New Zealand Journal of Agricultural Research abstracts
Effect of spring grazing management on perennial ryegrass and ryegrass-white
clover pastures
1. Tissue turnover and herbage accumulation
A. HERNÁNDEZ GARAY1
J. HODGSON
C. MATTHEW
Department of Plant Science
Massey University
Private Bag 11-222
Palmerston North, New Zealand
1 Present address: Programa de Ganaderia, Colegio de Postgraduados,
Montecillo, Texcoco Edo. de México, México CP 56230.
Abstract The aim of this study was to investigate the effects
of timing and duration of lax spring grazing on rates of leaf growth, botanical
composition, and pasture production in perennial ryegrass swards, with and
without white clover. In the first field experiment (September 1992-March
1993), swards of perennial ryegrass with and without white clover were
rotationally grazed by sheep every 21 days to residual heights of 70-100 mm
(lax) and every 14 days to 30-50 mm (hard). Two periods of lax grazing--short
release (SR) from 26 October to 8 December and long release (LR) from 15
September to 8 December--were compared with conventional hard grazing
throughout--early control (EC). All treatments were grazed to 30-50 mm every 14
days from 8 December until the end of March. Swards without white clover
received 28 kg nitrogen (N)/ha every 2 weeks as urea. Treatments were arranged
in a factorial design with three replicates. Overall, herbage accumulation in
the SR and LR treatments was increased by 20 and 30%, respectively, compared to
the EC treatment (P <= 0.001). Leaf growth in ryegrass and white
clover was also increased following lax grazing. In the second field experiment
(September 1993-April 1994) plots were subjected to similar grazing
managements, though all spring treatments were imposed at a consistent grazing
interval of 21 days and N use on non-clover swards was reduced to 14 kg/ha
every 2 weeks. SR and LR treatments increased herbage production during spring
by 24 and 28%, respectively, by increasing tiller weight, and during summer and
autumn by 16 and 26% by enhancing tiller population density and leaf growth per
tiller and/or stolon. Spring management effects were similar for swards with
and without white clover. It is concluded that lax spring grazing management of
ryegrass-white clover swards followed by hard grazing at the time of anthesis
enhances pasture production, particularly during the summer-autumn period, by
increasing both tiller population density and net leaf growth per tiller.
Effects were larger following an extended spell of lax grazing. Contribution of
tiller population density differences to these responses is discussed in the
second paper in this series (Hernandez et al. 1997, this issue).
Keywords spring grazing management; herbage production;
perennial ryegrass
New Zealand Journal of Agricultural Research, 1997, Vol. 40: 25-35
0028-8233/97/4001-0025 $2.50/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (868K); (scanned from paper original: notes about this process)
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