Water-saving ground cover rice production system reduces net greenhouse gas fluxes in an annual rice-based cropping system

[摘要] To safeguard food security and preserve precious water resources, thetechnology of water-saving ground cover rice production system (GCRPS) isbeing increasingly adopted for rice cultivation. However, changes insoil water status and temperature under GCRPS may affect soil biogeochemicalprocesses that control the biosphere–atmosphere exchanges of methane(CH₄), nitrous oxide (N₂O) and carbon dioxide (CO₂). Theoverall goal of this study is to better understand how net ecosystemgreenhouse gas exchanges (NEGE) and grain yields are affected by GCRPS in anannual rice-based cropping system. Our evaluation was based on measurementsof the CH₄ and N₂O fluxes and soil heterotrophic respiration(CO₂ emissions) over a complete year, and the estimated soilcarbon sequestration intensity for six different fertilizer treatments forconventional paddy and GCRPS. The fertilizer treatments included ureaapplication and no N fertilization for both conventional paddy (CUN and CNN)and GCRPS (GUN and GNN), and solely chicken manure (GCM) and combined urea andchicken manure applications (GUM) for GCRPS. Averaging across all thefertilizer treatments, GCRPS increased annual N₂O emission and grainyield by 40 and 9%, respectively, and decreased annual CH₄emission by 69%, while GCRPS did not affect soil CO₂ emissionsrelative to the conventional paddy. The annual direct emission factors ofN₂O were 4.01, 0.09 and 0.50% for GUN, GCM and GUM,respectively, and 1.52% for the conventional paddy (CUN). The annual soilcarbon sequestration intensity under GCRPS was estimated to be an average of−1.33 Mg C ha⁻¹ yr⁻¹, which is approximately 44% higher thanthe conventional paddy. The annual NEGE were 10.80–11.02 Mg CO₂-eq ha⁻¹ yr⁻¹for the conventional paddy and 3.05–9.37 Mg CO₂-eq ha⁻¹ yr⁻¹ for the GCRPS, suggesting the potential feasibility ofGCRPS in reducing net greenhouse effects from rice cultivation. Using organicfertilizers for GCRPS considerably reduced annual emissions of CH₄ andN₂O and increased soil carbon sequestration, resulting in the lowestNEGE (3.05–5.00 Mg CO₂-eq ha⁻¹ yr⁻¹). Accordingly,water-saving GCRPS with organic fertilizer amendments was considered themost promising management regime for simultaneously achieving relativelyhigh grain yield and reduced net greenhouse gas emission.

[学科分类] 地球化学与岩石