Abstract
We studied methane (CH4) flux rates from experimental excreta patches on a dairy pasture with a chamber technique during snow free seasons and with a gas gradient technique during winter from timothy-meadow fescue sward with mineral N fertilization (220 kg ha-1) and from grass-white clover mixture without fertilization. The dung and urine patches were applied in June or August two consecutive grazing seasons and the measurements were carried out for a year following each application. There were no significant differences in CH4 fluxes between plant species and emissions originated mainly from the fresh dung pats. The average annual CH4 fluxes from the control sites without excreta were -0.60±0.1 and with the excreta 0.47±0.3 kg CH4 ha-1. Thus, excreta originating from dairy cows can turn boreal swards from weak sinks to small sources of CH4. However, these emissions are only 0.2% of the total CH4 emissions from a dairy cow.
Highlights
Methane (CH4) is a strong greenhouse gas and it has a warming potential 25 times that of CO2 in a100-year reference period (Solomon et al 2007)
The most important terrestrial sinks for CH4 are forest soils, whereas well aerated, drained agricultural soils are only weak net sinks (Hütsch 2001). In these soils methanotrophic bacteria oxidize atmospheric methane diffused in the soil causing the CH4 sink (Hütsch 2001). If these soils are used as dairy pastures, the CH4 produced in the enteric fermentation by ruminants (Rossi et al 2001) and in dung may result in net CH4 emissions from the site
To test this hypothesis we investigated the effect of dairy cow excreta on CH4 fluxes from a boreal pasture soil using simulated dung and urine patches
Summary
Methane (CH4) is a strong greenhouse gas and it has a warming potential 25 times that of CO2 in a100-year reference period (Solomon et al 2007). The most important terrestrial sinks for CH4 are forest soils, whereas well aerated, drained agricultural soils are only weak net sinks (Hütsch 2001). In these soils methanotrophic bacteria oxidize atmospheric methane diffused in the soil causing the CH4 sink (Hütsch 2001). If these soils are used as dairy pastures, the CH4 produced in the enteric fermentation by ruminants (Rossi et al 2001) and in dung may result in net CH4 emissions from the site (emissions exceed uptake by soil). Methane fluxes from boreal pasture soils have not been reported earlier
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