Guidelines for Surveying Soil and Land Resources promotes the development and implementation of consistent methods and standards for conducting soil and land resource surveys in Australia. These surveys are primarily field operations that aim to identify, describe, map and evaluate the various kinds of soil or land resources in specific areas. The advent of geographic information systems, global positioning systems, airborne gamma radiometric remote sensing, digital terrain analysis, simulation modelling, efficient statistical analysis and internet-based delivery of information has dramatically changed the scene in the past two decades. As successor to the Australian Soil and Land Survey Handbook: Guidelines for Conducting Surveys, this authoritative guide incorporates these new methods and techniques for supporting natural resource management. Soil and land resource surveyors, engineering and environmental consultants, commissioners of surveys and funding agencies will benefit from the practical information provided on how best to use the new technologies that have been developed, as will professionals in the spatial sciences such as geomorphology, ecology and hydrology.
The accurate characterization of soil water and air properties is difficult in soil survey because of logistic constraints. Less reliable surrogates are commonly used to estimate these properties. The surrogates provide a method for moving from measures that tend to be static and semi-empirical to those characterizing soil processes. The utility of four schemes for predicting air-filled porosity, available water capacity and saturated hydraulic conductivity on the basis of field-determined soil morphology has been assessed using data from a limited number of profiles with features commonly encountered in Australia. None of the systems provided statistically significant predictions of available water capacity and the results for air-filled porosity were moderate (McKeague et al. (1986), r2 = 0.58; Hall et al. (19771, r2 = 0 -64; Williams et al. (1991), r2 = 0.70). Encouragingly, the Hollis and Woods (1989) system generated good predictions of field-saturated hydraulic conductivity (r2 = 0.77). It is concluded that better measurement methods and programs of data collection are needed for both the properties used as surrogates (e.g. morphology) and those for which predictions are required (e.g. air and water properties).
The effect of long-term farming on the cation exchange capacity (CEC), organic carbon content, soil solution composition, and aggregate stability was investigated using contrasting soils from 4 sites in the Mid North of South Australia. Undisturbed and farmed profiles were characterised at each site. Farming led to a 10–50% decrease, approximately, in organic matter and CEC in the surface horizon. Scanning electron microscopic study of the surface and selected subsurface soils revealed poor aggregation, compaction, reduced porosity, and a decrease in aggregate particle size in the farmed surface soils. Intra-aggregate binding in the undisturbed soils appeared to be largely due to fungal hypha, with the roots largely contributing to inter-aggregate binding of soil particles. Electrical conductivity (EC) of soil solutions was generally 2–3 times higher in the undisturbed soils than farmed soils, suggesting increased leaching of ions associated with loss of tree cover. This was also supported by a decrease in the concentrations of mobile ions such as Cl-and Na+ in the farmed soils. The concentrations of Na+ and K+ decreased with farming leading to a decrease in the Gapon selectivity constant for Na–Ca and K–Ca exchange. The changes in soil solution composition together with the decline in organic matter concentrations resulted in increased sensitivity of soils to dispersion.
A number of morphological attributes are commonly assumed to serve as surrogates for properties that cannot be practically measured on a routine basis This study investigates whether conventional soil morphology can be used for predicting soil properties of relevance to irrigated and dryland agriculture in the lower Macquarie Valley, N S W Measurements from 224 profiles were used to develop regression equations with morphological properties as explanatory variables Response variables included gravimetric moisture contents at -10 and -1500 kPa, available water capacity, ail-filled porosity, ESP, dispersion index, the coefficient of linear extensibility, bulk density and CEC The relationships between field texture and particle size classes were also determined Conventional sod morphology provided only moderate predictions of the agronomically more important properties In the lower Macquarie Valley, texture and colour were the most useful explanatory variables Most of the remaining morphological properties, and in particular conventional descriptors of structure, contributed little to improving prediction Options for more cost-effective and direct measurements, especially of profile macrostructure are considered.
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