Agriculture Reference
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Figure 9.7 Changes in Nardus stricta cover in a grassland under sheep and cattle
grazing treatments.(Adapted from Grant et al. ,1996.)
duction than other species in the sward. However, it was grazed much less by
sheep than by cattle. Cattle also uprooted N. stricta tillers while grazing. This
weedy tussock grass had lower tiller base weight and energy reserves under
cattle grazing, which reduced its ability to recover after defoliation.
Goat grazing is highly effective for weed and brush control in sheep or
cattle pastures (Wood, 1987; Underwood et al ., 1996). Rolston, Lambert &
Clark (1982) and Rolston et al . (1981) studied effects of mixed-species grazing
on a weedy pasture in New Zealand. Treatments included mob-grazing and
set-grazing of sheep, goats, or sheep and goats (continuous grazing at a fixed
level).The flock mix for sheep and goats was either 33%/67% or 67%/33%.The
presence of goats in any proportion effectively controlled Cirsium palustre and
C. vulgare (Table 9.2), but was ineffective against C. arvense . Goats at 100% and
66%,but not 33%,reduced Juncus spp.height (Table 9.2) and opened clumps to
invasion by forage species. Goats at 100% and 66% decreased Ulex europaeus
height and survival after two years of grazing (Table 9.2). Mob-grazed sheep
had nearly double the annual grazing days ha 1 of the set-grazed sheep and
proved highly effective for U. europaeus control. Mob-grazing was partially
effective against C. vulgare , C. palustre , and Juncus spp. (Table 9.2). Rolston et al .
(1981) emphasized that the experiment demonstrated the importance of the
use of an appropriate mix of grazing species, small paddocks, and high stock-
ing rates to achieve adequate grazing pressure for weed control and sward
vigor.
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