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Cattle Methane Emission and Pasture Carbon Dioxide Balance of a Grazed Grassland
Author(s) -
McGinn S. M.,
Beauchemin K. A.,
Coates T.,
McGeough E. J.
Publication year - 2014
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2013.09.0371
Subject(s) - grassland , environmental science , greenhouse gas , grazing , pasture , sink (geography) , stocking , rangeland , carbon dioxide , agronomy , livestock , methane , zoology , ecology , agroforestry , geography , biology , cartography
Grasslands constitute a major land use globally and are a potential sink of atmospheric carbon dioxide (CO 2 ). They are also an important habitat for wildlife and a source of feed that supports ruminant livestock production. However, the presence of ruminants grazing these grasslands is also a source of methane (CH 4 ) that contributes to buildup of greenhouse gases in the atmosphere. Our study measured enteric CH 4 from 40 confined heifers in 1‐ha paddocks using a dispersion model and CO 2 exchange from an adjacent grassland site using a micrometeorological technique. The study was conducted at a mixed prairie grassland located in southern Alberta, Canada. The mean (standard error) CH 4 emission was 189 (± 6) g animal −1 d −1 over four campaigns (over a 3‐yr period). The daily averaged CO 2 exchange from the grassland peaked at +2.2 g m −2 h −1 (sink) in early July and declined to negative values (source) in mid‐August. Annually, the grazed grassland was either a net sink for carbon (C) at +40 kg C ha −1 or a small source at −7 kg C ha −1 depending on a cattle stocking density of 0.1 or 0.2 animals ha −1 , respectively. However, in basing the exchange on CO 2 equivalence (CO 2_eq ), both stocking densities resulted in the grazed grassland being a source of greenhouse gas of −9 or −338 kg CO 2_eq ha −1 y −1 . This study illustrates the need to consider the cattle CH 4 emissions and the stocking density when evaluating the environmental sustainability of grazed grasslands.