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Issues ConditionThreatening Processes |
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At a glance 
The issue Soil characteristics, such as drainage status, texture, colour, pH, structural strength and nutrient status cause soils to have greater or lesser capacity to respond to land use management stress. Understanding soil types and their condition can assist management-from farm to regional and Statewide scales-in understanding land capability and in implementing best practice management. Nevertheless, there are large areas of Tasmania, including highly productive agricultural areas, where no soil maps exist. A decline in soil condition results in declining productivity and therefore declining profit. This has economic implications for individual farmers, regions and the State as a whole. Care is needed to ensure that increases in agricultural output in Tasmania are achieved sustainably without leading to a decline in soil condition, which would ultimately lead to a decrease in agricultural productivity. Some parts of the State are subject to pressure for greater intensity of agricultural production. These regions, such as the drier central and inland plains where duplex soils are found, may contain soils susceptible to structure decline and erosion. This 'At a glance' section provides an overview of soil condition. More detailed information is available in the Soil Condition Issue Report. Soil condition indicators are not available at a Tasmania-wide scale. The definition of soil condition and the identification of appropriate indicators that can be reliably measured on a repeatable basis, thereby allowing analysis of trends, is difficult. Water quality in catchments and receiving estuaries is an indirect measure of the health of Tasmania's soils. Accordingly, this Issue Report presents two indicators: Exceedences of Water Quality Guidelines: Inland Waters and Turbidity In Tasmanian Estuaries. Recommendations are provided on Strategic Land Resource Management and Productivity of Soils. Favourable news - Recent work by Cotching et. al. (in prep) indicates that most soils used for cropping in Tasmania are in good condition.
- Soil Management Guidelines have been prepared and published by the Department of Primary Industries, Water and Environment (DPIWE) and the Tasmanian Farmers and Graziers Association (Hamlett 2002). These voluntary guidelines are a broad set of best management practices. They relate to the use of soils for agriculture and include details on planning, maintaining soil structure and organic matter, reducing soil erosion, managing soil salinity, avoiding soil contamination, and managing riparian land. The guidelines complement a number of technical documents relating to land management published by the DPIWE including, Managing Tasmania's Cropping Soils (Chilvers 1996).
- Within forestry areas, the main soil types have been defined and keys for their identification developed. The Forest Practices Act 1985, through the Forest Practices Code, requires that management of forests (e.g. use of machinery, cultivation procedures, slope limits for harvest) is modified to take into account soil factors like erodibility. Guidelines implemented in 2003 have specified increased soil protection next to headwater streams in the forestry estate. These are now being trialled.
Unfavourable news- Grice (1995) estimated that approximately 15% (317,000 ha) of private land in Tasmania is affected by moderate to severe soil structure decline. A more recent comprehensive assessment of the condition of Tasmanian soils has not been undertaken.
- Recent work by Cotching et. al. (in prep.) showed signs of soil structure decline associated with long-term cropping on one third of paddocks on the four soil types investigated. Extrapolation of the results suggest that as much as 38,000 ha of cropping land could be experiencing similar levels of soil structure decline. The work indicates that, on the red Ferrosols of northern Tasmania, yield losses for potatoes resulting from soil structure decline could amount to 14,500 tonnes ($3.2m) per annum. However there remains no comprehensive assessment of soil condition within the agricultural areas of the State.
Uncertain news - Reconnaissance soil maps in Tasmania cover some of the agricultural areas and few of the designated reserves. Much of the reconnaissance soil mapping was undertaken by CSIRO in the 1940-60s. With the exception of some surveys undertaken by Forestry Tasmania in the north of the State, little regional scale mapping has been undertaken in recent years. There remain considerable areas of Tasmania, including highly productive agricultural areas, where no soil mapping exists.
- Soil structural impacts is an issue for land under production forestry. Monitoring of soil structural condition is undertaken in the Warra Reference Site in the Southern Forests. Soil survey data is not available broadly for State Forest, although visual assessment of soil condition in Tasmanian forests is undertaken in Forest Practices Board audits. However, data available are generally not suitable for reporting on the condition of soils under production forestry at Statewide scales.
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