Soil acidity is a significant issue for Kangaroo Island producers often resulting in poor pasture and crop growth.
While a natural process acidification can be often accelerated through under productive farming practices.
Acidic paddocks that are not limed can also result in the topsoil continuing to acidify with the acidic layer spreading down the soil profile.
Land management consultant with the Department of Primary Industries and Regions (PIRSA), Lyn Dohle said acidic layers between 5-15cm in depth were now becoming increasingly common around the Island, even where topsoils have been limed.
"Recent work across the island have shown cropping paddocks that have already been limed at 2.5t/ha, were still highly acidic below 5cm," she said.
"The presence of subsurface acidity is often masked by our conventional topsoil sampling methods (0-10 cm), with an often alkaline 0 to 3-5 cm layer diluting acidic bands below, resulting in an 'false' overall pH value that doesn't cause alarm".
The quickest and easiest way to find out if sub soil acidity is an issue on your property is using a pH test kit.
"If acidic areas have been identified using the pH test kit, additional soil sampling and more accurate laboratory pH measurement and other analysis is recommended," Ms Dohle said.
"If there is a sub soil acicity issue, acidic soils must then be limed.
"Lime treats acidity by neutralising the acid in the soil and should be applied at rates to keep the surface pHCa at 5.5 or more in the top 10cm".
As lime usually moves very slowly in soils, about 1cm a year at best, incorporating lime through strategic cultivation is recommended when treating subsoil acidity.
The more vigorous the soil disturbance after lime application, the faster the soil will be neutralised (spading or large offset discs is ideal). Deep ripping and delving offering less mixing of applied lime.
As many soils contain a combination of chemical and physical constraints, such as acidity and water repellence and/or compaction, strategic deep tillage to depth can help solve multiple issues in a single pass whilst maximising the potential gains in production.
PIRSA and AgKI, through funding from the federal government National Landcare Program, have free test kits to hand out to farmers.
For further information or to collect a kit, contact Lyn Dohle at the PIRSA Kingscote Office, 56 Dauncey St, Kingscote or call her on 0419 846 204.