Report of the GRASS Award Exchange
Professor Hong Di
Lincoln University
Introduction
I took up the GRASS Award in China between the 14 December 2011 and 3 March
2012. The main objective of this Fellowship was to conduct collaborative research on
nitrous oxide (N2O) emissions from agricultural soils and the inhibition of ammonia
oxidising bacteria (AOB) and ammonia oxidising archaea (AOA) by the nitrification
inhibitor dicyandiamide (DCD) to mitigate N2O emissions.
Nitrous oxide (N2O) is a greenhouse gas with a long-term global warming potential of
about 298 times that of carbon dioxide (CO2) (IPCC, 2007). The global atmospheric
concentration of N2O increased from a pre-industrial concentration of 270 ppb to
319 ppb in 2005 (IPCC, 2007). Agricultural soils are a major source of atmospheric
N2O due to the microbial transformations of nitrogen (N) that occur in the soil
(Firestone & Davidson, 1989; Mosier et al., 1998). N2O is produced as a by-product of
the nitrification process by nitrifying microbes converting ammonium (NH4+) to nitrate
(NO3-) under aerobic conditions. N2O is also released by denitrifying microbes when
NO3- is reduced to nitrite (NO2-), nitric oxide (NO), N2O and N2 under anaerobic
conditions. Research in New Zealand has shown that N2O emissions from grazed
grassland soils can be significantly reduced by the application of a nitrification
inhibitor DCD to the soil to inhibit the microbial communities responsible for ammonia
oxidation (e.g. Di and Cameron, 2002, 2003; Di et al., 2007). There is considerable
interest in the use of nitrification inhibitors to mitigate N2O emissions in China so the
GRASS Award provided an opportunity for us to conduct collaborative research,
share our research experiences, and exchange ideas on the use of nitrification
inhibitors to mitigate N2O emissions in agricultural soils.
Overview of the exchange
This has been a very successful and valuable GRASS fellowship which provided an
excellent opportunity for me to conduct collaborative research with my Chinese
collaborators on ammonia oxidizer (AO) communities and their role in N2O emissions,
exchange views, ideas and findings on the use of nitrification inhibitors to mitigate
N2O emissions, interact with postgraduate students, working on joint publications,
and develop long-term collaborations.
At the Research Centre for Eco-Environmental Sciences, Chinese Academy of
Sciences (CAS), I worked with Professor Jizheng He and his team on a collaborative
research project to study the role of AOB and AOA in N2O emissions and the
effectiveness of the nitrification inhibitor DCD. In order to make this trial relevant to
both China and New Zealand, soil samples were collected from a New Zealand
dairy farm and brought to the Chinese Academy of Sciences in Beijing so that it can
be used in a study to compare with a soil from China. Also brought to China for this
project was the DCD nitrification inhibitor that is used in New Zealand. The soil and
DCD were used in a laboratory incubation study to improve our fundamental
understanding on the origins of N2O, the role of AOB and AOA, and the effect of
DCD on N2O emissions.
In order to trace the origins of N2O, the N fertiliser source used in the incubation
study was labelled with stable isotopes . Measurements included soil mineral N
dynamics, nitrification and denitrification enzyme activities, N2O emissions, and AOB
and AOA community abundance and activity.. This was a project that was at the
forefront of the field, so a number of technical challenges needed to be overcome.
The project is continuing and samples will be analysed in the next few months. The
findings will significantly increase our understanding of the origins of N2O, the role of
different AO communities, and the effect of DCD on these microbial communities
and processes.
While at the CAS in Beijing, it also provided an opportunity to jointly work on a
manuscript for publication . The first draft has been produced and will be submitted
shortly after further editing and internal reviews. This article will provide a timely
update and a critical analysis on this topical area. The fact that I was in the CAS
laboratory in person made the discussion and my contribution to the work
programme so much easier than communicating through email. The results from the
collaborative research project will be published when all the trial work is completed
and all the samples have been analysed.
Another important aspect of the GRASS fellowship is that it provided a great
opportunity for me to interact with the postgraduate students at the CAS in Beijing
who are part of Professor He’s team. I held a seminar/discussion session with the
postgraduate students on the use of nitrification inhibitors to inhibit AOB and AOA in
the soil to reduce N2O emissions. I found this to be very useful for me to explain the
N2O work that we have been doing in New Zealand, and also for me to learn about
the work at the CAS.
In addition to working with Professor He’s team at the CAS in Beijing, I also visited
other research groups who are conducting research on N2O emissions and the use
of DCD to reduce N2O emissions. This included the Subtropical Institute of Agriculture
in Changsha that is working on N2O emissions in paddy fields (for rice production)
and the use of DCD to reduce N2O emissions; Huazhong Agricultural University that
has research programmes on N2O emissions from vegetable systems, and its
mitigation with DCD; Hebei Agricultural University that works on N2O emissions from
glasshouse vegetable production fields; and Zhejiang University with interests in N2O
emissions as affected by different soil management systems. Discussions with teams
in these institutions were very useful for me to learn about their work programmes,
the effect of soil and environmental conditions on the effectiveness of DCD, and for
me to share my research experience in New Zealand.
