Nitrous oxide emission from farm dairy effluent application in grazed grassland

Abstract

Intensification in dairying and increased production of farm dairy effluent (FDE) has raised concerns about gaseous nitrogen (N) losses and their environmental implications. This study was undertaken to monitor changes in mineral-N and soil water-filled pore-space (WFPS) in relation to N2O emission from application of FDE to dairy-grazed pasture. Pasture was irrigated with FDE in September 2003 (first irrigation) and January 2004 (second irrigation), preceded by grazing events. The N2O emission rate increased after application of FDE. Total amounts of N2O emitted from FDE application for first and second irrigation were 2% and 4.9%, respectively, of the total N added through effluents. Difference in emission rates between the two irrigation events were attributed to difference in time lapse between the grazing event and FDE application. When FDE was applied immediately after grazing (second irrigation) higher emissions were observed.