For more information about recovering from fire see DPIRD's Fire information page.
See wind erosion management for more information.
Land management recommendations
How much does fire increase wind erosion?
Fire will significantly increase erosion risk on loose, sandy soils, and slightly increase the risk on stable clay soils. Soils with a gravel surface are usually safe. Dust will blow from any soil if the surface has been loosened by livestock, vehicles or cultivation.
What should we do on burnt, erodible farming land?
- Remove livestock immediately and prevent them from returning.
- Minimise vehicle traffic that loosens the topsoil making it more vulnerable to wind erosion.
- Protect valuable or highly sensitive areas using soil treatment (spray, claying, gravel or old hay or straw to give a full cover).
- Leave weeds germinating after summer rainfall; these will help stabilise soil.
- Soil test and seek the advice of an agronomist on fertiliser rates.
- Grow a cover crop – if possible – where the soils are at risk..
Farm planning
Is there support for farm planning after a fire?
DPIRD can provide direct advice and support for farm planning areas affected by fire. Private consultants can provide more detailed advice and there may be support from the Western Australian Natural Disaster Relief and Recovery Arrangements (WANDRRA).
Water erosion
How can we control water erosion after a fire?
Do the same as you would for wind erosion: destock and reduce soil disturbance. Check erosion control earth works and repair if necessary. See water erosion control after fire and surface water management for more information.
Soil treatments - gravelling and claying
See wind erosion control after fire for detail.
Gravelling as an erosion control method
You can spread gravel at the same rates as clay spreading (75–100 t/ha) to get a stable surface. Gravel is preferred over clay on very susceptible and difficult areas like water trough aprons and at gates where stock tend to congregate. Gravelled areas will drain well when it starts raining.
What are the claying rates to minimise wind erosion?
Claying is a good option on very susceptible sands that also suffer from water repellence. Clay rich subsoil should be spread at rates of 75–100 t/ha to control wind erosion: higher rates are recommended to give the long term benefits of reduced water repellence, improved water and nutrient holding capacity, improved pasture use and reduced risk from frosting in some circumstances.
What is involved in claying, not only spreading but also the need to incorporate the clay before seeding?
Leave clay on the surface over the summer when wind erosion risk is at its highest, and incorporate the clay into the top 5–10 cm prior to seeding. Incorporation is needed to prevent clay forming a surface crust that reduces germination emergence and water infiltration.
Nitrogen
How much nitrogen is lost from soil as a result of erosion?
Nitrogen loss varies enormously depending on the soil type and the nutrient history. However, the top 10 mm of soil may contain 30% of the soil nitrogen, the most concentrated level of soil phosphorus and a large amount of the soil organic material. Loss of this layer due to wind erosion has resulted in poorer pasture growth and poorer crop establishment.
Should we soil test for nitrogen?
We recommended that you soil test severely eroded paddocks and consult your agronomist for specific advice.
Pasture and weed seed germination
Do wildfires reduce pasture and weed seed germination?
Intense pasture fires can destroy grass and other seeds on the surface and this may reduce pasture growth at the break of season. The best weed control benefits for cropping are from burning harvest residues in dense windrows. Recent studies suggest temperatures of 400°C for 10 seconds are needed to destroy ryegrass seeds and radish needs 20–30 seconds at that temperature, or 10 seconds for 500°C. Temperatures at this level are gained in windrows with large amounts of bulk in them, and in these circumstances may be that hot for up to three minutes. However, when the stubble is not dense or the fire is moving fast, some seed on or near the surface may not get hot enough for long enough and continue to be viable.
Should we control summer weeds after fire?
Delay spraying any summer weeds on burnt or eroded areas until there is about 50% cover. These weeds will help stabilise the soil. Seek local advice on timing of later weed control.
See Crop weeds: Reduce weed seed numbers in the soil: Burning residues for more information.
Crop advice
What are the best crops to sow after fire on eroded soils?
Where the risk of sand blasting is high – on loose, dry sand soils – we recommend growing cereal crops, as these have growing points below ground at germination and are more resistant to sand blasting. If the cereal only gets cut off one or two times the impact on yield is probably not severe enough to warrant re-seeding. We recommend that you do not plant lupins, peas or canola on wind eroded paddocks, because these are all highly susceptible to sand blasting losses.
What wind speed will damage crops from sand blasting?
Sand particles start moving at about 28 km/hr (threshold wind speed measured at 2 m) if the soil is loose and exposed, and the crop is very short. The amount of damage to crops from sandblasting will increase as the wind strength increases and the period of sandblasting increases. Wet soil is very unlikely to be affected by sand balsting or wind erosion. Crops four to six weeks after germination are usually safe from sandblasting, as there is usually sufficient ground cover to reduce wind speed below the threshold.
What are the yield losses from sand blasting?
Canola and lupins can suffer 100% loss from a single sand blasting. Wheat crops may have yield losses up to 50% when sand blasted three times and 10% or less from a single sand blasting.
Bush, revegetation and road reserves
What should we do about burnt bush, revegetation areas and roadside reserves?
Most of these areas are not very susceptible to wind erosion, especially if left undisturbed. We recommend that livestock are kept out of burnt and unburnt bush and revegetation areas; the fodder value is very low and the damage caused by livestock is likely to be long term. See bush and revegetation recovery after fire.
Acknowledgement
Most of this material was derived from the West Midlands Group's 'Badgingarra fire response: landholder information booklet' (25 January 2010). Some of the questions have been adapted and the answers have been updated.