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Australian Natural Resources Atlas

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Setting the scene

Summary

• Climate, soil quality, topography and the availability of irrigation water determine agricultural land use patterns and production potential in Australia.
• Development of agriculture has had to confront and overcome constraints imposed by an unreliable and generally semi-arid climate, and often fragile and infertile soils.
• Irrigated agriculture has expanded markedly in recent decades to over 2 million hectares. It now contributes about a quarter of the total gross value of national agricultural production.
• Agricultural land use systems and farming practices have progressively evolved. They continue to move towards being more efficient in resource use and becoming sustainable. These goals have yet to be universally or fully realised.
• Agricultural development has disturbed the rate and sometimes the direction of the ecological processes of natural landscapes. Some types of degradation (e.g. soil loss by erosion and dryland salinity) have long-term or irreversible consequences; other forms (e.g. leaching of nutrients, surface acidification) can be remedied with appropriate actions.
• Many Australian soils do not naturally have the qualities needed for sustained agricultural production without significant management inputs.

Economic and social dimensions of natural resource management

• Australian Agriculture Assessment 2001 reports on landscape processes, soil, nutrient and water movement and serves as a key input to the Audit report on the social and economic dimensions of natural resource management-Australians and Natural Resource Management 2001.

AUSTRALIAN AGRICULTURAL INDUSTRIES

Australia's modern agricultural industries have grown by progressively expanding in area, diversity and volume of production. Research, trial and error, and innovation have overcome the challenges posed by an unpredictable and variable climate, mainly infertile soils and large distance to markets. Much was learned and is still being learned as land use systems and farming practices continue to evolve and adjust to the Australian environment.

Today, Australia's agricultural landscapes are diverse, defined by interrelationships between landscape resources (especially hydrology, soil quality and topography), climatic constraints and the availability of irrigation water. Eleven broad agro-ecological regions (Figure 1.1) are recognised (SCARM 1998) and help the description of the dominant systems of land use (Figure 1.2).

Agro-ecological regions (AER)

• Vast areas of sparsely stocked, arid and semi-arid rangelands, that include conservation and aboriginal land areas (AER 1, 2, 3, 5, 11).
• Mixed farming regions, where livestock and crop production systems (or 'ley' or 'phase' farming) co-exist. These are mostly under dryland conditions-sometimes referred to as the 'wheat - sheep' zone-(AER 10) and the subtropical cropping_livestock zone (AER 6).
• Higher rainfall, permanently grazed pastures, sometimes interspersed with horticultural enterprises in the winter-dominant rainfall zones of southern Australia (AER 8 and 9).
• Sugar cane and horticultural production located on the wet tropical (AER 4) subtropical coastal regions (AER 7).
• Highly intensive pig and poultry industries and cattle feedlot systems, with the latter being located mainly on the coastal hinterland of Queensland and New South Wales, but occupying only small areas of land.
• Intensive horticulture and livestock are commonly located close to the capital cities.

During the past 45 years, the area of irrigated land (Figure 1.3) has quadrupled to over 2 million hectares, (or 1% of the total agricultural land). It produces 26% of the gross value of production from Australia's agriculture. Increases in irrigation have occurred in pastures used for dairying, cereal crops, cotton, sugar cane, fruit and vegetables.

Significant differences in agriculture occur when irrigation is possible. The efficient use of the applied water is of paramount importance for these intense forms of agricultural land uses.

A diverse range of agricultural products is produced for national consumption. Industries also earn valuable export income by supplying a significant proportion of world trade in wool, meats, grains and more recently in wine (see Profile of Australian Agriculture section).

Industry development is supported by transport (roads, rail and ports) and irrigation infrastructures, an agricultural service sector, and a research and extension capability. Value-adding secondary industries turn raw agricultural produce into food and fibre products.

Australian Agriculture Assessment 2001 has concentrated mainly within the 'intensive agriculture' regions, (as distinct from agriculture practised in the semi-arid rangelands). A key output is aggregated material budget data on the impacts of agriculture on river nutrient budgets and soil erosion presented at river basin scales Appendix 1).

AGRICULTURE IN AUSTRALIA'S NORTHERN 'TOP END' REGIONS

The so-called 'Top End' of Australia is defined as the tropical northern third of the Northern Territory and the Ord River Irrigation Area of north-west Western Australia (see Figure 1.2). Relative to other agricultural regions in Australia's intensive land use zone, the actual area used, the size of individual agricultural industries and supporting population are small. However, potential increase in agricultural production is considered high, provided systems suitable for the social and environmental conditions of this region can be developed (e.g. approximately 13 000 hectares of land is currently irrigated from the Ord River Stage 1, with an additional 43 000 hectares proposed for development under Stage 2).

Agricultural industries being pioneered and developed in these regions face many social, economic and environmental challenges, including relatively high freight costs. As a result, high value, niche market crops are produced to maximise returns and ensure market penetration within Australia or overseas.

Both successes and failures have occurred in the region, (as there have been elsewhere), but over the past two decades the agricultural base has slowly expanded and diversified. It continues to be an important component of the regional economy. There is a large capacity to further expand both dryland and irrigated agriculture in this region (see below), while ensuring current development and management practice supports concepts of sustainability.

The Top End also enjoys some distinct market advantages, because of its proximity to South East Asia and its ability to supply a diverse range of quality, early and out-of-season produce to southern Australian States and northern hemisphere markets.

The beef cattle industry

Cattle grazing is the dominant agricultural industry across this vast region of Australia. In 2000, the gross value of cattle produced ($189 million and a total of 449 000 head) from Northern Territory pastoral properties (including southern regions). This comprised 64% of the total gross value of the Territory's agricultural sector economy. A major proportion of cattle turned off were exported live overseas: 27% of Australia's total live cattle trade and 40% of sales to South East Asia are now exported through Port Darwin (240 000 head in 2000). Substantial cattle numbers were also shipped interstate.