Delivery against anticipated outcomes and outputs
All the anticipated outcomes and outputs as set out in the contract have been
successfully achieved. This is summarised in the following table.
Anticipated outcomes
To collaborate on research that
investigates the effectiveness of the
nitrification inhibitor DCD in reducing
nitrous oxide emission in China and NZ
To study the microbial mechanisms of
nitrification inhibition and nitrous oxide
emissions by DCD
To share and exchange information on
the mitigation approaches to nitrous
oxide emission in China and NZ to
facilitate the transfer of knowledge
about mitigation tools
To use the knowledge gained during the
Chinese trials to enhance the research
programme in NZ and further the
understanding on the various microbial,
soil and environmental factors that
affect nitrous oxide emissions from the
soil
A seminar given to the EcoEnvironmental Research Centre in CAS.
Transfer of research protocol on the use
of nitrification inhibitor to EcoEnvironmental Research Centre in CAS
A collaborative journal article submitted
to a peer reviewed journal
Delivery
Achieved successfully through the joint
collaborative research project.
Achieved through the collaborative
research project.
Achieved through seminar/discussions,
collaborative research project and joint
publications.
Achieved. The collaborative research
project will provide insights into the role
played by AOB and AOA in N2O
production and the effectiveness of DCD
in mitigating N2O emissions. The
discussions with the teams in the different
organisations have significantly
increased my understanding of the
efficacy of DCD in reducing N2O
emissions in intensive vegetable
production systems and in paddy fields.
This complements those trials that have
been conducted in New Zealand on
grazed pasture soils
Achieved
Achieved through the collaborative
research project
A manuscript has been drafted and after
further editing and internal reviews, will
be submitted
New research opportunities and enduring relationships/partnerships
Discussions were held at length with the research teams that I visited during the
exchange to identify new research opportunities and develop long-term
collaborative relationships. Three possible areas of continued collaboration were
identified: Joint application of research funding in China to fund joint research
projects; exchange of staff and students; and joint publications.
Concluding remarks
This GRASS Award has been extremely valuable. It enabled me to work in person in
the Chinese laboratories to conduct collaborative research, have informative
discussions, exchange views and ideas on N2O research and the use of DCD to
mitigate emissions, prepare joint grant applications, and contribute to joint
publications. The joint research project conducted will provide fundamental
knowledge on the origins of N2O, the role played by ammonia oxidising microbial
communities, and the efficacy of DCD in inhibiting the AOs and in reducing N2O
emissions.. The joint publications will enhance New Zealand’s reputation in this area,
particularly in China. The knowledge gained through the joint research projects,
exchanges and publications, will complement, inform and enhance similar research
in New Zealand. Hopefully these collaborations will lead to improved solutions to the
biggest challenge that humanity is faced with today – climate change. I hope more
scientists will take up this Award to enhance research collaborations among
different scientists in New Zealand and other countries. Climate change is a global
issue and it will require concerted efforts of all the nations on this planet to minimize
its impact. Collaboration of scientists from different countries is an important part of
this concerted effort.
Acknowledgement
I am grateful to MAF through NZAGRC for the provision of the GRASS Award.
References
Di, H.J. & Cameron, K.C. 2002. The use of a nitrification inhibitor, dicyandiamide
(DCD), to decrease nitrate leaching and nitrous oxide emissions in a simulated
grazed and irrigated grassland. Soil Use and Management 18, 395-403.
Di, H.J. & Cameron, K.C. 2003. Mitigation of nitrous oxide emissions in spray-irrigated
grazed grassland by treating the soil with dicyandiamide, a nitrification inhibitor,
Soil Use and Management 19, 184-290.
Di, H.J., Cameron, K.C. & Sherlock, R.R. 2007. Comparison of the effectiveness of a
nitrification inhibitor, dicyandiamide (DCD), in reducing nitrous oxide emissions
in four different soils under different climatic and management conditions. Soil
Use and Management 23, 1-9.
IPCC. 2007. Climate Change 2007: The Physical Science Basis. Contribution of
Working Group I to the Fourth Assessment Report of Intergovernmental Panel
on Climate Change. IPCC Secretariat, Geneva, Switzerland.
Firestone, M.K. & Davidson, E.A. 1989. Microbiological basis of NO and N2O
production and consumption in soils. In: Exchange of Trace Gases between
Terrestrial Ecosystems and the Atmosphere (eds M.O. Andreae & D.S. Schimel),
pp. 7-21. John Wiley & Sons, Chichester.
Mosier, A., Kroeze, C., Nevison, C., Oenema, O., Seitzinger, S. & van Cleemput, O.
1998. Closing the global N2O budget: nitrous oxide emissions through the
agricultural nitrogen cycle. Nutrient Cycling in Agroecosystems 52, 225-248.