Wind erosion is the process by which soil particles are detached and transported from the land surface by the action of wind (Moore et al. 1998). Transport occurs by suspension, saltation or creep. Wind erosion occurs sporadically because it requires both a soil surface that is susceptible to erosion and wind speeds strong enough to dislodge the soil particles. This combination of susceptible soil and wind makes it difficult to control wind erosion, as well as making it hard to monitor erosion events as they occur.
Wind erosion is a natural process that has assisted historically in shaping Australian landscapes. However, soil degradation by wind erosion is caused by inadequate or inappropriate land management. This damage to the soil resource has both on- and off-site impacts
Western Australian soils generally have low inherent soil fertility. Over the years farmers have built up soil fertility with fertilisers and good soil management. Wind erosion removes the finer fractions from the soil, which includes the clay, organic matter and soil nutrients. The loss of these particles reduces the water and nutrient holding capacity of the soil and hence soil fertility. Research has shown that for every 3% of the nitrogen that is removed from the soil, there is a 2% loss in yield of the following crop (McFarlane and Carter 1989). If the top 10 mm of soil are subjected to winnowing by the wind, crop yields may be reduced by 25% (Marsh 1982). Additional fertiliser applications will increase the soil fertility, but the soil may not return to its original productivity because of the loss of smaller particles which retain most of the nutrients.
Other on-site impacts include the deposition of sand on fence lines and in waterways and dams. This requires time and resources to remove.
Soil can be moved a few metres, or hundreds of kilometres depending on the particle size and wind speeds. These particles impact the community, environment and climate.
Management of susceptible soils focuses on minimisation of disturbance during cultivation (e.g. no-till sowing, direct drilling), reduced stocking rates and maintenance of adequate ground cover (e.g. use of improved perennial pastures and rotation of stock). Fencing-off and separate management of high-risk areas can be useful. Risk can be managed through natural windbreaks of trees and shrubs (e.g. alley farming, agroforestry) or the use of artificial barriers of shadecloth (for intensive horticultural crops). Earth-moving activities should be timed when the soil is wet and./or the risk of high velocity wind is small.
Some cropping regimes are less susceptible. For example, Brown (1984, cited in van Leir 1994) estimates that a corn, wheat and clover rotation will lead to an average annual soil loss of 2.7 t/ha. Continuous corn on the other hand would lead to an average annual soil loss of 19.7 t/ha.
Stubble burning is not acceptable.
Key messages across south-west Western Australia (DAFWA Report Card 2013)
Status and trend
- Wind erosion is a seasonal hazard in the south-west of WA.
- The indicator used for wind erosion hazard is erodibility – the potential for soil loss in erosive winds.
- More than half of the agricultural land had unacceptable hazard ratings (were below target values) at least one year in four during the period 2009–12.
- The Central Northern Wheatbelt Ag Soil Zone had the greatest hazard, with the zone being below target values in each of the four years 2009–12.
- Wind erosion hazard at the state level has reduced over time because of changed cropping and stubble management practices.
- Current land use practices still result in some degree of wind erosion, with an estimated opportunity cost of $71 million per year.
- Increasing the use of stable ground cover (including living and dead vegetation and gravels) to prevent loss of soil, fine particles, nutrients and soil organic carbon is a practical and profitable option.
- Climate variability and a drying climate will increase wind erosion hazard without improved management practices
Management actions to minimise wind erosion need to be targeted at areas that have a high hazard, especially Ag Soil Zones, such as the Central Northern Wheatbelt, where high hazard tends to occur each year. It should be noted however, that past hazard as described in the DAFWA Report Card 2013, is only a guide to future hazard, and vigilance is required on all soils throughout the south-west of WA that have the inherent potential to wind erode.
Specific recommendations include:
- Predictions of high wind erosion hazard are publicised before critical erodibility is reached, and extension campaigns highlight management options.
- The target condition of greater than 50% ground cover on-site, and less than 5% of the landscape with an unacceptable hazard, is the minimum standard for good practice wind erosion management.
- Stubble retention in cropping systems is the default for good practice wind erosion management. Wind erosion hazard is to be assessed first for all stubble handling problems.
- Soil constraints likely to increase soil erosion hazard are treated wherever feasible. Constraints to achieving sufficient groundcover include, but are not limited to, salinity, soil acidity, and waterrepellence.
- Grazing pressure on ground cover is calculated to prevent thresholds being exceeded.
- Improved technologies are developed to assist famers to manage protective ground cover in periods when erosion hazard is high.
Projects addressing wind erosion
SWCC supports a number of landholders and partners to undertake projects addressing agricultural practices including wind erosion. One project addressing wind erosion is:
- Lebeckia: A perennial legume for non-wetting deep sandy soils.
Further information on this project can be found on the Agtrialsites website here.
The Agtrialsites website is a cross regional NRM WA initiative that aims to provide information on sustainable agriculture projects across Western Australia.
- Carter D and Laycock J (2013). ‘Wind Erosion’. In: Report card on sustainable natural resource use in agriculture, Department of Agriculture and Food, Western Australia.
- Van Gool, D., Vernon, L. and Runge, W. (2008). Land Resources in the South-West Agricultural Region. A shire-based summary of land degradation and land capability. Department of Agriculture and Food Western Australia.