on fruit yield and quality, soil carbon (C) and N dynamics, and N losses are unclear. This study synthesized data from 76 studies (1261 datasets) to assess the effects of the SMCF strategy on orchard productivity, fruit quality, N losses, and soil health. The SMCF strategy significantly increased fruit yield by 12.0 % and single fruit weight by 3.8 % and enhanced fruit quality indicators, including soluble solids (+5.0 %), soluble sugars (+4.5 %), sugar–acid ratio (+12.4 %), and vitamin C (+5.2 %). The SMCF strategy reduced N losses by decreasing ammonia volatilization (−35.8 %), nitrous oxide emissions (−18.1 %), and nitrate accumulation (−29.8 %). Consequently, N use efficiency indicators (fruit yield per unit of N loss) significantly improved by 47.8, 30.1, and 42.0 % for NH3, N2O, and NO3− accumulation, respectively. Soil health markedly improved due to significant increases in the contents of organic C (13.1 %), dissolved organic C (48.5 %), microbial biomass C (61.3 %), and microbial biomass N (52.6 %). The effectiveness of SMCF was affected by the substitution rate, manure type, application duration, N input, initial soil organic C, pH, and climate. The application of plant- or animal-derived organic manure at a substitution rate of 25–50 % for over 2 years is recommended for optimizing yield, quality, and soil health and reducing N losses, especially in orchards with a low initial soil organic C content and high chemical N fertilizer inputs. These findings provide a scientific basis for optimizing the SMCF strategy to achieve productive and environmentally sustainable orchard management.