Publications
Acta Horticulturae Agriculture Agriculture Ecosystems and Environment Animal Production Science Biogeosciences Biology and Fertility of Soils Ecological Applications Ecological Modelling Ecosystems and Environment European Journal of Agronomy Global Change Biology Improved process understanding and new technologies Inhibitors for reducing emissions International Initiative Conference 2016 IOSR Journal of Engineering Nature Scientific Reports Nutrient Cycling in Agroecosystems Plant and Soil Program co-ordination Rapid Communications in Mass Spectrometry Reducing emissions through improved nitrogen use efficiency Science of the Total Environment Scientific Reports Soil Biology and Biochemistry Soil carbon in nitrous oxide emissions Soil Research 50 Soil Research 54 SpringerPlus Urban Ecosystems WIREs Climate Change
2017 |
de Klein, Cecile; Harvey, Mike Nitrous Oxide Chamber Methodology Guidelines Technical Manual 2017. Abstract | Links | BibTeX | Tags: Program co-ordination @manual{deKlein2017, title = {Nitrous Oxide Chamber Methodology Guidelines}, author = {Cecile de Klein and Mike Harvey}, url = {http://globalresearchalliance.org/wp-content/uploads/2015/11/Chamber_Methodology_Guidelines_Final-V1.1-2015.pdf}, year = {2017}, date = {2017-07-01}, abstract = {The Nitrous Oxide Chamber Methodology Guidelines was identified as a priority project by the Livestock Research Group of the Global Research Alliance at its meeting in Amsterdam in 2011. The New Zealand government requested proposals in December 2011 for the compilation of comprehensive guidelines for non-steady-state (N_{2}O) chambers, to detail the current state of knowledge of (N_{2}O) chamber methodologies and provide guidelines and recommendations for their use. In developing the guidelines, each chapter covers one of the key aspects – including design, deployment, air sample collection, storage and sample analysis, data analysis and data reporting – with additional chapters on automated systems and Health and Safety. The project was co-ordinated by AgResearch, a Crown Research Institute in New Zealand, who invited scientists from around the world to participate. The guidelines aim to provide practitioners with information on best practice and factors that need to be considered in design and operation of (N_{2}O) flux measurement programmes. Areas where there is no current consensus are described as evolving issues}, keywords = {Program co-ordination}, pubstate = {published}, tppubtype = {manual} } The Nitrous Oxide Chamber Methodology Guidelines was identified as a priority project by the Livestock Research Group of the Global Research Alliance at its meeting in Amsterdam in 2011. The New Zealand government requested proposals in December 2011 for the compilation of comprehensive guidelines for non-steady-state (N2O) chambers, to detail the current state of knowledge of (N2O) chamber methodologies and provide guidelines and recommendations for their use. In developing the guidelines, each chapter covers one of the key aspects – including design, deployment, air sample collection, storage and sample analysis, data analysis and data reporting – with additional chapters on automated systems and Health and Safety. The project was co-ordinated by AgResearch, a Crown Research Institute in New Zealand, who invited scientists from around the world to participate. The guidelines aim to provide practitioners with information on best practice and factors that need to be considered in design and operation of (N2O) flux measurement programmes. Areas where there is no current consensus are described as evolving issues |
Scheer, C; Rowlings, D W; Firrel, M; Deuter, P; Morris, S; Riches, D; Porter, I; Grace, P R Nitrification inhibitors can increase post-harvest nitrous oxide emissions in an intensive vegetable production system. Journal Article Scientific Reports, 2017. Abstract | Links | BibTeX | Tags: Scientific Reports @article{Scheer2017, title = {Nitrification inhibitors can increase post-harvest nitrous oxide emissions in an intensive vegetable production system.}, author = {C. Scheer and D. W. Rowlings and M. Firrel and P. Deuter and S. Morris and D. Riches and I. Porter and P. R. Grace}, doi = {10.1038/srep43677}, year = {2017}, date = {2017-01-29}, journal = {Scientific Reports}, abstract = {To investigate the effect of nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (3MP + TZ), on N_{2}O emissions and yield from a typical vegetable rotation in sub-tropical Australia we monitored soil N_{2}O fluxes continuously over an entire year using an automated greenhouse gas measurement system. The temporal variation of N_{2}O fluxes showed only low emissions over the vegetable cropping phases, but significantly higher emissions were observed post-harvest accounting for 50-70% of the annual emissions. NIs reduced N_{2}O emissions by 20-60% over the vegetable cropping phases; however, this mitigation was offset by elevated N_{2}O emissions from the NIs treatments over the post-harvest fallow period. Annual N_{2}O emissions from the conventional fertiliser, the DMPP treatment, and the 3MP + TZ treatment were 1.3, 1.1 and 1.6 (sem = 0.2) kg-N ha^{-1} year^{-1}, respectively. This study highlights that the use of NIs in vegetable systems can lead to elevated N_{2}O emissions by storing N in the soil profile that is available to soil microbes during the decomposition of the vegetable residues. Hence the use of NIs in vegetable systems has to be treated carefully and fertiliser rates need to be adjusted to avoid an oversupply of N during the post-harvest phase.}, keywords = {Scientific Reports}, pubstate = {published}, tppubtype = {article} } To investigate the effect of nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (3MP + TZ), on N2O emissions and yield from a typical vegetable rotation in sub-tropical Australia we monitored soil N2O fluxes continuously over an entire year using an automated greenhouse gas measurement system. The temporal variation of N2O fluxes showed only low emissions over the vegetable cropping phases, but significantly higher emissions were observed post-harvest accounting for 50-70% of the annual emissions. NIs reduced N2O emissions by 20-60% over the vegetable cropping phases; however, this mitigation was offset by elevated N2O emissions from the NIs treatments over the post-harvest fallow period. Annual N2O emissions from the conventional fertiliser, the DMPP treatment, and the 3MP + TZ treatment were 1.3, 1.1 and 1.6 (sem = 0.2) kg-N ha-1 year-1, respectively. This study highlights that the use of NIs in vegetable systems can lead to elevated N2O emissions by storing N in the soil profile that is available to soil microbes during the decomposition of the vegetable residues. Hence the use of NIs in vegetable systems has to be treated carefully and fertiliser rates need to be adjusted to avoid an oversupply of N during the post-harvest phase. |
