Looking back in time: can safe pasture utilisation rates be determined using commercial paddock data in the Northern Territory?

Abstract

A ‘safe’ pasture utilisation rate is defined as the proportion of annual forage growth that can be consumed by domestic livestock without adversely affecting land condition in the long term. Pasture utilisation rates are thus a cornerstone of a sustainable grazing industry because they directly determine livestock carrying capacity. Until now, it has only been possible to determine utilisation rates in the Northern Territory via expensive and time-consuming grazing trials. Reliance on this method has limited the validation of safe utilisation rates for the range of land types used for pastoral production. This study tested an alternative cost-effective method for calculating utilisation rates based on an approach used previously in Queensland. The method retrospectively calculates utilisation rates using cattle records and modelled pasture growth from commercial paddocks in good land condition. The assumption underpinning the method is that paddocks in good land condition, with a long history of grazing, must have been managed in such a way as to achieve a safe level of pasture utilisation. Utilisation rates were calculated for 10 commercial paddocks on three properties in the Barkly Tableland region of the Northern Territory from 1999 to 2009. Animal intake for each paddock was calculated from detailed cattle records held in property databases. Pasture growth was estimated using simulation models and cross-checked with field measurements. An average utilisation rate of up to 25% of annual pasture growth was found to be safe on highly uniform, grey cracking-clays supporting Mitchell grass (Astrebla F. Muell. spp.) pastures. However, this level of utilisation had negative impacts on land condition on less resilient and preferentially grazed pasture communities in paddocks with a mix of land types. The implications of the results for carrying capacity, animal productivity and seasonal risk management are explored in this paper.

Boosting the productivity and profitability of northern Australian beef enterprises: Exploring innovation options using simulation modelling and systems analysis

“…Consequently, the total numbers of breeders carried in the model herds were adjusted in the various simulation trials through a parameter that sets maximum breeder numbers so as to maintain safe pasture utilisation rates to maintain or improve land condition over the length of each trial. There has been considerable effort to determine sustainable utilisation rates for tropical rangelands in northern Australia (e.g., Scanlan et al, 1994;Walsh and Cowley, 2011) and this information was used in setting stock numbers to achieve safe utilisation rates in the simulation runs.…”

Accounting for liabilities related to ecosystem degradation

“…The sustainable use of the ecosystem for grazingi.e., its long-term carrying capacity for grazingis defined as the number of adult equivalent (AE) cattle that can be carried on the property over a range of seasons without negatively affecting the condition of the ecosystem. Long-term carrying capacity is calculated by multiplying estimates of long-term annual pasture growth by a proportion reflecting the amount available for sustainable consumption by livestock and then dividing by the biological annual forage demand for one AE (Walsh and Cowley 2011). Annual pasture production is a function of the type, extent and condition of the ecosystem asset and the seasonal conditions experienced.…”

Rain on the Rangelands - Adaptive management is alive and functioning

“…Johnston et al 1996). In their paper, Walsh and Cowley (2011) investigate the effectiveness of using the safe utilisation concept within a modelling framework to determine the number of livestock that can be profitably carried long-term yet still maintain land condition. They show that careful collection of historical information on commercial operations, together with comprehensive modelling of pasture production, can successfully lead to safe stocking rates in rangelands of the Northern Territory.…”

“…In its own way, each of these papers gives substance to adaptive management. Each has elements of defining and analysing problems (Whalley et al 2011); designing solutions (Russell et al 2011;Wakelin-King 2011); selecting and implementing changes (Walsh and Cowley 2011); monitoring, interpreting and evaluating indicators (Barnes et al 2011;Brown and MacLeod 2011); and going through the learning process repeatedly. Adaptive management, whether purposefully or intuitively, has been an approach taken by many rangeland managers and reported often.…”