Led by NSW Department of Primary Industries (DPI), the Grains Research and Development Corporation (GRDC) project is investigating the potential of deep ripping and deep placement of soil amendments to address subsoil acidity issues, which affect more than 20 million hectares of Australian agricultural land.

NSW DPI principal research scientist and project leader, Guangdi Li, said the on-farm experiment near Cootamundra compared crop responses to surface liming with deep placement, from 10 to 30 centimetres, of lime and lucerne pellets.

“There were visible responses to soil treatments from wheat, barley and canola crops at seedling and flowering stages,” Dr Li said.

“Early results from seedling samples showed deep ripping with lucerne pellets produced more dry matter than surface liming and ripping alone also improved crop growth.”

Subsoil acidity is a major constraint to crop productivity in the medium to high rainfall zone, 500 to 800 millimetres, of south-eastern Australia. Growers traditionally address acidity with surface applications of lime to lift crop yields and quality, but lime applied to the surface moves slowly through an acidic soil profile.

The Cootamundra site has a pH in calcium chloride of 4.2 at the soil surface and 4.5 to a depth of 30 centimetres.

A dual depth delivery, 3D, ripping machine has been developed by NSW DPI to deliver soil amendments where they are needed, deep in the subsoil. “Soil chemical, physical and biological properties will be monitored to understand how soil amendments work to combat soil acidity,” he said

“Novel material to be used in soil amendments, including magnesium silicate, will be tested in laboratory and greenhouse studies to identify promising material.

“Promising material will be tested in large-scale farm demonstration sites across south eastern NSW and Victoria’s north-east and south-west during the next three years.”