GroundCover™ Issue: 126
Deep-ripping mechanically breaks up compacted soil layers using heavy tynes working at depth to break up compacted soil layers. Tyne spacing, working depth, shallow leading tynes or discs, soil moisture content, timing and soil type all need to be taken into account before deep-ripping is considered.
Not all soils and crops respond positively to deep-ripping every season. But when they do, benefits usually last for about three seasons, or much longer if a controlled-traffic system is in place.
Deep-ripping is most effective where roots need to grow deep to access subsoil moisture.
However, if the soil below the ripping contains other constraints, such as acidity, poor structure from sodicity or subsoil salinity, the deep-ripping benefits will be limited. The addition of soil ameliorants such as lime or gypsum may be required to stabilise the soil.
It is possible to inject lime into acidic subsurface soil behind deep ripping tynes, however, this is a slow operation and difficult to implement on a large scale.
Costs and benefits
Grain yield responses to deep-ripping on deep sands and sandy earths have tended to be large and reliable, especially in high and medium rainfall areas (more than 350 millimetres). Benefits to these soils appear to last for at least three years, depending on crop rotation and soil type.
Deep-ripping of heavier-textured soils such as the sandy clay loams, loams and even sodic clays has often been found to be less reliable. More recent research has shown that the yield responses to deep-ripping can be large in the year the soil is ripped, however the benefits can be short-lived in subsequent years on these soil types.
Incorporation of organic matter and gypsum, and minimising or avoiding recompaction by installing a controlled-traffic system, help maintain the benefits of deep-ripping.
Deep-ripping duplex soils can be beneficial when the loamy layer is shallower than the depth of ripping so clay soil can be mixed with sandy topsoil increasing surface soil cation exchange capacity and reducing water repellence.
The cost is $40 to $50 per hectare for deep-ripping sandplain soils. The main influences on cost are the draft force required to pull the deep working tynes and the impact this has on fuel use and power requirements.
This can be reduced by using a shallow leading tyne ripper, which can reduce the draft force required to pull a deep-ripper.
- The ripping tynes must be able to penetrate just below the compacted soil layer.
- Soil must be moist enough to allow penetration of the ripping tynes but not so moist that the tynes cause smearing rather than fracturing and shattering the soil.
- A roller or soil packer behind the deep-ripper or attaching wings behind the tynes can minimise the risk of a rough soil surface or soil softness that can cause uneven seeding depth.
- Loosened soils can be more susceptible to compaction after deep-ripping if not managed carefully. It is recommended to leave deep-ripped soil to settle for at least two weeks before sowing.
- Research has shown that single shallow leading tynes working in-line and ahead of the deep-ripping tyne reduce the draft force by up to 18 per cent with the leading tyne working at 10 centimetres on clay-textured soil.
- On sandy-textured soils with the leading tyne working at 10cm draft force is reduced by 10 per cent.
TimingTiming involves finding the appropriate window when the soil is moist, while not conflicting with seeding. Options include:
- deep-rip after seeding but early enough not to disturb establishing plants too much (generally within three days of seeding), although this can also reduce crop establishment;
- deep-rip in the inter-row of crops sown on wide rows during the growing season; or
- deep-rip opportunistically after significant out-of-season rains.
In some situations, such as a dry finish to the season, faster water use and increased vegetative biomass caused by deep-ripping can leave insufficient stored soil water for grain filling, resulting in haying-off and reduced yields.