Ranking the reactivity of carbon sources in cattle slurry in modulating N-gas emissions

Abstract

Abstract Animal manures are important sources of nutrients for crop production, yet the effects of slurry carbon (C) components on soil nitrogen gaseous emissions are poorly understood. Six experiments were conducted in a He/O2 atmosphere aiming to determine the effects of cattle slurry and some of its C components on soil nitrous oxide (N2O) and dinitrogen (N2) emissions. The treatments were: 1) NO3−; 2) NO3− + glucose (experiments 1 to 4) or NO3− + NH4+ (experiments 5 and 6); and 3) NO3− + C source (this was either vanillin, cellulose, glucosamine, butyric acid, fresh cattle slurry or aged cattle slurry, experiments 1 to 6). Results showed that the reactivity order of individual C sources on total N2O-N + N2-N emissions was: glucose > glucosamine > butyric acid > vanillin > aged slurry > cellulose > fresh slurry. Aged cattle slurry generated relatively higher soil total N2O-N + N2-N emissions, but also further reduction to N2 than fresh cattle slurry after incorporation into the soil. In addition, the N2O/N2 ratio was relatively higher in the NO3− + NH4+ treatments (experiments 5 and 6), as well as in the NO3− + glucosamine treatment, due to the additional N application. We concluded that the availability/degradability of C in slurry is an important control of subsequent denitrification rates and the production and emission of N2O when applied to land suggesting that slurry management, i.e. storage period, can be optimised to influence C availability in cattle slurry, leading to a reduced risk of N2O production.