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NZAGRC Science Leadership Team
The role of NZAGRC Science Leadership Team (SLT) is to play a key part in the development, implementation and monitoring of all of the Centre’s science programmes and strategies. It consists of respected New Zealand-based researchers with excellent science credentials accompanied by strong leadership, communication, strategic and inter-personal skills with expertise in those areas of science covered in the NZAGRC Strategy and Science Plan.
Membership is agreed by the Steering Group and includes the NZAGRC Principal Investigators in addition to the NZAGRC Director and NZAGRC Operations Manager.
|Dr Graeme Attwood||AgResearch|
|Dr Cecile DeKlein||AgResearch|
|Professor Hong Di||Lincoln University|
|Dr Robyn Dynes||AgResearch|
|Dr Peter Janssen||AgResearch|
|Professor Frank Kelliher||AgResearch|
|Dr David Whitehead||Landcare Research|
Science leadership & capability building
The NZAGRC is committed to providing opportunities for researchers to be trained and work with leading experts in New Zealand. Some students go on to continue their studies or enter a postdoctoral position under guidance from NZAGRC science leaders, other enter into industry based positions.
The NZAGRC supports more than 50 researchers and students by providing funding via its core research programme or via its student scholarships programme.
Below are profiles of our scientists and past students.
Do glucosinolate hydrolysis products reduce nitrous oxide emissions from urine affected soil?
S.F. Balvert, J. Luo, L.A. Schipper, Do glucosinolate hydrolysis products reduce nitrous oxide emissions from urine affected soil?, Science of The Total Environment, Volume 603, 2017, Pages 370-380, ISSN 0048-9697, http://dx.doi.org/10.1016/j.scitotenv.2017.06.089.
- The effectiveness of glucosinolate hydrolysis products at inhibiting N2O emissions in a high N environment was tested.
- Laboratory and field trials measuring N2O production and soil mineral N cycling were conducted.
- Some glucosinolate hydrolysis products reduced nitrification rates.
- Where inhibition occurred it was short lived.
- Glucosinolate hydrolysis products with different R groups did not inhibit soil nitrogen processes to the same degree.
Read more (external link)
Dr Cecile de Klein: Principal Investigator
Cecile is an internationally recognised expert on nitrous oxide emissions from soils. Born and educated in The Netherlands, she came to New Zealand in 1995 following a postdoc in Cambridge, UK. As Principal Investigator of the NZAGRC she co-leads, with Prof HJ Di, the nitrous oxide mitigation research programme.
She also led an international Global Research Alliance project on developing guidelines for measuring N2O emissions using chamber methodologies. Cecile was New Zealand’s representative on the international panel to review the IPCC inventory methodology for estimating N2O emissions. In her role as Chair of the national nitrous oxide research network, NzOnet, she works closely with MPI Policy in coordinating and conducting national programmes on N2O emissions to improve the N2O inventory methodology.
Dr Peter Janssen, Principal Investigator
Dr Peter Janssen is the Principal Investigator of the PGgRc-NZAGRC methane mitigation programme at AgResearch, and co-ordinates and contributes to the different work streams developing technologies to reduce ruminant methane emissions. He has established methods for investigating the microbial ecology of the rumen ecosystem, and for isolating novel rumen microbes.
Peter has been involved in several global projects to increase knowledge of the rumen, most notably co-leading the Global Rumen Census project.
Peter is an internationally recognised expert in isolating so-called unculturable microbes.
Prior to joining AgResearch, he was an Associate Professor and Reader at the University of Melbourne, where his research team made recognised advances in solving the “Great Plate Count Anomaly”.
Professor Louis Schipper
Louis Schipper is a Professor at the University of Waikato who investigates soil biogeochemical processes at landscape scales and how they might be manipulated to achieve improved environmental performance while maintaining production. For the last decade, Louis has led teams determining changes in carbon stocks of pasture soils at paddock to national scales. This research demonstrated that while carbon in the majority of pastures on flat land was at steady state, some of our important soils had lost substantial carbon while hill-country soils have gained large amounts. These data have been central to developing a national picture of New Zealand’s carbon budget. They have also used micro-meteorological approaches to evaluate high-resolution fluxes of carbon at farm scales to identify practices that increase carbon stocks, generating in-depth understanding of climatic effects (e.g., drought, rainfall) and management impacts (pasture renewal, cultivation, new pasture species). Louis is an elected fellow of the New Zealand and American soil science societies with multiple awards from the NZ Society. He has published >130 papers (Scopus H-index of 36), supervised ~40 PhD/MSc students, and developed substantial soil and environmental resources for schools.
