Short-term measurement of N2O emissions from sheep-grazed pasture receiving increasing rates of fertiliser nitrogen in Otago, New Zealand
S. A. Letica A C D , C. A. M. de Klein A , C. J. Hoogendoorn B , R. W. Tillman C , R. P. Littlejohn A and A. J. Rutherford AA AgResearch Invermay, Private Bag 50034, Mosgiel, New Zealand.
B AgResearch Grasslands, Private Bag 11008, Palmerston North, New Zealand.
C Institute of Natural Resources, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
D Corresponding author. Email: selai.letica@agresearch.co.nz
Animal Production Science 50(1) 17-24 https://doi.org/10.1071/EA07281
Submitted: 17 August 2007 Accepted: 12 November 2009 Published: 17 December 2009
Abstract
The purpose of this short-term study was to investigate the effect of increasing fertiliser nitrogen (N) application rates on nitrous oxide (N2O) emissions over the late winter/early spring period from sheep-grazed pasture in Otago rolling hill country. We measured N2O gas emissions from plots on a mottled Fragic Pallic hill soil receiving 0, 100 and 500 kg N/ha.year for 2 years. Plots were sampled weekly for 10 weeks over the 2006 winter/spring period using a static chamber method. Increased N fertiliser rate and the attendant increase in stocking rate significantly increased total N2O emissions (P < 0.05). Total N2O emissions for the measurement period were estimated to be 0.08, 0.13 and 1.36 kg N2O-N/ha (s.e.m, 0.1, 0.18 and 0.45) for the 0, 100 and 500 N treatments, respectively. Our results suggest that high application rates of fertiliser N (i.e. 500 kg N/ha.year) and attendant increased stocking rates may significantly increase emissions of N2O even in dry winter/spring conditions in Otago rolling hill country. These results will assist in the development of best management guidelines for reducing N2O emissions from fertiliser N in hill country.
Acknowledgements
The assistance of the Invermay Agricultural Centre field staff and the laboratory staff at Massey University and at Grasslands Research Centre in carrying out this work is greatly appreciated. Anonymous reviewers are thanked for critical comments and suggestions. The authors thank Massey University and AgResearch Limited for providing the field and laboratory facilities, and the Foundation for Research Science and Technology and the New Zealand Fertiliser Manufacturers’ Research Association for scholarship funding for the senior author.
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