Assessment and Treatment of Subsurface Acidity

GRDC - Author: Melissa Fraser (PIRSA Rural Solutions SA)

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

The authors of this paper note in the conclusion: “Subsurface acidity is becoming increasingly prevalent across SA’s cropping land, leading to patchy plant growth and reduced grain yields, especially in pulses. Its presence often goes unnoticed until it is well developed, due to limited or inaccurate subsurface soil sampling and assessment. A strategic soil sampling approach is proposed to adequately identify stratified and subsurface bands of acidity, particularly in no-till systems. Lime application rates need to be developed that take into consideration the degree and depth of acidity, soil type and organic matter content, and lime quality. Growers should consider methods to incorporate applied lime to increase its efficacy in treating subsurface issues. PIRSA is working on developing new calculators to assist lime rate decisions to treat subsurface acidity and will assess incorporation methods suited to South Australian soils.”. Please access the full paper via the link below if this research interests you.

The take home messages from this GRDC funded research are below. Please access the full paper via the link below for methodology, references, acknowledgements and discussion.

Subsurface acidity and stratification are emerging as serious constraints to crop production across SA, NSW, Victoria, and WA.

Traditional soil sampling strategies can lead to misdiagnosis of subsurface issues; strategic sampling at specific depth intervals is required.

Lime rates need to be adjusted to account for subsurface pH, changes in soil texture and organic carbon content down the profile.

Strategic incorporation/tillage can aid the efficacy of lime application for treating subsurface issues; other subsoil constraints (e.g. compaction) should be taken into consideration to maximise treatment impact, along with the risks associated with soil disturbance.

Options for treating subsurface and stratification issues are being examined in the new GRDC Acid Soils SA Project.


Table 1. Severity of acidity as determined using a pH indicator kit, which is equivalent to the pH in water (pHW).

2020 - Australia - GRDC - Author: Melissa Fraser (PIRSA Rural Solutions SA)
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