The pH of Australian soils: field results from a national survey

Abstract

Abstract. The pH is one of the fundamental soil properties governing nutrient availability, metal mobility, elemental toxicity, microbial activity, and plant growth. The field pH of topsoil (0-0.10 m depth) and subsoil (~0.60-0.80 m depth) was measured on floodplain soils collected near the outlet of 1186 catchments covering >6 Mkm 2 (6 Â10 12 m 2 ) or~80% of Australia. Field pH duplicate data, obtained at 124 randomly selected sites, indicate a precision of 0.5 pH unit (or 7%), and mapped pH patterns are consistent and meaningful. The median topsoil pH is 6.5, while the subsoil pH has a median of 7 but is strongly bimodal (6-6.5 and 8-8.5). In most cases (64%) the topsoil and subsoil pH values are similar; among the sites exhibiting a pH contrast, those with more acidic topsoils are more common (28%) than those with more alkaline topsoils (7%). The distribution of soil pH at the national scale indicates the strong controls exerted by precipitation and ensuing leaching (e.g. low pH along the coastal fringe, high pH in the dry centre), aridity (e.g. high pH where calcrete is common in the regolith), vegetation (e.g. low pH reflecting abundant soil organic matter), and subsurface lithology (e.g. high pH over limestone bedrock). The new data, together with existing soil pH datasets, can support regional-scale decision-making relating to agricultural, environmental, infrastructural, and mineral exploration decisions.

On the Fundamental Causes of High Environmental Alkalinity (pH ≥ 9): An Assessment of Its Drivers and Global Distribution

“…It is important to highlight, however, that Australia hosts what is perhaps the largest fraction of very alkaline soils of all continents, many of which are outside these two hyperplains, located under more arid climates and in areas with higher slopes (De Caritat et al . ) where groundwater influence is not obvious in present times (Fan et al . ).…”

“…In Australia, two vast semiarid to subhumid hyperplains are found in the southeastern states around the mid‐basins of the Murray and Darling rivers where very alkaline soils and groundwaters have been reported (De Caritat et al . ) (Figure a, Numbers 12 and 13). It is important to highlight, however, that Australia hosts what is perhaps the largest fraction of very alkaline soils of all continents, many of which are outside these two hyperplains, located under more arid climates and in areas with higher slopes (De Caritat et al .…”

Factors affecting seed germination and emergence of button grass (Dactyloctenium radulans) (R.Br.) P.Beauv.

“…These ranges of pH (ranges 4–10) are those commonly reported in Australian soils (de Caritat et al . ). Prior to placing the different pH buffers in the petri dishes, the pH value of the solution was checked with a benchtop water quality meter (model 860033, SPEP scientific, Arizona, USA).…”

Mapping the Spatial Variability of Soil Acidity in Zambia

“…Its measure is indicated by soil pH, which is a fundamental property that can affect soil quality (acidity or alkalinity) and use [1,2]. In Zambia, soil acidity is a common problem in the high rainfall areas.…”