New Zealand Journal of Agricultural Research abstracts
Effect of oversown ryegrass (Lolium perenne) and white clover
(Trifolium repens) on the genetic structure of New Zealand hill
pastures
M. E. WEDDERBURN
AgResearch
Whatawhata Research Centre
Private Bag 3089
Hamilton, New Zealand
K. D. ADAM
Rayonier New Zealand Ltd
P.O. Box 9283, Newmarket
Auckland, New Zealand
L. A. GREAVES
J. L.CARTER
AgResearch
Whatawhata Research Centre
Private Bag 3089
Hamilton, New Zealand
Abstract The botanical composition and genetic structure of
North Island hill pastures were studied after oversowing. Three pre-sowing
treatments were applied: (a) no herbicide; (b) herbicide to suppress existing
pasture; and (c) herbicide to kill existing pasture. Four oversowing treatments
were imposed: (1) no oversowing; (2) hill country ryegrass and `Prop' white
clover; (3) `Yatsyn' ryegrass and `Prop' white clover; and (4) a mixture of
hill country grass species. Five times as many ryegrass seeds were oversown
than emerged from buried seed, giving the introduced material an advantage. The
ryegrass content was greater at the high-fertility sites than at the
low-fertility sites, both before and after oversowing. Killing the original
pasture tended to increase ryegrass content for 16 months at the low-fertility
sites but increased the ryegrass content for less than 9 months at the
high-fertility sites. The ryegrass content was not significantly different on
any of the sown and unsown plots, 16 months after oversowing. Ryegrass
populations, in sown plots on the high-fertility northerly aspect, comprised
70% of the introduced ryegrass and 30% of resident ryegrass, 2 years after
oversowing. The number of white clover seeds sown was 70% of that germinating
from buried seed, giving the resident material an advantage. As a result, the
white clover content was similar in sown and unsown plots, and the introduced
white clover germplasm contributed 30% of the clover plant population. At 5
months after oversowing, white clover content was greater under the suppress
herbicide. Soil fertility had the greatest influence on both ryegrass and white
clover content. Sowing "other grass" species increased their content in the
pasture and, after 16 months, Agrostis capillaris was the dominant other
grass followed by Dactylis glomerata and Holcus lanatus. The
results suggest that the genetic structure of ryegrass populations can be
changed at high fertility levels provided no large ryegrass seed pool exists,
but changes in the content and genetic composition of white clover are more
difficult to achieve. The seedling establishment phase is critical for
successful introduction of new genotypes and herbicide had little effect at
this time.
Keywords Lolium perenne; Trifolium repens;
Agrostis capillaris; low-fertility grass; weed; buried seed; seedling
number; herbicide; hill pasture; oversowing; allozymes
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 41-52
0028-8233/96/3901-0041 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (944K); (scanned from paper original: notes about this process)
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