Friedl, J; Scheer, C; Rowlings, D W; Mumford, M; Grace, P R Soil Biology & Biochemistry, 2017. Abstract | Links | BibTeX | Tags: Soil Biology and Biochemistry @article{Friedl2017, title = {The nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) reduces N_{2} emissions from intensively managed pastures in subtropical Australia, Soil Biology & Biochemistry}, author = {J. Friedl and C. Scheer and D.W. Rowlings and M. Mumford and P.R. Grace}, doi = {10.1016/j.soilbio.2017.01.016}, year = {2017}, date = {2017-01-22}, journal = {Soil Biology & Biochemistry}, abstract = {Intensively managed pastures receive high inputs ofnitrogen (N) fertilizer, rendering them prone to high N losses via denitrification following intensive rainfall events. Intense rainfall events, which are predicted to increase in frequency with changes in global climate, increase the risk of denitrification losses from agro-ecosystems. Nitrification inhibitors (NI) have been promoted to mitigate N losses, however their effect on total denitrification (N_{2} and N_{2}O) and therefore their agronomic viability remains largely unknown. This study investigated the efficacy of the NI 3,4-dimethylpyrazole phosphate (DMPP) to reduce N_{2} and N_{2}O emissions after heavy rainfall from three pastures with different soil textures in subtropical Australia. Emissions of N_{2} and N_{2}O were measured over three weeks following the application of ^{15}N urea (36.8 kg N ha^{−1}) with and without DMPP. An intense rainfall event was simulated 10 days after fertilization to create saturated conditions in the topsoil. Emissions of N_{2}O decreased after day 1, reflecting a rapid shift towards complete denitrification. Unlike N_{2}O, N_{2} fluxes responded to the rainfall event with peak fluxes up to 3.8 kg N_{2}-N ha^{−1} day^{−1}. The main product of denitrification was N_{2}, which accounted for more than 95% of cumulative denitrification losses across sites. Cumulative N_{2} losses over 21 days remained below 4 kg N ha^{−1} for the well-drained sandy loam, while up to 28 kg N_{2}-N ha^{−1} were emitted from the clay and loam soils, demonstrating N_{2} emissions as a major pathway of N loss from intensively managed pastures. The magnitude of N_{2} losses across pasture sites reflects the combined effect of reduced soil gas diffusivity and microbial oxygen consumption on denitrification. DMPP reduced these N_{2} losses by more than 70%, but had no effect on N_{2}O emissions, providing the first field based evidence that DMPP can substantially reduce N_{2} emissions. The reduction of agronomically significant N_{2} losses highlights the potential of DMPP to mitigate the impact of increased rainfall intensity on denitrification losses thereby improving N use efficiency for intensively managed pastures.}, keywords = {Soil Biology and Biochemistry}, pubstate = {published}, tppubtype = {article} } Intensively managed pastures receive high inputs ofnitrogen (N) fertilizer, rendering them prone to high N losses via denitrification following intensive rainfall events. Intense rainfall events, which are predicted to increase in frequency with changes in global climate, increase the risk of denitrification losses from agro-ecosystems. Nitrification inhibitors (NI) have been promoted to mitigate N losses, however their effect on total denitrification (N2 and N2O) and therefore their agronomic viability remains largely unknown. This study investigated the efficacy of the NI 3,4-dimethylpyrazole phosphate (DMPP) to reduce N2 and N2O emissions after heavy rainfall from three pastures with different soil textures in subtropical Australia. Emissions of N2 and N2O were measured over three weeks following the application of 15N urea (36.8 kg N ha−1) with and without DMPP. An intense rainfall event was simulated 10 days after fertilization to create saturated conditions in the topsoil. Emissions of N2O decreased after day 1, reflecting a rapid shift towards complete denitrification. Unlike N2O, N2 fluxes responded to the rainfall event with peak fluxes up to 3.8 kg N2-N ha−1 day−1. The main product of denitrification was N2, which accounted for more than 95% of cumulative denitrification losses across sites. Cumulative N2 losses over 21 days remained below 4 kg N ha−1 for the well-drained sandy loam, while up to 28 kg N2-N ha−1 were emitted from the clay and loam soils, demonstrating N2 emissions as a major pathway of N loss from intensively managed pastures. The magnitude of N2 losses across pasture sites reflects the combined effect of reduced soil gas diffusivity and microbial oxygen consumption on denitrification. DMPP reduced these N2 losses by more than 70%, but had no effect on N2O emissions, providing the first field based evidence that DMPP can substantially reduce N2 emissions. The reduction of agronomically significant N2 losses highlights the potential of DMPP to mitigate the impact of increased rainfall intensity on denitrification losses thereby improving N use efficiency for intensively managed pastures. |
Mielenz, H; Thorburn, P; Harris, R; Grace, P R; Officer, S Mitigating N2O emissions from cropping systems after conversion from pasture: A modelling approach. Journal Article European Journal of Agronomy, 82 (B), pp. 254–267, 2017. Abstract | Links | BibTeX | Tags: European Journal of Agronomy @article{Mielenz2017, title = {Mitigating N_{2}O emissions from cropping systems after conversion from pasture: A modelling approach.}, author = {H. Mielenz and P. Thorburn and R. Harris and P. R. Grace and S. Officer}, doi = {10.1016/j.eja.2016.06.007}, year = {2017}, date = {2017-01-01}, journal = {European Journal of Agronomy}, volume = {82}, number = {B}, pages = {254–267}, abstract = {Converting pasture to cropping is common in many of the world’s agricultural systems. This conversion results in substantial net mineralisation of soil organic matter that builds up during a phase of pasture. A few studies have shown that this mineralisation leads to increased nitrous oxide (N_{2}O) emissions compared to long-term pasture or long-term cropping. Understanding of interactions leading to these significant emissions is still scarce but is needed to identify mitigation options for this situation. In this study, the Agricultural Production Systems sIMulator (APSIM) was used to investigate the optimal timing of pasture termination (relative to crop planting) and management of nitrogen (N) in crops after pasture termination to maximise crop yield and limit N_{2}O emissions. Beforehand, APSIM’s performance in simulating yields and N_{2}O emissions was tested against data from field experiments conducted in the temperate