What is a subsoiler & what are the benefits of subsoiling?

Nov 16, 2023    Posted by Stewart Knight

A Subsoiler is a cultivation implement attached to a tractor three-point linkage, developed to do as the name suggests, disturbing the subsoil below the normal tillage depth of 100-200 mm. This pan below the normal tillage working depth sometimes called a “plow pan” can lead to poor water infiltration and drainage, reduced soil aeration, and diminished growth of crop roots.

The practice of tilling the subsoil often called “ripping” has been around since the early 1900’s since mechanical cultivation started. Traditional cultivation for seedbed preparation only relied on the topsoil being tilled creating a hard pan underneath. This pan caused the rainwater and irrigation to puddle on the surface resulting in shorter planting windows and poor plant establishment.

This hard pack below the surface also meant that the plant roots had very little room to expand, restricting their ability to grow and uptake nutrients. Combined with very little soil being exposed the oxygen plant growth is greatly restricted.

Hence the development of the subsoiler, consisting of straight shank leg usually around 500 mm in length, and spaced along a beam at 14 -15 inches apart (350 to 380 mm) it is able to penetrate deep into the plow pan and break through the hard layer of subsoil.

More recent additions to the traditional subsoilers include wings to the bottom of the shank to increase the soil disturbance deep in the sub layer, to help remove compaction and increase oxygen around the plant root area. These wings can also be higher up the shank to act as a “weed knife” skimming along just below the soil surface disrupting weed roots and exposing them to the sun.

Many subsoiler in today’s market are fitted with a variety of rear rollers, to assist with clod reduction and soil leveling after ripping. Most common would be the crumble roller, usually around 200 to 300mm in diameter with straight bars running the length of it is very effective at breaking down large clods and leaving a level finish for very little extra fuel burn.

The added benefit of rear roller is it will assist in maintaining a consistent depth without relying on the tractor linkage. Which can vary greatly depending on different makes and models and draft control features.

Subsoilers today also come with three different methods of safety releases, namely shear pin, spring release, or hydraulic release.

Shear Pin

A shear pin as the name suggests means the ripper shank has a hinge pin towards the rear and relies on the shear strength of a sacrificial pin mounted near the front. Should this ripper shank encounter a hard object e.g., a stone or large tree root the shear pin will snap and allow the shank to swing free rather than damaging the subsoiler frame or shock loading the tractor hitch. Then it's just a matter of lifting the ripper out of the ground and replacing the broken pin with a new one and it's right to go again.

Spring Release

A spring release works on a similar principle, using a vertical spring as the release point instead. So, if the shank encounters a solid object above the rated pressure of the spring it will release and allow the shank to ride up over the object without disturbing the other shanks. Once the affected shank is clear of the solid object it will automatically reset without the operator having to stop or even slowdown from his task. This simple but effective system can be adjusted to suit different soil conditions by a large nut mounted on top of the spring used to increase or lessen the spring load and thus breakout pressure of the affected shank.

Hydraulic

Hydraulic release works the same as a spring release but instead uses a hydraulic cylinder and accumulator to achieve the breakout rather than a spring.

Which unit is best for me?

When comparing these methods, it's important to note the following. A shear pin unit is best suited to a country that is free of obstacles like rocks, roots etc. This is because of the time and consumable savings in not having pins shear all the time. A spring release set up will work in all conditions, but it's ideally suited to rocky conditions where the auto reset feature shines. Hydraulic units work the same as a spring release which makes them ideal for rocky conditions the downside is simply the expense, high maintenance costs and the wear on all the hydraulic cylinders.

Today subsoilers are a widely used implement across cropping farms, for seedbed preparation to increase drainage and get a more consistent depth of moisture profile, increase oxygen at plant root depth or even help prevent erosion on freshly sown paddocks.

Do you want to learn more about subsoilers? Reach out to Delmade we are very happy to answer questions you may have. Phone 1800 335 623.