New Zealand Journal of Agricultural Research abstracts
Productivity of grazed perennial ryegrass dairy pastures from different
ecotypes under nitrogen and irrigation treatments
I. BAHMANI
E. R. THOM*
Dairying Research Corporation
Private Bag 3123
Hamilton, New Zealand
C. MATTHEW
Institute for Natural Resources
Massey University
Private Bag 11-222
Palmerston North, New Zealand
G. LEMAIRE
Institut National de la Recherche Agronomique
Unité d'Ecophysiologie des Plantes Fourragères
F-86600 Lusignan, France
Abstract A two-year experiment (1996-1998) was conducted at
Hamilton, New Zealand, to compare the productivity of perennial ryegrasses from
different ecotypes, under rotational grazing by dairy cows. `Ellett' ryegrass,
representing the Mangere ecotype, a major source of parent material for current
perennial ryegrass cultivars, was compared with `Grasslands Ruanui'
representing an older Hawke's Bay ecotype. Nitrogen (N) fertiliser and
irrigation were subplot and sub-subplot treatments, respectively. Total herbage
accumulation over two years was 13% greater for `Ellett' ryegrass than for
`Grasslands Ruanui', with higher herbage production occurring mainly in spring
and summer. `Ellett' ryegrass had a consistently higher tiller weight and lower
tiller density than `Grasslands Ruanui'. Tiller density response to N was much
greater for `Grasslands Ruanui' (+8698 tillers m-2) than for
`Ellett' (+969 tillers m-2) over the second year (spring 1997 to
autumn 1998). Both ryegrass cultivars showed increased herbage accumulation and
tiller weight when treated with N. Cultivar herbage accumulation was increased
on average by 30% over the whole trial in response to N, but by only 19% in
summer in response to irrigation. `Ellett' ryegrass showed more pulling than
did `Grasslands Ruanui' during grazings over summer and autumn, especially when
treated with N, but this had only minor effects on yield. Data on the
reproductive behaviour of perennial ryegrass cultivars and tillering responses
to N applied in spring-summer, could provide useful selection criteria for
persistence under intensive dairying. Ryegrass cultivars with different
morphologies and tillering responses to N may require different grazing
managements to optimise their performance. Pulling losses in summer are likely
to be greater for cultivars with large upright tillers and when N fertiliser is
applied.
Keywords `Ellett' ryegrass; `Grasslands Ruanui' ryegrass;
Lolium perenne; herbage accumulation; tiller density; tiller weight;
ryegrass pulling; pasture botanical composition; dairy cow grazing
New Zealand Journal of Agricultural Research, 2001, Vol. 44: 123-133
0028-8233/01/4402&3-0123 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (944K); (scanned from paper original: notes about this process)
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