New Zealand Journal of Agricultural Research abstracts
Contamination and persistence of endophyte-free ryegrass pastures established
by spray-drilling, and intensively grazed by dairy cows in the Waikato region
of New Zealand
V. T. BURGGRAAF
E. R. THOM*
Dairying Research Corporation
Private Bag 3123
Hamilton, New Zealand
Abstract The contamination of endophyte-free ryegrass
(Lolium perenne) pastures with volunteer endophyte-infected ryegrass,
and the persistence of endophyte-free ryegrass, were studied over three years
at the Dairying Research Corporation, Hamilton, New Zealand. Plots were sprayed
with glyphosate herbicide in mid March 1996 (sprayed: S), or mid March and
again in mid April (double sprayed: D). A sub-plot treatment allowed the
effects of the presence or absence of white clover (Trifolium repens) to
be studied. All plots were direct-drilled with endophyte-free perennial
ryegrass in late April 1996, and were subsequently rotationally grazed by dairy
cows. Sources of contamination were endophyte-infected ryegrass seed from
reseeding of existing ryegrass, seed consumed by cows and deposited in dung,
and seed buried in the soil, with endophyte infection levels after germination
of 66, 38, and 75%, respectively. Incomplete kill of existing
endophyte-infected ryegrass after herbicide applications was another possible
source of contamination with a 50% endophyte infection level. Contamination of
D plots was consistently less than in S, averaging 25 and 58%, respectively,
after three years, but was <10% of plants in D plots over the first two
years. Reseeding of existing endophyte-infected ryegrass was considered the
most important source of contamination and the soil seedbank the least. Double
spraying reduced competition for establishing endophyte-free ryegrass, which
consistently improved ryegrass survival compared with S, reflecting a higher
pasture ryegrass content for 12 months, but no improvement in herbage
accumulation. White clover level did not influence contamination. The trial
showed that an endophyte-free ryegrass pasture could be maintained for at least
3 years showing similar trends in yield and persistence as high-endophyte based
ryegrass pastures previously monitored at the site.
Keywords dairy cows; dung; endophyte contamination;
glyphosate herbicide; Lolium perenne; Neotyphodium lolii; natural
reseeding; perennial ryegrass; ryegrass pulling; seed transfer; volunteer
ryegrass; ryegrass seed-bank; white clover competition
New Zealand Journal of Agricultural Research 2000, Vol. 43: 163-173
0028-8233/00/4302-0163 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (968K); (scanned from paper original: notes about this process)
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