Soil sensors of dielectric permittivity and electrical conductivity are needed in salt-threatened areas to know when to irrigate, in order to avoid the occurrence of both water and salinity stresses on plants. However, these sensors must be reliably calibrated, and this can only be carried out using an appropriate equation, and a reference method for soil salinity assessment at actual field water contents, such as those used in this work. Irrigators and developers of soil salinity sensors will benefit from this work.

Although pedotransfer functions have successfully been applied to predict soil water retention parameters, the uncertainty associated with the predictions cannot be ignored. This study evaluates the uncertainty in predicting water retention parameters at the large scale with pedotransfer functions, showing that the uncertainty due to the spatial prediction of basic soil properties is more important than the uncertainty due to the limited number of samples used for deriving pedotransfer functions. Obtaining more accurate spatial distribution of basic soil properties is critical in the accurate estimation of water retention parameters.

Accurate estimation of soil water retention characteristic is important for agricultural and environmental assessments, especially in tropical regions where this soil information is usually missing due to its costly and cumbersome direct measurement. The present study shows that using descriptive soil structural information on top of the widely used predictors (e.g. bulk density, soil texture and organic carbon content) could improve the predictability of SWRC-PTFs, which were developed for tropical delta soils. The findings might contribute to the efforts to overcome the dearth of hydraulic information in tropical regions, particularly tropical humid deltas.

The relationships among soil properties and, their relationships with landscapes are essential for assessing soil quality and soil productivity. Here we demonstrated the roles of landform, land use and soil type on the spatial patterns of soils chemical properties and enzymatic activities and suggest that crops and orchards should be arranged on plateau land, and grasses and woodland on terraced and sloping land, respectively, for better economic and ecological efficiency in gully region of the Loess Plateau. This study will help managing the land in the similar regions worldwide.

Soil organic carbon stock can be significantly affected by the type of cropping systems and management practices. A modelling approach was used to predict the potential for soil organic carbon sequestration under representative cropping systems across the Australian grain-growing regions, and it ranged from 28 to 64 t ha^–1 with ~10% uncertainty caused by variation of cropping systems. Overall, an increase in soil organic carbon stock was predicted to be achievable under optimal nitrogen management together with stubble retention.

The depth distribution of soil organic carbon storage and stability was assessed using a combination of particle-size fractionation, elemental analysis and radiocarbon dating in a Terra Rossa Karst soil from South-eastern Australia. The radiocarbon age of subsoil organic carbon was centuries to millennia older than that of the organic carbon in the topsoil, implying enhanced carbon stability with increasing soil depth. At all depths, macroaggregate organic carbon was dated as the oldest, but the highest organic carbon storage was found within the finest fraction, implying that C stability may not necessarily be coupled with C storage in this soil.

An acidic soil was incubated, sometimes with a microbial inhibitor, to investigate the relative magnitude of manganese oxidation compared to manganese reduction over a range of soil pH, temperature and water potential. The incubations showed that relatively small changes in the soil environment could change the balance between these redox reactions in favour of oxidation (decreased manganese availability) or reduction (increased manganese availability). Steady-state situations of zero net change were also observed.

Biochar, a charcoal-like material produced from the waste biomass by thermal treatments under no or low O₂ conditions, has been promoted as a soil amendment to enhance carbon storage and to improve soil functions. In this study methodologies were developed to quantify the carbonate-C in biochars which is essential to understand both biochar liming properties and longevity in soils. Our results will contribute to a better characterisation of biochars, as needed if biochar technology is adopted as a climate change mitigation strategy.

Compared to treatment without biochar and crop residue application, after 5-year consecutive application biochar didn’t increase soil respiration, while significantly reduced soil respiration compared with the crop residue application treatment. Above results indicate that applying biochar into soil to be an effective measure in order to improve soil carbon sink without increasing soil carbon emission in our case.

Agricultural manure slurries pose a high risk to surface water quality, particularly in dairy-farming systems with confinement of large animals. The risk of nutrient and faecal microbe loss following manure application to soil was greatest when rainfall, of sufficient quantity to generate surface runoff, was received within the first two days since application. Timing manure slurries to ensure more than two days before rainfall events will limit nutrient and faecal microbe losses and help protect water quality.