@article{Scheer2013,
title = {Non-linear response of soil N_{2}O emissions to nitrogen fertiliser in a cotton–fallow rotation in sub-tropical Australia},
author = {Clemens Scheer and David Rowlings and Peter R. Grace},
doi = {10.1071/SR14328},
year = {2016},
date = {2016-07-06},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {494-499},
abstract = {Nitrogen (N) fertiliser is a major source of atmospheric nitrous oxide (N_{2}O), and over recent years there has been growing evidence for a non-linear, exponential relationship between N fertiliser application rate and N_{2}O emissions. However, there is still a high level of uncertainty around the relationship of N fertiliser rate and N_{2}O emissions for many cropping systems. We conducted year-round measurements of N_{2}O 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 non-linear exponential response of N_{2}O emissions to increasing N fertiliser rates with cumulative annual N_{2}O emissions of 0.55, 0.67, 1.07 and 1.89 kg N ha^{–1} for the four respective N fertiliser rates, but no N response to yield occurred above 180 kg N ha^{–1}. The annual N_{2}O emission factors induced by N fertiliser were 0.13, 0.29 and 0.50% for the 90, 180 and 270 kg N ha^{–1} treatments respectively, significantly lower than the IPCC Tier 1 default value of 1.0%. This nonlinear response suggests that an exponential N_{2}O emissions model may be more appropriate for estimating emission of N_{2}O from soils cultivated to cotton in Australia. It also demonstrates that improved agricultural N-management practices can be adopted in cotton to substantially reduce N_{2}O emissions without affecting yield.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Scheer2015,
title = {Non-linear response of soil N_{2}O emissions to nitrogen fertiliser in a cotton–fallow rotation in sub-tropical Australia},
author = { C Scheer and P.R Grace and D.W. Rowlings},
doi = {10.1071/SR14328},
year = {2016},
date = {2016-07-06},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {494-499},
abstract = {Nitrogen (N) fertiliser is a major source of atmospheric nitrous oxide (N_{2}O), and over recent years there has been growing evidence for a non-linear, exponential relationship between N fertiliser application rate and N_{2}O emissions. However, there is still a high level of uncertainty around the relationship of N fertiliser rate and N_{2}O emissions for many cropping systems. We conducted year-round measurements of N_{2}O 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 non-linear exponential response of N_{2}O emissions to increasing N fertiliser rates with cumulative annual N_{2}O emissions of 0.55, 0.67, 1.07 and 1.89 kg N ha^{–1} for the four respective N fertiliser rates, but no N response to yield occurred above 180 kg N ha^{–1}. The annual N_{2}O emission factors induced by N fertiliser were 0.13, 0.29 and 0.50% for the 90, 180 and 270 kg N ha^{–1} treatments respectively, significantly lower than the IPCC Tier 1 default value of 1.0%. This nonlinear response suggests that an exponential N_{2}O emissions model may be more appropriate for estimating emission of N_{2}O from soils cultivated to cotton in Australia. It also demonstrates that improved agricultural N-management practices can be adopted in cotton to substantially reduce N_{2}O emissions without affecting yield.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Biala2016,
title = {Greenhouse gas emissions from stockpiled and composted dairy manure residues and consideration of associated emission factors.},
author = {J. Biala and N. Lovrick and D. W. Rowlings and P. R. Grace},
doi = {10.1071/AN16009},
year = {2016},
date = {2016-07-05},
journal = {Animal Production Science},
volume = {56},
number = {9},
pages = {1432-1441},
abstract = {Emissions from stockpiled pond sludge and yard scrapings were compared with composted dairy-manure residues blended with shredded vegetation residues and chicken litter over a 5-month period at a farm in Victoria (Australia). Results showed that methane emissions occurred primarily during the first 30–60 days of stockpiling and composting, with daily emission rates being highest for stockpiled pond sludge. Cumulated methane (CH_{4}) emissions per tonne wet feedstock were highest for stockpiling of pond sludge (969 g CH_{4}/t), followed by composting (682 g CH_{4}/t) and stockpiling of yard scrapings (120 g CH_{4}/t). Sizeable nitrous oxide (N_{2}O) fluxes were observed only when temperatures inside the compost windrow fell below ~45-50°C. Cumulated N_{2}O emissions were highest for composting (159 g N_{2}O/t), followed by stockpiling of pond sludge (103 g N_{2}O/t) and yard scrapings (45 g N_{2}O/t). Adding chicken litter and lime to dairy-manure residues resulted in a very low carbon-to-nitrogen ratio (13 : 1) of the composting mix, and would have brought about significant N_{2}O losses during composting. These field observations suggested that decisions