18/09/2014 Get to grips with soil compaction.
How do you protect your soils from yield-sapping hardpan?
“Soil compaction is one of the most common problems farmers face today – it severely limits yields and impacts margins,” says Cameron McKenzie, Seeding & Tillage Product Marketing Manager for the farm equipment brand, Challenger. “However, key steps can be taken to deal with it through the use of proper soil management.”
“As the name implies, compaction occurs when soil particles are compacted together, restricting the amount of space for the air and water needed for optimum plant growth. Compaction can occur naturally or be caused by farming practices. Most often, compaction is created by today’s modern heavy equipment traffic. The key to controlling it is to understand your farm’s soils, ascertain the root cause of compaction and learn how to reduce its costly effects.”
“Compaction tends to build up over time and gets worse every time you work your fields - most particularly in wet conditions,” he says. “If you haven’t deep-ripped your fields for example, compaction from a wet spring three years ago can dramatically lower yields further down the line.”
Certain soils compact more easily than others. Soils made up of particles of about the same size compact less than soils with particles of varied sizes. Wet soils compact more easily than dry, while soils high in organic matter have a better structure and are more likely to resist compaction.
Some important things to remember:
- Most compaction is caused by equipment traffic
- Up to 80% of compaction in the field occurs on the first pass of the season
- Surface compaction is caused by high ground pressure created by reduced contact area
- Deep compaction is caused by high axle loads
- Slip compaction is caused by low surface contact areas and smearing of the topsoil
- Pinch-row compaction is caused by dual or triple wheels as ground pressure from the tyres shifts from the centre of the tyre to the outside
“The best approach is aggressive corrective action at the right time at the right depth to restore the soil structure and prevent the build-up of compaction in the future,” continues Cameron. “Dig a soil pit to identify exactly where the problem is and establish a good profile of your soil’s state of health.”
Tracked tractors – such as the Challenger MT 700E and MT800E Series – are proven to be kinder to the soil than wheeled tractors. The unique Challenger Mobil-Trac rubber tracks deliver exceptional traction and distribute the load over a larger footprint. This reduces ground pressure and cuts the risk of compaction during field operations.
There are a number of key tillage practices and a wide range associated implements which address the problem of compaction.
Vary tillage depth
When soil has been tilled to the same depth for a number of years, a compacted layer builds up below where the implement has worked through the soil. To avoid creating this hardpan, cultivate deeper – but choose a dry year, as the compacted layer is easier to shatter. Thereafter, vary the tillage depth.
A range of soil loosening tool designs is available aimed at dealing with deep compaction (up to 450mm) - such as the Challenger 4710 and 4730 In-Line Rippers and the Challenger 4600 Disc Ripper (see table).
Once problem areas have been identified, individual fields can be tilled specifically to eliminate compaction. A good time to undertake this operation is early autumn, when, more often than not, the soil is reasonably dry and therefore more easily broken up.
Where the soil surface – down to 250mm – is compacted, this can be easily dealt with using a chisel plough. Challenger offers a range of implements to shatter surface compaction and open up hard ground. Among them are the Challenger 2500 Chisel Plough, 4213 and 4233 Coulter Chisels (see table).
Of course, better still, is to avoid the actions which cause compaction. Remedying it can be very expensive. Prevention is better than cure!
Reduce tillage operations
Conventional tillage practices require a number of passes by tractors and implements which break down the soil aggregates and make the soil more likely to compact.
By reducing the number of passes over fields, good progress can be made in preventing the build-up of compaction, while the decision to move to a min-till or no-till regime can produce a number of additional benefits:
- Moisture retention
- Topsoil erosion is reduced
- Input and machinery costs are lower
- Less labour required
- Reduces through-field traffic
- Crop residues left on the soil surface prevent crusting
Reduce in-field traffic
With conventional equipment, around 80% of compaction is created during the first pass through a field. Therefore, keeping off the soil subsequently makes a major contribution to managing the problem.
Random traffic causes compaction damage over a large percentage of the field, so a planned traffic strategy will pay dividends. And don’t forget that it is also particularly important to manage harvest traffic which, in fact, has the potential to inflict far greater compaction damage than tractors and implements.
“The ultimate solution is get back to basics and select a tillage and traction regime which minimises compaction damage and maximises the crops’ opportunity to grow effectively,” adds Cameron McKenzie. “The soil is our greatest asset. Treat it with care and it will return that investment many times over.”
Challenger offers a line of implements ideal for managing soil compaction
- Challenger 4200 Rigid and Folding Coulter Chisels for tractors 140-460hp. Working depth: 250-300mm
- Challenger 4400 Disc Ripper for tractors 200-280hp.Workign depth: 355-458mm
- Challenger 4500 Disc Chisels for tractors 175-570hp. Working depth: 305-356mm
- Challenger 4600 Rigid and Folding Frame Disc Rippers for tractors 315-750hp. Working depth: 457mm
- Challenger 4700 In-Line Ripper and folding frame version for tractors 175-600hp. Working depth: 457 mm
- Challenger 2500 Chisel Plough for tractors up to 440hp. Working depth: 150mm
How do you know if you have a compaction problem?
- Compaction often shows up as plant deformities
- Slow emergence of seedlings and thin stands can be caused by compacted soils. Seedlings have a difficult time penetrating this soil and root growth can be restricted
- Uneven early growth can reflect restricted root growth due to compacted layers. Crops grown in compacted soils are generally shorter than normal plants at the end of the season
- Off-coloured leaves may reflect nutrient deficiencies and nitrogen starvation where compacted soil restricts root growth
- Abnormal rooting patterns, such as shallow, fibrous root systems running horizontally above a compacted layer, are frequently a symptom
- The need for increased power during tillage
- Excessive wear on tillage equipment
- Surface crusting - comes predominantly after a hard rain and often results in poor crop emergence
- Standing water indicates slow water infiltration.
- Slow decomposition of organic matter is often the result of a compaction layer that causes water-logged soil with a low oxygen content
- Excessive erosion may be due to either surface crusts or subsurface compaction. Excessive run-off on sloping lands often results from slow water infiltration