@article{Mielenz2016,
title = {Opportunities for mitigating nitrous oxide emissions in subtropical cereal and fibre cropping systems: a simulation study.},
author = { H Mielenz and P Thorburn and C Scheer and M.J Bell and M De Antoni Migliorati and P.R. Grace},
doi = {10.1016/j.agee.2015.11.008},
year = {2016},
date = {2016-02-15},
journal = {Agriculture, Ecosystems & Environment},
volume = {218},
pages = {11-27},
abstract = {23% of global agricultural land are situated in the subtropics. Nitrous oxide (N_{2}O) emissions were estimated to be higher under subtropical than under temperate climates. So mitigation of N_{2}O emissions from subtropical farming systems can make an important contribution to reducing global warming. Accordingly, in this study we explored long-term N_{2}O emissions and possible mitigation options for representative subtropical cropping systems (e.g., summer versus winter crops, inclusion of a legume in the rotation) and management practices (nitrogen fertilizer, irrigation) by calculating scenarios with the agricultural systems model APSIM. The model was tested against high temporal frequency data from experiments conducted on an oxisol and a vertisol in subtropical Australia, which comprised a number of fertilization and irrigation treatments. The threshold of water filled pore space above which denitrification starts was calibrated on a subset of the data while the rest of the large number of parameters controlling the carbon and nitrogen cycles were kept to default values. The validity of the model was confirmed with 11 validation data sets for yields of four different crops (\emph{R}^{2} = 0.92) and 16 validation data sets for seasonal N_{2}O emissions during crop and fallow periods (\emph{R}^{2} = 0.77). While these results show that the model performs well in sub-tropical environments, this modeling skill might not translate to other environments and the model would benefit from wider testing. In the scenario analyses, long-term average N_{2}O emissions from wheat, cotton, maize and sorghum were predicted to vary between 0.2 and 6.1 kg N ha^{−1} yr^{−1} and showed large interannual variability of N_{2}O emissions. This highlights the risk that results from short-term experiments may not be representative for the long-term behavior of these agro-ecosystems, and thus the value simulation studies add to experiments. The scenario analysis revealed that long-term average yields and N_{2}O emissions increased in response to the same management practices (e.g., increase in nitrogen rate), leading to a trade-off between maximizing yield and minimizing N_{2}O emissions. When crop yields were limited due to water stress either by low seasonal rainfall or by lack of irrigation, average N_{2}O emissions increased. Given the annual variability in climate and soil nitrogen stocks, mitigating N_{2}O emissions without compromizing in yield is not a simple task but requires an optimal nitrogen management considering other limiting factors such as water supply.},
keywords = {Agriculture, Ecosystems and Environment},
pubstate = {published},
tppubtype = {article}
}

@article{Migliorati2015,
title = {Legumes or nitrification inhibitors to reduce N_{2}O emissions from subtropical cereal cropping systems in Oxisols?},
author = { M De Antoni Migliorati and W.J Parton and S.J Del Grosso and P.R Grace and M.J Bell and A Strazzabosco and D.W Rowlings and C Scheer and G. Harch},
doi = {10.1016/j.agee.2015.08.010},
year = {2015},
date = {2015-08-10},
journal = {Agriculture, Ecosystems and Environment},
volume = {213},
pages = {228-240},
abstract = {The DAYCENT biogeochemical model was used to investigate how the use of fertilizers coated with nitrification inhibitors and the introduction of legumes in the crop rotation can affect subtropical cereal production and N_{2}O emissions. The model was validated using comprehensive multi-seasonal, high-frequency dataset from two field investigations conducted on an Oxisol, which is the most common soil type in subtropical regions. Different N fertilizer rates were tested for each N management strategy and simulated under varying weather conditions. DAYCENT was able to reliably predict soil N dynamics, seasonal N_{2}O emissions and crop production, although some discrepancies were observed in the treatments with low or no added N inputs and in the simulation of daily N_{2}O fluxes. Simulations highlighted that the high clay content and the relatively low C levels of the Oxisol analyzed in this study limit the chances for significant amounts of N to be lost via deep leaching or denitrification. The application of urea coated with a nitrification inhibitor was the most effective strategy to minimize N_{2}O emissions. This strategy however did not increase yields since the nitrification inhibitor did not substantially decrease overall N losses compared to conventional urea. Simulations indicated that replacing part of crop N requirements with N mineralized by legume residues is the most effective strategy to reduce N_{2}O emissions and support cereal productivity. The results of this study show that legumes have significant potential to enhance the sustainable and profitable intensification of subtropical cereal cropping systems in Oxisols.},
keywords = {Agriculture, Ecosystems and Environment},
pubstate = {published},
tppubtype = {article}
}

