Nitrous oxide and methane emissions from a dairy farm stand-off pad

Abstract

Stand-off pads (purpose built, drained loafing areas to hold livestock during wet winter periods when it is not suitable to have them on pasture) are increasingly used in New Zealand to avoid damage to pasture and to reduce emissions of the greenhouse gas nitrous oxide (N2O) and nitrate leaching. However, emissions of N2O and methane (CH4) also occur from stand-off pads. The objective of this study was to provide quantitative information on emission levels of N2O and CH4 from a stand-off pad. In this paper, we report the results of N2O and CH4 emissions measured over 3 months from a 300 m2 stand-off pad supporting 21 dairy cows. The stand-off pad consisted of screened crushed pine bark and sawdust. N2O fluxes from the stand-off pad were initially very low, but subsequently increased. The highest daily fluxes ~3 g N2O-N/300 m2.day were obtained in early July. Overall, 0.054 (± 0.018) kg N2O-N was emitted from the stand-off pad during the 3-month measurement period. These results suggest that only 0.01% of the excretal N deposited by the cows was emitted as N2O. Similar to N2O fluxes, initial CH4 emissions were very low. Methane fluxes became very high, reaching a peak value of 360 g CH4-C/300 m2.day in mid August after the cows ceased using the pad, and no flux measurements were made beyond this period. Overall, 3.0 (± 0.5) kg CH4-C was emitted during the 3-month period. This work shows that stand-off pads could be used to mitigate emissions of N2O and CH4 emanating from animal excretal deposition.