Information Technology and Innovation DSITI

Dutton, Australia

Information Technology and Innovation DSITI

Dutton, Australia
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Rezaei Rashti M.,Information Technology and Innovation DSITI | Rezaei Rashti M.,Griffith University | Wang W.J.,Information Technology and Innovation DSITI | Wang W.J.,Griffith University | And 3 more authors.
Science of the Total Environment | Year: 2017

Combined application of plant residues and N fertilisers strongly affect soil mineral N dynamics and N2O emissions depending on the quality of the plant residues, their application methods and other management strategies. We investigated the effect of combined application of two vegetable plant residues (cauliflower and sweet corn) and 15N fertiliser on N dynamics and N2O emission in a glasshouse pot study. The experiment was conducted under two residue management practices (soil incorporation vs surface mulching) over 98 days with growing basil (Ocimum basilicum) plants. We also assessed the efficacy of applying the nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP) to the plant residues, for reducing N loss and mitigating N2O emissions. Application of plant residues, both on the soil surface or into soil, resulted in net N mineralisation and increased cumulative N2O emission compared with the application of N fertiliser alone. Soil surface mulching of sweet corn decreased total and residue-induced cumulative N2O emission compared with the incorporation method, while it showed opposite effect on N2O emissions from cauliflower residue. The application of DMPP with sweet corn residue reduced total, residue- and fertiliser-induced N2O emissions; however its application with cauliflower residue did not show any mitigating effect on the N2O emissions. The residue application methods and the use of DMPP did not significantly affect 15N recovery by the basil plants. In contrast, soil incorporation of these residues doubled the microbial immobilisation of applied 15N into soil organic matter. Linear regression analysis of N2O emission during the experimental period indicated that in the treatments without DMPP application, soil NO3 −-N concentration was the most important factor in controlling the magnitude of N2O emissions, while the application of DMPP changed the dominant regulating factor from NO3 −-N to NH4 +-N concentration. © 2017

Rezaei Rashti M.,Information Technology and Innovation DSITI | Rezaei Rashti M.,Griffith University | Wang W.J.,Information Technology and Innovation DSITI | Wang W.J.,Griffith University | And 4 more authors.
Soil Biology and Biochemistry | Year: 2016

The magnitudes of nitrogen (N) mineralisation and nitrous oxide (N2O) emissions after the application of plant materials strongly depend on their quality. Despite the existence of some studies in this field, little is known about the underlying mechanisms and regulating factors of these processes, particularly for vegetable cropping systems. In this study, ten typical vegetable and/or vegetable farming rotation plant materials were finely ground, incorporated into the soil and incubated at 25 °C under fluctuating moisture conditions of 55–85% water-filled pore space (WFPS) without N (-N) or with N (+N) addition (100 mg N kg−1 soil as urea). The applied plant materials were characterised using solid state 13C nuclear magnetic resonance (NMR) spectroscopy and wet-chemical analysis. The dynamics of soil mineral N accumulation and N2O emissions were monitored over 169 days. Under the -N treatment, plant materials with total N (TN) contents ≥ 27 mg g−1 dry matter produced significantly higher cumulative N2O emissions than those with TN contents < 27 mg g−1 in the first 105 days of incubation. However, there was no significant difference in cumulative N2O emissions between these two groups at the end of the experiment due to higher N2O emissions for plant materials with TN contents <27 mg g−1 during the later stage of the incubation. Under the +N treatment, application of plant materials consistently increased the cumulative N2O emissions by the end of the incubation compared with the urea only treatment; although a few plant materials resulted in lower or similar N2O emissions in the initial 2–4 weeks. During the entire incubation, plant materials with high TN contents generally produced higher cumulative N2O emissions than others in the +N treatment. Stepwise regression analysis indicated a significant correlation between cumulative N2O emissions and TN, cellulose, lignin, O-aryl C and carbonyl C contents of the plant materials; TN content was the main regulating factor among all chemical and biochemical indices. © 2016

Wang W.,Information Technology and Innovation DSITI | Wang W.,Griffith University | Dalal R.C.,Information Technology and Innovation DSITI
European Journal of Agronomy | Year: 2015