high-rainfall zone of southern Australia where N_{2}O emissions were monitored with automatic gas collection chambers during the first year of cropping wheat after terminating long-term pasture on two adjacent sites in two consecutive years. Field experiments and simulation scenarios showed very high N_{2}O emissions (up to 48 kg N_{2}O-N ha^{−1} yr^{−1}) in the first year of wheat after pasture termination, even without N fertiliser application. Measured cumulative N_{2}O emissions, crop yields and soil mineral N and water content dynamics were simulated well with APSIM. Including a routine into APSIM to account for N_{2}O transport through the soil profile improved the simulation of daily N_{2}O emissions considerably, leading to up to 67% of the measured variability in daily N_{2}O emissions being explained by the model. We predicted that a short fallow between termination of pasture and sowing wheat, instead of a long fallow which is the common practice, reduces N_{2}O emissions by more than half in the first year of cropping without a noteworthy impact on crop yield. Reducing N fertiliser applications in the first few years after pasture termination by taking available soil mineral N into account, and applying the fertiliser six to twelve weeks after sowing instead of at sowing was predicted to further reduce N_{2}O emissions. Since the model was calibrated against experimental data during the first year after pasture termination only, experiments determining N_{2}O emissions in the first two or three years after terminating pasture are needed to confirm our predictions.}, keywords = {European Journal of Agronomy}, pubstate = {published}, tppubtype = {article} } Converting pasture to cropping is common in many of the world’s agricultural systems. This conversion results in substantial net mineralisation of soil organic matter that builds up during a phase of pasture. A few studies have shown that this mineralisation leads to increased nitrous oxide (N2O) emissions compared to long-term pasture or long-term cropping. Understanding of interactions leading to these significant emissions is still scarce but is needed to identify mitigation options for this situation. In this study, the Agricultural Production Systems sIMulator (APSIM) was used to investigate the optimal timing of pasture termination (relative to crop planting) and management of nitrogen (N) in crops after pasture termination to maximise crop yield and limit N2O emissions. Beforehand, APSIM’s performance in simulating yields and N2O emissions was tested against data from field experiments conducted in the temperate high-rainfall zone of southern Australia where N2O emissions were monitored with automatic gas collection chambers during the first year of cropping wheat after terminating long-term pasture on two adjacent sites in two consecutive years. Field experiments and simulation scenarios showed very high N2O emissions (up to 48 kg N2O-N ha−1 yr−1) in the first year of wheat after pasture termination, even without N fertiliser application. Measured cumulative N2O emissions, crop yields and soil mineral N and water content dynamics were simulated well with APSIM. Including a routine into APSIM to account for N2O transport through the soil profile improved the simulation of daily N2O emissions considerably, leading to up to 67% of the measured variability in daily N2O emissions being explained by the model. We predicted that a short fallow between termination of pasture and sowing wheat, instead of a long fallow which is the common practice, reduces N2O emissions by more than half in the first year of cropping without a noteworthy impact on crop yield. Reducing N fertiliser applications in the first few years after pasture termination by taking available soil mineral N into account, and applying the fertiliser six to twelve weeks after sowing instead of at sowing was predicted to further reduce N2O emissions. Since the model was calibrated against experimental data during the first year after pasture termination only, experiments determining N2O emissions in the first two or three years after terminating pasture are needed to confirm our predictions. |
2016 |
Scheer, C; Firrell, M; Deuter, P; Rowlings, D; Porter, I; Grace, P R Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Scheer2016d, title = {Effect of reduced fertiliser rates in combination with a nitrification inhibitor (DMPP) on soil nitrous oxide emissions and yield from an intensive vegetable production system in sub-tropical Australia.}, author = { C Scheer and M Firrell and P Deuter and D Rowlings and I Porter and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_Scheer_Clemens.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Vegetable production systems are characterised by intensive production with high inputs of nitrogen fertiliser and irrigation water. Consequently, high emissions of nitrous oxide have been reported. The use of nitrification inhibitors (NI) offers an effective method to reduce N_{2}O emissions, whilst maintaining yield and increasing nitrogen use efficiency. However, only limited data are currently available on the use of NI in vegetable cropping systems. A field experiment was conducted to investigate the effect of the nitrification inhibitor 3,4-Dimethylpyrazol phosphate (DMPP) in combination with reduced N fertilizer application rates on N_{2}O emissions and yield from a typical vegetable rotation in sub-tropical Australia. Annual N_{2}O emissions ranged from 0.59 to 1.37 kgN/ha for the different fertiliser treatments. A 40% reduced fertilizer rate combined with DMPP reduced N_{2}O emissions by more than half but achieved a comparable yield to the standard grower’s practice in two out of three crops. We conclude that DMPP shows a great potential for reducing N_{2}O emissions from vegetable systems. However, further research is required to understand under what conditions reduced N rates of DMPP coated fertiliser are applicable and to determine the long-term effect of such a fertiliser regime over extended cropping cycles.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Vegetable production systems are characterised by intensive production with high inputs of nitrogen fertiliser and irrigation water. Consequently, high emissions of nitrous oxide have been reported. The use of nitrification inhibitors (NI) offers an effective method to reduce N2O emissions, whilst maintaining yield and increasing nitrogen use efficiency. However, only limited data are currently available on the use of NI in vegetable cropping systems. A field experiment was conducted to investigate the effect of the nitrification inhibitor 3,4-Dimethylpyrazol phosphate (DMPP) in combination with reduced N fertilizer application rates on N2O emissions and yield from a typical vegetable rotation in sub-tropical Australia. Annual N2O emissions ranged from 0.59 to 1.37 kgN/ha for the different fertiliser treatments. A 40% reduced fertilizer rate combined with DMPP reduced N2O emissions by more than half but achieved a comparable yield to the standard grower’s practice in two out of three crops. We conclude that DMPP shows a great potential for reducing N2O emissions from vegetable systems. However, further research is required to understand under what conditions reduced N rates of DMPP coated fertiliser are applicable and to determine the long-term effect of such a fertiliser regime over extended cropping cycles. |