@article{Migliorati2014,
title = {Influence of different nitrogen rates and DMPP nitrification inhibitor on annual N_{2}O emissions from a subtropical wheat–maize cropping system},
author = { M De Antoni Migliorati and C Scheer and P. R. Grace and D. W. Rowlings and M Bell and J. McGree},
doi = {10.1016/j.agee.2014.01.016},
year = {2014},
date = {2014-03-15},
journal = {Agriculture, Ecosystems and Environment},
volume = {186},
number = {15},
pages = {33-43},
abstract = {Global cereal production will need to increase by 50% to 70% to feed a world population of about 9 billion by 2050. This intensification is forecast to occur mostly in subtropical regions, where warm and humid conditions can promote high N_{2}O losses from cropped soils. To secure high crop production without exacerbating N_{2}O emissions, new nitrogen (N) fertiliser management strategies are necessary. This one-year study evaluated the efficacy of a nitrification inhibitor (3,4-dimethylpyrazole phosphate—DMPP) and different N fertiliser rates to reduce N_{2}O emissions in a wheat–maize rotation in subtropical Australia. Annual N_{2}O emissions were monitored using a fully automated greenhouse gas measuring system. Four treatments were fertilized with different rates of urea, including a control (40 kg-N ha^{−1} year^{−1}), a conventional N fertiliser rate adjusted on estimated residual soil N (120 kg-N ha^{−1} year^{−1}), a conventional N fertiliser rate (240 kg-N ha^{−1} year^{−1}) and a conventional N fertiliser rate (240 kg-N ha^{−1} year^{−1}) with nitrification inhibitor (DMPP) applied at top dressing. The maize season was by far the main contributor to annual N_{2}O emissions due to the high soil moisture and temperature conditions, as well as the elevated N rates applied. Annual N_{2}O emissions in the four treatments amounted to 0.49, 0.84, 2.02 and 0.74 kg N_{2}O–N ha^{−1} year^{−1}, respectively, and corresponded to emission factors of 0.29%, 0.39%, 0.69% and 0.16% of total N applied. Halving the annual conventional N fertiliser rate in the adjusted N treatment led to N_{2}O emissions comparable to the DMPP treatment but extensively penalised maize yield. The application of DMPP produced a significant reduction in N_{2}O emissions only in the maize season. The use of DMPP with urea at the conventional N rate reduced annual N_{2}O emissions by more than 60% but did not affect crop yields. The results of this study indicate that: (i) future strategies aimed at securing subtropical cereal production without increasing N_{2}O emissions should focus on the fertilisation of the summer crop; (ii) adjusting conventional N fertiliser rates on estimated residual soil N is an effective practice to reduce N_{2}O emissions but can lead to substantial yield losses if the residual soil N is not assessed correctly; (iii) the application of DMPP is a feasible strategy to reduce annual N_{2}O emissions from sub-tropical wheat–maize rotations. However, at the N rates tested in this study DMPP urea did not increase crop yields, making it impossible to recoup extra costs associated with this fertiliser. The findings of this study will support farmers and policy makers to define effective fertilisation strategies to reduce N_{2}O emissions from subtropical cereal cropping systems while maintaining high crop productivity. More research is needed to assess the use of DMPP urea in terms of reducing conventional N fertiliser rates and subsequently enable a decrease of fertilisation costs and a further abatement of fertiliser-induced N_{2}O emissions.},
keywords = {Agriculture, Ecosystems and Environment},
pubstate = {published},
tppubtype = {article}
}

@article{Rowlings2013,
title = {Influence of nitrogen fertiliser application and timing on greenhouse gas emissions from a lychee (Litchi chinensis) orchard in humid subtropical Australia},
author = {D. W. Rowlings and P. R. Grace and C Scheer and R. Kiese},
doi = {10.1016/j.agee.2013.08.013},
year = {2013},
date = {2013-08-06},
journal = {Agriculture, Ecosystems and Environment},
volume = {179},
pages = {168-178},
abstract = {"Nitrous oxide emissions from intensive, fertilised agricultural systems have been identified as significant contributors to both Australia's and the global greenhouse gas (GHG) budget. This is expected to increase as rates of agriculture intensification and land use change accelerate to support population growth and food production. Limited data exists on N_{2}O trace gas fluxes from subtropical or tropical tree cropping soils critical for the development of effective mitigation strategies. This study aimed to quantify GHG emissions over two consecutive years (March 2007 to March 2009) from a 30 year (lychee) orchard in the humid subtropical region of Australia. GHG fluxes were measured using a combination of high temporal resolution automated sampling and manually sampled chambers. No fertiliser was added to the plots during the 2007 measurement season. A split application of nitrogen fertiliser (urea) was added at the rate of 265 kg N ha^{−1} during the autumn and spring of 2008. Emissions of N_{2}O were influenced by rainfall events and seasonal temperatures during 2007 and the fertilisation events in 2008. Annual N_{2}O emissions from the lychee canopy increased from 1.7 kg N_{2}O–N ha^{−1} yr^{−1} for 2007, to 7.6 kg N_{2}O–N ha^{−1} yr^{−1} following fertiliser application in 2008. This represented an emission factor of 1.56%, corrected for background emissions. The timing of the split application was found to be critical to N_{2}O emissions, with over twice as much lost following an application in spring (2.44%) compared to autumn (EF: 1.10%). This research suggests that avoiding fertiliser application during the hot and moist spring/summer period can reduce N_{2}O losses without compromising yields."},
keywords = {Agriculture, Ecosystems and Environment},
pubstate = {published},
tppubtype = {article}
}