ASRIS Technical Specifications V1.6

pH profileThe pH in a 1:5 CaCl 2 solution is estimated for the five layers in the soil profile. If measurements were on a1:5 soil-to-water, then use the conversion table in Appendix 1 taken from Henderson and Bui (2002). Theestimation method is shown in Table 26.Layer-1 pHThe Layer-1 pH is recorded as follows.• In most instances, the estimate applies to the upper 50 mm of the A1 horizon.• If the surface layer is an O horizon, the estimate applies to the upper 50 mm of the underlying Ahorizon.• If the surface layer is an O horizon and there is no underlying A horizon, the Layer-1 pH refers to the 50mm thick layer directly beneath the O horizon.• If the surface layer is a peat, the estimate applies to the upper 50 mm of the surface horizon.• If the A1 horizon is thinner than 50 mm, then the estimate is for the horizon.Table 26: Estimation method for pHEstimationMethodDescription1 Estimate based on measurements of pH for replicated soil profiles in the landunittract2 Estimate based on a single measurement of pH in the land-unit tract3 Estimate based on direct measurements of similar soils in the same land unittype (e.g. modal profiles)4 Estimate based on direct measurements of similar soils in the region or projectarea5 Estimate based on experience with similar soils (e.g. same taxa in theAustralian Soil Classification but from other regions).pH in Layers 2–5The pH for these layers is an average rather than an estimate for the upper portion. The guidelines on thedefinition of layers used for texture apply to Layers 2–5. If no B horizon is present and the sequenceconsists of an AC profile, the Layer-3 pH is taken from the layer 0.20 m directly below the A horizon. Again,the Layer-5 estimate refers to a depth between 1.5–2.0 m. If an R horizon or hard materials (including acalcrete pan, partially weathered rock or saprolite, or other hard materials) occurs at a shallower depth,and this is still below Layer 4, then the Layer-5 pH applies to the lowest 100 mm in the profile. Otherwisethe variable is recorded as missing.43