The authors of the ‘National Acid Sulfate Soils Guidance: National acid sulfate soils identification and laboratory methods manual’ (published 2018) have identified an error in the calculation of the correction factor for retained acidity (Snas).
Until the National Guidance can be updated, or the Queensland Acid Sulfate Soil Technical Manual Soil Management Guidelines Version 5 is published (in press) the following SNAS calculation should be adhered to:
SNAS (%) = (SHCl – SKCl) x 2.0
It is acknowledged this method for retained acidity determination may give an inflated SNAS result, particularly for highly organic soils. However, until further research is conducted, this methodology should be followed.
If you have any questions on this matter, or require further information, please contact Nicholas Ward, Technical Team Leader, Southern Cross University.