A three-year project led by the Department of Primary Industries and Regional Development (DPIRD) with Precision SoilTech and growers has highlighted gains in addressing soil acidity in the Avon River Basin.
DPIRD research scientist Alice Butler said results from more than 40,000 soil samples collected from 182 farms have demonstrated the effectiveness of using agricultural lime to increase soil pH.
“These sampling results highlight the positive efforts made by growers in the Avon River Basin to address soil acidity,” Ms Butler said.
The project was delivered as part of the Department of Water and Environmental Regulation’s Watering WA – Clean Waterways program.
Soil acidity has a significant impact on agricultural productivity due to its impact on plant root growth and nutrient use efficiency.
Agricultural lime is commonly used to increase soil pH, however current lime usage in WA is only 60 per cent of what is estimated to be required annually to combat soil acidification.
Between 2005 and 2012, a research collaboration led by DPIRD analysed a soil pH dataset for the WA grain growing region which offered insights into the state of soil acidity.
That report found only about 30 per cent of topsoils (0-10cm) had a pH level above the recommended minimum target of 5.5, and about 50 per cent of subsoils (10-20cm and 20-30cm) had a pH above the recommended minimum target of 4.8, indicating higher acidity.
The 2013 report served as a benchmark for the recent work conducted on soil acidity.
From 2020-21 to 2022-23, 40,470 soil samples were taken from 13,359 individual sample sites on farms located from Dalwallinu in the north to Lake Grace in the south.
The minimum target pH for the topsoil is above 5.5, while in the subsoil depths (10-30cm), the minimum target pH is above 4.8.
“We found 56 per cent of topsoil samples were above the target pH level, which is a significant improvement compared to the 2005-2012 study,” Ms Butler said.
“Similarly, there was improvement in subsoil pH levels, with 72 per cent of samples at 10-20cm and 78 per cent of samples at 20-30cm being above the target pH level.
“It should be noted that these growers are the ones who are being proactive in testing and managing soil acidity.”
The research also helped growers assess the best method to apply lime for management of soil acidity, with a focus on mixing or deeper incorporation of lime to accelerate the remediation of acidity (low pH) in subsurface soil.
Soil Science and Crop Nutrition research manager Chris Gazey said looking ahead, managing acidity would require a focus on higher lime application rates and strategic tillage in areas where it is economically feasible to effectively address subsurface acidity.
“Growers are encouraged to soil test to depth to ensure they understand soil acidity issues throughout the profile, allowing for the most economical method of management to be implemented,” Mr Gazey said.
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