Rowlings, D; Labadz, M; Scheer, C; Grace, P R Towards a complete nitrogen budget from subtropical dairy farms: three years of pasture nitrogen losses in surface runoff. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Rowlings2016b, title = {Towards a complete nitrogen budget from subtropical dairy farms: three years of pasture nitrogen losses in surface runoff.}, author = { D Rowlings and M Labadz and C Scheer and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_Rowlings_David3.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Dairy represents one of the most intensive and nitrogen (N) loaded production systems in the high rainfall regions of Queensland, Australia. Fertiliser application rates during the winter rye grass season (April-October) frequently surpass 300 kg N ha^{-1} year^{-1} yet the fate of much of the applied N is uncertain. The high (>1200 mm year^{-1}) and intensive rainfall and the proximity to environmentally sensitive areas such as the Great Barrier Reef make losses in surface water run-off of particular interest to the industry. Two run-off plots (416 m^{2}) were installed on an intensively irrigated and fertilised rye-grass/kikuyu pasture rotation near Gympie, Queensland and monitored over three (1 June to 31 May) measurement years. Runoff was measured using a tipping bucket and nutrients collected via an automated sampler. Runoff and losses were largest during the 2012-13 season when five of the nine runoff events over the measurement period occurred and total runoff exceeded 480 mm, corresponding to 37% of the annual rainfall. Total N load was dominated by NO_{3}^{–}, with largest losses during a four day, 448 mm rain event in January 2013 following an extended dry period resulting in 280 mm of runoff and 16.5 kg ha^{-1} of N losses. Total N losses over the remaining periods were typically negligible (< 1 kg ha^{-1} event^{-1}), with annual losses of 5.0 and 0.7 kg N ha^{-1} for 2013-14 and 2014-15 respectively. These results indicate that under current management systems intensive pastures contribute only minor nutrient loads, though losses can be high following extended dry periods.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Dairy represents one of the most intensive and nitrogen (N) loaded production systems in the high rainfall regions of Queensland, Australia. Fertiliser application rates during the winter rye grass season (April-October) frequently surpass 300 kg N ha-1 year-1 yet the fate of much of the applied N is uncertain. The high (>1200 mm year-1) and intensive rainfall and the proximity to environmentally sensitive areas such as the Great Barrier Reef make losses in surface water run-off of particular interest to the industry. Two run-off plots (416 m2) were installed on an intensively irrigated and fertilised rye-grass/kikuyu pasture rotation near Gympie, Queensland and monitored over three (1 June to 31 May) measurement years. Runoff was measured using a tipping bucket and nutrients collected via an automated sampler. Runoff and losses were largest during the 2012-13 season when five of the nine runoff events over the measurement period occurred and total runoff exceeded 480 mm, corresponding to 37% of the annual rainfall. Total N load was dominated by NO3–, with largest losses during a four day, 448 mm rain event in January 2013 following an extended dry period resulting in 280 mm of runoff and 16.5 kg ha-1 of N losses. Total N losses over the remaining periods were typically negligible (< 1 kg ha-1 event-1), with annual losses of 5.0 and 0.7 kg N ha-1 for 2013-14 and 2014-15 respectively. These results indicate that under current management systems intensive pastures contribute only minor nutrient loads, though losses can be high following extended dry periods. |
Quin, P; van Zwieten, L; Grace, P; Macdonald, L; Cowie, A; Erler, D; Young, I; Kimber, S Drainage losses of N2O and NO3- in Ferralsol is a major N-loss pathway. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Quin2016, title = {Drainage losses of N_{2}O and NO_{3}- in Ferralsol is a major N-loss pathway.}, author = { P Quin and L van Zwieten and P Grace and L Macdonald and A Cowie and D Erler and I Young and S. Kimber}, url = {http://www.ini2016.com/wp-content/uploads/2016/03/1200-1230-D-Peter-Quin.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Increasing concentrations of atmospheric nitrous oxide (N2O) are making a significant contribution to anthropogenic climate change and the depletion of stratospheric ozone. These increases are known to primarily result from the use of synthetic nitrogen fertilisers and manures. Our study aimed to answer some of the many remaining questions about the mechanisms of production and movement of N2O in soil. In a field study we injected ^{15}N-labelled nitrate into repacked columns of Ferralsol, at a depth of either 75 mm or 200 mm. We sampled soil gas at 3 depths and surface emissions. In-soil concentrations of N2O rose by approximately two orders of magnitude when water-filled pore space increased to >80 %. This coincided with periods of high hydraulic conductivity, potentially draining dissolved ^{15}N2O from the 75 mm injected columns at 189 µg ^{15}N-N2O m^{-2} h^{-1 }compared with a surface flux of 1.2 µg ^{15}N-N2O m^{-2} h^{-1 }and from 200 mm injected columns at 30 µg ^{15}N-N2O m^{-2} h^{-1 }compared with a surface flux of 0.24 µg ^{15}N-N2O m^{-2} h^{-1}. Data suggests that indirect emissions of N_{2}O by leaching and surface runoff from some soils may be much greater than the default 0.225 % of N applied recognised by the IPCC. This may go some way towards reconciling the discrepancy between ‘top down’(~4 %) and ‘bottom up’ (~1.3 %, IPCC default) estimates of direct N2O emissions from applied N. We also show that deeper placement of nitrate fertiliser may decrease direct N2O surface emissions, although the effect on indirect emissions remains unclear.