Managing soils

All surface and subsurface soils can be compacted - some more easily than others. Surface soil can easily be compacted by livestock and machinery and can be induced by natural soil conditions such as wetting and drying.   

Compacted subsoil, resulting from machinery traffic, restricts crop and pasture root growth. Almost no Western Australian agricultural soils have capacity to resist compaction or self-repair following compaction.  

The department provides information and support to help growers manage this soil constraint on their properties. 

Plant essential nutrients are required for profitable and sustainable agricultural production. An insufficient amount of any essential nutrient will lead to poor crop or pasture growth and limit production, reducing profit for growers. Fertiliser represents the largest farm input cost and overuse will reduce growers’ profits and can lead to run-off and leaching into waterways. 

WA soils are inherently infertile, so many farmers have built up soil nutrient levels and adopted a replacement approach to fertiliser management. This needs to be carefully managed and it is recommended that growers undertake regular monitoring of soil and plant nutrient levels. 

The department provides information with is research partner SoilsWest (soilswest.org.au) via the website, soilqualityknowledgebase.org.au, to help grain growers address this constraint on their properties. 

Soils in Western Australia are affected by three forms of salinity.  

1. Natural or primary salinity develops naturally, mainly in areas where rainfall is insufficient to leach salts from the soil profile, and evaporation is high. Moist and wet primary saline areas have very high natural diversity in Western Australia (WA), and are at risk from increased flooding, waterlogging, and increasing salinisation. Natural salt lake chains in WA follow ancient drainage lines. 
   
   
2. Dryland salinity is a major form of land degradation in WA; it is associated with the presence of a shallow watertable in the soil. Dryland salinity is caused by increased recharge under annual agricultural systems, leading to rising watertables and salt transport into the root zone. More than one million hectares of broadacre farmland are estimated to be affected by dryland salinity in WA. Most of this land is highly to extremely saline and is therefore too saline for cropping. 
   
   
3. Transient salinity is associated with soil sodicity and alkalinity. Transient salinity is present on many of the heavy textured soils in low rainfall areas of WA. Most of this land is slightly to moderately saline, and this land is therefore routinely cropped. About 3.5 million hectares of broadacre farmland could be affected by transient salinity in WA.  

The Soil and Land Conservation Act, 1945 regulates the conservation of soil and land resources. Land degradation includes water and wind erosion, salinity, eutrophication, and flooding; and the removal or deterioration of natural or introduced vegetation that may be detrimental to the present or future use of land. 

There are several practical options for increasing productivity from saline sites and reducing environmental damage.  

The department provides technical information to assist landholders and the community to diagnose the extent and effect of salinity and manage the impacts.  

Dryland farming systems rely on the soil to store and release water and nutrients to meet crop demand. Soil water storage is dynamic due to changes in water inputs, for example, rainfall, irrigation, and outputs, including evaporation, plant transpiration, runoff, and deep drainage beyond the root zone. 

The aim of soil water management is to improve the efficiency with which rainfall is converted into crop and pasture yield. This involves increasing the amount and depth of water storage (for example, via soil amelioration) and optimising the production system for a given level of water storage.  

Soil texture cannot be readily changed, so soil water storage amelioration focuses on enabling water flow into the soil profile and increasing access through increased rooting depth. Optimisation of the production system requires management of inputs (for example, fertiliser, pesticides) and relies on knowing how much plant available water is stored. This enables farmers to predict yields and maximise profits. 

Waterlogging occurs when there is too much water in a plant’s root zone, which decreases the oxygen available to roots. Waterlogging can be a major constraint to plant growth and production and, under certain conditions, will cause plant death. This constraint may not be apparent until the whole soil profile is saturated, and water appears on the surface.  

The department provides landholders with technical information and support on management options to recognise and reduce the impacts of waterlogging. 

Soil water repellence is a widespread problem that mostly affects soils with low clay content or high organic matter levels in the topsoil, in the medium to high rainfall zones. The expression of water repellence appears to be increasing in WA due to an increase in cropping frequency, dry and earlier sowing, minimum tillage, and reduced break of season rainfall.  

The department can provide technical information on a range of management options and new techniques to assist landholders to reduce water repellence impacts.  

Water erosion is a significant form of land degradation in Western Australian (WA) agriculture that is caused by intense rainfall and surface water runoff. The annual direct cost of water erosion to dryland farming in WA is estimated to be more than $10 million. 

The Soil and Land Conservation Act, 1945 regulates the conservation of soil and land resources. Land degradation includes water and wind erosion, salinity, eutrophication, and flooding; and the removal or deterioration of natural or introduced vegetation that may be detrimental to the present or future use of land. 

Water erosion on rainfed land (dryland) is associated with intense rainfall and land conditions that increase the risk of erosion. Risk factors include insufficient ground cover steep slopes, land surfaces on which tillage or livestock have detached soil, land features that concentrate water flow into long runs, controlled traffic lines, fences and vegetated alleys, steep slopes, and insufficient or inappropriate surface water flow-control structures. 

Soil loss from water erosion is a significant problem across large tracts of the rangelands, including the east Kimberley, west Pilbara, Gascoyne, and upper Murchison catchments. Water erosion during large storms in the southwest agricultural areas has caused major losses on farms and public infrastructure (for example, roads and rail). 

Water erosion on irrigated land is often associated with flooding that inundates the floodplains on which irrigation relies. 

The department provides information to landholders to reduce water erosion risk and recover from erosion. Advice and support are also available from our technical specialists.

Wind erosion is a major form of land degradation in Western Australia due to the interaction of the Mediterranean climate and predominantly sandy surfaced soils. Wind erosion involves the detachment, transportation, and redeposition of soil by wind. 

Productivity of crops and pastures is reduced by the removal of the most fertile component of the soil from the paddock and through sand-blasting of crops. Wind erosion can degrade infrastructure and dust particles can create air pollution. In 2022, DPIRD estimated the opportunity cost from wind erosion for the agricultural region as $62 million. 

The Soil and Land Conservation Act, 1945 regulates the conservation of soil and land resources. Land degradation includes water and wind erosion, salinity, eutrophication, and flooding; and the removal or deterioration of natural or introduced vegetation that may be detrimental to the present or future use of land. 

All soils are susceptible to wind erosion, which can be minimised by maintaining more than 50% ground cover to reduce wind-speed at ground level, and minimising soil disturbance. Where water erosion is also of concern, groundcover should exceed 70%.  

Wind erosion risk can be increased by some agronomic practices if not carried out as recommended.   

The department provides information and technical support for farmers to reduce the wind erosion risk and options to rehabilitate wind eroded sites.  

See also

Wind erosion

Dryland salinity (salinity on non-irrigated land) is one of the greatest environmental threats facing Western Australia's agricultural land, water, biodiversity and infrastructure. It's commonly defined as salinity at or near the soil surface causing reduced plant growth, reduced water quality and damage to infrastructure.

The department recommends that saltland management is part of a whole farm, or preferable whole catchment, plan.