at composting operations, as in many other businesses, are driven more by practical and economic considerations rather than efforts to minimise greenhouse-gas emissions. Total greenhouse-gas emissions (CH_{4} + N_{2}O), expressed as CO_{2}-e per tonne wet feedstock, were highest for composting (64.4 kg), followed by those for stockpiling of pond sludge (54.5 kg) and yard scraping (16.3 kg). This meant that emissions for composting and stockpiling of pond sludge exceeded the new Australian default emission factors for ‘waste composting’ (49 kg). This paper proposes to express greenhouse-gas emissions from secondary manure-management systems (e.g. composting) also as emissions per tonne wet feedstock, so as to align them with the approach taken for ‘waste composting’ and to facilitate the development of emission-reduction methodologies for improved manure management at the farm level.},
keywords = {Animal Production Science},
pubstate = {published},
tppubtype = {article}
}

@article{Belyaeva2016,
title = {Use of the agricultural practice of pasture termination in reducing soil N_{2}O emissions in high-rainfall cropping systems of south-eastern Australia},
author = {Oxana N. Belyaeva and Sally J. Officer and Roger D. Armstrong and Rob H. Harris and Ashley Wallace and Debra L. Partington and Kirsten Fogarty and Andrew J. Phelan},
doi = {10.1071/SR15307},
year = {2016},
date = {2016-06-28},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {585-597},
abstract = {Conversion of long-term pasture to cropping was investigated for its effects on nitrous oxide (N_{2}O) emissions in a 2-year field experiment in the high-rainfall zone of south-western Victoria. Early termination (pasture terminated 6 months before sowing) followed by winter (ETw) and spring (ETs) crops and late termination (pasture terminated 1 month before sowing) followed by a winter crop (LTw) were compared with continuous, mown pasture (MP). Emissions of N_{2}O were measured with an automated gas sampling and analysing system.
Emissions from MP were the lowest throughout the study, resulting in annual losses of 0.13 kg N_{2}O-N ha^{–1} in the first and the second years of the experiment. N_{2}O-N loss was 0.6 kg ha^{–1} from treatments without fallow in both years (LTw in 2013 and ETs in 2014). In the first year, annual losses from previous fallow in ETw and ETs plots were 7.1 and 3.6 kg N_{2}O-N ha^{–1}, respectively. Higher annual N_{2}O losses from treatments with fallow periods continued in the second year of the study and were 2.0 and 1.3 kg N_{2}O-N ha^{–1} from ETw and LTw treatments, respectively. High emissions were associated with N mineralisation and the accumulation of NO_{3}-N in the soil during the extensive fallow period after early pasture termination or wheat harvest. Soil water content was a key factor influencing the temporal fluctuations in N_{2}O emissions. Low emissions occurred when water-filled pore space was <30%, whereas high emissions occurred when it was >65%, suggesting that denitrification was the major source of N_{2}O emission. Crop grain yield was not affected by the duration of fallow (and therefore timing of pasture termination) in the first year, but was lower (\textit{P} < 0.05) in the treatment without fallow in the second year. Terminating pasture late rather than early, thus reducing the length of the fallow period, is a practical way of reducing N_{2}O emissions from mixed pasture–cropping systems.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Farquharson2016,
title = {Nitrification rates and associated nitrous oxide emissions from agricultural soils – a synopsis},
author = {Ryan Farquharson},
doi = {10.1071/SR15304},
year = {2016},
date = {2016-06-27},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {469-480},
abstract = {Laboratory incubations were performed to estimate nitrification rates and the associated nitrous oxide (N_{2}O) emissions under aerobic conditions on a range of soils from National Agricultural Nitrous Oxide Research Program field sites. Significant site-to-site variability in nitrification rates and associated N_{2}O emissions was observed under standardised conditions, indicating the need for site-specific model parameterisation. Generally, nitrification rates and N_{2}O emissions increased with higher water content, ammonium concentration and temperature, although there were exceptions. It is recommended that site-specific model parameterisation be informed by such data. Importantly, the ratio of N_{2}O emitted to net nitrified N under aerobic conditions was small (<0.2% for the majority of measurements) but did vary from 0.03% to 1%. Some models now include variation in the proportion of nitrified N emitted as N_{2}O as a function of water content; however, strong support for this was not found across all of our experiments, and the results demonstrate a potential role of pH and ammonium availability. Further research into fluctuating oxygen availability and the coupling of biotic and abiotic processes will be required to progress the process understanding of N_{2}O emissions from nitrification.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Schwenke2016,