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Increasing concentrations of atmospheric nitrous oxide (N2O) are making a significant contribution to anthropogenic climate change and the depletion of stratospheric ozone. These increases are known to primarily result from the use of synthetic nitrogen fertilisers and manures. Our study aimed to answer some of the many remaining questions about the mechanisms of production and movement of N2O in soil. In a field study we injected 15N-labelled nitrate into repacked columns of Ferralsol, at a depth of either 75 mm or 200 mm. We sampled soil gas at 3 depths and surface emissions. In-soil concentrations of N2O rose by approximately two orders of magnitude when water-filled pore space increased to >80 %. This coincided with periods of high hydraulic conductivity, potentially draining dissolved 15N2O from the 75 mm injected columns at 189 µg 15N-N2O m-2 h-1 compared with a surface flux of 1.2 µg 15N-N2O m-2 h-1 and from 200 mm injected columns at 30 µg 15N-N2O m-2 h-1 compared with a surface flux of 0.24 µg 15N-N2O m-2 h-1. Data suggests that indirect emissions of N2O by leaching and surface runoff from some soils may be much greater than the default 0.225 % of N applied recognised by the IPCC. This may go some way towards reconciling the discrepancy between ‘top down’(~4 %) and ‘bottom up’ (~1.3 %, IPCC default) estimates of direct N2O emissions from applied N. We also show that deeper placement of nitrate fertiliser may decrease direct N2O surface emissions, although the effect on indirect emissions remains unclear. |
Rosa, De D; Rowlings, D; Biala, J; Scheer, C; Basso, B; Migliorati, De Antoni M; Grace, P R Monitoring the N release from organic amendments using proximal sensing. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{DeRosa2016, title = {Monitoring the N release from organic amendments using proximal sensing.}, author = { D De Rosa and D Rowlings and J Biala and C Scheer and B Basso and M De Antoni Migliorati and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_DeRosa_Daniele.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {The use of proximal sensed vegetation indices can reduce the uncertainty linked to the N supplied by organic amendments in a horticultural field by detecting in-season crop N status. This research assessed the applicability of the three vegetation indices (VI) of NDVI, NDRE and CCCI to evaluate the in-season long term optimized strategy of applying organic amendments to a horticultural crop (lettuce) over two seasons. A conventional urea application rate (CONV) was compared with raw (Ma) feedlot manure and Ma combined with standard (Ma+CONV) and optimized urea rate (Ma+Op). NDRE most accurately predicted crop N status at the late stage of lettuce development with an R^{2} of 0.67 (RMSE 0.61), compared to 0.60 (RMSE 0.67) and 0.62 (RMSE 0.66) for NDVI and CCCI respectively. The in-season acquisition of crop reflectance proved to be a valid technique to determine the efficiency of an optimized combination between organic amendments and N-fertilizer.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } The use of proximal sensed vegetation indices can reduce the uncertainty linked to the N supplied by organic amendments in a horticultural field by detecting in-season crop N status. This research assessed the applicability of the three vegetation indices (VI) of NDVI, NDRE and CCCI to evaluate the in-season long term optimized strategy of applying organic amendments to a horticultural crop (lettuce) over two seasons. A conventional urea application rate (CONV) was compared with raw (Ma) feedlot manure and Ma combined with standard (Ma+CONV) and optimized urea rate (Ma+Op). NDRE most accurately predicted crop N status at the late stage of lettuce development with an R2 of 0.67 (RMSE 0.61), compared to 0.60 (RMSE 0.67) and 0.62 (RMSE 0.66) for NDVI and CCCI respectively. The in-season acquisition of crop reflectance proved to be a valid technique to determine the efficiency of an optimized combination between organic amendments and N-fertilizer. |
Liyanage, A; Grace, P R; Rowlings, D W; Scheer, C Influence of nitrogen fertilizer and compost mix application on greenhouse gas emissions from humid subtropical soils. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Liyanage2016, title = {Influence of nitrogen fertilizer and compost mix application on greenhouse gas emissions from humid subtropical soils.}, author = { A Liyanage and P. R. Grace and D.W Rowlings and C. Scheer}, url = {http://www.ini2016.com/pdf-papers/INI2016_Grace_Peter1.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {The application of organic amendments (OA) is a strategy to improve soil fertility and offset the high cost of mineral fertilizers used in agricultural systems. However, information on the interaction of OAs with synthetic fertilizers and the resulting greenhouse gas emissions from these combinations are not well understood for different soil types. A 36 day laboratory incubation experiment (3 compost x 3 N rates) was conducted to quantify soil N_{2}O emissions along with CO_{2} and mineral N from subtropical soils in Gatton, Australia. Nitrous oxide emissions decreased by 68% and 57% in 60N and 120N treatments respectively with the increase in compost applications rates up to 30 t/ha and 60 t/ha. Adding 60 t/ha compost and 120 kg N/ha is considered as the optimum fertilizer rate to minimize N_{2}O and CO_{2} emissions from a sub-tropical Vertosol and potentially conserving soil physical, chemical and biological properties for a sustainable crop growth.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } The application of organic amendments (OA) is a strategy to improve soil fertility and offset the high cost of mineral fertilizers used in agricultural systems. However, information on the interaction of OAs with synthetic fertilizers and the resulting greenhouse gas emissions from these combinations are not well understood for different soil types. A 36 day laboratory incubation experiment (3 compost x 3 N rates) was conducted to quantify soil N2O emissions along with CO2 and mineral N from subtropical soils in Gatton, Australia. Nitrous oxide emissions decreased by 68% and 57% in 60N and 120N treatments respectively with the increase in compost applications rates up to 30 t/ha and 60 t/ha. Adding 60 t/ha compost and 120 kg N/ha is considered as the optimum fertilizer rate to minimize N2O and CO2 emissions from a sub-tropical Vertosol and potentially conserving soil physical, chemical and biological properties for a sustainable crop growth. |
