Air dry moisture content (2A1)

This method is required to adjust soil chemical results based on air-dry samples to an oven-dry (105^oC)
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

Electrical conductivity (EC) of 1:5 soil/water extract (3A1)

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 (I_0.1) can be calculated as follows: I_0.1 = [0.0446*EC_1:5 – 0.000173], where I_0.1 has units of mM, and EC_1:5 has units of dS/m @ 25^oC.