New Zealand Journal of Agricultural Research abstracts
Effects of variation in shade level, shade duration and light
quality on perennial pastures
M. B. Dodd
A. W. McGowan
I. L. Power
AgResearch Ltd
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand
mike.dodd@agresearch.co.nz
B. S. Thorrold
Dexcel Ltd
Private Bag 3221
Hamilton, New Zealand
Abstract Two experiments examining the effect of
artificial shade on pasture net herbage accumulation (NHA), botanical
composition and soil characteristics were conducted between 1994 and
1999 at Whatawhata Research Centre. Both experiments included a range
of shade levels (0–94%) and shade durations (3–12 months per year).
Experiment 1 also included a light quality treatment, incorporating a
range in the red:far red ratio (0.49–1.00). All three shading factors
decreased annual NHA, with the most influential being the level of
shade, which accounted for 68% of the variation and reduced NHA by
20–80% compared with open pasture. The second most influential factor
was shade duration, which accounted for only 6% of the variation in
NHA. Shading also led to changes in pasture botanical composition, most
notably a decline in legume content in both experiments. There was no
evidence that hairy pasture species (grasses or legumes) had any
advantage over glabrous species under shade. At shade levels >60%,
herbage nitrogen concentrations were elevated by 0.2 percentage points
on a per unit dry weight basis, although reduced pasture NHA under
higher shading meant lower demand for soil nitrogen. Potential nitrogen
mineralisation measurements also indicated that nitrogen cycling is
likely to be reduced under shading.
Keywords light quality; nitrogen; pasture net
herbage accumulation; shade level; shade duration
A04104; Received 9 December 2004; accepted 1 August 2005; Online
publication date 18 October 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48:
531–543
0028–8233/05/4804–0531 © The Royal Society of New Zealand 2005
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