Soil Erosion: An Advisory Leaflet for Preventing Wind Erosion (PB5820b)

Soil Erosion: Preventing soil erosion by wind

PB5820B
2001, rev 2005

 

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This chapter explains the problems caused by wind erosion, where it is most likely to occur and ways of reducing the risks of damage.

The problem

Erosion by wind can result in:

  • Loss of topsoil.
  • Loss of seed, fertiliser and agrochemicals.
  • Damage to crops by abrasion.
  • Soil blocking roads.
  • Ditches filled with soil.
  • Streams and rivers polluted by soil and agrochemicals.

Where does it occur?

Risk Areas

Susceptible soils in the drier parts of the country are most at risk i.e. parts of the East Midlands, Yorkshire and East Anglia (click here for map).

Soil types

Wind erosion is most likely to occur on:

  • Fine sandy soils with soil particles of 0.1-0.2 mm diameter.
  • Light peaty soils with soil particles of about 1 mm diameter.

Clay particles help to make stable crumbs and clods which resist movement. Organic matter contents of up to 20-30% help but above this the risk increases because of lower soil density and looser structure.

Other Factors

Wind erosion is most common:

  • When wind speed is greater than 20 mph.
  • On bare arable land between the months of March and June.
  • On fine dry seedbeds e.g. for sugar beet, carrots and onions.

Sugar beet and carrots are vulnerable for up to 5 weeks after emergence and onions for up to 9 weeks. Rainfall decreases the risk of wind erosion because moist soil particles stick to each other and resist movement.

Methods of control

Wind erosion can be reduced by measures which:

  • Reduce wind speed at the soil surface.
  • Stabilise the soil surface.
  • Trap soil particles already in motion.

The costs of different measures can vary greatly. The most appropriate method for a particular farm or field will depend on soil type, cropping, the size of the area affected and the availability of any specialist equipment or materials required.

Shelter Belts

Hedgerows and belts of trees will provide protection downwind for up to 20 times their height.

To be most effective they should:

  • Permit 30-50% of the wind to pass through.
  • Be evenly permeable from top to bottom.
  • Run at right angles to the damaging winds.

Allow existing hedgerows to grow taller in vulnerable areas but do not allow gaps to develop at the bottom.

Payments for establishing new hedgerows and belts of trees may be available under the Environmental Stewardship Scheme (from March 2005 onwards) or the England Woodland Grant Scheme (from July 2005 onwards).

Artificial windbreaks such as polyethylene netting or webbing can be appropriate for protecting small areas of high value crops.

Cultivations

On sandy soils, cultivations which leave a rough or cloddy surface can be the most cost-effective methods of erosion control for sugar beet. A number of techniques are practised. Consider using:

Furrow Press - plough and furrow press the land using a 45° angle press to leave steep ridges. Drill at an angle to the  ridges. To be effective the soil must contain sufficient clay for the ridges to be stable.

Loosened Stubble - remove compaction by underloosening and drill the crop directly into stubble. The system can be designed so that drill units directly follow the subsoiler tines.

Clod Forming - plough the land early in the year. Follow with a Cambridge roller when the soil is still wet to create a surface crust. Break the crust into clods with a slow moving tined harrow. Use press wheels or tines on the drill unit to break the clods around the seed. Remember - low ground pressure machinery is essential when working wet soil.

Nurse Crops

These may be used on very erodible peaty soils and sandy soils where higher value crops are grown. Barley is commonly used as a nurse to protect the row crop and may be broadcast or drilled.

Broadcast - spread barley seed in time for it to establish ahead of the row crop. This can give good overall protection.

Drilled - sow barley between each, or between some, of the proposed crop rows. Consider using machines which form beds and drill barley in one pass. Damaging blows can occasionally cause erosion along the rows.

Both techniques can give good protection but require careful management of the nurse crop. Ensure it is established in time to provide adequate protection and does not reduce yield by competition.

Sowing dates and seed rates of the nurse crop must be carefully selected. Appropriate rates of selective herbicides must be used to control growth and to remove the nurse crop.

Straw Planting

This technique has been used successfully on peaty soils and some light sands. Straw is planted between the crop rows just before or after drilling. The operation is slow and requires special machinery, but has advantages over nurse crops of:

  • Giving immediate protection.
  • No risk of competition.
  • No requirement for extra herbicide applications so can be used with sensitive crops.
  • Suitable for organic farming systems.

Synthetic Stabilisers

Proprietary soil stabilisers including PVA (polyvinylacetate) emulsions or PAM (polyacrylamides) can provide temporary protection when sprayed onto sands after drilling. They are not suitable for peats and are generally expensive but can be:

  • Applied quickly and easily if a blow is forecast.
  • Useful in protecting small areas of high value crops.
Mulches

Mulches applied to the surface after drilling can provide effective control for sugar beet seedbeds. They are not generally suitable for vegetables. Materials applied at 5-15 t/ha include:

  • Farmyard manure.
  • Sugar beet factory lime.

Thin even spreading is necessary to minimise risks of reduced crop emergence or poorer weed control. Take care not to apply excess nutrients, lime or contaminants by complying with the Defra 'Soil Code' and 'Water Code'. Certain industrial wastes may also be suitable but you must consult the Environment Agency and take expert advice before spreading.

Clay Addition/Marling

Increasing the clay content of surface soils is a long-term solution to wind erosion. Application rates of 400-1000 t/ha are likely to be needed to achieve a suitable increase in clay content. This may be practicable if marl or clay rich waste materials such as lake dredgings are available locally. Seek professional advice before using waste materials. You must consult the Environment Agency before dredgings or industrial wastes, including waste soil, are spread.


DEFRA PB5820B, 2001, revised 2005
© Crown Copyright. Reproduced for ADLib under Licence.

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