Potential greenhouse gas abatement from converting croplands to pastures negated by emissions from livestock

Meier, E.A.1*, Thorburn, P.J.1, Bell, L.W.1, Harrison, M.T.2, Biggs, J.S.1, Dumbrell, N.P.3 and Kragt, M.E.4

1 CSIRO Agriculture and Food, Queensland Bioscience Precinct, The University of Queensland, 306 Carmody Road, St Lucia QLD 4067 Australia, www.csiro.au, elizabeth.meier@csiro.au

2 Tasmanian Institute of Agriculture, University of Tasmania, TAS 7320

3 Centre for Global Food and Resources, The University of Adelaide, 10 Pulteney St, Adelaide SA 5005

4 University of Western Australia, 35 Stirling Highway, Perth WA 6009

Abstract

Australian agriculture is a significant emitter of global greenhouse gases (GHG) and so has a role in reducing those emissions. Replacing cropland with permanent pastures is a practice that has potential to provide abatement by increasing stocks of soil organic carbon (SOC) and thereby reducing the flux of atmospheric carbon dioxide (CO2). However, pastures frequently support livestock, which produce other GHG emissions (principally methane, CH4) that could negate abatement from increases in SOC. Three contrasting cropping and livestock systems were simulated at Kellerberrin (Western Australia), Southern Mallee (Victoria) and Chinchilla (Queensland). Cropping scenarios were defined that had increasing amounts of dry matter inputs: C1, crop residues burned before sowing; C2, crop residues retained; and C3, uncropped fallow phases replaced with short-term green manure legume crops. The on-farm GHG emissions profile of the cropping scenarios was calculated and compared with that from two livestock scenarios utilising continuous stocking on: L1, permanent grass pasture; and L2, permanent grass-legume pasture. We found that the permanent grazed pastures in livestock systems did not necessarily provide net GHG emissions reductions compared to cropping systems when the emissions from livestock were included. This finding highlights the importance of including all emissions when calculating the net GHG profile for practices.

Host

The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography david_marland@hotmail.com Southern Farming Systems Agriculture Victoria

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