Greenhouse gas emissions and net ecosystem carbon budget from tobacco-planted soil with different organic amendments

Inputs of organic materials are recommended to increase soil carbon (C) sequestration and crop growth. However, organic amendments may increase greenhouse gas (GHG) emissions. To comprehensively evaluate the effect of organic amendments on the net ecosystem C budget (NECB) and net global warming potential (net GWP) in a successive tobacco cultivation system, methane (CH4) and nitrous oxide (N2O) fluxes and main components of the NECB under different treatments were measured in a pot experiment. The experiment with cultivated tobacco plants included five treatments: no fertiliser (NF), NPK, NPK plus wheat straw, NPK plus sesame cake (NPKC) and NPK plus biochar made from tobacco stalks. The results of NECB and estimated SOC changes implied that the tobacco-cultivated ecosystems acted as a C source under the NF, NPK and NPKC treatments, whereas the systems acted as a C sink with the application of straw and biochar. N2O emissions were significantly increased by 53.7% and 96.2% in soils amended with straw and sesame cake respectively. Biochar addition had no effect on N2O emissions. CH4 uptake was not affected by organic amendments. As a result, the application of straw and biochar significantly decreased the net GWP and GHG intensity, but sesame cake amendments had no such significant effects. Therefore, in comparison to the other treatments, the straw and biochar treatments were more effective GHG mitigation practices that increased the yield and NECB in the tobacco cultivation system, and this was especially true for the biochar treatment.