New Zealand Journal of Agricultural Research abstracts
Quantifying different causes of leaf and tiller death in grazed
perennial ryegrass swards
S. J. R. WOODWARD
AgResearch Ruakura
Private Bag 3123
Hamilton, New Zealand
Abstract Death of plant material in grazed perennial swards results from a number
of processes, particularly leaf senescence, tiller death, and grazing. These
processes must be understood in detail to manage supply of high quality pasture
for, especially, dairy cattle through the reproductive season. Although measurements
have been made under a variety of pasture conditions, a generalised model has
not yet been established. This paper reviews experimental evidence for the
rates of leaf and tiller death resulting from five independent physical and
physiological mechanisms operating in a grazed ryegrass-dominant pasture. First-order
(linear) models are formulated to predict the rates of leaf and stem death
on vegetative and reproductive tillers in such a pasture. Leaf death rate accounts
for 90% of dead matter production in the non-reproductive season, and was found
to be linearly correlated to soil temperature. During reproduction, decapitation
of reproductive stems, usually prior to ear emergence, is the dominant source
of dead material. These models provide an essential component of the detailed
modelling of grazed pasture tissue dynamics.
Keywords senescence; model; pasture; Lolium perenne; reproductive development;
flag-leaf; stem; ear-emergence; maturity-stage; grazing; defoliation; decapitation;
temperature; flowering
New Zealand Journal of Agricultural Research, 1998, Vol. 41: 149-159
0028-8233/98/4102-0149 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (1189K); (scanned from paper original: notes about this process)
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