The export beef industry in the Territory is also supported by an irrigated hay industry located at Katherine, Douglas/Daly and Darwin. Forage sorghum, maize and leucaena (a forage legume shrub) are also grown on the Ord to finish off rangeland cattle.

Horticultural industries

A diverse range of horticultural fruit and vegetable crops is produced under irrigation in the Ord River Valley ($31 million in 1998) and the Northern Territory ($88 million in 2000) and is destined to reach domestic markets in southern Australia and some overseas destinations. Melons and pumpkins alone comprised 40% of the total agricultural productivity generated in the Ord Valley in 1998 (Anon 1999). Horticultural crops, including mangoes, table grapes, bananas and vegetables constitute about 30% of the gross value of agricultural production from the Northern Territory, with 80% being shipped to Australian States.

It is projected that irrigated horticultural enterprises will continue to expand in the Top End as suitable land and water resources are released.

Other industries

In the Ord River Irrigation Area, sugar cane has emerged as a significant crop. Insect-resistant cotton is also being re-examined. Hybrid seed crops of sorghum, sunflower, maize and millet are also established industries in the Ord Valley.

New irrigation prospects

The development of Stage 2 of the Ord River Project could eventually bring expanded areas of irrigated field crops (e.g. sugar cane) and smaller areas for intensive horticulture (e.g. bananas, mangoes and tropical fruits and vegetables) into production. Approximately half of this cropping expansion, utilising water from the Ord River, will be located in the Northern Territory. Expansion in these commodities will also occur in the other parts of the Northern Territory as land becomes available.

In the Northern Territory, government resource planners estimate that the area of irrigated agriculture could sustainably expand 30 to 40 times greater than its present level. Based on an annual water consumption of 10 megalitres per hectare, the area for potential irrigation in the Top End was projected to be 85 600 and 27 500 hectares respectively for surface and ground water reserves. This assessment (Table 1.1) required no in-stream dams to be constructed, ensured adequate water allocations were available for environmental river flows (80% of stream flow and/or recharge) and required land clearances in river basins of less than 4%.

Table 1.1 Projected area with potential for irrigation development in the Top End region.

• Top End irrigation potential (at 10 ML/ha/yr)
• Groundwater irrigated area 27 500 ha
• Surface water irrigated area 85 600 ha
• Off-stream dams 25 700 ha
• Lake Argyle dam 125 000 ha

River basin	Basin area	Annual irrigation 10ML/ha/yr)	Total basin clearing (irrigation, fallow, dams)
	(km2)	(ha/year)	(ha)	% of Basin
Ord River	55380
Groundwater		nil	nil	nil
Surface water		56 000	181 000	3.3
Victoria River	77 230
Groundwater		nil	nil
Surface water		10 400	34 300	0.5
Moyle River	7 020
Groundwater		5 000	15 000	2.2
Surface water		nil	nil	nil
Adelaide River	7 430
Groundwater		nil	nil	nil
Surface water		4 000	13 200	1.8
Mary River	8 060
Groundwater		2 500	7 500	1.0
Surface water		nil	nil	nil
Blyth River	9 080
Groundwater		2 500	7 500	0.9
Surface water		nil	nil	nil
Roper River	79 130
Groundwater		3 000	9 000	0.1
Surface water		14 400	47 500	0.6
Daly River	52 940
Groundwater		14 500	43 500	0.8
Surface water		40 000	132 000	2.5
McArthur River	19 200
Groundwater		nil	nil	nil
Surface water	19 220	16 800	55 400	2.9

Source: Northern Territory Department of Lands, Planning and Environment

AUSTRALIAN AGRICULTURAL ENVIRONMENT

Landscape

Australia's 760 million hectares possess some unique and diverse features when compared with other continents:

The continent is broad and flat with few hills and basins. Its low average elevation and relief (rarely greater than 1600 metres and the lowest of any continent) is partly due to the absence of volcanic and tectonic activity in recent geological time and to prolonged wind and water erosion. The Great Dividing Range, located inland from the eastern seaboard provides the main upland topographic relief and alpine areas (Figure 1.4).

Australia has few major rivers or fresh water bodies. Most rivers flow irregularly (due to rainfall variability) and slowly (because of low topographic relief). Some drain inland and eventually evaporate, while coastal rivers in steeper terrain can drain rapidly to marine environments. Water yields from run-off are usually very low (except in Tasmania). Some 246 river basins have been defined (Figure 1.4) and used as the basis for aggregate reporting in Australian Agriculture Assessment 2001 (see Appendix 1). The Murray - Darling Basin is Australia's largest drainage basin used for intensive agriculture. Its contributing rivers flow relatively slowly.

Most rivers and groundwater systems are very sluggish (since the continent is flat, and dominated by a gentle fall towards its interior) with little capacity to drain the continent of its salt and water. As a consequence, enormous stores of salt characterise Australian landscapes.

Australia's variable climate

Rainfall

Australia is the driest inhabited continent in the world. It has extreme variations in climatic conditions (Figures 1.6, 1.7) covering tropical, subtropical, desert, temperate, Mediterranean and subalpine climates (Figure 1.8).

Australia's seasonal pattern of rainfall has a 'flip-flop' character-it is wet in the tropics and dry in the south during the southern summer, and the reverse occurs in the southern winter.

Rainfall variability from year to year is linked with changing currents and water temperatures in the Pacific, Indian and Southern oceans, with a significant correlation between annual continental rainfall and the El Nino - Southern Oscillation phenomenon in the Pacific Ocean.

Distribution of rainfall is strongly non-uniform-approximately one third of the continent is classed as arid and another third as semi-arid. Yearly variation is also very high by global standards (Figure 1.9), with Australia's climate being punctuated by extreme meteorological and associated events (droughts, floods, fires, frosts, dust storms).

