A test of a winter farm management option for mitigating nitrous oxide emissions from a dairy farm

A trial was conducted in 2004 and 2005 to evaluate the effect of a stand-off winter stock management system on nitrous oxide (N(2)O) emissions from a dairy farm in New Zealand. The management system consisted of removing cows from pasture after grazing for 6 h per day and keeping them on a standoff pad for the rest of the day during the late autumn/winter seasons in order to reduce soil physical damage because of grazing on wet soils. The N(2)O emissions were measured on pasture that was grazed either for all day or for 6 h. The N(2)O emissions from the stand-off pad were also measured. A closed chamber technique was used for measuring N(2)O fluxes. The New Zealand International Panel for Climate Change inventory methodology was used to calculate annual N(2)O emissions from land application of farm effluent, leached and volatilized N. Significantly lower (P < 0.05) N(2)O emission rates were found when the stand-off grazed pasture was compared to the control in the winter seasons when soil was wet. Total N(2)O emission rates measured over one grazing interval in the late autumn/winter (May-August) in 2004 were 2.72 and 1.21 kg N(2)O-N/ha for the control and the stand-off grazed pastures, respectively. The respective emissions in 2005 were 0.97 and 0.22 kg N(2)O-N/ha. When all possible sources contributing to emissions of N2O ( both measured and calculated from the non-measured sources) were included, total annual emissions of 7.7 and 7.0 kg N(2)O-N per hectare of grazed pasture in the control and stand-off treatments, respectively, were estimated. These results suggest that the use of stand-off pads as a management practice during the wet seasons can be effective at reducing N(2)O emissions from dairy farm systems.