Soil Structure Decline

Soil structure decline is a phenomenon caused mainly by excessive tillage. DPIRD estimates the cost of lost crop and pasture production from subsoil compaction at $330 million for WA’s agricultural soils. Soils with poor structure typically exhibit symptoms of ‘crusting’ and ‘hard-setting’ of the surface. Degraded soils are characterised by reduced infiltration, increased runoff and increased compaction. Ideal soil structure has a large proportion of aggregates from 0.5 to 2 mm, which are not easily broken down.

What Causes Soil Structure Decline?

1. Excessive and/or poorly timed cultivation (especially wet soils);
2. Stock trampling (especially wet soils);
3. Loss of organic matter through stubble burning and/or tillage; and
4. Compaction by vehicles.

Solutions and Preventions

• Reduce tillage frequency and time it to occur when soils are not excessively wet or dry;
• Consider tilling areas of high structure decline to break up compaction and improve water holding capacity e.g. deep ripping, mould boarding, spading etc.;
• Reduce vehicle compaction by controlling vehicle movement;
• Remove livestock from paddocks before overgrazing occurs; and
• Fence or carefully managing stock access to fragile soils e.g. near waterways.

Further Reading

Armstrong, R. D., Eagle, C. and Flood, R. 2014. ‘Improving grain yields on a sodic clay soil in a temperate, medium-rainfall cropping environment.’ Crop and Pasture Science. 66(5): 492-505.

Australian Soil Club. Accessed 26/04/2018. ‘Soil Structure and Soil Texture: How do they affect Soil Health and Fertility?’

Davies, S. and Lacey, A. 2011. ‘Subsurface compaction a guide for WA farmers and consultants.’ Department of Agriculture (WA).

Department of Primary Industries and Regional Development (DPIRD). 2017. ‘Deep ripping for soil compaction.’

Grains Research and Development Commission (GRDC). 2018. ‘Carbon storage for healthy WA soils.’

Liebe Group. 2011. ‘Revisiting Gypsum for improved soil structure.’