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Estimating safe carrying capacities for grazing properties

Johnston, P.W. Dr; Ph: (07) 3362 9577; Fax (07) 3362 9429; mailto:johnstonp@dpi.qld.gov.au

Research organisation: Queensland Department of Primary Industries, Sheep and Wool Institute, GPO Box 3129, Brisbane Q 4001

Sponsors: NHT: Natural Heritage Trust (945078A and 945078C), Queensland Department of Primary Industries, Queensland Department of Natural Resources, Queensland Treasury (South West Strategy)

Objectives:

1. To conduct an objective assessment of the safe long-term livestock carrying capacity of each property in south west Queensland.

2. To provide an objective basis for evaluating property build up schemes.

Methodology: Safe carrying capacity assessments formed part of the Natural Resource Management component of the South West Strategy. The South West Strategy was and is still a regional recovery program aimed at addressing the problems of economical sustainable production, natural resource management, social issues and regional development.

The work evolved from the demand for an objective examination of "stocking rates" and "carrying capacities" across south west Queensland in the late 1980's and early 1990's. Three independent reports documented this demand (Warrego Graziers Association 1988, Mills et al. 1989 and Anon. 1993). Based on this demand a model to objectively assess the long-term livestock carrying capacity of individual properties was developed (Johnston et al. 1996a). The model was evaluated on 20 benchmark properties by two graziers employed as consultants. Following this evaluation the grazier consultants recommended the broader application of the model (Crichton 1995 and Cooney 1995).

The broader application occurred in two separate activities conducted under the South West Strategy:

The first was the voluntary participation by graziers in an assessment of the long-term livestock carrying capacities conducted by staff of the DPI. Voluntary participation by graziers was seen as critical to reducing the perceived threat of the work and increasing the learning from the work.

The second activity involved the assessment of the long-term livestock carrying capacities by staff of the DNR as part of an evaluation to access financial assistance under the Enterprise Reconstruction component of the South West Strategy. The same methodology was applied by both agencies.

The aim of an assessment was to objectively assess the long-term livestock carrying capacity of an individual property. An assessment involved the preparation of detailed maps of the paddocks and land systems on a property. After a survey of current land condition, average annual long-term forage production (kg/ha) from the different land systems was estimated. These estimates were the product of an average annual rainfall use efficiency (kg/ha/mm) for each land system and the average annual rainfall (mm) for the property. The rainfall use efficiency values were estimated from primary productivity measurements and pasture growth modelling using the GRASP model. The number of livestock that could be run in order to utilise a safe portion of this forage was then calculated. Safe utilisation levels were derived from grazing trials from the Charleville area, consensus of local knowledge and grazing practices on 'benchmark' properties. As each property was comprised of a unique mix of land systems the assessed livestock carrying capacity was unique to the property.

Progress: A total of 217 properties had participated in objective carrying capacity assessments between February 1994 and August 1998. This represented 37 per cent of the properties in the Murweh, Paroo, Quilpie, Bulloo and Barcoo shires covering an area of 137,439 km2 (45 per cent of the area of the above shires).

A phone survey of participating and non-participating graziers was conducted in April 1998. Participants valued the paddock and land system mapping conducted as part of the assessment. They believed they gained an improved understanding of their property resources, paddock sizes and their relative carrying capacities. One third of participating graziers indicated they had made some change to their grazing management practices following an assessment. Two thirds of these have seen some change in pasture condition since implementing the changes. Graziers reported that where they agreed with the results, they used the information as a benchmark or reference for making stocking decisions or as a check of what they were presently doing.

Period: starting date 1993-01; completion date 1998-08

Status: Suspended, pending new funding from NHT under the South West Strategy to combine the safe carrying capacity and total grazing pressure work (NHT reference 982630).

Keywords: Carrying capacity, stocking rate, rangelands, grazing management, forage utilisation, models, South West Strategy, Queensland.

Publications:

Cooney, D. (1995). Mulga lands carrying capacity survey report. Report to the Queensland Department of Lands, Brisbane.

Crichton, R. (1995). Mulga lands carrying capacity survey report. Report to the Queensland Department of Lands, Brisbane.

Johnston, P.W., McKeon, G.M. and Day, K.A. (1996). Objective 'safe' grazing capacities for south-west Queensland Australia: Development of a model for individual properties. Rangeland Journal 18(2), 244-258.

Johnston, P.W., Tannock, P.R. and Beale, I.F. (1996). Objective 'safe' grazing capacities for south-west Queensland Australia: Model application and evaluation. Rangeland Journal 18(2), 259-269.

 

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