Green waste compost reduces nitrous oxide emissions from feedlot manure applied to soil

摘要

Australia produces in excess of 1 million tonnes of feedlot manure (FLM) annually. Application of FLM to grain cropping and grazing soils could provide a valuable nutrient resource. However, because of high nutrient concentration, especially of N (>2%), FLM has the potential for environmental pollution, for example, N pollution to the water bodies and NO emission to the atmosphere. Therefore, controlling N supply from FLM is essential for the judicious utilisation of FLM in the field as well as reducing NO emission to the atmosphere. We utilised the low N concentration green waste compost (GWC, about 3 million tonnes produced annually) as a potential management tool to assess its effectiveness in regulating N release from FLM and controlling the rates of NO emission from field application when both FLM and GWC were applied together to sorghum (Sorghum bicolor Moench) grown on a Vertisol. We measured NO emission rates during the sorghum crop and clean fallowing over one-year period in the field. Annual soil NO emissions were 5.0kgNOhap# from urea applied at 150kgNhap#, 5.1 and 5.5kgNOhap# from FLM applied at 10 and 20thap# respectively, 2.2kgNOhap# from GWC applied at 10thap#, 4.3kgNOhap# from FLM and GWC applied together at 10thap# each, and 3.3kgNOhap# from the unamended soil. Thus, we found that GWC application reduced NO emissions below those from an unamended soil while annual emission rate from FLM approached that from fertiliser N application (o0.7%NO emission factor). A mixture of FLM+GWC applied at 10thap# each reduced NO emission factor by 64% (the emission factor was 0.22%), most likely by reducing the amount of mineral N in the soil because soil NH-N and NO-N and the rate of NO emission were significantly correlated in this soil. Since the global warming potential of NO is 298 times that of CO, even a small reduction in NO emission from GWC application has a significant and positive impact on reducing global warming.