Temperature, humidity and evaporation

In southern Australia, temperatures are cold to mild in winter and warm to hot in summer. In the north, daytime temperatures are continuously warm to hot. Inland semi-arid and arid regions are subject in summer to some of the world's hottest conditions (air temperatures over 50^oC and surface temperatures up to 80^oC).

Humidity decreases strongly with distance from the coast, and follows the same 'flip-flop' seasonal pattern as rainfall. Only along the southern coast in winter and tropical regions in the wet season is the air truly humid; elsewhere relative humidity is moderate (near the coast) to low (inland).

Potential or free-water evaporation over the Australian continent is generally high, significantly exceeding rainfall in all but the wettest areas. Significant run-off is therefore confined to these wet areas.

SOILS USED FOR AGRICULTURE

Australia's agricultural landscapes support a great range of soils. Most are ancient, strongly weathered and infertile by world standards. Those on floodplains are younger and more fertile. This variety along with the natural limitations of many soils and their interactions with climate, have made it difficult to develop sustainable agricultural systems. Productivity is also limited by human impacts on soils and while some forms of degradation (e.g. nutrient deficiencies) can be corrected, others are either irreversible (e.g. soil erosion) or difficult to remedy (e.g. subsoil acidity).

Australian soils have many distinctive features:

• soils with surface layers containing low organic matter content are often poorly structured-a condition made worse by various agricultural practices;
• soils with subsurface layers that have a sharp increase in clay content are widespread (Kurosol, Chromosol and Sodosol soil orders [see Figure 1.10]) and
  can restrict drainage and root growth. These soils also commonly have bleached layers with very low nutrient levels;
• soils affected by salt, either now or in earlier geological times, cover large portions of the arable lands of the continent (Sodosols) and have various nutrient and physical limitations;
• cracking clays that are relatively fertile but exhibit physical limitations (Vertosols) cover very large areas;
• soils formed in aeolian sands (Rudosols and Tenosols) fringe the southern cropping lands, but are more extensive in the arid zone; and
• the remaining ancient land surfaces (particularly in northern Australia) that have very deep and strongly weathered soils (Kandosols) with very low levels of nutrients.

Table 1.2 Broad overview of the distribution and use of Australia's major agricultural soil types using Australian Soil Classification Orders (million hectares).

	Naturala	Production from native pastureb	Dryland	Horticulture agriculturec	Irrigated agricultured	Othere	Total
Calcarosol	23.89	41.9	3.7	0.05	0.04	0.8	70
Chromosol	2.78	15.6	4.3	0.04	0.06	0.2	23
Dermosol	3.6	7.3	0.9	0.02	0.06	0.2	12
Ferrosol	1.6	3.9	0.6	0.02	0.02	0.1	6
Hydrosol	5.3	6.5	0.4	0.01	0.02	4.4	17
Kandosol	31.9	89.9	5.1	0.02	0.11	0.7	128
Kurosol	2.0	3.4	1.0	0.02	0.03	0.2	7
Organosol	0.7	0.1	< 0.1	0.00	0.00	0.1	1
Podosol	1.0	0.9	0.6	0.01	0.02	0.2	3
Rudosol	64.4	41.7	0.4	0.00	0.01	0.7	107
Sodosol	12.2	68.7	16.3	0.07	1.00	1.3	100
Tenosol	108.8	88.8	2.8	0.02	0.05	1.4	202
Vertosol	5.9	75.0	5.2	0.04	0.51	1.9	88

^a Conservation and natural environments

^b Production from native environments

^c Dryland agriculture and plantations (excluding horticulture)

^d Irrigated agriculture and plantations (excluding horticulture)

^e Built environment and other

AUSTRALIA'S SOILS*

Soils with calcium carbonate: Calcarosols

Solonised brown soils, grey-brown and red calcareous soils, calcareous sands

• contain calcium carbonate as soft or hard fragments or as a solid layer
• occur in areas with low rainfall and are used for cereal growing and irrigated horticulture in the south and sparse grazing in the north
• limitations for agriculture include shallow depth, low water retention and wind erosion on the sandier forms. High salinity, alkalinity and sodicity may also be a problem
• soil nutrient deficiencies are widespread

Acidic soils with an abrupt increase in clay: Kurosols

Podzolic soils, soloths, and texture contrast soils

• strongly acid soils with an abrupt increase in clay down the soil profile
• extend from southern Queensland, through coastal and sub-coastal New South Wales to Tasmania; less common in south-west Western Australia

Some of these soils have been cleared and used for dairying on improved pastures; in the higher rainfall areas of New South Wales and Tasmania, Kurosols are used for forestry; small areas in Western Australia are used for cereal growing and support sparse grazing in lower rainfall, woodland areas.

Soils high in sodium and with an abrupt increase in clay: Sodosols

Solodized solonetz, solodic soils, soloths and red-brown earths, texture contrast soils

• have an abrupt clay increase down the profile and high sodium content, that may lead to clay dispersion and unstable soil structure
• seasonally perched water tables are common on these soils due to the structure of the subsoil
• usually associated with a dry climate
• widely distributed in the eastern half of Australia and the western portion of Western Australia
• common land uses include grazing of native or improved pastures for both dryland and irrigated agriculture, and forestry
• usually very hard when dry and are prone to form surface crusts
• dispersive subsoil makes them prone to tunnel and gully erosion

Soils with an abrupt increase in clay: Chromosols

Non-calcic brown soils, red-brown earths and podzolic soils

• have an abrupt increase in clay content down the soil profile
• do not have high levels of sodium and are not strongly acidic in the subsoil
• occur in most districts and are common in the cereal belt of southern New South Wales, Victoria and parts of South Australia; in the tropics, these soils are mainly used for cattle grazing of native pastures.
• have hardsetting surfaces with structural degradation caused by agricultural practices and may have impeded internal drainage

