New Zealand Journal of Agricultural Research abstracts
Effects of improved, adapted white clover (Trifolium repens L.)
germplasm on the productive properties of a hill pasture
D. F. Chapman*
J. R. Caradus
AgResearch Grasslands
Private Bag 11008
Palmerston North, New Zealand
*Present address: Department of Agriculture and Resource Management,
University of Melbourne, Parkville, Victoria 3052, Australia.
Abstract White clover (Trifolium repens L.)
herbage accumulation rate, nitrogen (N) fixation rate and efficiency, and plant
growth characteristics were compared in pastures based on eight white clover
lines on north- and south-facing sites under sheep grazing in southern North
Island hill country during years 4-7 following oversowing. The lines compared
included three cultivars (`Grasslands Tahora', `Grasslands Prestige', and Prop)
bred for hill country and/or sheep grazing systems with (notionally, at least)
a moderate-high degree of adaptation to the environment, and two cultivars
(`Grasslands Huia' and `Grasslands Kopu') known to have moderate-low
adaptation. The control treatment comprised pastures based on the resident
clover ecotype of the site, seed of which was sown at the same rate as the
other lines. Two of the adapted lines (Tahora, Prestige) yielded significantly
more white clover herbage than the resident ecotype over 3 full years of
measurement. Prestige displayed consistently greater cool-season growth in late
winter-early spring than all other lines. All three adapted cultivars fixed
significantly more N than the resident ecotype over 12 months (mean for
resident = estimated 64 kg N/ha per year compared to mean for three
cultivars = 100 kg N/ha per year). There was a close linear relationship
between white clover herbage accumulation rate and clover stolon density in
most years and on both aspects. The adapted lines developed greater stolon
densities through superior branching ability (higher frequency of occurrence of
branches at stolon nodes). There was evidence that the adapted clover lines
were able to compete more effectively with grasses for growth resources at some
times of the year, e.g., for mineralised N in late winter-early spring,
resulting in lower N fixation efficiencies for Tahora and Prestige (mean
43 kg N fixed/t clover DM grown, versus 122 kg N/t clover DM for the
resident ecotype). There were no statistically significant effects of clover
line on total annual pasture herbage accumulation, but a difference between
Prestige and all other lines in total pasture growth in winter gradually
strengthened over 4 years of measurement so that, in the final year measured
(year 7 after sowing), a statistically significant effect of line was
recorded. In this winter, Prestige-based pastures grew 1130 kg DM/ha over
65 days from early June to late August, whereas resident pastures grew
570 kg DM/ha. The results are discussed within the context of pasture
improvement strategies in hill country. Several important effects of adapted
germplasm on the productive properties of hill pastures are identified.
Keywords white clover; Trifolium repens L.; hill
country; cultivars; adaptation; plant growth; nitrogen fixation; pasture
productivity
New Zealand Journal of Agricultural Research, 1997, Vol. 40: 207-221
0028-8233/97/4002-0207 $7.00/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (1180K); (scanned from paper original: notes about this process)
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