THERE’S almost irrefutable evidence these days that bigger tractors, boomsprayers, road trains, heavier seeding rigs and chaser bins are causing deeper subsoil compaction.
It has led to a plethora of deep ripper machines on the market, witnessed recently by eight different models demonstrated at a Mullewa field day.
More than 30 years ago, you could deep rip between 25 and 30cm (10-12in) to break up hardpans and gain a significant yield response, typically in barley or wheat.
But bigger machinery is seeing ripping move to depths between 40 and 60cm (16-24in).
Leaving aside issues, such as low soil pH at depth or sodicity, there is plenty of anecdotal and trial evidence that suggests you can expect a crop yield response from going deeper.
But the question of how long the benefit remains before you have to rip again is somewhat of a moot point.
Your residual period will be longer, especially in heavier soils, if you have ripped and then employed a controlled traffic system or if you have mouldboarded and ripped in typical sandplain country.
According to the GRDC, the response to deep ripping can last for many years.
In responsive soils the residual benefit of the ripping in the second year is about half the initial response and declines further over time due to re-compaction by traffic, natural soil settling and cementation and the greater removal of nutrients and water by the previous year’s higher-yielding crop.
So, in essence, deep ripping cannot be regarded as a set-and-forget job.
It’s the reason Mullewa farmers Ian and Rob Kitto own two deep rippers, with a 6m (20ft) Bednar Terraland employed every four years to rip to depths between 600 and 700mm (24-28in) then they come back every two years with a 12.2m (40ft) Ausplow Easitill, operating to a depth of 400mm (16in) to break up surface compaction in the 200-300mm (8-12in) zone.
The obvious wider width means the ability to cover more ground during optimum windows.
The two rippers also play a role in a program to elevate soil pH.
The Terraland can ameliorate the soil (and lime sand) and the Easitill also can assist lime sand movement by breaking up the surface compaction.
Ideally, by keeping soils “open”, they will become more structured and with an elevating soil pH, more responsive.
Ken Wilson
Farm Weekly's machinery writer.
Farm Weekly's machinery writer.
