Ar. Lawson et al., EFFECT OF DEFOLIATION FREQUENCY ON AN IRRIGATED PERENNIAL PASTURE IN NORTHERN VICTORIA .1. SEASONAL PRODUCTION AND SWARD COMPOSITION, Australian Journal of Agricultural Research, 48(6), 1997, pp. 811-817
A field experiment was carried out to investigate whether changes in w
inter and post-winter defoliation frequency would increase the white c
lover content of an irrigated perennial ryegrass-white clover pasture
in northern Victoria. Pastures defoliated every 4 weeks during winter
had higher white clover growing point (stolen apices with at least 2 n
odes) density at the end of winter than pastures defoliated every 8 we
eks or those receiving a single defoliation after 16 weeks, but these
differences did not affect the clover content in the spring. Reasons f
or this are suggested. Pastures defoliated at 8-week intervals in wint
er were the most productive over winter-early spring. Less frequent de
foliation (4 v. 2 weeks) during the post-winter, September-May period
reduced white clover growing point and perennial ryegrass tiller densi
ties. However, the white clover growth rate during this period was inc
reased by less frequent defoliation, whereas the ryegrass growth rate
was reduced, resulting in an increase of 10% in the white clover conte
nt, and a 1.9 t dry matter (DM)/ha increase in total DM produced. This
higher clover content and pasture yield during spring-autumn with les
s frequent defoliation has important implications for the management o
f irrigated perennial pastures for the dairy industry in northern Vict
oria.