Comparative genomics of rumen methanogens
Li, Y. (2016). Comparative genomics of rumen methanogens, Massey University. Doctor of Philosophy in Biochemistry: 550.
Methane (CH4) emissions from agriculture represent around 9% of global anthropogenic greenhouse gas emissions. The single largest source of this CH4 is animal enteric fermentation, predominantly from ruminant livestock, where it is produced mainly in their fermentative forestomach (or reticulo-rumen) by a group of archaea known as methanogens. In order to reduce CH4 emissions from ruminants, it is necessary to understand the role of methanogenic archaea in the rumen, and to identify their distinguishing characteristics that can be used to develop CH4 mitigation technologies. To gain insights into the role of methanogens in the rumen environment, two methanogens have been isolated from ovine rumen and their genomes were sequenced: methanogenic archaeon ISO4-H5 of the order Methanomassiliicoccales and Methanobrevibacter sp. D5 of Methanobrevibacter gottschalkii clade. Genomic analysis suggests ISO4-H5 is an obligate hydrogen-dependent methylotrophic methanogen, able to use methanol and methylamines as substrates for methanogenesis. Like other organisms within this order, ISO4-H5 does not possess genes required for the first six steps of hydrogenotrophic methanogenesis. Comparison between the genomes of different members of the order Methanomassiliicoccales revealed strong conservation in energy metabolism, particularly in genes of the methylotrophic methanogenesis pathway, as well as in the biosynthesis and use of pyrrolysine. Unlike members of Methanomassiliicoccales from human sources, ISO4-H5 does not contain the genes required for production of coenzyme M (CoM), and requires external supply of CoM to survive. Methanobrevibacter sp. D5 is a hydrogenotrophic methanogen predicted to utilise CO2 + H2 and formate as substrates. Comparisons between the available Methanobrevibacter genomes has revealed a high conservation in energy metabolism and characteristics specific to each clade. The coexistence of different Methanobrevibacter species in the rumen may be partly due to the physical association Methanobrevibacter species with different microorganisms and host surface, which allow unique niches to be established.
Read more (external link)
Potential for forage diet manipulation in New Zealand pasture ecosystems to mitigate ruminant urine derived N2O emissions: a review
Gardiner, C. A., T. J. Clough, et al. (2016). "Potential for forage diet manipulation in New Zealand pasture ecosystems to mitigate ruminant urine derived N2O emissions: a review." New Zealand Journal of Agricultural Research 59(3): 301-317.
Nitrous oxide (N2O) emissions from agricultural soils account for more than 10% of New Zealand’s greenhouse gas emissions. Livestock urine deposition drives N2O losses from these soils. It has been speculated that non-urea nitrogen compounds (UNCs) in ruminant urine could reduce or inhibit urine patch N2O emissions. However, we hypothesise that UNCs will have no effect on N2O emissions due to their potentially rapid degradation by plants and soil microbes. Our review suggests that plant secondary metabolites (PSMs) are more likely to perform a role in reducing N2O emissions since many PSMs have known antimicrobial properties. Aucubin, found in Plantago, and isothiocyanates, found in Brassica, have been shown to inhibit a key step in N2O production. Future studies should explore this promising research gap by evaluating forages for potential inhibitory PSMs, assessing whether PSMs are excreted in urine after consumption, and determine whether excretal PSM concentrations are sufficient to reduce N2O emissions.
Read more (external link)
Camilla Gardiner moved to Canterbury from the USA at the end of July 2015. Originally from Seattle, Camilla has had a passion for agriculture since high school. "I spent a term at a farm school in rural Vermont in my third year of high school", Camilla says. "Four months with forty-five other sixteen year olds, spending three hours a day on the farm plus learning about the land-based environmental sciences. I was hooked". This interest in farming led Camilla to UC Berkeley to study Environmental Sciences with honours in Soil Biogeochemistry. It was a mentor at Berkeley that encouraged her to investigate PhD options in New Zealand and provided some key contacts. Fortuitously Dr Tim Clough was looking for a student at the time and the rest is now history.
Camilla's previous research work at Berkeley primarily focused on the use of compost to sequester soil carbon, so the move to focus on nitrous oxide and urine patches has involved a steep learning curve. Her PhD project involves studying nitrogen compounds and plant metabolites in urine and identifying those which might minimise N2O emissions. The project started with a literature review and this has produced a number of interesting leads, particularly from plantain. This review is currently being revised for publication, with an aim to publish by mid-2016.
