The degree of soil cracking influences water percolation during irrigation events. Time lapse series of 3 dimensional electrical resistivity images were collected in the field. The image series successfully identified different percolation patterns. When surface cracks of >30 mm width were observed prior to the irrigation, wetting of the 1.2 m deep profile occurred from the bottom up, while the soil moisture propagated downwards when cracks of <2 mm were observed prior to the irrigation.

The paper focuses on soil salinisation issue, which is widespread in arid and semi-arid regions and has become a major concern throughout the world. Humification degree of soil organic matter, which indicates levels of maturation, exhibits appreciably different among the four halophyte communities. Six parameters obtained through UV spectra technique, can easily indicate humification degree of soi.

Soil bulk density is essential for estimating the amount of carbon in soils, but it is difficult and time consuming to measure. Measurements using standard destructive methods and a neutron density meter introduced similar amounts of uncertainty into soil organic carbon estimates even in dry, coarse-textured, and gravelly soils, but the neutron density meter was more efficient for field sampling. Given the maximum variability measured, soil carbon stock changes in southern Australia should be monitored on a decadal scale.

Nitrous oxide (N₂O) is a potent greenhouse gas and a by-product of microbial transformations of nitrogen (N) compounds in soil (typically animal dung and urine, fixed N₂, or fertiliser N). To assess the use of nitrification inhibitor DCD to mitigate N₂O emissions we investigated its effectiveness in reducing N₂O emissions from a dairy-grazed pasture using both chamber measurements and a process-based model. Both the model and the chamber measurements showed a reduction in N₂O emissions when DCD was applied (although for the chambers the possibility of a sampling error cannot be excluded).

A mosaic of two soils (Gleysol and Andosol) was used to examine the influence of common pasture management practices on soil invertebrates (earthworms, small soil arthropods, and nematodes). In both soil types livestock treading was found to reduce soil porosity and negatively affect soil invertebrate decomposers. The decline in decomposer community in intensive pastures may be limiting the incorporation of organic matter from the soil surface into the soil profile, which decreases the ability of the soil to store carbon.

The microbial oxidation of ammonium in soils is an important controlling step in conversion of ammonium to nitrate. Nitrate is readily available to plants, but is easily lost to the atmosphere or by leaching. Recently, a new microbial group capable of this step was discovered, the ammonia oxidising archaea. This paper describes their abundance and diversity in agricultural soils from Western Australia. The findings show that ammonia oxidising archaea are important members of the nitrogen-cycling community in WA pasture soils.

Soil microorganisms play an important role in maintaining soil fertility and promoting plant health. Different groups of nitrogen fixing bacteria were isolated from the soil adhered to the roots of wheat crop which were screened for biochemical and functional activities and identified on molecular basis. These nitrogen fixing bacteria help in improving the soil health as well as plant growth promotion by making available major nutrients as nitrogen and growth-promoting substances.

Soil quality assessment is needed to evaluate sustainability of soil management practices. Our research showed that microbiological indices have the same sensitivity as the indices integrated by physical, chemical and biological indicators. However, the use of soil quality indices that includes all these soil properties gives a more complete picture of the overall soil quality, increasing certainty for soil management decisions.