Structureless soils: Kandosols

Red, yellow and grey earths, calcareous red earths, massive sesquioxidic soils

• mostly well-drained, permeable soils, although some yellow and most grey forms have impeded subsoil drainage
• common in all States except Victoria and Tasmania
• used for extensive agriculture in the wheatbelt of southern New South Wales and south-west Western Australia-in the higher rainfall areas they are used for a range of horticultural crops
• most have low natural fertility and land use is restricted to grazing of native pastures
• grazing lands are susceptible to surface soil degradation such as hardsetting and crusting even where grazing intensity is low

Weakly developed soils: Tenosols

Lithosols, siliceous and earthy sands, alpine humus soils and alluvial soils, massive sesquioxidic soils, shallow stony soils, and deep sands

• widespread in the eastern half of the continent where vast areas occur as red and yellow sand-plains. Large areas also exist in Western Australia and have red loamy soils with a red-brown hardpan at shallow depths
• due to poor water retention, almost universally have low natural fertility and occur in regions of low and erratic rainfall
• mainly used for the grazing of native pastures
• in the better-watered areas, landform prevents cultivation, but limited areas support forestry (east coast and south-west Western Australia)

Structured soils: Dermosols

Prairie soils, chocolate soils, red and yellow podzolic soils, structured sesquioxidic soils

• occur as moderately deep and well-drained soils in the wetter areas of eastern Australia
• may be strongly acid in the high rainfall areas or highly alkaline if they contain calcium carbonate
• support a wide range of land uses including cattle and sheep grazing of native pastures, forestry and sugar cane. Cereal crops, especially wheat, are commonly grown on the more fertile Dermosols

Iron rich soils: Ferrosols

Krasnozems, euchrozems, xanthrozems, chocolate soils, and structured sesquioxidic soils

• have high free iron and clay contents
• occur along the eastern coastline, in northern parts of Western Australia and the Northern Territory
• may be very deep and well drained in high rainfall zones
• land uses include dairying on improved pastures, horticultural crops, some plantation forestry, and sugar cane in Queensland. In northern Australia the shallow and stony soil types support beef cattle grazing
• may be degraded by erosion and compaction caused by cropping practices. May also suffer from acidification despite being amongst the best soils for a wide range of agricultural pursuits

Minimal soil development: Rudosols

Lithosols, alluvial soils, calcareous and siliceous sands, solonchaks, shallow stony soils, and deep sands

• widespread and diverse
• most have few commercial land uses because of their properties or occurrence in arid regions, or both-the largest areas occur in the desert regions of arid central and north-west Australia and support grazing of native pastures
• fertile variants formed in alluvium are used for cropping and improved pastures.
• some dune soils of the Riverine Plain in the Murray - Darling Basin are irrigated for citrus and vines

Shrink and swell clay soils: Vertosols

Black earths, grey clays, brown clays, red clays, and cracking clays

• shrink and swell, and crack as the soil dries
• used for grazing of native and improved pastures, extensive dryland agriculture where rainfall is adequate, and irrigated agriculture
• problems of water entry are usually related to tillage practices and adverse soil physical conditions at least partly induced by high sodium in the upper part of many profiles

Soil orders rarely used for agriculture

• other soil types less commonly used for agriculture include Hydrosols (seasonally wet or permanently wet soils), Organosols (organic or peat soils mainly in coastal or alpine regions), Podosols (usually infertile sandy soils with organic materials and aluminium, with or without iron) and Anthroposols (soils resulting from human activity)

* Terminology from the Australian Soil Classification (Isbell 1996) is used as a frame of reference because of its practical focus. A generalised map of soil orders is provided in Figure 1.10. More detailed descriptions of each of the soil orders are presented in the Appendix 3.

Australian Soil Resources Information System

An understanding of the distribution and properties of Australia's natural resource base is fundamental to sound natural resource management. The best Australia-wide coverage of soils information prior to the Audit was the Atlas of Australian Soils (at a scale of 1:2 000 000) completed by CSIRO in 1968. This information was inadequate to answer the key natural resource management questions at a scale relevant to regional planning and development. At the time the Audit was initiated many, more detailed regional-scale data sets existed that could be used to compile a revised Australia-wide data set.

The Australian Soil Resources Information System was designed to build a nationally conformable database from the extensive soil point and survey map data that has been collected and collated by the State and Territory agencies since the early 1970s. Much of this information has been collected over the last 10 years through national programs such as the
National Landcare Program and more recently the Natural Heritage Trust. The Australian Soil Resources Information System was developed as a joint project between Bureau of Rural Sciences, CSIRO and State and Territory agencies responsible for soil and land management, using the collaborative framework established by the Australian Collaborative Land Evaluation Program.

Soil attributes from the Australian Soil Resources Information System (Table 1.3) are those most commonly required to characterise, model or predict land resource processes that drive plant productivity, measure resource sustainability or control rates of resource degradation.

The soil attributes, lithology and relief maps were prepared to assist the Audit's modelled assessments of water-borne erosion and river nutrient transport, the current and projected extent of soil acidification, and landscape productivity. These are available through the Australian Natural Resources Atlas and Data Library (see Appendix 2 for a description and map of each attribute).

Australian Soil Resources Information System

• A set of spatially distributed estimates of soil attributes and their data quality, as gridded (raster) maps of soil properties for topsoil and subsoil. These maps were produced from the collated data sets using several modelling methods (below). These data are displayed on the Australian Natural Resources Atlas and can be downloaded from the Australian Natural Resources Data Library.
• A compilation (from data held by Commonwealth, State and Territory agencies) of 160 000 soil profile data sets into a single standardised database (SITES-Peluso & McDonald 1995) is available from the Audit data library, subject to some licence conditions.
• A compilation (from data held by Commonwealth, State and Territory agencies) of soil and land resources maps at varying scales. The underlying data were used in modelling work undertaken by the Audit. Descriptions are available from the Audit Atlas and Data Library. The data can be obtained only from the original custodians.
• Various ancillary data sets relevant to soils were used to model soil properties, including: 9 second digital elevation model and derived terrain attributes, lithology (derived from geological mapping), climate surfaces, and satellite imagery (Landsat multi-spectral scanner).