Preferring to be out in the field, rather than at the lab bench, Camilla is looking forward to her first field trial. She is currently running a lab-scale study, whilst gearing up to a larger on-farm trial. "Planning a big trial is a huge learning experience", she says. "I've previously only worked with established trials". Camilla is surrounded by a wealth of knowledge though. "I'm the youngest member in the team by quite a long way", says Camilla. "There is a lot of expertise around here to tap into!"
Moving to New Zealand has turned out to be everything that Camilla thought it would be, and more. As a keen skier and tramper, Camilla has been out exploring the scenic South Island as much as she can. The relaxed kiwi lifestyle is also growing on her. "Up until now I've lived in busy big cities. I love the laid back approach to life here in New Zealand".
Providing funding to students and early career scientists to increase capability in the agricultural greenhouse gas emissions mitigation research area and boost international collaboration is a key activity for the NZAGRC.
The NZAGRC nitrous oxide team was joined by two new PhD students in 2015 and they are both now well underway with their studies.
Sheree Balvert has been fascinated by farming from a very young age. She was raised on a dairy farm in the Lake Rotorua catchment area and this led her into the study of fresh water ecology for her Honours and Master's degrees. A realisation that research earlier in the farming process may have more of an impact overall led her to a change of direction after completing her study. "Looking at water sometimes felt like being the ambulance at the bottom of the cliff", says Sheree. "The damage had already been done. By moving to research which focussed on on-farm processes, I felt I could be more effective".
About 10 years ago, Sheree took up a technician role at AgResearch's Ruakura campus. Her focus was soil science and nitrogen loss mitigation. Interested in developing her career further, when an NZAGRC PhD project became available in 2015, she decided to resign from her job and move back to study. Sheree feels that she's initially had it easier than some PhD students. "I'm continuing to study in the area that I worked in", she says. "However, I've still had to learn a whole lot more in a very short space of time".
Sheree's PhD project involves studying a diverse range of forages, their influence on the nitrogen cycle and the loss of N from farm systems. She has a particular interest in brassicas. "My goal is that by understanding the effects of different forages, I can provide farmers with another tool to help them to reduce their environmental impact", says Sheree. She has just completed a laboratory study assessing the impacts of selected compounds from brassicas on the soil nitrogen cycle and their potential for reducing nitrogen leaching. The next step is to take the promising compounds forward into a field trial.
Outside of her study, Sheree has a love of getting active in the great NZ outdoors. Whilst she's reluctant to call them "adventure" sports, she is a keen scuba-diver, white water kayaker and snow-boarder. One impact of the move back to student life is that, for the foreseeable future, skiing trips will be confined to the North Island. "New Zealand is a fantastic place to work and play", says Sheree. "I guess that's what keeps me here".
KuDos to Aaron Wall of Waikato University
University of Waikato technician, and a pivotal player in the NZAGRC-funded soil carbon programme, Aaron Wall was a winner in last month’s 2015 KuDos Hamilton Science Excellence Awards.
The School of Science Technical Officer picked up the top award in the Hill Laboratories Laboratory Technologist Award section.
Aaron spends much of his time expertly managing the Troughton farm site for the NZAGRC programme. Additionally, he also manages the access to the site for related research by AgResearch, Plant and Food Research and Landcare Research. His excellent relationship with the farm owners, and unsung heros of the whole operation, Ben and Sarah, enables everything to run smoothly.
On top of overseeing what goes on and when at the Troughton site, Aaron is a key part of the NZAGRC research team. He has made considerable novel advances in analysis of eddy covariance data, collation of non-CO2 data and pushed the team to collect additional data that are now proving to be crucial. Aaron is able to bring together deeply technical analysis tools with on-farm understanding and his colleagues feel extremely lucky to have him in their team.
Well done Aaron!
See Aaron in action here: https://youtu.be/qFYZ4R1f-RA
KuDos to Jiafa Luo of AgResearch
"Humbled and surprised” is how AgResearch Senior Scientist and NZAGRC Project Leader Dr Jiafa Luo describes his reaction to hearing his name read out as the winner of the Gallagher Agricultural Science Award at this year’s KuDos Hamilton Science Excellence Awards.
