Studies on the Mitchell Grass Association in South-Western Queensland. 3. Pasture and Wool Production Under Different Rates of Stocking and Continuous or Rotational Grazing.

Abstract

Pasture productivity and wool production on the Warrego Mitchell grass (Astrebla spp.) rangeland in south-westem Queensland were studied over a period of 13 years under continuous or rotational grazing, each at three stocking rates. The stocking rates were one sheep to three, two or one hectares and the rotational grazing was a six- monthly system of summer or winter grazing. The grazing treatments were applied over two five- year terms with a nil-grazing period at the conclusion of each. The latter periods provided a means of measuring the cumulative effects of the grazing treatments. Drought conditions prevailed during the first term so that supplementary feeding was necessary, but the second experienced above average rainfall. Quarterly measurements were made of the pasture dry matter on offer and its botanical and chemical composition. Monthly sheep liveweights, annual wool production and sheep size development in each term were also measured and monetary returns from wool calculated. Rainfall had a major influence on the results recorded and tended to nullify the effects of grazing treatments. Its unpredictability precludes the reliable use of complex techniques in management planning. The overall results suggested that the optimum grazing management of this Mitchell grass rangeland would be continuous grazing at a stocking rate of one sheep to two hectares. Supplementary feeding during drought would be obligatory and should be budgeted for in long-term planning. There was a 50% higher monetary return from this grazing treatment than from the lighter stocking rate and pasture stability (maintenance of Astrebla spp.) was sustained. Pasture stability was adversely affected by the heavier stocking rate. There was no srlstained advantage from rotational grazing compared with continuous grazing.

What drives plant biodiversity in the clay floodplain grasslands of NSW?

“…when grass cover is high) (Wright 2001) Moderate decrease Cultivation, extended periods of over-grazing Extended periods of drought often in combination with livestock grazing (Francis 1935;Williams and Roe 1975;Orr 1981), increased flooding frequency during growing season (Hall 1982;Bowman et al 1997) Moderate increase Removal of livestock grazing (e.g. Kirramingly Nature Reserve), although this may not be sufficient after extended periods of cultivation Careful grazing management involving rests from grazing and low stocking rates to allow recruitment of all native species (including long-lived perennial grasses) (Campbell 1989;Roe and Allen 1993;Campbell et al 1996;Bowman et al 1997), a series of good seasons (i.e. with above average summer rainfall) (Orr 1981;Orr and Holmes 1984;Fensham et al 2000) Major decrease Extended periods of cultivation (>10 years consecutive) Extended periods of over-grazing (Francis 1935;Beadle 1948;Williams and Roe 1975;Orr 1980a;Bowman et al 1997;Phelps and Bosch 2002), note: recovery from such disturbance from the seed bank is more likely than following extended periods of cultivation…”

Impacts of level of utilisation by grazing on an Astrebla (Mitchell grass) grassland in north-western Queensland between 1984 and 2010. 2. Plant species richness and abundance

“…are the ecological matrix species (Grubb 1986), these grasslands also contain a diverse range of interstitial grass and forb species (Weston and Moir 1969;Lorimer 1978;Hall and Lee 1980;Orr 1981Orr , 1986Roe and Allen 1993;Phelps and Bosch 2002). The presence or absence of these interstitial species is strongly influenced by the distribution and trends in seasonal rainfall (Lorimer 1978;Orr 1981Orr , 1986Orr et al 1988;Roe and Allen 1993). Summer rainfall results in the presence of a range of perennial grasses e.g.…”

Managing for rainfall variability: effect of grazing strategy on cattle production in a dry tropical savanna

“…The paradigm of 'more cattle equal more money' is difficult to challenge, given the disparate experimental and anecdotal evidence available. The majority of previous grazing trials in Queensland are of limited relevance to the extensive native pastures of the north, either because they involved exotic legumes and/or grasses (Winks et al 1974;Jones 2003) or were conducted in southern (Shaw and t'Mannetjie 1970;Scattini 1973), central or western Queensland (Roe and Allen 1993).…”