Cattle Methane Emission and Pasture Carbon Dioxide Balance of a Grazed Grassland
- S. M. McGinn *,
- K. A. Beauchemin,
- T. Coates and
- E. J. McGeough
Grasslands constitute a major land use globally and are a potential sink of atmospheric carbon dioxide (CO2). 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 (CH4) that contributes to buildup of greenhouse gases in the atmosphere. Our study measured enteric CH4 from 40 confined heifers in 1-ha paddocks using a dispersion model and CO2 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) CH4 emission was 189 (± 6) g animal−1 d−1 over four campaigns (over a 3-yr period). The daily averaged CO2 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 CO2 equivalence (CO2_eq), both stocking densities resulted in the grazed grassland being a source of greenhouse gas of −9 or −338 kg CO2_eq ha−1 y−1. This study illustrates the need to consider the cattle CH4 emissions and the stocking density when evaluating the environmental sustainability of grazed grasslands.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2014. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.