Friedl, J; Scheer, C; Trappe, J; Rowlings, D; Grace, P R Nitrogen turnover and N2:N2O partitioning from agricultural soils – a simplified incubation assay. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Friedl2016, title = {Nitrogen turnover and N_{2}:N_{2}O partitioning from agricultural soils – a simplified incubation assay.}, author = { J Friedl and C Scheer and J Trappe and D Rowlings and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_Friedl_Johannes.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Nitrogen turnover and related denitrification losses are a major uncertainty when estimating N loss and replacement from agro-ecosystems, due to methodological constraints quantifying N_{2} and laborious analytical procedures. We present a novel, simplified incubation assay that combines the ^{15}N gas flux method with the ^{15}N pool dilution method, to quantify denitrification losses as a function of N turnover. This assay was tested using a pasture soil from sub-tropical Australia. N-fertiliser (35 µg g^{-1} soil) was applied either as a single (NH_{4}^{15}NO_{3}^{–}) or double (^{15}NH_{4}^{15}NO_{3}) labelled treatment at 10 atom %, with a third treatment (NH_{4}^{15}NO_{3}^{–}) at 60 atom % to quantify N_{2} emissions. Gross rates of N mineralisation, nitrification and related N_{2} and N_{2}O emissions were measured during 48 hours of incubation at 80% WFPS. Gross N production and gross N consumption was consistent with the directly measured N pool sizes, with denitrification losses (N_{2}+N_{2}O) at 7.0 \underline{+} 1.4 µg N g^{-1} soil accounting for 62% of the calculated NO_{3}^{–} consumption. N turnover was dominated by mineralisation and nitrification, increasing the NO_{3}^{–} pool by a factor of 3. High NO_{3}^{–} concentrations shifted the N_{2}:N_{2}O ratio towards N_{2}O, with 60 % of denitrification losses emitted as N_{2}O. More than 25% of the applied ^{15}N fertiliser was lost via denitrification, showing the significance of denitrification as a major pathway of N loss from agro-ecosystems. The simplified incubation assay proved to be an efficient tool to quantify N pools and emissions, and as such is an effective method to establish comprehensive datasets of denitrification losses linked to N turnover from agro-ecosystems.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Nitrogen turnover and related denitrification losses are a major uncertainty when estimating N loss and replacement from agro-ecosystems, due to methodological constraints quantifying N2 and laborious analytical procedures. We present a novel, simplified incubation assay that combines the 15N gas flux method with the 15N pool dilution method, to quantify denitrification losses as a function of N turnover. This assay was tested using a pasture soil from sub-tropical Australia. N-fertiliser (35 µg g-1 soil) was applied either as a single (NH415NO3–) or double (15NH415NO3) labelled treatment at 10 atom %, with a third treatment (NH415NO3–) at 60 atom % to quantify N2 emissions. Gross rates of N mineralisation, nitrification and related N2 and N2O emissions were measured during 48 hours of incubation at 80% WFPS. Gross N production and gross N consumption was consistent with the directly measured N pool sizes, with denitrification losses (N2+N2O) at 7.0 + 1.4 µg N g-1 soil accounting for 62% of the calculated NO3– consumption. N turnover was dominated by mineralisation and nitrification, increasing the NO3– pool by a factor of 3. High NO3– concentrations shifted the N2:N2O ratio towards N2O, with 60 % of denitrification losses emitted as N2O. More than 25% of the applied 15N fertiliser was lost via denitrification, showing the significance of denitrification as a major pathway of N loss from agro-ecosystems. The simplified incubation assay proved to be an efficient tool to quantify N pools and emissions, and as such is an effective method to establish comprehensive datasets of denitrification losses linked to N turnover from agro-ecosystems. |
Biala, J; Rosa, De D; Rowlings, D; Grace, P R Developing a decision support tool for optimising organo-mineral fertilisation strategies and improving nitrogen use efficiency. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Biala2016b, title = {Developing a decision support tool for optimising organo-mineral fertilisation strategies and improving nitrogen use efficiency.}, author = { J Biala and D De Rosa and D Rowlings and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_Rowlings_David1.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Farmers are under pressure to operate more efficiently and reduce negative environmental impacts while maintaining or increasing production. Accurate accounting for nutrients supplied with organic soil amendments and appropriate reduction of mineral fertiliser inputs provides an easy way of achieving these goals. This paper outlines what is necessary to develop a decision support tool for optimising fertilisation strategies that utilise both organic and synthetic nutrient sources and improve nitrogen use efficiency. Novel aspects of the proposed calculator are that (i) it integrates organic and synthetic N sources, (ii) it caters for repeat applications and accounts for long-term nutrient release, (iii) it incorporates a paddock-scale nutrient budget, and (iv) it has scope for future expansion to include changes in soil properties brought about by the use of organic soil amendments.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Farmers are under pressure to operate more efficiently and reduce negative environmental impacts while maintaining or increasing production. Accurate accounting for nutrients supplied with organic soil amendments and appropriate reduction of mineral fertiliser inputs provides an easy way of achieving these goals. This paper outlines what is necessary to develop a decision support tool for optimising fertilisation strategies that utilise both organic and synthetic nutrient sources and improve nitrogen use efficiency. Novel aspects of the proposed calculator are that (i) it integrates organic and synthetic N sources, (ii) it caters for repeat applications and accounts for long-term nutrient release, (iii) it incorporates a paddock-scale nutrient budget, and (iv) it has scope for future expansion to include changes in soil properties brought about by the use of organic soil amendments. |