He says he didn’t think he would be the winner, as he was up against strong competition from the other finalist, LIC (Livestock Improvement Corporation), in the awards, which are held annually, celebrating Waikato scientists and their world-leading research and innovation. As well as agricultural science, the categories include environmental science, medical science, science educator and lab technician.
Jiafa is a key player in the New Zealand nitrous oxide research space and his work is having impacts both nationally and internationally. For the past 10 years Jiafa has been planning and leading many large-scale research programmes investigating country-specific nitrous oxide emission factors for deposited excreta in grazed pasture systems. His work has included investigations into nitrous oxide emissions from sheep, beef and dairy cow excreta on a range of soil types, land topographies and farming systems throughout New Zealand. Results from his work have directly impacted the NZ GHG inventory calculations, making them significantly more accurate.
Jiafa has also led several research projects investigating N2O emissions from applied nitrogen fertilisers and farm dairy effluents. The data from these projects is the first of this kind in New Zealand and has also been used as scientific evidence to support the country-specific N2O emission factors for nitrogen fertilisers and farm dairy effluent in grazed pasture systems.
Jiafa has led several research programme objectives examining mitigation technologies and practices for reducing N2O emissions from grazed pasture systems. The NZAGRC, GPLER and MPI funded programmes have tested and quantified the economic and environmental benefits from adopting N2O mitigation strategies (such as restricting grazing, nitrification inhibitors, novel plant species, and timing of dairy farm effluent and nitrogen fertiliser application) into New Zealand dairy farming systems. Results have been widely used by the pastoral sector and published in a number of refereed journal and conference papers.
Well done Jiafa!
See Jiafa in action here: https://youtu.be/FUuNppW0bL4
Co-leader of breeding programme keen to make a positive contribution to farming
Dr Suzanne Rowe, co-leader of the NZAGRC-PGgRc programme to breed low methane ruminants, has always been passionate about farming. Originally from Devon, in the UK, she grew up in the city and left home at 16 to work on a horse breeding stud. Suzanne then moved on to milking cows, which she enjoyed for many years. She found herself milking for a progressive farmer, Herbert Mitchell, who, with his son, was breeding dairy cows for production with a huge emphasis on recording. Tregear farm had been in the family for more than 100 years and the 150 cows were averaging about 10,000 litres of milk. “In terms of production index, at one point it was second only to Scotland’s Rural College research farm, which is an outstanding achievement for a small family farm”, Suzanne remembers.
Tregear was a great place to learn and it was here that Suzanne became interested in making a difference to the agricultural sector. In between milkings, she studied for her A-levels and then attended agricultural college, continuing to milk at weekends and at any other occasional opportunity that she could. From there, she moved to Edinburgh to study quantitative genetics and genomics at the University of Edinburgh. “With my fascination with breeding, it really was the best place in the world that I could have studied”, she reflects. In the second year of her degree, Suzanne was required to spend a year working on a farm. Given she had spent so much time milking cows in the UK, she did not think it made sense to stay there. There was a job advertised on an African farm and, despite a warning from the careers advisor at the University who said it was too dangerous, she decided to take it. She and her husband Tim worked as a team on the remote property in Kalomo, southern Zambia, with Suzanne running the dairy and her husband running the workshop. She hand-milked cows, made butter and cheese, and they grew cash crops such as maize and tobacco. There was a mix of Zebu and Friesian cattle on the property. “The Friesians were great for milk but their tick resistance was extremely low. A massive amount of work went into just keeping them alive”, Suzanne says. “It was a fantastic experience which taught me a lot about agriculture because it was so basic compared with what I’d learnt at home”.
Suzanne completed her masters degree, followed by a PhD in quantitative genetics, and then stayed for some post-doctoral work. Always a firm believer that, in science, you should not stay in one group for an entire career, Suzanne decided that the next move that she made would be a big one. With that in mind, the Rowe family moved to Otago two years ago. One of the biggest attractions was the strong team at AgResearch’s Invermay campus, with the likes of Dr John McEwan, who is world-renowned in genomics, and Dr Ken Dodds. Suzanne was also attracted to New Zealand by the value and importance of agriculture to our economy.
In addition to working on the NZAGRC-PGgRc breeding programme, Suzanne has also found time to work on the development of genomic tools for the deer industry and genetic mapping of genes associated with disease and production traits in sheep. She has also been looking at gene by environment interactions in the New Zealand sheep flock and is interested in the development of a dairy sheep industry in New Zealand. “I’m never bored. There’s plenty to do here,” Suzanne told us. “I’m really enjoying working at Invermay. It’s pretty unique to get this level of expertise in all these different areas in one place. I feel that I’m putting my skills to great use here and I’m positive about making a real contribution to the future of NZ agriculture”.
