Soil acidity affects more than 50 per cent of intensively used agricultural land in NSW and about 23 per cent in Victoria. It is especially prevalent in the higher rainfall areas in our region.
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If we do not address acid soils now, further acidification will threaten future agricultural production.
Holbrook Landcare Network is working with partners on various acid soil related projects, including two new trial sites. For more on these projects, visit the soils program page at holbrooklandcare.org.au
Recent research on soils in the NSW Southern Slopes suggests in most cases, current rates of lime application are not addressing the current soil acidification rate.
An effective liming program should aim to increase soil pH (CaCl2) to a target of 5.5 in the top 10cm (not 5.0 as has been the current practice).
This will provide sufficient lime to raise pH in the surface soil and allow for excess lime to leach into deeper subsurface layers and slowly increase pH at depth.
Lime that is top-dressed moves slowly into the subsurface layers depending on soil type, rainfall and lime application rate.
Effective incorporation of lime after spreading "speeds up" the reaction of lime with the soil, to the depth of cultivation.
This is challenging prevailing conservation farming practices and throwing up new questions about the cost/benefit of cultivation. HLN and NSWDPI have set up two new trial sites that will be looking at these questions - different liming rates, top-dressing lime vs incorporating and the effects on crop and pasture growth.
As an industry, we need to do more to protect our soil asset - the old 2.5 t/ha every 10 years rule-of-thumb may not be adequate in many cases.
The message is to establish a soil testing program, put on as much lime as you can afford to maintain a pH (CaCl2) of 5.5 in the top 10cm, or apply lower rates more frequently.