Warner, D; Scheer, C; Rowlings, D; Grace, P R New mobile, field based continuous-flow isotope ratio mass spectrometer system for automated denitrification studies. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Warner2016, title = {New mobile, field based continuous-flow isotope ratio mass spectrometer system for automated denitrification studies.}, author = { D Warner and C Scheer and D Rowlings and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_Grace_Peter.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Terrestrial denitrification, the reduction of oxidized nitrogen (N) to nitrous oxide (N_{2}O) and dinitrogen (N_{2}), is considered the least well understood process in the global nitrogen cycle. This study introduces a novel continuous-flow isotope ratio mass spectrometer (IR-MS) system that can be deployed in the field and continuously measure N_{2} and N_{2}O emissions. Utilizing the ^{15}N gas flux method this system can provide a better understanding of terrestrial denitrification. The system was tested over 14 days on 2 different agricultural soils (vertosol and ferrosol) which were fertilized with the equivalent of 100 kg ha^{-1} of N added in the form of KNO_{3} where the N was 60 at.% ^{15}N. Total gaseous N losses over the 14 day monitoring period resulted in 14.1± 0.53 kg ha^{-1} and 5.7± 0.92 kg ha^{-1} for the ferrosol and vertosol soils, respectively. These results clearly demonstrate the ability of the field based IR-MS to measure N_{2} and N_{2}O emissions from denitrification under field conditions. This system has the potential to improve our understanding of terrestrial denitrification and improve efforts to reduce gaseous N emissions from agricultural systems.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Terrestrial denitrification, the reduction of oxidized nitrogen (N) to nitrous oxide (N2O) and dinitrogen (N2), is considered the least well understood process in the global nitrogen cycle. This study introduces a novel continuous-flow isotope ratio mass spectrometer (IR-MS) system that can be deployed in the field and continuously measure N2 and N2O emissions. Utilizing the 15N gas flux method this system can provide a better understanding of terrestrial denitrification. The system was tested over 14 days on 2 different agricultural soils (vertosol and ferrosol) which were fertilized with the equivalent of 100 kg ha-1 of N added in the form of KNO3 where the N was 60 at.% 15N. Total gaseous N losses over the 14 day monitoring period resulted in 14.1± 0.53 kg ha-1 and 5.7± 0.92 kg ha-1 for the ferrosol and vertosol soils, respectively. These results clearly demonstrate the ability of the field based IR-MS to measure N2 and N2O emissions from denitrification under field conditions. This system has the potential to improve our understanding of terrestrial denitrification and improve efforts to reduce gaseous N emissions from agricultural systems. |
Labadz, M; Scheer, C; Rowlings, D; Henry, B; Parton, W; Hayman, P; Alves, O; Young, G; Grace, P R Improving nitrogen use efficiency in subtropical dairy systems – A modelling approach using POAMA and DayCent. Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Labadz2016, title = {Improving nitrogen use efficiency in subtropical dairy systems – A modelling approach using POAMA and DayCent.}, author = { M Labadz and C Scheer and D Rowlings and B Henry and W Parton and P Hayman and O Alves and G Young and P. R. Grace}, url = {http://www.ini2016.com/pdf-papers/INI2016_Rowlings_David2.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {The DayCent biogeochemical model was used to assess the applicability of POAMA-2 weather forecasts to assist dairy farmers in future nitrogen fertiliser decisions. Simulated soil mineral nitrogen, water-filled pore space, and biomass was calibrated and validated against field measurements from a dairy farm in subtropical Queensland, Australia, for the season 2012/2013 with a ryegrass/kikuyu rotation. DayCent was able to predict water movement in the soil profile, soil nitrogen dynamics and biomass production; however, there were some discrepancies between simulated and measured mineral nitrogen content in the soil and biomass production. This study showed that combining weather forecasts with biogeochemical models as a decision support tool for farmers to estimate mineralisation and assess N fertiliser demand is a promising approach to avoid excessive nitrogen application for dairy cropping systems. However, there are still shortcomings in an accurate simulation of soil nitrogen turnover and plant nitrogen uptake, in particular in highly fertilised systems such as the one presented here. More confidence in the accurate representation of the complex nitrogen transformation processes on dairy farms in biogeochemical models is necessary to use weather forecasts as fertiliser nitrogen decision support tool.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } The DayCent biogeochemical model was used to assess the applicability of POAMA-2 weather forecasts to assist dairy farmers in future nitrogen fertiliser decisions. Simulated soil mineral nitrogen, water-filled pore space, and biomass was calibrated and validated against field measurements from a dairy farm in subtropical Queensland, Australia, for the season 2012/2013 with a ryegrass/kikuyu rotation. DayCent was able to predict water movement in the soil profile, soil nitrogen dynamics and biomass production; however, there were some discrepancies between simulated and measured mineral nitrogen content in the soil and biomass production. This study showed that combining weather forecasts with biogeochemical models as a decision support tool for farmers to estimate mineralisation and assess N fertiliser demand is a promising approach to avoid excessive nitrogen application for dairy cropping systems. However, there are still shortcomings in an accurate simulation of soil nitrogen turnover and plant nitrogen uptake, in particular in highly fertilised systems such as the one presented here. More confidence in the accurate representation of the complex nitrogen transformation processes on dairy farms in biogeochemical models is necessary to use weather forecasts as fertiliser nitrogen decision support tool. |
Wallace, A; Armstrong, R; Harris, R; Bellyaeva, O; Grace, P; Scheer, C Nitrous oxide emissions from wheat grown in a medium rainfall environment in SE Australia are low compared to overall nitrogen losses Journal Article Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’, 2016, (Melbourne, Australia.). Abstract | Links | BibTeX | Tags: International Initiative Conference 2016 @article{Wallace2016, title = {Nitrous oxide emissions from wheat grown in a medium rainfall environment in SE Australia are low compared to overall nitrogen losses}, author = { A Wallace and R Armstrong and R Harris and O Bellyaeva and P Grace and C. Scheer}, url = {http://www.ini2016.com/wp-content/uploads/2016/03/INI2016-Wallace-aj-finalpaper.pdf}, year = {2016}, date = {2016-12-04}, journal = {Proceedings 2016 International Nitrogen Initiative Conference, ‘Solutions to improve nitrogen use efficiency for the world’}, abstract = {Efficient management of nitrogen (N) is critical to the profitability and sustainability of agricultural systems. Losses of N can both reduce productivity and in the case of nitrous oxide (N_{2}O) emissions contribute to global warming and ozone depletion. The limited number of studies from medium rainfall cropping systems have indicated that N_{2}O losses tend to be low to moderate, but that