Nitrous oxide emissions from fertilised grassland: A 2-year study of the effects of N fertiliser form and environmental conditions |
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Authors: | H Clayton I P McTaggart J Parker L Swan K A Smith |
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Institution: | (1) Institute of Ecology and Resource Management, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JG, UK, GB;(2) Soils Department, Scottish Agricultural College, West Mains Road, Edinburgh, EH9 3JG, UK, GB |
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Abstract: | The aim was to investigate the effects of different N fertilisers on nitrous oxide (N2O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N2O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam
grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry
supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N2O flux and soil and environmental variables. The loss of N2O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from
AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower
than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled
pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total
annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2,
1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd
year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that
similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed
to minimise N2O emissions from agricultural land.
Received: 30 August 1996 |
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Keywords: | Grassland Denitrification N-fertiliser Nitrification Nitrous oxide emissions Global warming Ozone layer |
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