Table 1.3 Australian Soil Resources Information System-soil attributes.

Soil attributes	Units	Map availability
		Topsoil (layer 1)	First subsoil (layer 2)
River basins containing intensive agriculture
pH	pH scale 1 to 14
Organic carbon	%
Total phosphorus	%
Extractable phosphorus (New South Wales and Victoria)	%
Total nitrogen (derived from carbon:nitrogen relationship)	%
Texture	texture class
Clay	% fine earth fraction
Australia-wide coverage*
Clay % (prepared from map data only)	% fine earth fraction
Silt %	% fine earth fraction
Sand %	% fine earth fraction
Thickness	metre
Solum depth	metre
Bulk density	g/cm3
Available water	mm
Saturated hydraulic conductivity	mm/hr
Erodibility	t ha h/ha MJ mm

* Data quality and accuracy is variable across Australia. Land resource information is more limited in Australia's arid regions.

Achievements of the Australian Soil Resources Information System

Data: product, protocols and quality assurance

• Prepared 27 new data sets of key soil attributes using the best available information
• Demonstrated the use of soil point and polygon data for spatial modelling and prediction of soil attribute over large areas
• Facilitated quality assurance procedures for Australia's soil data, thereby improving the information base.
• Implemented and refined protocols of the Soil Information Transfer and Evaluation System (SITES)
• Identified data quality inadequacies such as geo-referencing, sample bias and lack of representativeness in existing data
• Identified significant new data sets that could be included in the national data set
• Initiated the development of a polygon database and data transfer standard

Tools developed

• Range of methods for estimating soil attributes, appropriate to the availability and accuracy of input data
• Sophisticated spatial analysis procedures and tools for handling a mixture of point and polygon (taxonomic) data.
• Tools for assessing the quality of the spatial predictions of soil properties

Legacy outcomes

• Tool set for preparing future soil attribute maps
• National database of quality soil point data for future applications
• Institutional arrangements (through a partnership of Commonwealth, State/Territory agencies) to maintain, update and develop new applications using the Australian Soil Resources Information System

AUSTRALIAN AGRICULTURAL SYSTEMS

Innovation, research and development, have lifted the potential for agricultural productivity (see Profile of Australian Agriculture section) imposed by natural environmental constraints. New systems, information and technologies continue to improve farm productivity and respond to market signals. Increased profitability permits increased investments in farm natural resources and infrastructure.

Dryland regions

• Farming inputs are geared to match expectations of yield; they range from being more conservative, lower input systems in the more arid, mixed farming regions to higher input, more diverse rotations in the more climatically reliable regions.

Medium and higher rainfall regions

• Greater opportunities exist for intensifying and diversifying land use and enterprise mixes in these areas. Many farmers are now changing their rotations or systems of land use to produce a range of products that result in achieving greater and more sustained business profits (through more effective use of resources and capturing synergies between rotations); reducing financial risk (through crop diversification) or improving sustainability of the resource base (through reduced exposure to weeds and diseases or soil erosion through the adoption of minimum tillage practices). Examples include changing from wool to prime lamb or beef; undertaking more diversified cropping with less grazing; growing durum wheat, pulses or canola in rotation with traditional bread wheat varieties; introducing higher-input perennial and annual pasture systems and replacing sheep grazing with horticulture.

Irrigated agriculture

• The capacity to increase water supply to plants offers opportunities to increase production or to enter into new systems of land use (e.g. the recent development of a potato industry in the dry southern Mallee regions of South Australia, where previously dryland crop - pasture rotations were used).

With the adoption of new land use systems, comes the need for new farming practices. Research and innovations are usually needed to meet emerging challenges (e.g. herbicide-resistant weeds, fertiliser requirements, tillage systems). Progressive improvements in site-specific management provide future confidence to farmers and enable them to become more sustainable.

Changed systems of land use have occurred in some regions of Australia over the past 20 years, including:

• more intensive and diversified cropping rotations (e.g. the use of oilseed and pulse crops with cereals in the more reliable wheat - sheep zone of southern Australia) accompanied by a range of new soil and crop husbandry practices;
• progressive introduction of higher input to higher return grazing systems in the dairy and higher rainfall grazing regions;
• development of conservation farming in dryland areas of southern Australia, the northern subtropical cropping regions (where a more diverse range of summer crops have replaced long fallows) and sugar cane regions to minimise risks of soil erosion; and
• growth of cattle feedlot systems, centred around regions with reliable supplies of grain and breeding stock.

All new and proven systems of land use are not immediately or universally accepted. Typically, there is a considerable lag delay in adoption.

Impact of agriculture on landscape resource condition

Unintended consequences of changes imposed by agriculture on soil and landscape processes are often insidious, but are now beginning to affect farm productivity and the future sustainability of agricultural landscapes.

• Development of land (e.g. clearing of native vegetation) induces widespread changes to the functioning of natural ecosystems through altering landscape water balance. This in turn alters key soil processes and the quantity of water, sediments and nutrients transported across landscapes to surface water bodies or into groundwater aquifers.
• Improved productivity is often gained by reducing weeds, pests and diseases.

Agriculture inevitably alters the characteristics of the landscape, with modifications generally being more significant where farming intensity or land disturbance is greater (Tables 1.4, 1.5).

The rate at which a particular landscape responds to changing processes varies significantly and movement towards a new equilibrium may not always be positive for productive agriculture (e.g. dryland salinity is the surface expression of groundwater systems adjusting to a new water balance mainly as result of a change in vegetative cover [NLWRA 2001a]). Similarly, accelerated erosion and soil acidification (see later sections) induced by some agricultural practices need to be recognised and minimised.

Table 1.4 Main forms of land degradation, the changes to land properties and processes and the agricultural systems involved, and associated water quality problems.