Introducing Dr Jha
The NZAGRC would like to take this opportunity to congratulate Dr Neha Jha on recently completing her PhD and thank her for her contribution to date to the NZAGRC's nitrous oxide research programme.
Neha's PhD study involved steep learning curves on a number of different levels. Originally from Bihar in India, before her arrival in NZ she had never seen such big pastures, let alone cows and sheep grazing outside all day and night. Neha has a Master's degree in soil science and microbiology and these studies focused on Indian agriculture, which is much more diverse than the NZ pastoral system. "Dairying is also big in India", states Neha," but it is very different and the key issues that farmers face are not the same".
After completing her Master's degree, Neha was interested in developing her soil and microbiology skills further and sent through a proposal relating to nitrous oxide emissions from soil to Professor Surinder Saggar (LCR/Massey) and Dr Donna Giltrap (LCR). This proposal resulted in the offer of a PhD position at Massey University and involvement in the NZAGRC-funded denitrification research programme.
Neha's PhD focussed on understanding denitrification processes in different types of soils. During her PhD study, Neha spent a significant amount of time out in those rolling NZ pastures collecting soil samples of differing types from different geographical locations, then investigating their chemical and physical properties and the microbial communities present back in the lab. Key findings were that different soils have differing denitrification potentials, primarily due to the microbes present and soil management history. The end goal of this research is to recognise the soil and environmental factors that have potential to enhance the activity of denitrifiers in reducing nitrous oxide to nitrogen gas. This is vital for the development of novel and effective nitrous oxide mitigation technologies.
Dr Jha is currently completing a one-year postdoctoral position at Landcare Research, still working alongside Surinder Saggar. Her interests in soil, microbiology and greenhouse gases remain high and she is keen to continue publishing and working towards becoming a renowned and respected scientist. Her PhD has led to a number of presentations and she currently has two journal articles submitted for publication. Neha has enjoyed her time in NZ so far and, now that she feels she has conquered the kiwi accent and understands the culture, she is keen to remain here for the foreseeable future.
Honours Student: Larissa Kingsbury
Larissa is in her fourth year (Honours) of a Bachelor of Agricultural Science in the Agricultural life sciences (AGLS) department at Lincoln University. Larissa is supervised by Dr Rachael Bryant.
Larissa is undertaking a research project looking at whether pre-mowing pasture affects pasture intake, quality, milk production, nitrogen intake and subsequent nitrogen partitioning.
Having grown up on northern Otago (Waitaki Plains) farm, Larissa has a strong interest in the sector and the science: "I find the science behind both the running and success of a farm extremely interesting"
Through tertiary study Larissa has "developed knowledge on animal nutrition, which includes animal health, feeding, soil science and animal production" that will help in her as an animal nutritionist. Larissa is keen to help develop on-farm solutions so that farmers can get the best from their farm and animals.
Masters Student: Olivia Jordan
Olivia with NZ PM Rt Hon John Key (Oliva is second from the left)
Olivia is conducting an MSc thesis examining root biomass of different pasture swards in a trial at a New Zealand industry research farm.
This work is aligned to an investigation of above-ground plant traits by Landcare Research.
Olivia is supervised by Professor Louis Schipper at the University of Waikato.
Olivia has a background in farming is very interested in finding a career in the farming industry.
Honours Student: Daniel Martin-Hendrie
Daniel Martin-Hendrie is a fourth year agricultural science student at Lincoln University. Under the supervision of Professor Tim Clough, Daniel is investigating DCD and ammonium in a lowland Canterbury Stream and what effect stream bed sediments, aquatic plants, and aeration regime have on their fate in a mesocosm study.
Daniel is a rural South Cantabrian whose discovered his interest in soil science once he started studying at Lincoln University. He is co-president of the Lincoln University Soil Society and is aiming for a career focused on rural soil management.
Undergraduate Student: Martina Alvarez Camps
"My name is Martina Alvarez. I am 19 years old and about to start my second year of Chemical and Materials Engineering at the University of Auckland."
Martina spent the summer with Dr Carolyn Hedley and Dr Pierre Roudier at Landcare Research looking at the effect of moisture on soil spectra and the use of the External Parameter Orthogonalisation (EPO) algorithm to predict carbon content of field moist soil using air dry soil spectra models.
