Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Ann Hamblin, Bureau of Rural Sciences, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06748 5
Nutrient and carbon cycling (continued)
Adoption of regular soil and plant testing is an excellent indicator of good farming practice, but depends on having sufficient servicing infrastructure to conduct necessary analyses. Some testing was offered by State agricultural agencies in the past, but since the 1980s, fertiliser companies have taken over this function. The Western Australian fertiliser company CSBP was the first to initiate a large-scale testing service for a suite of plant nutrients and soil properties. Their data, recorded in a GIS database, has proved to be an invaluable resource for monitoring trends in soil fertility (Hamblin and Kyneur 1993).
The growth of soil testing has been slower in other agricultural regions. Figure 67, based on work by Peverill (1993) and Reuter (2001), demonstrates that there has been a big increase in the 1990s, with the advent of a quality assurance scheme for testing laboratories. This increase is still dominated by the Western Australian component, which represents over 60% of the total. Density of sampling is also high in all horticultural and broadacre cropping regions, and most intensive grazing regions of South Australia, but numbers are lower throughout eastern Australia. The actual number of landholders testing soil has been recorded from time to time through surveys. The proportion of landholders who use testing ranges from 30-70% across different industries, years and regions (SCARM 1998).
Figure 67: Number of soil test samples from farms analysed, 1987-1999.
Sources: Peverill (1993), Reuter (pers. comm.)
As with various land uses, nutrients are not in balance in most cropping soils. Potassium is not being replaced when it becomes deficient in many lower-input farming regions, whereas phosphorus and nitrogen are in excess in highly intensive farming regions. This is a particular concern in higher rainfall regions, such as coastal regions growing sugarcane, horticultural crops and dairy pastures, where nutrient discharges are contributing to reduction in water quality. This observation is true for most of the eastern half of the Murray-Darling Basin, and east coast catchments in New South Wales and Queensland.
While the number of soil tests has doubled in the past decade, a substantial proportion of farmers in the Intensive Land-use Zone still do not test their soils. The explanation for this is complex but it includes a spectrum from unprofitable farms that cannot afford good environmental management, to poor management practice, including excessive nutrient application contributing to off-site impacts with adverse environmental effects.