TRIALS of deep ripping to greater than 450 millimetres revealed a potential cumulative return on investment of $1 to $29 per hectare over four years by reducing soil strength.
Deep ripping of soils to hardpan depths can produce positive yield responses in a variety of soil types, according to Department of Primary Industries and Regional Development (DPIRD) research.
The results of a five-year project undertaken by DPIRD, with Grains Research and Development Corporation (GRDC) co-investment, will be presented at GRDC's upcoming Grains Research Updates in Perth.
Department research scientist Wayne Parker will present on deep ripping trials in eight different soil types, at six sites around the State, which began in 2015.
"It was hypothesised that the economic return from deep ripping would be increased by ripping to a greater depth and through the use of topsoil slotting plates," Mr Parker said.
"We found that ripping deeper than 400mm produced a positive yield response in sand, loamy earth and gritty grey clay soil.
"However, the trials found no benefit from deep ripping in a sodic, calcareous loamy earth, commonly known as a Morrel soil."
Trials were conducted within a controlled traffic farming system with growers sowing and managing trials as part of their day-to-day activities.
This avoided machinery re-compaction of the soil that was loosened by the deep ripping.
Improvements in some areas were also achieved by fitting topsoil slotting plates during ripping, which helped to incorporate organic matter and soil ameliorants deeper in the soil.
These topsoil slotting plates increased yields but also costs, some of which could be reduced by modifications of the plates to minimise draft and its associated fuel and maintenance costs.
Mr Parker said ripping sandy soils to depths of 300 to 350mm had been common farming practice since deep ripping was first introduced more than 30 years ago.
"Ripping sandy soils to these depths no longer produces the results farmers need," he said.
"Compaction below 300mm still impacts root growth, which reduces the ability of plants to access moisture and withstand stress.
"Current thinking is that ripping deeper is better, though growers need to understand their depth of compaction to guide their ripping depth and maximise investment.
"Further investigation of variables in deeper ripping programs is still required to maximise returns and improve decisions on crop choice, crop establishment and fertiliser requirements."
More information: visit giwa.org.au/2020researchupdates