Wind erosion control after fire in Western Australia

What you can do soon after the fire

Act to limit further erosion:

• Remove livestock and keep them off burnt paddocks: they can be put into a confinement feeding area, an unburnt paddock or agisted.
• Minimise vehicle traffic.
• Protect highly susceptible and valuable areas, such as house, garden, sheds, yards, gateways and laneways with binding spray, claying, gravel, old hay or straw to give a full cover. A dust-free living and working environment is particularly important after a fire.
• Leave burnt residue on roadsides, revegetation and bush areas to decrease the risk of wind erosion. If clearing is necessary, it should be left until after the break of season.

Protect valuable infrastructure and susceptible soils

Summer rain and cover crops on burnt, broad areas (crop or pasture)

• Check if a cover crop is needed: crop crowns or good pasture roots surviving the fire may provide enough protection. If erosion is starting, choose from the options below.
• About 10 mm of rain on sands and 15–20 mm on loams is enough to germinate cereal seed. This is more likely in southern and coastal areas. For areas unlikely to get summer rain, see the next section on claying.
• 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 weed control.
• Use on-farm smoke- or fire-affected cereal seed if available. Test for germination and adapt the seeding rate to allow for reduced germination. Cereals are less damaged by sand-blasting than are broad-leaf crops. There is evidence that barley establishes better than wheat as a broadcast crop.
• Topdress cereals at normal rates if possible. Lower rates (half to one-third of normal rates) will achieve surface cover, but there is little margin for error.
• Broadcast seed: it is faster than drilling and causes less soil disturbance.
• Soil disturbance can be minimised by spreading from tramlines or spraying-tracks. You may not get 100% coverage, but the strips that miss out on seed should be protected by those that do receive seed.  Contract spreading is available to do this.

Claying, gravel, sprays and clods to protect the surface

• Claying is a good option on very susceptible sands that also suffer from water repellence. Do not use delving or other soil disturbance to bring clay to the surface – these operations greatly increase the risk of wind erosion. Claying is expensive when done at the higher rates and has technical risks. We recommend you get advice from a professional or experienced operator before choosing this option.
• 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.
• Leave clay on the surface over the summer when wind erosion risk is highest, and incorporate the clay into the top 5–10 cm before seeding. Incorporation is needed to prevent clay forming a surface crust that reduces seedling establishment and water infiltration.
• Gravel can be spread at the same rates as clay spreading to get a stable surface. Gravel is preferred over clay on very susceptible and difficult areas like water trough aprons and at gates where livestock tend to congregate. Gravelled areas will drain well when it starts raining.
• Chemical stabilisers (e.g. hydromulch, DustBloc®, Dustex®, Gluon^TM) will give short-term dust control. These chemicals are expensive (>$1000/ha). Dustex® and Gluon^TM require water at 1 litre per square metre (10 000 L/ha). Note that the crust they form is easily broken by any form of traffic.

How about cultivating to reduce the risk of erosion?

In most cases we do not recommend cultivating to bring clods to the surface, or scraping ditches and ridges to reduce windspeed right at the surface, and to trap moving soil particles. Why? Because many of our agricultural soils are too sandy to produce stable clods, and the risk of wind and water erosion from summer storms is increased on cultivated soil.

Delving or ploughing wet soils to lift large enough clay clods (more than 2 cm in diameter) can protect the soil from more erosion by reducing wind speeds at the soil surface. However, cultivation will increase the likelihood and impact of wind erosion if good-practice guidelines are not followed.

See Soil inversion to ameliorate soil water repellence for more information on risks and good practice.

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At the break of season

The aim is to achieve and maintain a groundcover of at least 50% of anchored biomass, equivalent to about 800 kg/ha dry matter. The target for safe levels of ground cover should be 70%.

Pasture recovery at break of season

Fire-affected paddocks usually recover slowly because fire removes seed reserves of grasses, and the condition favours weedy species. And, because most groundcover has been removed, the paddock is susceptible to more erosion at the break of season.

We recommend that you:

• Defer grazing until there is about 800 kg/ha of securely germinated pasture dry matter and at least 50% groundcover.
• Continue supplementary feeding of sheep in safe areas.
• Establish cover crops on the most eroded and susceptible areas, then graze when there is sufficient ground cover, to allow pasture plants to develop.

Carrying capacity will be reduced for the first season and it may take 2 to 3 years to achieve full production from severely burnt annual pastures.

For more information, refer to the Agriculture Victoria page on recovery after fire, and the quick reference guide flow chart on pasture recovery after fire.

Cover crops to reduce wind erosion risk in pastures

Annual pastures might be slow to produce adequate ground cover after a fire. Sowing fast-growing cereals can reduce the risk of wind and water erosion if established early. Cereals can be topdressed or broadcast on wind erosion prone soils, or seeded with minimum tillage on more stable soils.

Some guidelines for fire-recovery cover crops

• Cereals can withstand sand-blasting better than most other crops.
• A seeding rate of about 30 kg/ha of cereal seed is generally adequate.
• Oats produce more stubble than wheat or barley, and are the preferred option for a cover crop.
• Do not start grazing until there is a minimum of 800 kg/ha dry matter and at least 50% groundcover.
• Aim to have a minimum of 50% groundcover over the following summer. See managing wind erosion for more detail.

Cropping eroded areas

We recommend cereals are established with minimum soil disturbance on eroded areas. Cereals have better tolerance to sand-blasting than lupins, canola and peas.

Eroded areas may need additional nutrients, so consult an agronomist on the need to do a soil test.

Managers who have retained sheep after a fire may need extra feed early in the season and grazing crops is an option. Stock numbers and crop area can be increased on a farm using grazing crops because there is less reliance on slow-growing early pastures in a grazing crop system.

Water supply

Dams and soaks

Wind and water erosion following a fire can reduce the water quality in dams by blowing or washing ash and soil from burnt paddocks and bushland into the water. Nutrients in the soil and ash could lead to bacteria and algae growing in the water and reduced suitability for livestock. See contamination of farm dams for information on clearing or treating contaminated water.

See Water supply management after a fire for more information.

Creeklines

Soil washed from burnt paddocks can cause sedimentation and blocking of creeklines. There is no cheap and easy way to prevent this, but earthworks can reduce the problem of future erosion ending up in the creek. DPIRD recommends integrated surface water management to reduce erosion and sedimentation risks.

Other resources:

• Aquatic and riparien vegetation (Department of Water and Environmental Regulation)

Learning from this fire and preparing for risk of future fires

Fires are a seasonal hazard in the agricultural areas of the south-west of Western Australia due to several factors:

• The Mediterranean climate – cool wet winters followed by a long, warm to hot, dry summer.
• Crops and pastures are mostly annual – they dry-off in spring and become highly flammable in the hot dry summer.
• Lightning strikes during thunderstorms are common during the dry part of the year.

We recommend managers develop a preventative program and a recovery program to prepare for fire and wind erosion.

For more information see bushfire survival plans for landholders, and Fire on farms in Western Australia – Reducing the risks.