title = {The interaction of seasonal rainfall and nitrogen fertiliser rate on soil N_{2}O emission, total N loss and crop yield of dryland sorghum and sunflower grown on sub-tropical Vertosols},
author = {G. D. Schwenke and B. M. Haigh},
doi = {10.1071/SR15286},
year = {2016},
date = {2016-06-27},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {604-618},
abstract = {Summer crop production on slow-draining Vertosols in a sub-tropical climate has the potential for large emissions of soil nitrous oxide (N_{2}O) from denitrification of applied nitrogen (N) fertiliser. While it is well established that applying N fertiliser will increase N_{2}O emissions above background levels, previous research in temperate climates has shown that increasing N fertiliser rates can increase N_{2}O emissions linearly, exponentially or not at all. Little such data exists for summer cropping in sub-tropical regions. In four field experiments at two locations across two summers, we assessed the impact of increasing N fertiliser rate on both soil N_{2}O emissions and crop yield of grain sorghum (\textit{Sorghum bicolor} L.) or sunflower (\textit{Helianthus annuus} L.) in Vertosols of sub-tropical Australia. Rates of N fertiliser, applied as urea at sowing, included a nil application, an optimum N rate and a double-optimum rate.

Daily N_{2}O fluxes ranged from –3.8 to 2734 g N_{2}O-N ha^{–1} day^{–1} and cumulative N_{2}O emissions ranged from 96 to 6659 g N_{2}O-N ha^{–1} during crop growth. Emissions of N_{2}O increased with increased N fertiliser rates at all experimental sites, but the rate of N loss was five times greater in wetter-than-average seasons than in drier conditions. For two of the four experiments, periods of intense rainfall resulted in N_{2}O emission factors (EF, percent of applied N emitted) in the range of 1.2–3.2%. In contrast, the EFs for the two drier experiments were 0.41–0.56% with no effect of N fertiliser rate.
Additional ^{15}N mini-plots aimed to determine whether N fertiliser rate affected total N lost from the soil–plant system between sowing and harvest. Total ^{15}N unaccounted was in the range of 28–45% of applied N and was presumed to be emitted as N_{2}O + N_{2}. At the drier site, the ratio of N_{2} (estimated by difference) to N_{2}O (measured) lost was a constant 43%, whereas the ratio declined from 29% to 12% with increased N fertiliser rate for the wetter experiment.
Choosing an N fertiliser rate aimed at optimum crop production mitigates potentially high environmental (N_{2}O) and agronomic (N_{2} + N_{2}O) gaseous N losses from over-application, particularly in seasons with high intensity rainfall occurring soon after fertiliser application.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Schwenke2016b,
title = {Greenhouse gas (N_{2}O and CH_{4}) fluxes under nitrogen-fertilised dryland wheat and barley on subtropical Vertosols: risk, rainfall and alternatives},
author = {G. D. Schwenke and David F. Herridge and Clemens Scheer and David W. Rowlings and Bruce M. Haigh and K. Guy McMullen},
doi = {10.1071/SR15338},
year = {2016},
date = {2016-06-21},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {634-650},
abstract = {The northern Australian grains industry relies on nitrogen (N) fertiliser to optimise yield and protein, but N fertiliser can increase soil fluxes of nitrous oxide (N_{2}O) and methane (CH_{4}). We measured soil N_{2}O and CH_{4} fluxes associated with wheat (\textit{Triticum aestivum}) and barley (\textit{Hordeum vulgare}) using automated (Expts 1, 3) and manual chambers (Expts 2, 4, 5). Experiments were conducted on subtropical Vertosol soils fertilised with N rates of 0–160 kg N ha^{–1}.
In Expt 1 (2010), intense rainfall for a month before and after sowing elevated N_{2}O emissions from N-fertilised (80 kg N ha^{–1}) wheat, with 417 g N_{2}O-N ha^{–1} emitted compared with 80 g N_{2}O-N ha^{–1} for non-fertilised wheat. Once crop N uptake reduced soil mineral N, there was no further treatment difference in N_{2}O. Expt 2 (2010) showed similar results, however, the reduced sampling frequency using manual chambers gave a lower cumulative N_{2}O. By contrast, very low rainfall before and for several months after sowing Expt 3 (2011) resulted in no difference in N_{2}O emissions between N-fertilised and non-fertilised barley. N_{2}O emission factors were 0.42, 0.20 and –0.02 for Expts 1, 2 and 3, respectively. In Expts 4 and 5 (2011), N_{2}O emissions increased with increasing rate of N fertiliser. Emissions were reduced by 45% when the N fertiliser was applied in a 50 : 50 split between sowing and mid-tillering, or by 70% when urea was applied with the nitrification inhibitor 3,4-dimethylpyrazole-phosphate.
