Organic Fertilizer Substitution Could Shift Chinese Orchards from a Greenhouse Gas Source to a Sink

Fruits play a vital role in global agriculture, yet the greenhouse gas (GHG) balance of orchard ecosystems remains poorly constrained due to the lack of integrated assessments of soil organic carbon (SOC) sequestration and non-CO2 emissions. Given China’s substantial share of global fruit production, resolving this gap is critical for advancing low-carbon agricultural strategies. Here, we provide the first data-driven, system-level quantification of GHG balance in Chinese orchards by explicitly integrating SOC sequestration and nitrous oxide (N2O) emissions within a unified analytical framework. A comprehensive database containing 170 observations of SOC change and 82 observations of N2O emissions was compiled, and nonlinear relationships between environmental/management drivers and GHG fluxes were captured using random forest models, which showed robust predictive performance (R2 = 0.71 and 0.66 for SOC and N2O, respectively). Organic matter input and SOC content were identified as the most influential predictors for the SOC and N2O models, respectively. Model simulations estimated that in 2021, Chinese orchards sequestered 4.53 Tg C in the standardized 0–20 cm soil layer, with an average sequestration rate of 0.34 t C ha−1 yr−1, while emitting 89.37 Gg N2O, corresponding to an emission intensity of 6.76 kg N2O ha−1. The net GHG balance of Chinese orchards was estimated at 7.78 Tg CO2-eq, with stone fruit and citrus orchards identified as the main contributors to net positive GHG emissions. Scenario analysis revealed that replacing 20% of mineral nitrogen fertilizer with organic fertilizer could shift the net GHG balance from a source to a sink (–1.03 Tg CO2-eq), while a 50% substitution scenario could achieve a net carbon sink of up to –14.37 Tg CO2-eq. These findings redefine the relative roles of SOC sequestration and N2O mitigation in perennial systems and highlight organic matter management as a pivotal pathway toward carbon neutrality in orchard agriculture.