Updating the Australian digital soil texture mapping (Part 1*): re-calibration of field soil texture class centroids and description of a field soil texture conversion algorithm

Soil texture (% sand, silt and clay sized particles) is one of the most important of soil characteristics affecting the function of soils. To better understand the behaviour of soils, reliable spatial estimates of soil texture need to be available. Digital soil mapping has been an enabler in delivering this sort of information. Delivered as two connected pieces, we present new efforts to update the soil texture maps for Australia (Version 1 was delivered in 2015). The main distinguishing enhancement is the merging of field descriptions of soil texture with the traditional laboratory analysed data. This greatly increases the number of available data, yet also calls for an elaboration of methods of how to convert texture class data into continuous variables, how to deal with the associated uncertainties of these conversions, and how these can be propagated in any sort of spatial modelling. Here we report on research to re-calibrate the soil texture centroids that were first determined by Minasny et al. (2007). Then we describe our approach on how the centroids and their uncertainty can be used to generate acceptable soil texture fractions for all qualitive soil profile texture descriptions in the Australian soil database.