Salmon Gums farmer Rory Graham (left), Ben Hatter, Munglinup, Mark Biven, Beaumont and David Campbell, Scaddan.SOIL acidity is akin to chasing your tail.
And Department of Agriculture and Food researcher Chris Gazey admits it’s a long process to ameliorate soils with lime applications.
But his blunt appraisal is that the problem is not going to go away while there is agriculture.
“All farm cropping practices along with nitrogen fertiliser use, induce acidity,” he said.
Liming does help elevate soil pH but Esperance farmers agreed they are liming blind when it comes to quality, which should determine application rates.
“How do you get a lime supplier to say his quality is good?” one farmer asked.
General discussion raised the focus on the lime industry’s code of practice and the fact that Lime WA Inc members were subject to voluntary independent audits.
“You can also encourage your supplier to present you with an independent test of the quality,” Mr Gazey said.
He said lower quality of lime was endemic in the structure of the geology in the area but there were no alternatives.
“Maybe long term we might look to the Nullabor Plain as a source,” he said.
Mr Gazey said growers had access to information on DAFWA’s website (soilquality.org419论坛) to use an online lime calculator to compare the cost effectiveness of agricultural limes.
A Lime Comparision Calculator allowed comparison of the total cost per hectare for the equivalent of 100 per cent neutralising value of lime, taking into account the cost of the lime, cost of transport, cost of spreading, particle size distribution of the lime and neutralising value of each particle size.
Mr Gazey said 75 per cent of the topsoil in WA’s Wheatbelt was less than the preferred 5.5ph and 45pc of subsurface soils were below 4.8pH.
The department’s long-term trials have shown higher rates (7-8t/ha) may be needed to arrest pH decline.
Mr Gazey said the extent and severity of acidity varied geographically and with soil types.
One farmer, who has been recording soil pH on his property for the past 35 years, showed pH levels between high fives and mid fours.
“But the soil pH is still dropping,” he said.
Mr Gazey provided farmers with a copy of DAFWA’s second edition Soil acidity, A guide for WA farmers and consultants.
Which was a good move for the farmer asking the difference between limesand and ground limestone.
In the book, Mr Gazey said while the quality of agricultural limes can vary widely, high quality lime is available from limesand, limestone and dolomite lime sources.
“Suppliers of limestone and dolomitic lime crush and screen their products and suppliers of limesand may screen to remove vegetation if necessary,” he said.
“Suppliers should provide details of the particle size distribution of their product and farmers should ensure that products contain an adequate proportion of fine particles to meet their needs.
“Coarse and fine limes with the same neutralising value treat the same amount of acidity but the fine lime does it quicker.”
Interestingly in the second edition book, 74 per cent of 334 Wheatbelt farmers considered soil acidity to be a moderate or greater problem on their farm.
Future use of lime would include lifting rates from 1-1.5t/ha to 1.5t/ha to 2t/ha.
Mr Gazey said most of these farms would need to apply at least 2t/ha every three to four years over a 10-year period to achieve appropriate soil pH and after that, maintenance liming of 1-2t/ha every four to seven years would be required to maintain soil pH.
But the department’s long-term liming trials suggested some subsoil areas in WA may no longer be cost effective to treat.
Mr Gazey said the “Rolls Royce” of equipment to effectively incorporate lime was a spader, which proved too expensive for many farmers.
Likewise the use of liquid lime with the aim of accelerating the lime reaction to elevate soil Ph was no longer regarded as an option because of cost and the volume needed to produce a neutralising effect.
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