Analytes Certified for in 2020
This method is required to adjust soil chemical results based on air-dry samples to an oven-dry (105oC)
basis. When the air-dry moisture content (M%) is known, the correction from air-dry
to oven-dry is as follows:
Oven-dry result = [Air-dry result x (100+ M%)]/100
This extractable P test on milled air-dry sample uses a weakly acidic fluoride containing extractant (0.025M HCl and 0.03M NH4F). The soil/extractant ratio of 1:7 and a very short extraction time of 60 sec, making it prone to significant variability. It is used to predict yield responses in legumne-based pastures on acid to neutral soils in NSW, but not really used elsewhere. Method 9E1 involves a manual, molybdenum-blue colorimetric finish with a preferred absorbance at 882 nm.
This test on milled air-dry sample at a soil/water ratio of 1:5 for 1 h is suitable for use on all soils, irrespective of whether acidic or alkaline. It usually underestimates the soluble salt status of soils containing natural or added gypsum, particularly if ³ 1% of gypsum is present. Such soils would have an EC of about 2 dS/m. Soil EC x 0.336 (Method 3B1) approximates percent total soluble salts, while approximate soil ionic strength (Method 3C1) at 0.1 bar (I0.1) can be calculated as follows: I0.1 = [0.0446*EC1:5 – 0.000173], where I0.1 has units of mM, and EC1:5 has units of dS/m @ 25oC.
Method for measuring exchangeable bases (Ca2+, Mg2+, Na+, K+) - 1M ammonium chloride at pH 7.0
Suited for use on all soils, irrespective of whether acidic or alkaline, but preferred on acidic to weakly alkaline soils not dominated by solid-phase carbonates. Method 15A1 has no pre-treatment to remove soluble salts, with alternatives to remove them chemically (15A2) or to adjust for the presence of soluble sodium (15A3).
The laboratory either did not specify the method used or uses a mix of methods when submitting to the certification body