Simulated impacts of wet season spelling and intensive rotational grazing on pasture condition in a degraded northern Mitchell grass savanna

Simulated impacts of wet season spelling and intensive rotational grazing on pasture condition in a degraded northern Mitchell grass savanna Conference Proceedings

Australian Rangeland Society 19th Biennial Conference: Transition to Transformation

• Author(s): Robyn Cowley, Dionne Walsh, Jane Douglas
• Published: 2017
• Publisher: Australian Rangeland Society

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Abstract: The northern Australian pastoral industry is intensifying development and grazing systems to facilitate greater productivity and capital value. A three year field trial in the Barkly region of the Northern Territory (Beetaloo) comparing intensive rotational grazing (IRG) combined with wet season spelling (WSS) to set stocking (SS) at similar average annual stocking rates (SR) and paddock sizes, found no change in pasture condition in either grazing system. Given the short duration of the trial we used GRASP to simulate how the intensified grazing system might influence pasture condition in the longer term (30 years) comparing: 1) continuous SS; 2) SS with an annual 3 month WSS; and 3) annual WSS with IRG; for a range of graze dates, climate windows, starting pasture conditions and SR. SR that facilitated pasture recovery in drier climate windows or from C condition pastures were 2/3 of safe SR in wetter climate windows or B condition pastures. Adding WSS to SS facilitated faster pasture recovery times at higher safe SR. For WSS + IRG, if any of the grazes were during the growing season, the SR that promoted pasture recovery was one to two thirds less than the safe SR when grazing occurred only during the dry season. Dry season IRG + WSS had higher safe SR and shorter recovery times than the Grazing Land Management (GLM) derived carrying capacity with continuous grazing, or SS + WSS. This study suggests that WSS + IRG may be a useful tool to enhance recovery of degraded grasslands. However, recovery timeframes were still in the order of decades and any wet season IRG should be avoided or carefully managed to prevent further pasture condition decline.

• Urls: https://www.austrangesoc.com.au/wp-content/uploads/2019/05/Cowley_et_al_Paper_45.pdf, https://web.archive.org/web/20190305173901/https://www.austrangesoc.com.au/data/ARSC2017/2017_Conference_Papers/Cowley_et_al_Paper_45.pdf
• Publisher Location: Port Augusta
• Keywords: land condition, rangeland management, modelling, grazing systems, spelling