New Zealand Journal of Agricultural Research abstracts

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A review of emissions of methane, ammonia, and nitrous oxide from animal excreta deposition and farm effluent application in grazed pastures

Surinder Saggar¹
N. S. Bolan²
R. Bhandral²
C. B. Hedley¹
J. Luo³

¹Landcare Research
Private Bag 11 052
Palmerston North, New Zealand

²Department of Soil and Earth Sciences
Institute of Natural Resources
Massey University
Private Bag 11 222
Palmerston North, New Zealand

³Land and Environmental Management
AgResearch Ltd
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand

Abstract  The agricultural sector in New Zealand is the major contributor to ammonia (NH₃), nitrous oxide (N₂O), and methane (CH₄) emissions to the atmosphere. These gases cause environmental degradation through their effects on soil acidification, eutrophication, and stratospheric ozone depletion. With its strong agricultural base and relatively low level of heavy industrial activity, New Zealand is unique in having a greenhouse-gas-emissions inventory dominated by the agricultural trace gases, CH₄ and N₂O, instead of carbon dioxide which dominates in most other countries. About 96% of this anthropogenic CH₄ is emitted by ruminant animals as a by-product during the process of enteric fermentation. Methane is also produced by anaerobic fermentation of animal manure and many other organic substrates. In pastoral soils, NH₃ and N₂O gases are generated from N originating from dung, urine, biologically fixed N₂, and fertiliser. The amount of these gaseous emissions depends on complex interactions between soil properties, climatic factors, and agricultural practices. In this review paper, the animal-excretal inputs and farm-effluent applications to New Zealand pastures are quantified. Data from overseas and New Zealand studies on CH₄, NH₃, and N₂O emissions from excretal deposition and animal effluents, and the factors affecting these emissions, are synthesised with an aim to improve the New Zealand estimates of emissions from these sources. The practical implications of these emissions are described in relation to environmental impacts and management strategies for reducing these emissions.

Keywords  ammonia; best management practices; effluent; grazed pasture; manure slurry; methane; nitrous oxide

A04068; ; Online publication date 15 December 2004Received 30 June 2004; accepted 6 September 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47: 513–544
0028–8233/04/4704–0513 © The Royal Society of New Zealand 2004

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