Stephen R. Cattle

From Pedotransfer functions to soil inference systems

Abstract Pedotransfer functions (PTFs) have become a ‘white-hot’ topic in the area of soil science and environmental research. Most current PTF research focuses only on the development of new functions for predicting soil physical and chemical properties for different geographical areas or soil types while there are also efforts to collate and use the available PTFs. This paper reviews the brief history of the use of pedotransfer functions and discusses types of PTFs that exist. Different approaches to developing PTFs are considered and we suggest some principles for developing and using PTFs. We propose the concept of the soil inference systems (SINFERS), where pedotransfer functions are the knowledge rules for inference engines. A soil inference system takes measurements we more-or-less know with a given level of (un)certainty, and infers data that we do not know with minimal inaccuracy, by means of properly and logically conjoined pedotransfer functions. The soil inference system has a source, an organiser and a predictor. The sources of knowledge to predict soil properties are collections of pedotransfer functions and soil databases. The organiser arranges and categorises the PTFs with respect to their required inputs and the soil types from which they were generated. The inference engine is a collection of logical rules selecting the PTFs with the minimum variance. Uncertainty of the prediction can be assessed using Monte Carlo simulations. The inference system will return the predictions of soil physical and chemical properties with their uncertainties based on the information provided. Uncertainty in the prediction can be quantified in terms of the model uncertainty and input data uncertainty. In order to avoid extrapolation, a method was developed to quantify the degree of belonging of a soil sample within the training set of a PTF. With the first approach to a soil inference system, we can optimally predict various important physical and chemical properties from the information we have utilising PTFs as the knowledge rules.

Use and understanding of organic amendments in Australian agriculture: a review

A wide range of organic amendments (OA) is currently available to Australian farmers. These products have numerous agronomic applications, including the supply of plant nutrients, control of pests and diseases, and in management of soil health. Several of these products are also used in contaminated and degraded land remediation. The most commonly identifiable groups of OA in Australia are composts, compost teas, vermicasts, humic substances, meat, blood and bone meal, fish hydrolysates, seaweed extracts, bio-inoculants, biodynamic products, and biochars. Many of these OA contain nutrients within organic molecular structures; these nutrients are usually not immediately available to plants and must first be mineralised. Mineralisation often occurs as OA are consumed by microbes, thereby stimulating soil microbial activity. The application of OA such as bio-inoculants, humic substances, and seaweed extracts can potentially stimulate crop growth and development through the actions of plant growth-promoting hormones, including cytokinins, auxins, and gibberellins. Yet despite these apparent benefits, the widespread adoption of OA in Australia has been limited, due in part to the high application rates required to produce agronomic benefits, a lack of consistency in the composition of some products, a poor public perception of their utility, and a lack of unbiased scientific research into the agricultural potential of these products.

Æolian dust contributions to soil of the Namoi Valley, northern NSW, Australia

Abstract AEolian processes have been regarded as having little relevance to pedogenesis in the subhumid regions of eastern Australia, due perhaps to a perceived paucity of clear evidence of dust deposition and to difficulties of measuring an aeolian dust component within soils. Contrary to earlier opinions, an aeolian soil component may occur in eastern Australia, as appreciable amounts of dust are deposited annually. We report dust deposition rates and some dust characteristics at Gunnedah, and measured granulometric, mineralogical and geochemical attributes of four soil profiles found in different physiographic areas of the Namoi Valley. Estimates of dust deposition rates indicate that a deposit at least 20 cm thick could have formed over the last 13,000 years. The soil profile which most clearly indicates the presence of dust overlies basalt at Bald Hill. Here, the topsoil contains a conspicuous population of particles with a modal diameter of 40–50 μm and has been enriched in Si by the addition of quartz, which cannot have originated from the basalt or from colluvial or alluvial processes. A clayey floodplain soil profile (Boonawa) also contained a large dust-particle population and also illite and moderate concentrations of K of possible aeolian origin. Two sandy profiles at Round Swamp displayed the same conspicuous dust-particle populations, and one exhibited an interstratified illite–smectite component, suggesting dust additions. Local aeolian processes were also indicated by the well-sorted, coarse sand-sized particles of the Round Swamp East profile, located on a low lunette adjacent to the swamp. These fine-grained, quartz-rich, aeolian dust deposits differ considerably from the benchmark Australian aeolian dust mantles, which form the clay-aggregated, calcareous parna soils of southern New South Wales.

