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 (N₂O) 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 stand‐off 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 N₂O emissions were measured on pasture that was grazed either for all day or for 6 h. The N₂O emissions from the stand‐off pad were also measured. A closed chamber technique was used for measuring N₂O fluxes. The New Zealand International Panel for Climate Change inventory methodology was used to calculate annual N₂O emissions from land application of farm effluent, leached and volatilized N. Significantly lower (P < 0.05) N₂O emission rates were found when the stand‐off grazed pasture was compared to the control in the winter seasons when soil was wet. Total N₂O emission rates measured over one grazing interval in the late autumn/winter (May–August) in 2004 were 2.72 and 1.21 kg N₂O‐N/ha for the control and the stand‐off grazed pastures, respectively. The respective emissions in 2005 were 0.97 and 0.22 kg N₂O‐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 N₂O‐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 N₂O emissions from dairy farm systems.