Losses of N2O, CH4 and NH3 from a grass sward used for overwintering beef heifers
2011
This study evaluated losses of N₂O, CH₄ and NH₃ from a rotational grazing system for overwintering beef cattle which spend 1 month on pasture. The cattle density was 71 heifers/ha and they were moved weekly to a new feeding area within the main pasture. The N₂O, CH₄ and NH₃ losses were determined in two feeding areas that were severely trampled (ST) or less trampled (LT) and in a control area from which cattle were excluded. The N input to the pasture was measured. The NH₃ losses were measured by micrometeorological mass balance in two periods with heifers present. The N₂O and CH₄ were measured using a closed chamber method with 9 chambers within each area on 10 occasions after heifers were removed from the pasture. The N input was 510kgN/ha. The NH₄-N contents in the clay loam topsoil were 45, 28 and 11kg/ha in the ST, LT and control areas, respectively. Losses of NH₃ were low due to rainy and cold conditions, corresponding to maximum 0.3kgN/ha/d. The soil was water logged and this, with the cold conditions, may have lowered N₂O emissions. Maximum N₂O losses were 7, 30 and 18gN₂O-N/ha/d from ST, LT and control areas, respectively. This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.
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