Modifications to a method of rapid assessment of soil macropore structure by image analysis

Abstract The use of image analysis in pore structural studies is reviewed with the general conclusion that methods tend to be slow. A method of rapid assessment of soil pore structure is discussed, and three modifications to the original technique are presented. These are: (1) development of a technique for obtaining and video-digitising a single vertical structural monolith to 0.7 m; (2) use of resins containing different coloured dyes in the field and laboratory, allowing assessment of a larger number of parameters to discriminate between total and surface-connected pore space; (3) adaptation of the technique to measure roots in situ. These modifications are illustrated for comparison of natural and cultivated soil profiles, compaction trials from eastern Australia, and from laboratory experiments. Future modifications and enhancements including colour digitisation, computed axial tomographic (CAT) scanning and the use of random-process models are discussed. It is concluded that image processing and measurement techniques coupled with suitable laboratory and field methods and simple, yet sensible, models of the soil geometry provide powerful new techniques for visualising and measuring soil structure. These new techniques should be used to complement more conventional methods, however.

The effect of cultivation on the properties of a Rhodoxeralf from the wheat/sheep belt of New South Wales

Abstract Adjacent cultivated and never-cultivated areas of land were compared for a variety of chemical and physical properties to determine the effect of traditional cultivation practices on an Australian Rhodoxeralf. Those properties which changed most as a result of clearing and cultivation were pH, electrical conductivity, organic carbon, nitrogen and profile macroporosity. These changes are due to various processes including soil mixing, fertilizing, crop-growing and an altered water balance. The heterogeneity of the sites was also investigated in order to ascertain the effect of cultivation on the natural variability of the soil. The cultivated soil was found to be much less diverse than the adjoining virgin soil. Whether this is of ultimate benefit to crops is open to conjecture.

Using radiometric data to identify æolian dust additions to topsoil of the Hillston district, western NSW

The identification and characterisation of aeolian dust additions to Australian soil profiles has been attempted using a wide range of analytical techniques. Such techniques are often reliant on specialised equipment and operator expertise, but do not necessarily yield information on the spatial distribution of deposited dust across the landscape. An airborne geophysical technique which measures naturally occurring gamma-rays may now assist in the rapid assessment of dust accumulation sites at the catchment scale. This technique, known as gamma ray spectrometry or radiometrics, assesses the potassium (K), uranium (U), and thorium (Th) contents of the Earths surface, and may potentially distinguish aeolian sediments from the underlying rock or in situ developed soil profile by their differing K, U, and/or Th-bearing mineral suites. This paper summarises a study of this technique for identifying aeolian dust in topsoils of the Hillston district in western New South Wales. Using airborne with follow-up ground-based radiometric data, a variable relationship was established between large K signatures and apparent topsoil dust accumulations, which were identified as containing appreciable feldspar and illite. The previously established correlation between topsoil clay content and eTh (equivalent Th) concentration was also observed in this region, indicating that the technique may allow for rapid identification of landform features with significant clay and silt enrichment, as often occurs with dust accession. Despite the ubiquity of aeolian sediments in this region, the radiometric data were moderately effective in discriminating different dune systems and may therefore represent a useful initial technique for discerning likely areas of dust accumulation in this environment. However, in areas influenced by fluvial sediments, the radiometric signatures were not necessarily indicative of the topsoil dust content.

The hydrology of Vertosols used for cotton production: I. Hydraulic, structural and fundamental soil properties

This paper describes the hydraulic, structural and fundamental soil properties for 23 Vertosol horizons from 18 sampling sites in New South Wales and southern Queensland. At each site a combination of infiltration measurements and soil sampling was conducted. Samples were collected for determination of the soil water characteristic, shrink–swell relationships, and fundamental soil properties such as particle size distributions, pH, electrical conductivity (EC), exchangeable cations (Ca2+, Mg2+, K+, Na+), extractable P contents, extractable sulfate and Fe contents, and CaCO3 and total C contents. Large cores were sampled, impregnated with resin, and sectioned for image analysis. The program SOLICON v2.1 was used to calculate structural form parameters from the images. Measured hydraulic conductivities of the surface soils were large compared with earlier reported research for Vertosols. However, a sharp decrease in hydraulic conductivity occurred with depth in the profiles, which is assumed to be due to increased bulk densities and exchangeable sodium percentages (ESP). The data also indicated a general north–south trend in the structural development of these Vertosols. Surface soils from the northern areas, such as the Gwydir and Namoi valleys, exhibited more porous structural forms, and as a result, greater average hydraulic conductivities. This appears to be due to differences in ESP, clay content and the mineralogical suite of the clay; surface samples with smaller ESPs and larger proportions of smectitic clay tended to have the greatest values of hydraulic conductivity. Other fundamental soil properties such as extractable Fe and P contents, and CaCO3 content, were found to have little or no correlation to the hydraulic or structural properties of these Vertosols, while differences in measured shrink-swell and water retention properties were largely a function of soil depth. The database developed has given an overview of the hydraulic properties of Vertosols used for cotton production in south-eastern Australia.

