New Zealand Journal of Agricultural Research abstracts
Nitrous oxide emissions from application of urea on
New Zealand
pasture
J. Luo
S. F. Ledgard
S. B. Lindsey
AgResearch Ruakura
Private Bag 3123
Hamilton
3240,
New Zealand
jiafa.luo@agresearch.co.nz
Abstract The use of nitrogen
(N) fertiliser
has been
identified as a possible important source of nitrous oxide (N2O)
from pastoral soils, and urea is the main form of N fertiliser used in New
Zealand. The aim of this study was to
examine the effects of urea application on N2O emissions
from
pastoral soil. A closed soil chamber technique was used to measure the N2O
emissions from a pasture which received either 0 (control) or 50 kg N
ha–1 (as urea) per application during different seasons
between 2003
and 2005. Overall, urea fertiliser application generally increased N2O
fluxes above control levels for up to 30 days, but the duration for
which N2O
levels were elevated depended on the season. These increases in the N2O
fluxes were largely caused by a combination of changes in the soil
mineral N
level due to urea application, and moisture content of soil in
different
seasons. Nitrous oxide emissions were higher during the winter and
spring
measurement periods when the soil water-filled pore space (WFPS) was
mostly
above field capacity, and the emissions were lower during the summer
and autumn
measurement periods when the soil WFPS was below field capacity. The
estimated
N2O emission factors for urea ranged between 0 and 1.56% of
the
urea-N applied, with a calculated average emission factor of 0.56%. The
findings of the seasonal measurements suggests that a reduction in the
use of N
fertilisers under wet winter or wet spring conditions in New Zealand
could
potentially reduce N2O emissions from pastoral soil.
Keywords nitrous oxide; N
fertiliser; urea;
nitrogen;
pasture; soil; New Zealand
Online publication date 28 February
2007; Received 15 May 2006;
accepted 8 November 2006.
New Zealand
Journal of Agricultural Research, 2007, Vol. 50: 1–11
0028–8233/07/5001–0001 © The Royal Society
of New Zealand
2007
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