Chadwick, 2011 – Manure Management: Implications for greenhouse gas emissions

Slurry, farmyard manure and poultry manure are inevitable consequences of livestock prodects generated from housed animals. These manures are recycled back to land for plants to use nutrients they contain. However, since they contain inorganice N. microbially available sourses of C and water, they provide the essential substrates required for the microbial production of N2O and CH4. These greenhouse gases can be produced and emiteed at each stage of the ‘manure management continuum’ being the livestock buliding, manure stores, manure treatment and manure spreading to land. The contribution that manure management makes to total national agricultural emissions of N2O and CH4 vary, but can exceed 50% in countries reporting to the NFUCCC in 2009. On farm management decisions interact with enviroment controls such as temperature and water availability of key microbial processes (i.e. nitrification, denitrification, methanogenisis, CH4 oxidation)  affecting the magnitude of emission from each stage of the manure management continuum. We review the current understanding of how manure management influences direct and indirect N2O and CH4 emission, introduce new data comparing direct N2O emissions following spreading of a range of manure types by differnet methods, and high light some of the mitigations being considered  by researchers and policy makers in developed and developing countries.