New Zealand Journal of Agricultural Research abstracts
Symbiotic nitrogen fixation by Trifolium arvense in
semi-arid short tussock grasslands
C. C. Boswell
W. L. Lowther
A. J. Rutherford
AgResearch
Invermay Agricultural Centre
Private Bag 50034
Mosgiel 9053, New Zealand
alison.rutherford@agresearch.co.nz
Abstract We have measured symbiotic N
fixation from the
widespread annual Trifolium arvense (haresfoot clover) in two
studies in the semi-arid zone of the Mackenzie Basin using a 15N
dilution technique over two growing seasons. Apart from one low value
of 69%, the percentage of plant nitrogen derived from the atmosphere
(%Ndfa) was consistently high in one study at Tomahawk Gully (82–91%).
Calculated inputs of symbiotic N fixation from T. arvense was
highly variable over the landscape, and between seasons. Calculated
symbiotic N fixation inputs on different landscape units in Tomahawk
Gully ranged from <0.1 to 3.4 kg N ha–1 in 2000–01, and
from <0.1 to 11.4 kg N ha–1 in 2001–02 when there was
more favourable summer rainfall. Weighted mean rates of N fixation over
the whole Tomahawk Gully catchment were 0.5 and 1.6 kg N ha–1,
in the respective seasons. In a study at St Cuthbert, the results were
variable in the absence of sulphur (S) fertiliser (56–76%). However,
the application of 25 kg ha–1 of fertiliser S was
associated with an increase in the %Ndfa to 89–92% and a 5½-fold
increase in the symbiotically fixed N. Application of small
amounts of S fertiliser to areas with naturalised legumes within
semi-arid grassland offers potential for improving the sustainability
of grazed tussock grasslands.
Keywords haresfoot clover; N fixation;
nutrient balance;
sulphur; sustainability; Trifolium arvense; tussock grasslands
A04060; Online publication date 2 November 2007; Received 10 June
2004; accepted 16 August 2007
New Zealand Journal of Agricultural Research, 2007, Vol. 50:
511–521
0028–8233/07/5004–0511 © The Royal Society of New Zealand 2007
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