Effects of biosolids addition (composted manure and activated sludge) and spiking the soils with orthophosphate, phytic acid or humic acid, on soil aggregate stability of semi-arid loamy sand, loam and clay soils were tested before and after subjecting the soils to six consecutive rainstorms. Contribution of the amendments to pre- and post-rain aggregate stability was inconsistent. Relative to the control, stability of pre-rain aggregates was improved by all of the tested amendments while stability of the post-rain aggregates was improved by some amendments and deteriorated by others.

Coastal acid sulphate soils display high spatial heterogeneity. Here we identify their extent using ancillary data (i.e. EM and DEM) and a numerical clustering algorithm (i.e. FKM). The mean-squared prediction error variance of the class mean of various soil properties (e.g. EC_1:5 and pH) demonstrate the applicability of the overall approach with the final soil map being consistent with existing knowledge.

Soil structure has important influences on edaphic conditions and environment, which is often related to aggregate stability. In this study, we have analysed the effects of land-use type and soil organic matter content on the soil aggregate distribution and water stability of aggregates, investigated the effects of land-use type, water supply method and mean weight diameter, and their interactions, on saturated hydraulic conductivity (K_s) during different water supply processes. These findings may further the general understanding of soil structure and their future improvement.

This study demonstrates the use of different statistical approaches for assessing changes in SOC within a catchment at different spatial scales, from 90 m raster to whole-of-catchment changes.  This is considered in the context of using legacy soil data as the baseline survey. Furthermore, it also reports some of the issues encountered when dealing with legacy SOC data, which will be useful in designing future sampling schemes for monitoring changes in SOC.

Mixing of residues is common in many ecosystems. We studied respiration, microbial biomass C and available N in the initial stages of root and shoot residues of barley and the perennial grass Stipa sp. Mixing of residues with similar decomposition rates stimulated microbial activity (respiration) but had little effect on microbial growth or concentrations of available N.

Site-specific changes to the apparent electrical conductivity (ΔEC_a) of a non-saline, heavy clay soil, correlated strongly to neutron probe determinations of soil moisture removed from the root zone by a cotton crop (r = 0.94). This augers well for interpreting maps of ΔEC_a from surveys using instruments like the EM38 (Geonics ™) as maps of changes to soil moisture content for crop management purposes.

TOC abstract Capacitance sensors to measure soil water content are easier to install and operate than alternate instruments, but require calibration to measure in saline soils. The DIVINER 2000 was used in an irrigation trial on a salt-affected soil and was calibrated using water of the same salinity as the irrigation water. The accuracy of the soil-specific field calibration was better than the factory calibration and gave overall a RMSE = 0.03 cm³ cm^–3.

Deep drainage and depletion of soil C, N and some nutrients were evident under continuous cropping in the alluvial clays of the drier cropping areas of the northern Darling Basin together with high concentrations of naturally occurring subsoil chloride. Simulation modelling suggested that deep drainage may be increased 5–10-fold under zero-tillage winter cropping compared with traditional practices. Flushing of salt from the root zone and correction of nutrient deficiency would enhance crop water use and productivity.

Changes in soil properties may indicate potentially beneficial or degradative effects of a given management practice, so it is important to select the most sensitive soil properties to act as quality indicators. This research evaluated different approaches to selecting soil quality indicators in the construction of soil quality indices (SQIs). The sensitivity of integrative SQIs, constructed by considering diverse chemical, physical, and biological properties, was compared with biological SQIs, using only biochemical and microbiological indicators, to assess soil quality in an intensive horticultural production system under short- and long-term organic and conventional management.