Methane fluxes were typically small and mostly negative in all experiments, especially in dry soils. Cumulative CH_{4} uptake ranged from 242 to 435 g CH_{4}-C ha^{–1} year^{–1}, with no effect of N fertiliser treatment. Considered in terms of CO_{2} equivalents, soil CH_{4} uptake offset 8–56% of soil N_{2}O emissions, with larger offsets occurring in non-N-fertilised soils.
The first few months from N fertiliser application to the period of rapid crop N uptake pose the main risk for N_{2}O losses from rainfed cereal cropping on subtropical Vertosols, but the realisation of this risk is dependent on rainfall. Strategies that reduce the soil mineral N pool during this time can reduce the risk of N_{2}O loss.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Li2016,
title = {Tillage does not increase nitrous oxide emissions under dryland canola (Brassica napus L.) in a semiarid environment of south-eastern Australia},
author = {Guangdi D. Li and Mark K. Conyers and G. D. Schwenke and Richard C. Hayes and De Li Liu and Adam J. Lowrie and Graeme J. Poile and Albert A. Oates and Richard J. Lowrie},
doi = {10.1071/SR15289},
year = {2016},
date = {2016-06-21},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {512-522},
abstract = {Dryland cereal production systems of south-eastern Australia require viable options for reducing nitrous oxide (N_{2}O) emissions without compromising productivity and profitability. A 4-year rotational experiment with wheat (\textit{Triticum aestivum} L.)–canola (\textit{Brassica napus} L.)–grain legumes–wheat in sequence was established at Wagga Wagga, NSW, Australia, in a semiarid Mediterranean-type environment where long-term average annual rainfall is 541 mm and the incidence of summer rainfall is episodic and unreliable. The objectives of the experiment were to investigate whether (i) tillage increases N_{2}O emissions and (ii) nitrogen (N) application can improve productivity without increasing N_{2}O emissions. The base experimental design for each crop phase was a split-plot design with tillage treatment (tilled versus no-till) as the whole plot, and N fertiliser rate (0, 25, 50 and 100 kg N/ha) as the subplot, replicated three times. This paper reports high resolution N_{2}O emission data under a canola crop. The daily N_{2}O emission rate averaged 0.55 g N_{2}O-N/ha.day, ranging between –0.81 and 6.71 g N_{2}O-N/ha.day. The annual cumulative N_{2}O-N emitted was 175.6 and 224.3 g N_{2}O-N/ha under 0 and 100 kg N/ha treatments respectively. There was no evidence to support the first hypothesis that tillage increases N_{2}O emissions, a result which may give farmers more confidence to use tillage strategically to manage weeds and diseases where necessary. However, increasing N fertiliser rate tended to increase N_{2}O emissions, but did not increase crop production at this site.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@article{Rosa2016,
title = {Effect of organic and mineral N fertilizers on N_{2}O emissions from an intensive vegetable rotation},
author = {D. De Rosa and D. W. Rowlings and C. Scheer and B. Basso and J. McGree and P. R. Grace},
doi = {10.1007/s00374-016-1117-5},
year = {2016},
date = {2016-05-18},
journal = {Biology and Fertility of Soils},
volume = {52},
number = {6},
pages = {895–908},
abstract = {Predicting and accounting for the nitrogen (N) supplied by organic amendments can reduce the application of mineral N fertilizer without yield penalty as well as decreasing N_{2}O emissions. Automated chambers were employed over 12 months to measure N_{2}O emissions together with soil mineral N and crop yields from optimized organic and conventional N management in an intensive, irrigated vegetable rotation in subtropical Australia. Five different fertilizer strategies were investigated. The conventional urea application rate (CONV) was compared to raw (Ma) and composted (Co) chicken manure at a conventional (Ma + CONV, Co + CONV) and reduced urea rate (Ma + Rd, Co + Rd). The reduced rates represented an 18–20 % less urea being applied and were calculated by accounting for the potential N mineralized from organic amendments. Three consecutive crops (green beans, broccoli, and lettuce) plus a cover crop (sorghum) showed no significant differences in yield and biomass production between treatments receiving either organic or mineral fertilizer. Overall, fertilizer-induced emissions were low and were unaffected by compost addition. Raw organic amendments increased N_{2}O emissions with the first crop in the rotation contributing the highest emissions, 38–57 % of the annual cumulative N_{2}O. The incorporation of post-harvest crop residues was a substantial trigger for N_{2}O emissions, while the application of N fertilizer and heavy rainfall events had only marginal effects. Highest cumulative N_{2}O emissions of 1748 g N_{2}O-N ha^{−1} yr^{−1} were measured in the Ma + Rd treatment, with the compost treatments reducing N_{2}O emissions by up to 45 % with emissions similar to the zero N application (0N). This study demonstrated that the strategic application of composted organic amendments integrated with reducing N fertilizer rates by up to 20 % can be an effective pathway to reduce greenhouse gas (GHG) emissions without compromising crop growth and yield.},
