A comparison of methane emissions from sheep grazing pastures with differing management intensities
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Methane emissions were measured from sheep grazing on pastures that received one of three managements, either 70 or 270 kg N fertiliser ha−1 or one which had a high proportion of white clover present. A system for measuring the emissions is described which enables measurements to be made under near natural grazing conditions. Continuous measurements of emissions were made over periods of 4 days. There were no significant differences in the amount of CH4 produced per unit body weight over the study period. Animals feeding on both the grass pastures showed strong diurnal patterns of CH4 emission with peak emissions between 15:00 and 17:00 h and levels gradually falling throughout the night before starting to rise at around 08:00 h. Those animals feeding on the clover swards also had peak emissions at around the same time in the afternoon, however, levels of CH4 production did not decline over the night and peaked again in the morning before falling sharply to a low at noon. It is concluded from the present studies that the level of inputs to the sward tends to play little part in the overall levels of CH4 emissions from grazing sheep, but can influence the diurnal part em of CH4 production.
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