Effect of chemical removal of grasses from pasture leys on pasture and sheep production

Abstract

Pasture production, pasture composition and quality, and liveweight, body condition and wool growth of Merino weaner wethers were monitored over 2 seasons and at 2 stocking rates (4 and 8 sheep/ha) on a mixed annual grass-legume pasture sprayed with propyzamide to control grasses. Propyzamide virtually eliminated annual grasses from the pasture (less than 5 kg/ha of grass dry matter in spring v. 403 kg/ha on untreated pasture in 1981) and this carried over into the second season (61 kg/ha v. 647 kg/ha in spring 1982). Propyzamide treated pastures had less total dry matter (P = 0.05) throughout 1981: however, except for a single sample date, there was no effect of propyzamide on total available pasture in the second season. Increased growth of clover and capeweed compensated for the absence of the grasses. The higher stocking rate reduced available clover, capeweed and total dry matter (P = 0.05) throughout both years. Sheep grazing grass-free pastures had lower liveweights during winter in both years, but made compensatory gains during late spring and summer consistent with the higher quality (1.6 v. 1.07% nitrogen when sampled in January) of propyzamide treated pastures. In 198 1, wool growth rates were reduced at the higher stocking rate and total clean wool production was reduced from 4.55 kg/sheep at 4/ha to 3.65 kg/sheep at 8/ha. Pasture treatment had no effect on wool production in either year. The implications of using selective herbicides to remove the annual grass component of legume-based annual pastures in south-western Australia are dis cussed in relation to pasture and sheep production.

The Impact of Herbicide Application and Defoliation on Barley Grass (Hordeum murinum subsp. glaucum) Management in Mixed Pasture Legumes

“…The subsequent invasion of Vulpia spp. and other weeds and the consequent increase in clover biomass following barley grass removal are consistent with findings of previous studies investigating annual weed management in pasture legumes [25]. Such shifts in botanical composition were also likely supported by previous annual superphosphate applications [14] and the limited competition afforded by the sparse legume population.…”

“…Such shifts in botanical composition were also likely supported by previous annual superphosphate applications [14] and the limited competition afforded by the sparse legume population. Successful pasture production encompasses practices which assist the maintenance of an established, competitive legume pasture following herbicide application to limit future annual grass invasion and prevent their occupation in niches created by barley grass control earlier in the season [25,57].…”

Response of Mediterranean grassland to phosphate and stocking rates: livestock production

“…Farmers send sheep to communally owned grasslands in spring (Cocks & Thomson 1988) once pasture availability reaches c. 500 kg/ha, the amount necessary to maintain liveweight in non-lactating sheep (Willoughby 1959;Broom & Arnold 1986;Thorn & Perry 1987). Lactating sheep continue to receive supplementation, often throughout the spring, or until available herbage reaches 1500 kg/ha.…”