keywords = {Biology and Fertility of Soils},
pubstate = {published},
tppubtype = {article}
}

@article{Jamali2016,
title = {Mitigation of N_{2}O emissions from surface-irrigated cropping systems using water management and the nitrification inhibitor DMPP},
author = {Hizbullah Jamali and Wendy Quayle and Clemens Scheer and Jeff Baldock},
doi = {10.1071/SR15315},
year = {2016},
date = {2016-03-11},
journal = {Soil Research},
volume = {54},
number = {5},
pages = {481-493},
abstract = {Soils under irrigated agriculture are a significant source of nitrous oxide (N_{2}O) owing to high inputs of nitrogen (N) fertiliser and water. This study investigated the potential for N_{2}O mitigation by manipulating the soil moisture deficit through irrigation scheduling in combination with, and in comparison to, using the nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP). Lysimeter cores planted with wheat were fitted with automated chambers for continuous measurements of N_{2}O fluxes. Treatments included conventional irrigation (CONV), reduced deficit irrigation (RED), CONV-DMPP and RED-DMPP. The total seasonal volume of irrigation water applied was constant for all treatments but the timing and quantity in individual irrigation applications varied among treatments. ^{15}N-labelled urea was used to track the source of N_{2}O emissions and plant N uptake. The majority of N_{2}O emissions occurred immediately after irrigations began on 1 September 2014. Applying RED and DMPP individually slightly decreased N_{2}O emissions but when applied in combination (RED-DMPP) the greatest reductions in N_{2}O emissions were observed. There was no effect of treatments on plant N uptake, ^{15}N recovery or yield possibly because the system was not N limited. Half of the plant N and 53% to 87% of N_{2}O was derived from non-fertiliser sources in soil, highlighting the opportunity to further exploit this valuable N pool.},
keywords = {Soil Research 54},
pubstate = {published},
tppubtype = {article}
}

@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{Nguyen2016,
title = {Rice husk biochar and crop residue amendment in subtropical cropping soils: effect on biomass production, nitrogen use efficiency and greenhouse gas emissions.},
author = { D. H Nguyen and C Scheer and D Rowlings and P. Grace},
doi = {10.1007/s00374-015-1074-4},
year = {2016},
date = {2016-02-01},
journal = {Biology and Fertility of Soils},
volume = {52},
number = {2},
pages = {261-270},
abstract = {We investigated the effect of maize residues and rice husk biochar on biomass production, fertiliser nitrogen recovery (FNR) and nitrous oxide (N_{2}O) emissions for three different subtropical cropping soils. Maize residues at two rates (0 and 10 t ha^{−1}) combined with three rates (0, 15 and 30 t ha^{-1}) of rice husk biochar were added to three soil types in a pot trial with maize plants. Soil N_{2}O emissions were monitored with static chambers for 91 days. Isotopic ^{15}N-labelled urea was applied to the treatments without added crop residues to measure the FNR. Crop residue incorporation significantly reduced N uptake in all treatments but did not affect overall FNR. Rice husk biochar amendment had no effect on plant growth and N uptake but significantly reduced N_{2}O and carbon dioxide (CO_{2}) emissions in two of the three soils. The incorporation of crop residues had a contrasting effect on soil N_{2}O emissions depending on the mineral N status of the soil. The study shows that effects of crop residues depend on soil properties at the time of application. Adding crop residues with a high C/N ratio to soil can immobilise N in the soil profile and hence reduce N uptake and/or total biomass production. Crop residue incorporation can either stimulate or reduce N_{2}O emissions depending on the mineral N content of the soil. Crop residues pyrolysed to biochar can potentially stabilise native soil C (negative priming) and reduce N_{2}O emissions from cropping soils thus providing climate change mitigation potential beyond the biochar C storage in soils. Incorporation of crop residues as an approach to recycle organic materials and reduce synthetic N fertiliser use in agricultural production requires a thorough evaluation, both in terms of biomass production and greenhouse gas emissions.},
