Iron-rich nodules are widespread in Australian soils and are often assumed to be the relicts of prolonged periods of tropical weathering in the geologic past. This study shows that iron nodules can also form by contemporaneous erosion and weathering of iron-rich sedimentary rocks, the burrowing activity of ants then concentrating them in particular soil horizons. The nodules found in many soils may thus be recent, without requiring long periods of weathering or mobilisation of large quantities of dissolved iron for their formation.

Modelling the transport of water and solute in the soil is an important tool in environmental studies.  However, most models require a detailed description of hydraulic functions, which are difficult to obtain.  In this paper we analysed several published PTF functions that have been developed to estimate the soil hydraulic functions based on easily measurable soil properties.  We propose and test the use of an ensemble of selected PTFs as the best option for use with New Zealand soils.

The interactions between soil properties and environmental factors may vary with spatial scales. Our study provided a quantitative insight into the complex scale-dependent correlations between soil physico-chemical properties and pertinent environment factors across the entire Loess Plateau. The results may help to identify the key factors controlling soil processes at different spatial scales on the study region.

Grassland degradation, typically characterised by encroachments of woody plants, is a crucial global issue in drylands. Simulated rainfall experiments were conducted to investigate the responses of resource losses to the vegetation replacement. The results showed that runoff and triggered sediment, C and N losses significantly increased following the invasion of shrub communities. This increased resource loss will inevitably result in a dysfunctional ecosystem and an increased vulnerability to further desertification.

Changes in carbon stocks with impacts on emissions of greenhouse gases may result from the stratification of organic matter as a result of soil use. This study evaluated the impact of soil management systems on soil carbon stocks and stratification ratios of soil organic matter pools. We found that the labile fractions are highly sensitive to the dynamics of organic matter in weathered soils of tropical regions.

Composting and vermicomposting are interesting options for recycling organic wastes in infertile tropical soils. We tested the quality of composts and vermicomposts of cattle manure and green wastes, and found that vermicomposting increased the content of phosphorus and calcium, and the stability of the organic matter of the amendments. These characteristics are key factors for the adoption of this practice in the tropics.

Australian wheat-cropped Vertosols emit substantial nitrous oxide due to the N fertilisation, poor soil drainage and favourable climate, and the long-term field experiment has proven that the non-till land management reduces nitrous oxide emissions. The WNMM simulations suggested that the deep placement of liquid fertilisers below the 35 cm depth can further reduce nitrous oxide emissions from the non-till Vertosols by almost 40%. UAN series fertilisers may have a role to play in Australian Vertosols to mitigate nitrous oxide emissions.