Farm management affects the global greenhouse gas (GHG) budget by changing not only soil organic carbon (SOC) stocks and nitrous oxide (N2O) emissions but also other pre-farm, on-farm and off-site emissions. The life cycle assessment (LCA) approach has been widely adopted to assess the "carbon footprint" of agricultural products, but rarely used as a tool to identify effective mitigation strategies. In this study, the global warming impacts of no-till (NT) vs. conventional till (CT), stubble retention (SR) vs. stubble burning (SB), and N fertilization (NF) vs. no N fertilization (N0) in an Australian wheat cropping system were assessed using in situ measurements of N2O fluxes over three years, SOC changes over forty years and including other supply chain GHG sources and sinks. The results demonstrated the importance of full GHG accounting compared to considering SOC changes or N2O emissions alone for assessing the global warming impacts of different management practices, and highlighted the significance of accurately accounting for SOC changes and N2O emissions in LCAs. The GHG footprints of wheat production were on averaged 475kg carbon dioxide equivalent (CO2-e) ha-1 (or 186kg CO2-e t-1 grain) higher under NF than N0. Where fertilizer N was applied (70kgNha-1), the life cycle emissions were 200kg CO2-e ha-1 (or 87t-1 grain) lower under NT than CT and 364kg CO2-e ha-1 (or 155t-1 grain) lower under SR than SB. Classification of the emission sources/sinks and re-calculation of published data indicated that under the common practices of SR combined with NT, N-related GHG emissions contributed 60-95% of the life cycle emissions in the predominantly rain-fed wheat production systems in Australia. Therefore, future mitigation efforts should aim to improve N use efficiency, explore non-synthetic N sources, and most importantly avoid excessive N fertilizer use whilst practising NT and SR. © 2015 Elsevier B.V.

Rezaei Rashti M.,Information Technology and Innovation DSITI | Rezaei Rashti M.,Griffith University | Wang W.J.,Information Technology and Innovation DSITI | Wang W.J.,Griffith University | And 5 more authors.
Soil Research | Year: 2015

The greenhouse gas fluxes and effective mitigation strategies in subtropical vegetable cropping systems remain unclear. In this field experiment, nitrous oxide (N2O) and methane (CH4) fluxes from an irrigated lettuce cropping system in subtropical Queensland, Australia, were measured using manual sampling chambers. Four treatments were included: Control (no fertiliser), U100 (100kg N ha-1 as urea), U200 (200kg N ha-1 as urea) and N100 (100kg N ha-1 as nitrate-based fertilisers). The N fertilisers were applied in three splits and irrigation was delivered sparingly and frequently to keep soil moisture around the field capacity. The cumulative N2O emissions from the control, U100, U200 and N100 treatments over the 68-day cropping season were 30, 151, 206 and 68g N2O-N ha-1, respectively. Methane emission and uptake were negligible. Using N2O emission from the Control treatment as the background emission, direct emission factors for U100, U200 and N100 treatments were 0.12%, 0.09% and 0.04% of applied fertiliser N, respectively. Soil ammonium (NH4+) concentration, instead of nitrate (NO3-) concentration, exhibited a significant correlation with N2O emissions at the site where the soil moisture was controlled within 50%-64% water-filled pore space. Furthermore, soil temperature rather than water content was the main regulating factor of N2O fluxes in the fertilised treatments. Fertiliser type and application rates had no significant effects on yield parameters. Partial N balance analysis indicated that approximately 80% and 52% of fertiliser N was recovered in plants and soil in the treatments receiving 100kg N ha-1 and 200kg N ha-1, respectively. Therefore, in combination with frequent and low-intensity irrigation and split application of fertiliser N, substitution of NO3-based fertilisers for urea and reduction in fertiliser N application rates were considered promising mitigation strategies to maintain yield and minimise N2O emissions during the low rainfall season. © 2015 CSIRO.

Schmidt M.,Information Technology and Innovation DSITI | Schmidt M.,University of Queensland | Tindall D.,Information Technology and Innovation DSITI | Tindall D.,University of Queensland
European Space Agency, (Special Publication) ESA SP | Year: 2016

Crop extent and frequency maps are an important input to inform the debate around land value and competitive land uses, food security and sustainability of agricultural practices. Such spatial datasets are likely to support decisions on natural resource management, planning and policy. The complete Landsat Time Series (LTS) archive for 23 Landsat footprints in western Queensland from 1987 to 2015 was used in a multi-temporal mapping approach. Spatial, spectral and temporal information were combined in multiple crop-modelling steps, supported by on ground training data sampled across space and time for the classes Crop and No-Crop. Temporal information within summer and winter growing seasons for each year were summarised, and combined with various vegetation indices and band ratios computed from a mid-season spectral-composite image. All available temporal information was spatially aggregated to the scale of image segments in the midseason composite for each growing season and used to train a random forest classifier for a Crop and No- Crop classification. Validation revealed that the predictive accuracy varied by growing season and region to be within κ = 0.88 to 0.97 and are thus suitable for mapping current and historic cropping activity. Crop frequency maps were produced for all regions at different time intervals. The crop frequency maps were validated separately with a historic crop information time series. Different land use intensities and conversions e.g. from agricultural to pastures are apparent and potential drivers of these conversions are discussed.

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