Formation of acid sulfate soils	Nutrient loss
Caused by change in oxidation status of particular sulfide minerals (mostly iron pyrites) within coastal sediments, inland discharge areas and around weathering rock piles from mining operations. Generalised type of disturbance and farming practices Drainage of sediments exposing sulfide minerals to aerated conditions Any agricultural industries-predominantly sugar and dairying-involving clearing and drainage of coastal plains formed on marine sediments containing susceptible sulfide minerals. Associated water quality problems Acidification and release of heavy metal cations from soil clays, including aluminium, iron and manganese; fish mortalities; clogging of wells and aquifers Management options Avoid disturbing/draining coastal wetlands Control of water table levels in wetlands Exclusion of stock in inland discharge zone Apply lime Plant salt/acid tolerant perennials	Caused by Changes in biogeochemical cycles and components of the hydrological cycle Soil erosion by wind and water Nutrient exports in harvested farm products Generalised type of disturbance and farming practices Alteration of vegetation, particularly perenniality, leaf area index, root depth and total biomass production; harvesting of produce and export beyond the farm and catchment; addition of inappropriate fertilisers on sandy soils or surface application of fertilisers on sloping or irrigated land Crops or pasture types selected and rotations (will affect nutrients removed in produce; potential for nutrient leaching beyond the root zone), excess fertiliser application, tillage, residue management and fallowing practices All agricultural industries have the potential to cause nutrient loss Associated water quality problems Eutrophication and nitrate pollution where nutrient loss is associated with runoff and/or leaching rather than product export Management options Adopt rotations to optimise legume nitrogen accretion Optimise fertiliser applications Optimise soil ameliorant applications Treat nutritional disorders in livestock Forward plan and record fertiliser decisions in rotations Use fertiliser decision support systems, which optimise productivity and are environmentally benign
Organic matter loss	Salinisation
Caused by Change to total biomass production and biomass return to the soil; chemical transformations following soil disturbance Wind and water erosion of top soil Generalised type of disturbance and farming practices Primarily changes to the vegetation, harvesting of produce and produce export beyond the farm and catchment Also increased exposure of surface soil and soil disruption causing loss by erosion and/or oxidation Selection of crop or pasture type, fertiliser addition; tillage and residue management practices, grazing intensity Generally most pronounced in cropping systems (cotton, grains, sugar and horticulture) Excessive soil cultivation (e.g. long fallow) Increased by irrigation Associated water quality problems Dissolved organic matter Management options Maintain adequate plant residue cover Adopt minimum/zero tillage systems Adopt stubble retention/incorporation systems Avoid cultivating in high erosion risk periods Avoid burning stubbles Avoid over grazing vegetation Match feed supply to stock demand (feed budgeting)	Caused by Changes in components of the hydrological cycle, particularly a decrease in the volume of water lost through interception and evapotranspiration and an increase in deep drainage of soil water, where there is a high salt storage in the catchment regolith or groundwater Generalised type of disturbance and farming practices Primarily alteration of vegetation, particularly in perenniality, leaf area index, and root depth Crops or pasture type selected (including tree crops) and rotations, fallowing practices, fertiliser application and grazing intensity Also practices which affect soil structure-as described below can affect the downward movement of water through the soil All agricultural industries have the potential to cause salinity if they are located in catchments with high salt stores in the regolith or groundwater Associated water quality problems Increased water salinity Management options Pasture management: permanently fence off areas/exclude stock Install surface/subsurface drains Plant perennial pastures and trees/shrubs in recharge areas. Trees also provide shelter belts. Introduce lucerne phase farming (where practical) Construct reverse interceptor banks Optimising dryland and irrigation water use efficiency by plants
Soil loss	Waterlogging
Caused by Changes in the balances and transfer of energy in the system and in components of the hydrological cycle (e.g. exposure of surface soil results in energy of rainfall no longer being absorbed by vegetation cover and this energy is then available for detaching particles from soil aggregates and transporting them) Similarly, for erosion of exposed top soil by wind energy Generalised type of disturbance and farming practices Increased removal of vegetation and exposure of surface soil (exposes soil to the energy of rainfall impact and wind; loss of roots and other soil organic matter reduces cohesion of soil aggregates); increased soil disturbance through cultivation and pressure on soils (primarily from vehicles and implements, sheep and cattle) Tillage and residue management practices, crop or pasture type selected, grazing intensity (affects ground cover and soil organic matter), and vehicle and implement characteristics Particularly prevalent in cropping industries due to top soil exposure; still an issue for grazing industries Associated water quality problems Increased stream sediment loads, dissolved organic matter and turbidity Management options Plant pastures instead of crops Maintain adequate plant residue cover Adopt minimum/zero tillage systems Adopt stubble retention/incorporation systems Avoid cultivating in high erosion risk periods Avoid burning stubbles Adopt chemical fallowing Use contour banks/grassed waterways Reduce impact of feral fauna Avoid over grazing vegetation. Match feed supply to stock demand (feed budgeting) Fence to land class through a developed farm plan Avoid grazing erosion-prone areas. Fence these areas Adopt drought management strategies- destocking Paddock feedlots, fodder conservation Intensive strip grazing/cropping Improve degraded riparian buffer zones	Caused by Primarily changes in components of the hydrological cycle, particularly a decrease in the volume of water lost through interception and evapotranspiration; waterlogging can also result from a decrease in soil permeability of subsoil layers (plough pans) Generalised type of disturbance and farming practices Disturbances and farming practices involved as for 'salinisation' Plant growth is markedly reduced All agricultural industries have the potential to cause waterlogging if they are located in low topographic positions within landscapes Associated water quality problems Changes in redox potential of the soil can result in release of acid drainage, dissolved organic carbon and other compounds to streams, rivers and reservoirs with significant effects on water quality Management options Soil drainage or upslope water interception and diversion schemes Rotationally graze or destock affected areas
Soil acidification	Soil structure decline
Caused by Changes in biogeochemical cycles of carbon and nitrogen (increased nitrogen input and loss of nutrients in produce) and in the hydrological cycle (increased leaching of nitrate and soil cations) Generalised type of disturbance and farming practices As for 'nutrient loss' described above. Inclusion of legumes in crops or pastures and types of fertiliser used, and removal of legume hay are particularly important Tends to be associated with grain growing and grazing industries (sheep, beef and dairying). However, other industries can be affected Associated water quality problems Some streams have shown a decline in pH attributable to acidification of surrounding soils. The extent of this phenomenon is unknown Management options Apply liming materials/lime pellet seed Grow acid tolerant plants Minimise use of ammonium-based fertilisers Minimise nitrate leaching by improving water use efficiency Sow crops early Plant perennials Feed hay where harvested Adopt reduced tillage and stubble retention Spread sodic clays Subsoil acidity Deep soil ripping and lime Lime slotting Application of calcium enriched materials	Caused by Processes can operate on top soils and subsoils and include excessive and/or inappropriate tillage, soil compaction by machinery and livestock, poor soil drainage, sodic soil conditions, depleted soil organic matter, exposure of hard setting topsoil by overgrazing or soil erosion Generalised type of disturbance and farming practices Disturbances and farming practices involved as for 'soil loss' Risk factors include the use of heavy machinery in cropping industries involving cultivation-cotton, grains, sugar and some horticultural industries and overgrazing Associated water quality problems Indirectly affects water quality through the potential for increased erosion Management options Increase soil organic matter content Adopt green trash blankets (sugar cane) Grow more pastures in cropping rotations Encourage grasses (extensive root systems) Apply gypsum (calcium input) Adopt reduced/zero tillage. Use chemical fallow Adopt stubble retention systems Adopt controlled traffic lines in cropped land Change grazing management

