The hydraulic conductivity of riverbeds (K_r) is a key control on water exchange between rivers and alluvial aquifers, but is seldom measured. K_r was measured in four tributaries of the Murray-Darling Basin, where groundwater extraction from alluvial aquifers is extensive. While within site variability in K_r was large, the river reaches studied could be classified as having a low or high K_r, consistent with the two main types of riverbed texture present (clay or silty sand).

Water fluxes within soil-vegetation-atmosphere (SVA) systems are an important factor in determining the migration and cycling of nutrients and contaminants. Quantifying such water fluxes requires numerical simulators with a level of complexity commensurate with the intended application and soil hydraulic properties that match the model complexity. We demonstrated that global inverse parameter optimisation routines such as genetic algorithms are powerful tools to determine field-scale hydraulic properties of heterogeneous soil profiles for simple and complex models. Inverse parameter optimisation has great potential to help resolve the scaling problem that hydrologists face when they measure properties with small soil cores and then use these to simulate complex processes over larger areas.

Conversion of pastoral land to shrubland offers opportunity for carbon sequestration and erosion control; and we therefore investigated soil processes relating to carbon sequestration. Results provided evidence for strong climatic control on gas fluxes, as well as the spatially variability and sporadic nature of gaseous emissions from soils, controlled by edaphic processes in micro-sites. The site-specific characteristics: biomass, nutrient availability, porosity and bulk density explained ≥80% of the variance in cumulative soil respiration at three of the four sites studied.

The distribution of organic carbon (OC) and nitrogen (N) in soils is critical for understanding the behaviour of C and N in soils. Here we find that soil texture play an important role in assessing the distributions of soil OC and N and that aspen woodland would result in greater accumulation of OC and N in loam soils of the semi-arid Loess Plateau. This study will help evaluating the potentials of woodland in C sequestration in semiarid region.

Development of sustainable soil management practices is important for food security. Cultivation is widely recognized as a source of declining soil fertility in semi-arid regions however, conservation tillage systems through recycling of residues improved overall soil fertility. Use of these conservation tillage systems should contribute to better maintenance of soil and water resources in semi-arid regions.

Withholding phosphorus (P) fertiliser on P enriched soils is a potential strategy to decrease P loss to surface waters. This study used isotope exchange kinetics to examine the changes in different pools of soil phosphorus over time following a halt to P fertiliser inputs. The results suggest that halting P fertiliser inputs will decrease environmentally important soil P pools but that the rate of decline is slow and P enriched soils are likely to impact on water quality long after fertilisation is stopped.

The availability of phosphate (P) fertiliser to plants in acid soils is low, as most of the applied phosphate is bound to soil particles, and cannot be accessed by plant roots. This proof-of-concept paper demonstrated that combining small organic carbon compounds (organic and phenolic acids) with phosphate fertiliser can increase the amount of plant-available P. Upon validation of these results at a field-scale, coating of fertiliser granules with organic/phenolic compounds may enhance phosphate fertiliser efficiency in acidic cropping soils.

Soil tillage fosters CO₂ emissions by favouring organic matter degradation, a quality loss that predisposes soils to erosion, among other problems. A better understanding of how tillage and site conditions (e.g. compaction moisture, temperature) affect CO₂ emissions, particularly in irrigated bed planting systems recently developed in Spain, is required. In our study, bed preparation promoted CO₂ emissions from beds rather than furrows, while vertical tillage increased emissions in furrows, reducing organic matter contents.

The substitution of mineral fertilizers with swine manure applied in a pig slurry (PS) and pig litter (PL) form, has been proposed in locations where high densities of confined livestock are raised. Applications PS and PL residues to the soil surface in a no-tillage system (NTS) may increase the total organic carbon (TOC) and improve the physical properties of the soil. The PL increased the aggregate stability and macroporosity, and reduced PR. Eight years of adding PS to successive cultivations of soil managed under NTS produced no changes in the physical features or the TOC of the soil, whereas the application of PL produced improvements in physical attributes of the soil and increased soil TOC.