The plozza plough and seeder

Kojonup farmer Ben Webb is taking action on water repellent soils in an effort to improve crop emergence. Water repellence, which is commonly associated with sandy topsoils, results in uneven wetting of the soil and patchy crop emergence.

Based on recent research and discussion with his peers, Ben decided to adapt an old chamberlain plough with Plozza discs.

“The discs go in 25cm and inverts the soil and mixes it a bit too. The aim is to get a bit of that higher percentage clay soil onto the top. We will also mix through some of the lime we’ve been spreading and activate a lot of that.”

While ploughing and lime incorporation can also address other constraints such as soil acidity and compaction, subsoil testing revealed that Ben’s pH increases with depth from around 5.4 up to 5.7. He doesn’t consider compaction on the gravelly paddock to be a constraint.

“A lot of this country has never been ploughed. This is a one-off plough.”

“It’s taken a while to get it all working properly. Loosening everything up is a bit of a challenge. From the few runs I’ve done I’m not getting quite enough subsoil on top, but I think the crop residue is causing some issues.”

Soil is often repellent when it has less than five per cent clay. So where more clayey soil is just below the surface, the plozza plough is a good option. This was shown with a simple demonstration. Water poured onto an unploughed area sat on the surface. Whereas on a ploughed area with clay on the surface, the water infiltrated immediately.

Water repellent topsoil (right) and subsoil (left) where water has infiltrated

The Southern cropping areas are prone to erosion after strategic tillage that is conducted during summer or autumn. Implementing strategic tillage in late winter or early spring means that summer crops can be planted at the same time to protect the soil over the drier months.

Ben is no stranger to summer cropping but would usually sow without tillage. In this case he is sowing millet between the discs and press-wheels to get some roots and structure into the soil.

“I’ve done summer cropping before but not like this. Generally, we would graze the summer crop, but I’m a bit worried about this paddock because it’s a bit fragile for the sheep. So, we’ll see how it goes.”

The Department of Primary Industries and Regional Development (DPIRD) will look more closely at the technique through its new Soil Reengineering project supported by GRDC. DPIRD’s Glenn McDonald praised the initiative taken by Mr Webb.

“It’s great for the project to have collaborative growers like Ben to work with so the project and other growers can learn with Ben,” Mr McDonald said.

“For any strategic tillage operation, getting the right combination of machine, soil type, soil moisture and timing is important. For the plozza plough discs, there are different disc concave angles, for which the soil type and desired tillage effect will influence which disc angle is chosen.”