Martina's work has given her the opportunity to learn new skills and expertise in this field of soil science.
"I have learned about Visual-Near Infrared (VisNIR) spectroscopy and its benefits to soil science due to its quick soil carbon content predictions. I have also become aware of how samples are handled and scanned, the need for pre-processing of spectra and its application using the computer programming language R and how to accommodate the experiment to unexpected occurrences."
Undergraduate student: Alex Tressler
Alex Tressler is a fourth year undergraduate student at the University of Waikato. He is currently in his final year of a BMS studying Agribusiness and Strategic Management.
Alex's recent NZAGRC research project was to examine the potential for effective economic policy in regards to soil carbon within pastoral agriculture in New Zealand.
"The research included exploration of foreign policy and initiatives as well as comparisons of our own proposals, whilst assessing the viability of these ideas based on academic literature and theoretical real world applications."
Alex plans to complete his BMS and continue working in agribusiness to "help maintain and improve our country's competitive advantage."
Honours Student: Bianca Dias
Bianca's Honours year was funded by the NZAGRC Student Scholarship Fund. For her Honours project, Bianca worked on diurnal fluctuations of nitrous oxide from the soil. She was supervised by Professor Tim Clough.
Bianca was also a Future Leader Scholar in the Environmental Science Programme at Lincoln University. She was a Co-Founder of the Lincoln University Soil Society with Aimee Robinson (NZAGRC Masters Student).
Bianca is undertaking her PhD in Australia (Brisbane) and received a Doctoral Scholarship.
Summer Student: Calvin Ball
Calvin Ball worked with Professor Jacqueline Rowarth, Professor Tony Parsons and Dr Susanne Rasmussen during the summer. The research Calvin undertook, to examine the way gibberellic acid could make plant growth and metabolism more nitrogen efficient, has been published (Ball et al 2012; Parsons et al 2013).
Calvin went on to undertake his honours dissertation on C cycling and sequestration in grazed grassland with the same research team , during his B Sci Agriculture Honours year, 2012.
Calvin Ball has been employed by Ballance (Agrinutrients).
Summer Student: Priya Soni
Priya has a BSc in Biotechnology from India and came to New Zealand to study for a graduate certificate in Science and Technology specialising in microbial biotechnology.
Priya's NZAGRC funded summer research placed her in Dr Graeme Attwood's laboratory at AgResearch in Palmerston North, where she investigated the relationships that occur between methanogens and bacteria in the rumen environment through gene expression studies.
Priya completed her Graduate Certificate in 2012.
Changes in denitrification rate and N2O/N2 ratio with varying soil moisture conditions in New Zealand pasture soils
Jha, N., Saggar, S., Tillman, R., & Giltrap, D. (2012). Changes in denitrification rate and N2O/N2 ratio with varying soil moisture conditions in New Zealand pasture soils In: Advanced Nutrient Management: Gains from the Past - Goals for the Future. (Eds L.D. Currie and C L. Christensen).
Denitrification is the primary process of N2O production in temperate grassland soils and accounts for 60% of the total N2O emissions globally. There are various soil and environmental factors that regulate denitrification and affect denitrification rate (DR) and N2O/ N2 ratio. Among these, soil moisture is the most important. Generally, DR increases and N2O/N2 ratio decreases with increasing soil water content. However, the effect of changing soil moisture on DR and N2O/N2 ratio may vary with the type of soil, its nutrient status and the management practices followed on the farm. The interrelationships among the various factors affecting DR are not very well quantified.
Therefore, the current study was planned to investigate the effect of soil moisture on DR and N2O/N2 ratio in five different New Zealand pasture soils with varying physical and chemical characteristics such as soil texture, total porosity, pH, NO3- and NH4+ content, total nitrogen (TN), total carbon (TC), microbial biomass carbon (MBC) and denitrification enzyme activity (DEA). The experiment involved incubation of surface (0-10cm) and subsurface (10-20cm) soil samples at field capacity (FC) and complete saturation at constant temperature (25oC). DR and N2O/N2 ratio were estimated using an acetylene inhibition (AI) technique.
Denitrification rates were higher in soils incubated at saturation than in soils incubated at FC. Similarly, the N2O/N2 ratio decreased in soils when incubated at saturation as compared to FC. The extent of these increases in DR and decreases in N2O/N2 ratio with increasing moisture content varied among the soils due to differences in NO3- and NH4+ content, MBC and DEA of the soils.
Read more (external website)