Dynamics of nitrate-nitrogen removal in experimental stormwater biofilters under intermittent wetting and drying

High concentrations of nitrate-nitrogen degrade the quality of aquatic environments. The primary mechanism by which nitrate-nitrogen is removed (denitrification) requires anoxic conditions and electron donors. While removal of total and ammonium-nitrogen is often high in stormwater biofilters, poor removal or even the release of nitrate-nitrogen in the outflow has often been observed. Five Perspex biofilter columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material. Columns were operated at 875  mm/h 875  mm/h and fed with simulated stormwater with different antecedent dry days (ADDs) and concentrations of nitrate-nitrogen. Samples were collected from the outflow at different time intervals between 2 and 150 min and were tested for nitrate-nitrogen. The removal of nitrate-nitrogen varied during an event from a high removal percentage (60–90%) in the initial outflow that gradually decreased in the first 30 min and settled at 0–15% removal thereafter. This remained consistent during all simulated events independent of the number of ADDs or inflow concentrations. ADDs and previous event feed concentrations affected the outflow nitrate-nitrogen concentration in the first 30 min of the current event. Therefore, from this study it is concluded that denitrification within stormwater biofilters occurs mainly during drying periods rather than wetting periods.

Annual nitrogen dynamics and urea fertilizer recoveries from a dairy pasture using 15N; effect of nitrification inhibitor DMPP and reduced application rates

Direct nitrogen (N) losses from pastures contribute to the poor nitrogen use efficiency of the dairy industry, though the exact fate of applied N and the processes involved are largely unknown. Nitrification inhibitors such as DMPP can potentially increase fertilizer N use efficiency (NUE), though few studies globally have examined the effectiveness of DMPP coated urea in pastures. This study quantified the NUE of DMPP combined with reduced application rates, and the effect on N dynamics and plant–soil interactions over an annual ryegrass/kikuyu rotation in Queensland, Australia. Labeled 15N urea and DMPP was applied over 7 winter applications at standard farmer (45 kg N ha−1) and half (23 kg N ha−1) rates. Fertilizer recoveries and NUE were calculated over 13 harvests, and the contribution of fertilizer and soil N estimated. Up to 85% of the annual N harvested was from soil organic matter. DMPP at the lower rate increased annual yields by 31% compared to the equivalent urea treatment with no difference to the high N rates. Almost 40% of the N added at the conventional fertilizer application rate as urea was lost to the environment; 80 kg N ha−1 higher than the low DMPP. Combining the nitrification inhibitor DMPP with reduced fertilizer application rates shows substantial potential to reduce N losses to the environment while sustaining productivity in subtropical dairy pastures.

Non-linear response of soil N2O emissions to nitrogen fertiliser in a cotton-fallow rotation in sub-tropical Australia

Nitrogen fertiliser is a major source of atmospheric N2O and over recent years there is growing evidence for a non-linear, exponential relationship between N fertiliser application rate and N2O emissions. However, there is still high uncertainty around the relationship of N fertiliser rate and N2O emissions for many cropping systems. We conducted year-round measurements of N2O emission and lint yield in four N rate treatments (0, 90, 180 and 270 kg N ha-1) in a cotton-fallow rotation on a black vertosol in Australia. We observed a nonlinear exponential response of N2O emissions to increasing N fertiliser rates with cumulative annual N2O emissions of 0.55 kg N ha-1, 0.67kg N ha-1, 1.07 kg N ha-1 and 1.89 kg N ha-1 for the four respective N fertiliser rates while no N response to yield occurred above 180N. The N fertiliser induced annual N2O EF factors increased from 0.13% to 0.29% and 0.50% for the 90N, 180N and 270N treatments respectively, significantly lower than the IPCC Tier 1 default value (1.0 %). This non-linear response suggests that an exponential N2O emissions model may be more appropriate for use in estimating emission of N2O from soils cultivated to cotton in Australia. It also demonstrates that improved agricultural N management practices can be adopted in cotton to substantially reduce N2O emissions without affecting yield potential.

Retention and graduation of Australian Aboriginal and Torres Strait Islander students in initial teacher education

This paper reports on an Australian national project to address retention, success and graduation of Aboriginal and Torres Strait Islander teacher education students. The project, led by the Australian Council of Deans of Education and managed by Queensland University of Technology, forms a sub-set of the More Aboriginal and Torres Strait Islander Teachers Initiative (MATSITI) directed by the David Unaipon College of Indigenous Education and Research and funded by the Department of Education, Employment and Workplace Relations. MATSITI will develop Action Plans within participating universities (n=33) to improve the retention/graduation rates of Aboriginal and Torres Strait Islander teachers. The paper provides an overview of the teacher education component of the MATSITI project and presents preliminary research from 33 Australian universities.

Establishing a framework for transforming student engagement, success and retention in higher education institutions

This poster summarises the outcomes of a national project to develop and provide a holistic framework consisting of a series of sequential and increasingly sophisticated stages that will allow higher education institutions (HEIs) to manage and improve their student engagement and retention strategies/programs.

A cultural assessment of family dispute resolution: Findings about access, retention and outcomes from the evaluation of a Family Relationship Centre

The cultural appropriateness of human service processes is a major factor in determining the effectiveness of their delivery. Sensitivity to issues of culture is particularly critical in dealing with family disputes, which are generally highly emotive and require difficult decisions to be made regarding children, material assets and ongoing relationships. In this article we draw on findings from an evaluation of the Family Relationship Centre at Broadmeadows (FRCB) to offer some insights into and suggestions about managing cultural matters in the current practice of family dispute resolution (FDR) in Australia. The brief for the original research was to evaluate the cultural appropriateness of FDR services offered to culturally and linguistically diverse (CALD) communities living within the FRCB’s catchment area, specifically members of the Lebanese, Turkish and Iraqi communities. The conclusions of the evaluations were substantially positive. The work of the Centre was found to illustrate many aspects of best practice but also raised questions worthy of future exploration. The current article reports on issues of access, retention and outcomes obtained by CALD clients at various stages of the FRCB service.