New Zealand Journal of Agricultural Research abstracts
Relationship of tillering and morphological characteristics of two perennial
ryegrass lines to “pulling” when grazed by dairy cows
E. R. Thom
V. T. Burggraaf
R. J. Watts
R. J. Hooper
Dexcel
Private Bag 3221
Hamilton, New Zealand
Abstract The morphology and sward structural characteristics
of two perennial ryegrass pipeline (pre-commercial) selections that showed
different “pulling” tolerances, were studied at Hamilton, New Zealand. Pulling
was defined as the removal of clumps of ryegrass plants from the sward during
grazing. One line, coded as NZA1, was less tolerant of pulling than was the
other, coded as NZA3. NZA3 is now commercially available as the cultivar
‘Bronsyn’. The ryegrass lines were established in small plots in May 1994
on a silt loam and a peaty silt loam soil. Half the area of each plot received
nitrogen (N) fertiliser (30 kg N ha-1) after each grazing, and
tiller dynamics were monitored from September 1995 to April 1996. NZA1 had
a higher leaf shear strength (6.21 versus 5.91 kg, standard error of difference
(SED) = 0.087), wider leaves (3.621 versus 3.252 mm, SED = 0.0535), and a
lower clump shear strength (13.4 versus 14.9 kg, SED = 0.57) than did NZA3.
N fertiliser did not affect leaf shear strength, and tillering responses
to N fertiliser were inconsistent. It is argued that better anchorage combined
with leaves that break more easily when grazed contributed to less pulling
of NZA3 than of NZA1 clumps during dry summers.
Keywords ‘Bronsyn’ ryegrass; Lolium perenne;
tiller dynamics; leaf morphology; leaf appearance rate; leaf shear strength;
clump shear strength; nitrogen fertiliser; dairy cow grazing
A02034 Received 27 June 2002; accepted 5 November 2002; published 26 March
2003
New Zealand Journal of Agricultural Research, 2003, Vol. 46: 15-25
0028-8233/03/4601-0015 $7.00/0 © The Royal Society of New Zealand
2003
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