Role of eolian dust deposits in landscape development and soil degradation in southeastern Australia

Eolian dust plays a significant role in landscape development and landscape processes in Australia. Thin dust mantles, rarely exceeding 3 m in thickness, have been identified across many parts of the Australian landscape, particularly in southeastern Australia. The nature and properties of these dust materials can have a major influence on environmental degradation processes such as salinisation and soil erosion. Despite the existing body of research regarding this topic, there are still conflicting views about the likely sources, transport modes and properties of eolian dust in the Australian landscape. The aim of this review is to synthesise much of the available information and put forward a working hypothesis for the distribution and fundamental properties of dust deposits in southeastern Australia. A conceptual model describing the various dust sources and sinks, and the modes of transport of dust materials both into and out of these source areas, is introduced. The model identifies key source areas, such as the alluvial and lacustrine environments of the Lake Eyre and Murray–Darling Basins, and sinks, such as the Eastern Highlands. Transport rates and paths for eolian-dust materials across the Australian continent are also outlined. The model places particular emphasis on the recycling of dust, whereby sediments sourced from the Eastern Highlands are transported westward via the major alluvial networks, and deposited on floodplains or in terminal drainage systems. These sediments are then available to be reworked into local eolian landforms prior to re-entrainment of the finer materials in the easterly dust pathway. The characteristics of deposited eolian sediments are then outlined in detail, focusing particularly on their particle-size distribution, mineralogical composition, and geophysical and geochemical properties. The review also presents data and images of dust materials sampled from source areas, sink areas, as well as materials that have been deposited by modern dust events. Finally, the role of dust materials in land-degradation processes, particularly soil erosion, is discussed. The degree of reworking of the eolian sediments, the extent of leaching and the level of sodicity are all important in determining soil structural stability and hence erosion potential of these materials.

Adoption of Soil Health Improvement Strategies by Australian Farmers: I. Attitudes, Management and Extension Implications

Abstract Purpose: There is inconsistency in the design, understanding, implementation and monitoring of soil health programmes. Despite mounting scientific evidence for the credibility of certain soil health indicators, an increase in the reporting of programme benefits, and progress in communicating these benefits, many farmers remain hesitant to implement structured management plans and strategies tailored to address soil health. The purpose of this research is to investigate the proportion of Lachlan and Macquarie Valley landholders who implement a structured soil health programme and to better understand the role of extension in the management of these. Design: Non-parametric analysis of a mail-based survey supported with content analysis of landholder comments was used. Findings: Results suggests that the overall landholder attitude towards soil health management is positive, although soil health management programmes are often inconsistent, unstructured, or ad hoc. Ongoing communication between landholders, agronomists, extension agencies and scientists is shown to be vital in the adoption of soil health management programmes. Practical implication: By understanding landholder attitudes and management practices, as well as the role of extension, extension efforts can become more targeted and effective. Value: This article shows that soil health management is a primary focus of Australian farmers and elucidates the importance of extension efforts in management and planning. Areas where extension should be focussed are identified.

Bioaccessibility of lead in urban soil of Broken Hill, Australia: A study based on in vitro digestion and the IEUBK model

This study was conducted to investigate lead (Pb) bioaccessibility in urban soil and to assess health risk to children in the city of Broken Hill, Australia, which was established around one of the worlds largest lead-zinc-silver mines. Fifty-three topsoil (0-0.1m) and 50 subsoil (0.3-0.5m) samples were collected from earthen footpaths, nature strips, parks or vacant land throughout the urban area. The soil samples were analysed for total Pb concentration, Pb bioaccessibility and Pb mineral phases, together with important soil physicochemical properties known to influence Pb bioaccessibility. Lead bioaccessibility ranged from 24% to 89% in topsoil and from 16% to 100% in subsoil, exhibiting a generally decreasing pattern with increasing distance from the orebody. Lead bioaccessibility was strongly positively related to total Pb concentration in both the topsoil and subsoil. In subsoil, a moderate negative correlation existed between Pb bioaccessibility and soil pH, while a moderate positive correlation existed between Pb bioaccessibility and soil organic matter (OM) content. In contrast, only a weak positive correlation existed between Pb bioaccessibility and OM content in topsoil. The presence of different Pb mineral phases also appeared to have caused variation in soil Pb bioaccessibility, with galena (PbS)-rich samples tending to exhibit lower Pb bioaccessibility. The prediction of blood lead (PbB) levels in Broken Hill children aged 1-4years using the IEUBK model well matched the measured data from a recent PbB screening, suggesting a high risk of childhood chronic low-level Pb exposure (PbB levels >5μg/dL) in Broken Hill, especially in the vicinity of the orebody. Future Pb abatement programs in Broken Hill should utilise the IEUBK model to establish target soil Pb values in an effort to achieve particular child PbB outcomes.