keywords = {Biology and Fertility of Soils},
pubstate = {published},
tppubtype = {article}
}

@article{Delden2016,
title = {Establishing turf grass increase soil greenhouse gas emissions in a peri-urban environment.},
author = {L. Van Delden and E. Larsen and D. W. Rowlings and C. Scheer and P. R. Grace},
doi = {10.1007/s11252-016-0529-1},
year = {2016},
date = {2016-01-18},
journal = {Urban Ecosystems},
volume = {19},
number = {2},
pages = {749–762},
abstract = {Urbanization is becoming increasingly important in terms of climate change and ecosystem functionality worldwide. We are only beginning to understand how the processes of urbanization influence ecosystem dynamics and how peri-urban environments contribute to climate change. Brisbane in South East Queensland (SEQ) currently has the most extensive urban sprawl of all Australian cities. This leads to substantial land use changes in urban and peri-urban environments and the subsequent gaseous emissions from soils are to date neglected for IPCC climate change estimations. This research examines how land use change effects methane (CH_{4}) and nitrous oxide (N_{2}O) fluxes from peri-urban soils and consequently influences the Global Warming Potential (GWP) of rural ecosystems in agricultural use undergoing urbanization. Therefore, manual and fully automated static chamber measurements determined soil gas fluxes over a full year and an intensive sampling campaign of 80 days after land use change. Turf grass, as the major peri-urban land cover, increased the GWP by 415 kg CO_{2}-e ha^{−1} over the first 80 days after conversion from a well-established pasture. This results principally from increased daily average N_{2}O emissions of 0.5 g N_{2}O ha^{−1} d^{−1} from the pasture to 18.3 g N_{2}O ha^{−1} d^{−1} from the turf grass due to fertilizer application during conversion. Compared to the native dry sclerophyll eucalypt forest, turf grass establishment increases the GWP by another 30 kg CO_{2}-e ha^{−1}. The results presented in this study clearly indicate the substantial impact of urbanization on soil-atmosphere gas exchange in form of non-CO_{2} greenhouse gas emissions particularly after turf grass establishment.},
keywords = {Urban Ecosystems},
pubstate = {published},
tppubtype = {article}
}

@article{Rowlings2016,
title = {Annual nitrogen dynamics and urea fertilizer recoveries from a dairy pasture using 15N; effect of nitrification inhibitor DMPP and reduced application rates},
author = { D.W Rowlings and C Scheer and S Liu and P.R. Grace},
doi = {10.1016/j.agee.2015.09.025},
year = {2016},
date = {2016-01-15},
journal = {Agriculture Ecosystems and Environment},
volume = {216},
pages = {216-225},
abstract = {"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 ^{15}N 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."},
keywords = {Agriculture Ecosystems and Environment},
pubstate = {published},
tppubtype = {article}
}

@article{Barton2010,
title = {Sampling frequency affects estimates of annual nitrous oxide fluxes},
author = { Barton. L and B Wolf and D Rowlings and C Scheer and R Kiese and P Grace and K Stefanova and K. Butterbach-Bahl},
doi = {10.1038/srep15912},
year = {2015},
date = {2015-10-02},
journal = {Nature Scientific Reports},
volume = {5},
number = {15912},
abstract = {Quantifying nitrous oxide (N_{2}O) fluxes, a potent greenhouse gas, from soils is necessary to improve our knowledge of terrestrial N_{2}O losses. Developing universal sampling frequencies for calculating annual N_{2}O fluxes is difficult, as fluxes are renowned for their high temporal variability. We demonstrate daily sampling was largely required to achieve annual N_{2}O fluxes within 10% of the ‘best’ estimate for 28 annual datasets collected from three continents—Australia, Europe and Asia. Decreasing the regularity of measurements either under- or overestimated annual N_{2}O fluxes, with a maximum overestimation of 935%. Measurement frequency was lowered using a sampling strategy based on environmental factors known to affect temporal variability, but still required sampling more than once a week. Consequently, uncertainty in current global terrestrial N_{2}O budgets associated with the upscaling of field-based datasets can be decreased significantly using adequate sampling frequencies.},
keywords = {Nature Scientific Reports},
pubstate = {published},
tppubtype = {article}
}