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Deep ripping and delving solve different constraints. Get the diagnosis wrong and you can spend real money loosening soil that didn't need loosening, or fail to fix the layer that was actually holding your yield back. Here's how the two compare, and how growers and researchers are working out which one a paddock needs.
Soil constraints represent a significant cost to Australian grain growers, and the research is clear on one point above all: there's no single fix. The right tool depends entirely on what's actually limiting the paddock.
Deep ripping, delving, spading, inversion ploughing: growers and researchers group all of these under "strategic deep tillage", but they don't do the same job. GRDC groups strategic tillage into three broad categories: ripping, mixing and inversion, each with a different effect on the topsoil and on any amendments applied. Delving sits in the mixing category. Deep ripping is its own category. Knowing which one your paddock needs starts with knowing which constraint you're actually dealing with.
Deep ripping uses strong tynes to fracture compacted or hard-setting soil at depth, typically 30 to 60 cm depending on the constraint and the machine. The aim is physical: shatter the dense layer so roots and water can move through it. It's the most established of the strategic tillage tools, with WA growers using it on sandplain soils for decades to break up compacted layers.
The research backs it up on the right soil type. GRDC reporting shows deep ripping delivers consistent benefits on deep sands, with less clear advantages on other soil types. That's an important caveat: ripping loosens the ground, but it doesn't change what the ground is made of. Rip a nutrient-poor sand and you get a looser nutrient-poor sand.
Delving is a soil modification practice rather than a loosening one. A delver drives large angled tynes below a subsurface clay layer and drags clay up into the sandy topsoil above, where it's later worked in. DPIRD's factsheet on claying to manage soil water repellence sets out the scale involved: delving tynes can run up to 2.5 m long, spaced 80 to 100 cm apart, working at roughly a 45-degree angle, and typically need a tractor of 400 hp or more to pull them. The clay lifted to the surface still needs to be broken up and mixed through the topsoil, usually with a spader, smudge bar, cultivator or roller in a follow-up pass. The same DPIRD guidance notes contract clay spreading runs in the order of $6 per tonne, before incorporation costs.
The payoff is that clay holds what sand can't. A modest amount of clay mixed through a sandy topsoil improves water-holding capacity, reduces water repellence and lifts nutrient retention, which is why delving is described as transforming the soil rather than simply treating it.
Sodicity is a separate constraint again, and it's a costly one. Sodic soil has an exchangeable sodium percentage above 6, and the excess sodium weakens the bonds between clay particles, causing the soil to disperse and lose structure when wet. According to the Soil Quality Knowledge Base, wheat yield losses on sodic soil run 30 to 60 per cent compared with unconstrained soil, with an estimated cost to WA agriculture alone of $31 to $128 per hectare per year.
Sodic layers usually sit below the topsoil, in the same position a bleach layer or hardpan might. Breaking through to the clay beneath and improving structure through the profile is the same broad job as tackling a hardpan or a bleach layer, which is why growers dealing with sodicity often reach for the same deep ripping and delving toolkit.
| Deep ripping | Delving | |
|---|---|---|
| Category | Ripping | Mixing |
| Primary job | Fracture compaction and hardpans | Lift subsoil clay into sandy topsoil |
| Changes the soil? | Loosens it | Modifies its composition |
| Typical depth | 30 to 60 cm (up to 75 cm on heavy-duty rippers) | Below the clay boundary, machine-dependent |
| Best suited to | Compaction, hardpans, traffic pans on deep sands | Sand over accessible, suitable-quality clay |
| Follow-up required | Usually minimal | Almost always: spading, smudging or rolling to break up clods |
| Main risk | Doesn't address chemical or fertility constraints | Poor-quality subsoil clay (sodic, saline, boron) can make things worse |
GRDC's grower handbook on tackling amelioration is built around a simple principle: identify the constraint before you choose the fix. In practice that means digging a pit or taking cores in representative or known problem areas, rather than guessing from the surface. Electromagnetic (EM) surveys are useful here too, particularly for mapping the depth to clay or gravel across a paddock, which helps decide whether ripping, delving, claying or inversion is the right call.
GRDC's guidance on matching implements to constraints recommends sampling in layers, often every 10 to 20 cm, to identify pH extremes, sodicity, toxicities and nutrient deficiencies through the profile, alongside push probes or penetrometers to locate hardpans. As a rough guide: a physical barrier with an otherwise reasonable profile points to ripping; sand sitting over good-quality, tested clay within reach points to delving or clay incorporation; a compacted layer combined with sodicity, acidity or a bleach layer often points to a combination of both in the one pass.
Diagnosis is only half the job. Timing and follow-through matter just as much. GRDC agronomists note that growers who plan and implement soil amelioration programs well have lifted profits by an average of $100 per hectare, but the same guidance is blunt about the downside of getting it wrong: work in conditions that are too wet and the equipment won't perform, and can add to compaction rather than fixing it.
A few principles hold regardless of which tool you're running. Work when there's some subsoil moisture; bone-dry clay shatters into clods that fight you all season, and wet clay smears rather than breaking up. Plan the follow-up pass before you start, not after. Have any subsoil you're planning to bring up tested for pH, sodicity, salinity and boron. And treat the first paddock as a trial strip so you can measure the response before committing the whole program.
Standard rippers are built to fracture compaction. On sand-over-clay country, that's often not the full job: a ripper that also has the strength to drive under the clay boundary, lift and shatter clay through the profile, and hold the slot open with inclusion plates for ameliorants to fall through, can cover ripping and a meaningful share of delving's benefit in the one pass. That's the role our AP102 was built for, and it's the approach we've documented in detail in a case study from a sand-over-clay property on the Eyre Peninsula.
It's still a deep ripper first. A dedicated delver moving large clods at wide spacings remains the right call on some profiles, particularly where the clay sits deeper than a ripper shank can reach. The AP102's advantage is in the country where a single, correctly configured machine can do both jobs without a second pass.
For preparation, timing and moisture guidance, see Things to Consider When Deep Ripping.
Contact us to talk through your soil constraints and the right machine and configuration for your country.