there is the potential to reduce these losses through altered fertiliser management. This study investigated the magnitude of N_{2}O flux from a medium rainfall cropping system in south eastern Australia and the potential to mitigate N_{2}O losses through altered timing (at sowing compared with in-season) of N application and the use of both nitrification and urease inhibitors. This study also measured overall N fertiliser losses and crop productivity. Losses of N_{2}O and overall fertiliser losses were measured using static chamber and ^{15}N mass balance techniques respectively, as part of a field experiment conducted in the Victorian Wimmera during 2012. Cumulative N_{2}O loss from sowing until harvest of the wheat crop amounted to between 75 and 270 g N_{2}O-N/ha with fertiliser application significantly increasing losses. In contrast, total losses of fertiliser N ranged from 7‑11 kg N/ha (14-22% of applied N), indicating that N_{2}O losses were low in comparison to both crop requirements and overall N losses.}, note = {Melbourne, Australia.}, keywords = {International Initiative Conference 2016}, pubstate = {published}, tppubtype = {article} } Efficient management of nitrogen (N) is critical to the profitability and sustainability of agricultural systems. Losses of N can both reduce productivity and in the case of nitrous oxide (N2O) emissions contribute to global warming and ozone depletion. The limited number of studies from medium rainfall cropping systems have indicated that N2O losses tend to be low to moderate, but that there is the potential to reduce these losses through altered fertiliser management. This study investigated the magnitude of N2O flux from a medium rainfall cropping system in south eastern Australia and the potential to mitigate N2O losses through altered timing (at sowing compared with in-season) of N application and the use of both nitrification and urease inhibitors. This study also measured overall N fertiliser losses and crop productivity. Losses of N2O and overall fertiliser losses were measured using static chamber and 15N mass balance techniques respectively, as part of a field experiment conducted in the Victorian Wimmera during 2012. Cumulative N2O loss from sowing until harvest of the wheat crop amounted to between 75 and 270 g N2O-N/ha with fertiliser application significantly increasing losses. In contrast, total losses of fertiliser N ranged from 7‑11 kg N/ha (14-22% of applied N), indicating that N2O losses were low in comparison to both crop requirements and overall N losses. |
Scheer, C; Deuter, P; Rowlings, D W; Grace, P R Effect of the nitrification inhibitor (DMPP) on soil nitrous oxide emissions and yield in a lettuce crop in Queensland, Australia. Journal Article Acta Horticulturae, 1123 , pp. 101-107, 2016. Abstract | Links | BibTeX | Tags: Acta Horticulturae @article{Scheer2016, title = {Effect of the nitrification inhibitor (DMPP) on soil nitrous oxide emissions and yield in a lettuce crop in Queensland, Australia.}, author = { C Scheer and P Deuter and D. W. Rowlings and P. R. Grace}, doi = {10.17660/ActaHortic.2016.1123.14}, year = {2016}, date = {2016-11-23}, journal = {Acta Horticulturae}, volume = {1123}, pages = {101-107}, abstract = {The use of nitrification inhibitors, in combination with ammonium based fertilisers, has been promoted recently as an effective method to reduce nitrous oxide ( N_{2}O) emissions from fertilised agricultural fields, whilst increasing yield and nitrogen use efficiency. However, to date no data is available on the use of nitrification inhibitors in sub-tropical vegetable systems. A field experiment investigated the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N_{2}O emissions and yield from lettuce production in sub-tropical Australia. Soil N_{2}O fluxes were monitored continuously over 120 days with a fully automated system. Measurements were taken from three subplots for each treatment within a randomized complete blocks design. Cumulative N_{2}O emissions over the 120 day observation period amounted to 191, 93 and 46 g-N ha-1 in the conventional fertiliser (CONV), the DMPP treatment and the zero fertiliser (0N) respectively. Consequently, the use of DMPP decreased seasonal N_{2}O emissions by more than 50%, but had no significant impact on lettuce yield. The temporal variation of N_{2}O fluxes showed only low emissions over the lettuce cropping period in all treatments, but significantly elevated emissions were observed in the CONV fertilized and DMPP treatment postharvest, following lettuce residues being incorporated into the soil. This study highlights that DMPP can substantially reduce N_{2}O emissions from vegetable cropping systems. It also emphasizes that N input from vegetable crop residues incorporated into the soil after harvest can lead to substantially elevated N_{2}O emission. Hence, in such systems post-harvest emissions need to be in the centre of attention for developing N_{2}O mitigation strategies.}, keywords = {Acta Horticulturae}, pubstate = {published}, tppubtype = {article} } The use of nitrification inhibitors, in combination with ammonium based fertilisers, has been promoted recently as an effective method to reduce nitrous oxide ( N2O) emissions from fertilised agricultural fields, whilst increasing yield and nitrogen use efficiency. However, to date no data is available on the use of nitrification inhibitors in sub-tropical vegetable systems. A field experiment investigated the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N2O emissions and yield from lettuce production in sub-tropical Australia. Soil N2O fluxes were monitored continuously over 120 days with a fully automated system. Measurements were taken from three subplots for each treatment within a randomized complete blocks design. Cumulative N2O emissions over the 120 day observation period amounted to 191, 93 and 46 g-N ha-1 in the conventional fertiliser (CONV), the DMPP treatment and the zero fertiliser (0N) respectively. Consequently, the use of DMPP decreased seasonal N2O emissions by more than 50%, but had no significant impact on lettuce yield. The temporal variation of N2O fluxes showed only low emissions over the lettuce cropping period in all treatments, but significantly elevated emissions were observed in the CONV fertilized and DMPP treatment postharvest, following lettuce residues being incorporated into the soil. This study highlights that DMPP can substantially reduce N2O emissions from vegetable cropping systems. It also emphasizes that N input from vegetable crop residues incorporated into the soil after harvest can lead to substantially elevated N2O emission. Hence, in such systems post-harvest emissions need to be in the centre of attention for developing N2O mitigation strategies. |