Impacts of vermicompost application on crop yield, ammonia volatilization and greenhouse gases emission on upland in Southwest China

Ammonia (NH3) volatilization and greenhouse gas (GHG) emission are important environment pollution sources in upland agro-ecosystems. Vermicompost was used for amending purple soil and comparing NH3 and GHG emissions. A field experiment was conducted with a comparison of organic and inorganic fertilizers in a wheat-maize rotation system in the Sichuan Basin, China. The five treatments were conventional inorganic fertilizers, NPK as control; vermicompost prepared with cow dung (VCM); and pig manure (VPM); cow dung and pig manure vermicompost, re-spectively (VCMNPK, VPMNPK). Total nitrogen rates of all treatments were the same. Soil NH3 volatilization and GHG emissions were monitored with the static chamber method. The results showed that NH3 volatilization occurred in the first two weeks following nitrogen (N) fertilization. The cumulative fluxes of NH3 recorded in the NPK, VCM, VPM, VCMNPK, and VPMNPK treatments were 15.4, 5.7, 6.3, 10.32, and 10.29 kg N ha-1 yr-1, respectively, in the winter and 4.8, 5.5, 19.83, 12.8, and 11.9 kg N ha-1 yr-1 respectively, in the summer. The global warming potential (GWP) 773.6 and 803.9 g CO2-eq m-2 in VCM and VPM, respectively, during the wheat season 540.6 and 576.2 g CO2-eq m-2, respectively, during the maize season. The GWPs in NPK treatment were 1032.4 and 570.7 g CO2-eq m-2 during the wheat and maize seasons, respectively. The increasing effects of nutrient loops, particularly 18 % soil total nitrogen (TN) and 31 % soil organic carbon (SOC) in VCM, and crop productivity of vermicompost treatments during the wheat-maize rotation had been evaluated. This study recommends that VCM can be considered as a better organic amendment, promoting plant growth while decreasing the environmental costs of gas emissions.