Gaps in use of lime to fight acidity in Wheatbelt

New mapping has highlighted significant gaps in the use of liming to combat soil acidity across Western Australia, despite more than one million tonnes of lime being applied to paddocks last year.

Department of Agriculture and Food senior research officer Chris Gazey said more growers were using lime to manage soil acidity, but new mapping of soil pH levels across the Wheatbelt showed there were enormous opportunities still not being realised.

“Mapping of soil acidity through a collaborative project with Precision SoilTech and the Federal Government’s Caring for Our Country program has generated a comprehensive analysis of soil pH for the WA Wheatbelt, ” Mr Gazey said.

“It is estimated that 2.5 million tonnes of lime is required each year for the next 10 years to recover soil pH and address ongoing soil acidification.”

This investment will help to achieve yield potential, largely through improved access to water and nutrients deeper in the soil.

“Based on results from over 25 years of trials we would expect a yield response of 10 to 30 per cent, ” he said.

The latest maps and more findings from soil acidity research will be presented at the 2013 Agribusiness Crop Updates.

The event, hosted by the department and Grains Research and Development Corporation, will be held on February 25 and 26 in Perth. Mr Gazey said at farm scale, good knowledge of the soil pH profile to at least 30cm was needed to develop a management plan to remove soil acidity as a key constraint to crop and pasture production.

Since 2005, 161,000 samples from 93,380 sites have been taken from across the WA Wheatbelt with approximately 67,000 of these samples being collected from the subsurface layers.

“The proportion of samples below the department’s soil acidity targets of pHCa 5.5 for the 0–10 cm layer and pHCa 4.8 for the 10–20 and 20–30 cm layers were calculated for each of 18 major soil types, ” Mr Gazey said.

“Overall 72 per cent of samples collected from to 0–10 cm layer were below the target and 45 per cent of samples from the remaining layers were below target.”

The extent and severity of acidity varied geographically and with soil type.

Mr Gazey said data from long-term trials, including 2012 results from sites at Kellerberrin and Moora, illustrated the benefits of managing soil acidity and the need for ongoing monitoring of pH.

“Managing soil acidity has been demonstrated to be economically beneficial but requires a longer-term approach than many inputs and could be considered in the same manner as a capital investment, ” he said.

“While the maps provide a picture regionally and state-wide, targeted information about soil pH to at least 30 cm through testing is crucial to inform lime applications on-farm.”