Table 1.5 Other issues faced in agricultural landscapes.

Occurrence of chemical residues	Weed establishment
Caused by Introduction of new chemicals to the soil environment Disturbance Application of primarily fertiliser (including sewage effluent and sludges) and pesticide or herbicide applications Associated water quality problem Chemical pollution Associated agricultural industries All intensive agricultural systems utilising fertilisers, pesticides and herbicides. Severity of residue problems depends partly on chemical or fertiliser composition, and application methods, rates and timing	Caused by Increased light at soil surface; human-aided introduction of weed seeds can be important with some species Disturbance includes Change in condition, connectivity and abundance of native flora and/or fauna Exotic weeds hosting root diseases Farming practices causing change Trafficking by animals and vehicles, tillage, grazing intensity, import of livestock, and crop and pasture seeds Associated water quality problems Changes in riparian vegetation through weed establishment affecting light and temperature regimes of the adjacent water body; it can also affect nutrient input from litter Associated agricultural industries All agricultural industries since they aid weed establishment; severity of the weed problem depends on climate and soil type (potential for particular weeds to establish), and eradication programs
Loss of flora and fauna
Caused by Direct change to land properties (vegetation) rather than to processes; secondary loss can result from land degradation processes Disturbance Alteration of vegetation, particularly species composition and vegetation structure Farming practices causing change Clearing, grazing intensity, changing fire regimes, types of crops and pasture types selected Associated water quality problems Loss of riparian vegetation that can affect the light and temperature regime of the adjacent water body; this can also affect nutrient input from litter and the structure of habitat (e.g. loss of woody vegetation which has provided 'snags') Associated agricultural industries All agricultural industries; loss is particularly associated with cropping industries (cotton, grains, horticulture and sugar) due to the extensive clearing that has taken place

RESOURCE SUSTAINABILITY AND STEWARDSHIP

The Standing Committee of Agriculture in Australia defined sustainable agriculture as:

'the use of farming practices and systems which maintain or enhance the economic viability of agricultural production; the natural resource base; and other ecosystems, which are influenced by agricultural activities'

SCA 1991

The guiding principles for sustainable agriculture were stated as:

• farm productivity is sustained or enhanced over the long term;
• adverse impacts on the natural resource base of agricultural and associated ecosystems are ameliorated, minimised or avoided;
• residues resulting from the use of chemicals in agriculture are minimised;
• the net social benefit derived from agriculture is maximised; and
• farming systems are sufficiently flexible to manage risks associated with the vagaries of climate and markets.

These succinct definitions imply the need to manage agricultural systems to be both profitable and environmentally sound, through adoption of efficient and environmentally benign management practices.

Agricultural industries are confronting issues of resource degradation, following a 200 year 'experiment' in land use. Earlier, short term economic gains must now be measured against longer term resource degradation and the costs of repairing rural landscapes (Lovering & Crabb 1998). Continuing investments are needed to develop more sustainable farming systems and to minimise or arrest their continued impacts into the future.

Agricultural industries and farming communities have responsibilities to ensure that land is maintained or enhanced for future generations and that land use impacts are not transferred to the wider catchment or downstream. Importantly, many agricultural industries and their supporting service industries have either established or are moving towards establishing codes of practice which promote quality assurance in the agricultural sector-quality on-farm resource management and delivery of safe food and fibre products to markets-a process that could be styled product stewardship.

Renewed emphasis and farmer participation in Landcare and implementing property management plans are most positive signals. Over the last decade, Government initiatives, such as Landcare, encouraged rural communities and individual landholders to become more aware of and to participate in the conservation and repair of natural resources in their regions. In all States, community led catchment management bodies have also worked to plan and implement actions to ensure that significant resource issues are identified and their impacts minimised. Such initiatives are all about resource stewardship, defined by Roberts (1990) as:

...the act of being entrusted with the management of another's property. With regard to land, this implies that the manager of the land... acts as a trustee on behalf of all the community, with the land managed responsibly and held in perpetual trust for future generations. Management must be equated with stewardship... Stewardship means that present land users...are trustees, not end-users.

Announcement of the National Action Plan for Salinity and Water Quality in late 2000 signifies that Australia is poised to tackle such critically important and complex natural resource management issues at national and regional scales.

