Updating the Australian digital soil texture mapping (Part 1

Brendan Malone,Ross Searle

doi:10.1071/sr20283

Abstract

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.

Highlights

Evaluating the functional characteristics of soils inevitably requires a study of its soil texture characteristics
Comparing the soil texture fractions reported here with those previously done by Minasny et al (2007), this newer work would be best described as a consolidation of that done previously
The greatest differences were found for the medium heavy clay (MHC) and heavy clay (HC) soil texture class (STC) where a 3–4% difference in the clay % mean was observed

Summary

Introduction

Evaluating the functional characteristics of soils inevitably requires a study of its soil texture characteristics. Understanding the storage, transport and cycling of water, gas phases and nutrients within soil at a given site requires a good understanding of soil texture. It is not surprising that there has been a significant amount of research put into understanding what the spatial patterns of soil texture fractions are across spatial extents from field plots right up to the entire globe. Testament to this are organised and well-resourced national, continental and global programs to digitally map soil resources at these extents; e.g. Testament to this are organised and well-resourced national, continental and global programs to digitally map soil resources at these extents; e.g. Grundy et al (2015), Ballabio et al (2016) and Hengl et al (2017), in which soil texture is possibly one of the most thoroughly explored

Objectives

Methods

Results

Conclusion