Land Capability Assessment and Estimation of Pastoral Potential of Semiarid Rangeland in South Australia

Abstract

An Environmental Resource Assessment and Management System (ERAMS), a computer-aided decision support system developed for determination of present and potential pastoral productivity of arid and semiarid regions, was used in this study on rangelands that have been cropped or grazed by sheep or both for 150 years. ERAMS determines productivity of mapped land units on the basis of soil-water availability. This in turn is dependent on annual rainfall, slope, soil depth, salinity, and physical and chemical constraints. Stock carrying capacity is dependent on vegetation type and condition, based on foliage cover and botanical composition, and nutritive value of the pasture. Physical and biological features are determined by field survey. ERAMS has been used to examine the likely impacts of management strategies that alter either the vegetation type, vegetation state, or degree of erosion. Six Land Capability classes were derived from combinations of rainfall, slope, soil depth, and salinity. Total dry matter production was calculated and ranged from 58 kg−1 ha−1 to 1980 kg−1 ha−1 Rainfall use efficiency (kg−1 ha−1 of total dry matter mm−1 of mean annual rainfall) ranged from 3.05 to 4.07. Comparison of present and potential production indicates the likely benefits of programs designed to increase carrying capacity through improved vegetation cover and land stability.