Scope of the Australian Agriculture Assessment 2001

Australian Agriculture Assessment 2001 focuses on natural resource issues in areas containing intensive agriculture. However, this report should also be read in the context of water balance and land management issues discussed in Australian Dryland Salinity Assessment 2000 (NLWRA 2001a) and water use and water availability reported in Australian Water Resources Assessment 2000 (NLWRA 2001b). The impact of all land uses on Australia's native vegetation, catchments, rivers and estuaries from an ecological perspective are also reported in other Audit reports.

Australian Agriculture Assessment 2001 concentrated on soil and land degradation issues most significant to the future viability and sustainability of agriculture. The issues selected for assessment were those induced by agriculture and for which there is some scope or capacity to manage or minimise. Australian Agriculture Assessment 2001 presents:

• shows how and to what extent agriculture has changed water and nutrient balances;
• assesses nutrient inputs and outputs from agriculture and the implications for nutrient management on-farm;
• forecasts the impact of soil acidification on agricultural soils and productivity;
• presents the first comprehensive assessment of water-borne erosion and sediment transport for Australia's agricultural catchments and rivers and highlights implications for soil, river and estuary management;
• presents river nutrient budgets and changes for nitrogen and phosphorus;
• describes characteristics of Australia's soils that influence production, and soil and landscape processes;
• highlights the progress of agricultural industries in meeting natural resource challenges; and
• identifies key components of land condition monitoring so that natural resource changes and outcomes can be measured in the future.

The socioeconomic dimensions of agriculture are reported in a companion to Audit report-Australians and Natural Resource Management 2001. This report details the economic benefits that agriculture delivers to the Australian economy and the costs of resource use, particularly off-farm.

Soil issues not addressed by Australian Agriculture Assessment 2001

Other soil-based issues, while not assessed by the Audit (based on stakeholder priorities, time and resources available and/or availability of Australia-wide data) remain important considerations for integrated farm and catchment management. These issues are listed below, with recent Australian reviews or assessments:

• wind erosion (to be reported in Australian State of Environment 2001);
• soil sodicity (Naidu et al. 1996, Fitzpatrick et al. 1994);
• soil structure decline (Chan & Pratley 1998, Reeves et al. 1998)
• soil waterlogging except that associated with dryland salinity (Reeves et al. 1998);
• soil water repellence (Doerr et al. 2000; Harper et al. 2000);
• acid sulfate soils (White et al. 1998);
• soil contaminants (Kookana et al. 1998; McLaughlin et al. 1996); and
• soil biological health (Pankhurst et al. 1994).

REFERENCES

Anon 1999, Ord River Irrigation Area, Kununurra Western Australia (sixth edition) Agriculture, Western Australia Bulletin 4369.

Chan K.Y. & Pratley J. 1998, 'Soil structural decline- can the trend be reversed?' in Agriculture and the environmental imperative', J. Pratley & A. Robertson (eds), pp. 129 - 63, CSIRO Publishing, Melbourne.

Doerr S.H., Shakesby R.A., Walsh R.P.D. 2000, 'Soil water repellency: its causes, characteristics and hydro-geomorphological significance', Earth-Science Reviews vol. 51, pp. 33 - 65.

Fitzpatrick R.W., Boucher S.C., Naidu R. & Fritsch E. 1994, 'Environmental consequences of soil sodicity', Australian Journal of Soil Research vol. 32, pp. 1069 - 93.

Harper R.J., McKissock I., Gilkes R.J., Carter D.J. & Blackwell P.S. 2000, 'A multivariate framework for interpreting the effects of soil properties, soil management and landuse on water repellency', Journal of Hydrology vol. 231, pp. 371 - 383.

Isbell R.F., 1996, Australian Soil Classification. The Australian Soil and Land Survey Handbook series, CSIRO Publishing.

Kookana R.S., Baskaran S. & Naidu R, 1998, 'Pesticide fate and behaviour in Australian soils in relation to contamination and management of soil and water: a review', Australian Journal of Soil Research vol. 36, pp. 715 - 64.

Lovering J.F. & Crabb P. 1998, 'Australia's 200-year experiment in agricultural sustainability', Agricultural Science vol. 11, pp. 17 - 25.

McLaughlin M.J., Tiller K.G., Naidu R. & Stevens D.P. 1996, 'Review: the behaviour and environmental impact of contaminants in fertilisers', Australian Journal of Soil Research vol. 34, pp. 1 - 54.

Naidu R., Kookuna R.S., Oliver D.P., Rogers S. & McLaughlin M.J. (eds) 1996, Contaminants and the soil environment in the Australasia-Pacific region, Kluwer Academic Publishers, Great Britain.

NLWRA 2001a, Australian Dryland Salinity Assessment 2000, National Land and Water Resources Audit.

NLWRA 2001b, Australian Water Resources Assessment 2000, National Land and Water Resources Audit.

Pankhurst C.E.P., Doube B.M., Gupta V.V.S.R. & Grace P.R. (eds) 1994, Soil biota- management in sustainable farming systems, CSIRO Publishing, Melbourne.

Reeves G., Breckwoldt R. & Chartres C. 1998, Does the answer lies in the soil- a national review of soil health issues, Land and Water Resources Research and Development Corporation Occasional Paper No. 17/97.

Roberts R.W. 1990, Land conservation in Australia-200 year stocktake, Soil and Water Conservation Association of Australia.

SCA 1991, Sustainable agriculture, Standing Committee on Agriculture Technical report no. 36, CSIRO Publishing, Melbourne.

SCARM 1998, Sustainable Agriculture: assessing Australia's recent performance, CSIRO Publishing, Melbourne.

White R.E. & Kookana R.S. 1998, 'Measuring nutrient and pesticide movement in soils: benefits for catchment management', Australian Journal of Experimental Agriculture vol. 38, pp. 725 - 43.

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