Land: Soil compaction
- Author
- Reviewer
- Key findings
- Indicators and summary of status
- Importance
- Pressure and condition
- Response
- References
Author
Bruce Carey, Department of Natural Resources and Water
Reviewer
David Freebairn, Department of Natural Resources and Water
Key findings
- Soil compaction is a major impediment to soil productivity on all cropping and grazing lands in Queensland. It is caused by tillage implements, tyres and animal hoofs, particularly when they traverse moist to wet soil. Soil compaction leads to yield loss and decreased water and fertiliser efficiencies. Cultivating compacted soils requires higher amounts of energy.
- Practical land management practices can be implemented to repair compacted soils and to ensure the prevention of future compaction. Such practices have a range of benefits besides the alleviation of compaction and are being adopted in a variety of cropping situations.
Indicators and summary of status
Indicator |
Status of indicator |
Adoption of practices to reduce soil compaction |
Over the past 10 years, the grains, sugarcane and cotton industries have made considerable advances in managing the effects of soil compaction. |
Importance
Soil compaction is a problem common to all cropping and grazing lands in Queensland. It is caused by tillage implements, tyres and animal hoofs, particularly when they traverse moist to wet soil. The outcome is most serious in soils that are initially well structured and therefore of high agricultural value. It is also a serious problem in soils that are inherently poorly structured, because compaction exacerbates their hard-setting or crusting nature. Examples of soil compaction span all soils, the cropping, grazing and forestry industries, small- to large-scale enterprises, and all climatic zones.
Clay soils are most susceptible to compaction because their fine particles hold more water for a longer period than sandy or loamy soils. As a result, clay soils remain in a plastic state, sometimes for the whole year. This means they will compress and shear when a load is applied to them.
A compacted soil lacks the interconnected air spaces that are essential to the movement of water, gases and plant roots. This lack impedes critical processes that are essential for a biologically healthy soil. Crop yields are affected most in dry years when plant roots, unable to penetrate compacted layers, cannot access much-needed subsoil water. Water use efficiency is greatly reduced as rain or irrigation water is unable to penetrate the compacted layers of soil to refill the subsoil. This results in more runoff and evaporation.
Compacted soil requires more horsepower (and fuel) to cultivate. Planting implements are less effective in compacted soil and poor germination is the result. Fertiliser efficiency is also reduced as the large blocks of compacted soil give few surfaces for the fertiliser to activate.
Pressure and condition
The adoption of practices such as controlled traffic farming to minimise soil compaction involves a significant change in land management practices and thus represents a significant hurdle for many landholders. Major items such as tractors, spray rigs, planters and harvesters all need to have compatible wheel spacings. The purchase of new equipment involves significant expenditure and the difficulty of obtaining suitable machinery with compatible wheel spacings can greatly limit the options available.
It is very difficult to survey and map the extent of soil compaction because of its subsoil nature. Measurements have been conducted at sporadic, individual (trial) sites, but no systematic and documented measurements of condition and trend in any cropping industry have been undertaken. Only a few individual studies exist for the grazing and forestry industries.
An alternative approach to the direct measurement of soil compaction would be to monitor the adoption of practices that minimise the occurrence of soil compaction. Examples of such practices include:
- reduced or zero tillage;
- controlled traffic farming (reducing the compacted area by confining as many tillage and traffic operations as possible to the same wheel tracks);
- avoiding traffic and tillage when the soil is moist or wet;
- using narrow tyres with a large diameter (they compact a smaller area than small wide tyres or dual tyres); and
- using flotation (low pressure) tyres on all equipment if controlled traffic or narrow tyres are not an option.
Response
A number of industry-based programs are in place to encourage landholders to adopt best management practices including those that minimise soil compaction. No dedicated systems are in place to collect data on the adoption of these practices, although a range of agencies would have collected some information for specific industries in selected locations.
The National Landcare programme is a longstanding programme within the Department of Agriculture, Fisheries and Forestry which supports the sustainable use and management of natural resources. The National Landcare Programme encourages farmers to adopt sustainable land management practices, and improve the land condition both on and off farms. Additionally, the Memorandum of Understanding between the Queensland Government and the Queensland Farmers' Federation on Farm Management Systems encourages the take-up of a range of management practices by agricultural operators that minimise, and in some cases eliminate, adverse environmental impacts. These include the Property Management Systems Initiative announced in the Blueprint for the Bush, the FutureCane program to promote sustainability and adjustment in the canegrowing industry, and the research, development and extension efforts of the Department of Primary Industries and Fisheries.
A new initiative, the State Rural Leasehold Strategy, will provide a framework for managing and using state land leased for grazing and agriculture, which represents more than half of the state's total land area. The strategy will use a mix of regulatory and reward-based approaches to improve the productivity, profitability and sustainability of leasehold land.
Over the past 10 years, the grains, sugarcane and cotton cropping industries have made considerable advances in managing the effects of soil compaction.
While no published data are available, agronomists working with farmers in the cereal cropping lands of central Queensland and the Western Downs have estimated that controlled traffic farming has been implemented on around 50% of the cropped area. While minimising soil compaction is one of the benefits, farmers are also attracted by the efficiencies associated with controlled traffic such as the reduction in costs of fuel, seed, fertilisers and agricultural chemicals. There has, however, been some evidence of soil erosion associated with wheel tracks concentrating runoff.
The FutureCane project conducted by the Department of Primary Industries and Fisheries and the Bureau of Sugar Experiment Stations encourages and assists farmers to adopt a number of practices with both environmental and economic benefits, including those that minimise soil compaction. These include changing row spacing to match the wheel spacings of harvesters and haul-out machinery, reduced tillage, and the use of rotation or break crops, such as soybeans. Adoption rates of controlled traffic in the cane industry are relatively low at 12% (Wrigley 2005), but interest in the practice has grown as farmers become more aware of the benefits.
In horticultural situations, controlled traffic is normally confined to tree crops or crops grown in rows. There is scope, however, for the adoption of controlled traffic in the production of vegetables and fruits such as strawberries that are grown in beds. This represents a significant change in management practices, and the adoption of controlled traffic is restricted by the varying wheel spacings of the machinery in use. The practice has been adopted by a small number of farmers.
References
Wrigley, T. 2005, Canegrowers Public Environment Report 2005 , Canegrowers, Brisbane.
Return to State of the Environment Queensland 2007 content page
Last reviewed 16 May 2011
Last updated 4 September 2007