Managing for rainfall variability: long-term profitability of different grazing strategies in a northern Australian tropical savanna

Abstract

Several grazing strategies are recommended to manage sustainably for rainfall variability in northern Australia, but there is little objective data on their profitability relative to less sustainable management systems such as heavy stocking. In 1997, a large cattle grazing trial was initiated in northern Queensland to quantify the relative performance of a range of grazing strategies in a variable climate. These strategies were (i) moderate stocking (MSR) stocked at the calculated long-term carrying capacity (LTCC), (ii) heavy stocking (HSR) at twice LTCC, (iii) rotational wet-season spelling (R/Spell) at 1.5 LTCC, (iv) variable stocking (VAR), with stocking rates adjusted in May based on available forage and (v) a southern oscillation index (SOI)-variable strategy, with stocking rates adjusted in November based on available forage and SOI-based seasonal forecasts.Rainfall varied over the 12-year trial period, with sequences of dry and wet years. Gross margins (GM) in the HSR were initially high but collapsed in drier years due to high costs and reduced product value. GMs only recovered in later years with a reduced stocking rate and increased rainfall. The VAR and SOI were also initially very profitable, but GMs plunged as rainfall declined due to reduced animal performance and the sale of poor-condition cattle. This sharp cut in stocking rates nevertheless allowed GMs to recover well in subsequent years. In the MSR, GMs remained relatively constant across most years due to low costs and a higher product value. The R/Spell also performed relatively well despite being compromised by an ill-timed fire, drought and the subsequent sale of poor-condition cattle.

Comparing the climate experienced during the Cicerone farmlet experiment against the climatic record

“…Ideally, given the marked influence climate has on pasture and livestock outcomes (Jones et al 1995;O'Reagain et al 2011), the length of the experimental period for farming systems research should be sufficient to allow adequate representation of the expected range of climatic conditions (Walker 1988). This would enable sufficient demonstration of treatment responses and would reduce the need for assumptions or modelling to extrapolate responses to climatic conditions for which there are no data to support calibration.…”

“…climatic records over the long term (Laws et al 2000;O'Reagain et al 2011). Climate is especially important when the treatments being evaluated, such as changes in soil fertility and botanical composition, are known to take many years to reach equilibrium (Walker 1988;Jones et al 1995).…”

Plant adaptation to climate change—opportunities and priorities in breeding

“…A local impact of intense low-pressure systems, including cyclones, is the combination of intense rainfall and high wind speeds, which causes lodging and reduction of sugar content in sugarcane (Singh et al 2002) and, potentially, damage to plantation forests. Northern inland pasture systems are generally favoured by La Niña events (Park et al 2003) and could respond positively to climate change in terms of productivity, albeit with a need to buffer production between years of high and low rainfall (O'Reagain et al 2011). Any increase in growing season temperature or in high-temperature events will affect the dynamics of production, but adaptation can be implemented through pasture and animal management .…”

Integrated overview of results from a farmlet experiment which compared the effects of pasture inputs and grazing management on profitability and sustainability

“…In a study of different grazing strategies in northern Queensland, O'Reagain et al (2011) found that, under variable climatic conditions, the best financial and sustainable outcomes over the long term were achieved through a variable stocking strategy that allowed the adjustment of stocking rate early in each dry season. Such a system is similar to the flexible grazing management employed on farmlets A and B in the present experiment.…”