FOR Mullewa farmers Rod and Andrew Messina, continuous cropping went under the microscope in 2011.
“We had no references back then but we decided to start mouldboard ploughing,” Rod said.
“It was a concept borne mainly out of frustration of droughting crops from limited rain between 200 millimetres and 300mm.”
Armed with a theory that mouldboard ploughing could be another tool in the toolbox – to overcome non-wettings sands, mainly herbicide-resistant ryegrass and elevate subsoil pH with the introduction of lime at depth – 900 hectares of their 12,500ha (30,875 acre) property was mouldboarded.
That practice, along with deep ripping, continued for six years with most of the farm now renovated.
“It was about adopting a more holistic approach to improving the farm’s productivity, especially on our less productive soils and building soil structure to improve sustainability,” Rod said.
“Hopefully we’ve fixed the 200-300mm of topsoil with an average six tonnes a hectare of lime between 2012 and 2016, elevating soil pH to 5-5-5.8.
“Now we’ve got zones between 0-400mm where soil pH is 4.7 at 400mm and up to 6.5 at surface.
“So if we can get that pH up in that sub zone hopefully the roots will keep going down.”
Andrew said historically roots haven’t been getting to that deep depth because of compaction and low pH.
“Although having said that, you still get wheat roots at 1.2-1.5 metres,” Andrew said.
“But there are not a lot of them.”
That’s where the Messinas see benefits in digging deeper.
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“By digging deeper more lime can move through the profile to that depth because it’s not needed in the top soil, so hopefully it can start to elevate soil pH,” Andrew said.
His only disappointment was not putting on enough lime from the start.
“We started with rates of 1.3 tonnes a hectare, then 1.5t/ha and finally 2t/ha,” he said.
“If I got to do it again I would put on 2t/ha the year before mouldboarding then apply 2t/ha in that first mouldboard pass, so you’d end up with 4t/ha of lime at depth for the next two years.”