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AgResearch includes teams of researchers with skills relevant to the Centre in rumen function, rumen microbiology, ruminant physiology, soil science, environmental science, agricultural systems management, forage plant growth and development, on-farm practice change, social science, technology uptake, genomics, proteomics and metabolomics of animals, plants and microorganisms.
Searching deep within for methane battlers
The role of microbes in producing methane is being studied by an Irish scientist, writes Jarrod Booker.
While science is helping us discover vast new worlds beyond our own, the worlds explored by Sinead Leahy are far too small to be seen by the naked eye.
This world of microbes – tiny bugs such as bacteria that could fit by the millions in the eye of a needle – are all around us and keep the planet functioning. For Leahy, a senior scientist at AgResearch, her focus over the last decade has been on the complex world of microbes in the stomachs of ruminants like cows and sheep – and the huge implications these tiny single-cell organisms have for both New Zealand's economy and environment.
"We know so little about this microbial world, because people don't see it and they don't realise how important it is to us in New Zealand. It's only recently that we have started to get DNA sequencing technologies that allow us to study these worlds with new insight," Leahy says.
"The microbes in the sheep or cow's rumen (a chamber of the stomach) powers the animal by allowing it to break down the grass it eats, and gives us the products like milk, meat and wool that New Zealand sells to the world."
It is not only the size of the microbes in the rumen that makes them difficult to identify and study, it's also the environment they exist in – without oxygen – and the highly complex roles they play, and how they interact with each other.
Irish-born and raised Leahy, alongside her colleagues in rumen microbiology at AgResearch, has spent the last decade in New Zealand learning more about these microbes, to help farmers produce healthier, more productive animals and lift New Zealand's economy. But the potential is also huge when it comes to methane gas produced by the animals, given that methane is the largest contributor to New Zealand's greenhouse gas emissions.
As scientists at AgResearch and elsewhere press to find ways to reduce the amount of methane produced – including potential for a methane vaccine – Leahy says the role of microbes here is crucial. By learning more about the microbes that are part of the process of producing the methane in the animals, there is the opportunity to find new ways to address it.
Leahy was part of an international project led out of AgResearch, called Hungate1000, in which the genomes of hundreds of different microbes from ruminants from around the world were mapped to provide an important resource for researchers globally.
While New Zealand should be proud of its rugby players and rowers, they should also recognise that in areas like rumen microbiology, New Zealand is a world leader, she says.
Though she and her Irish-born husband are now also New Zealand citizens, along with their two New Zealand-born children, there is no question where her loyalties lie when it comes to the rugby arena. She looks back on the famous Irish victory over the All Blacks in Chicago last year as "one of the greatest days of my life".
"It was a long time coming. After all the pain of the last 10 years, I finally got to come to work in my Ireland jersey and lord it over everyone for a change."
Leahy, 38, was one of nine children growing up in the Irish township of Bilboa – she had more siblings than there were pupils in her primary school class. Her grandfather's small farm nearby had her exposed early to rural life – "we grew up with milk straight from the cow".
Her family was very strong in mathematics, and she remembers telling them at a young age she was going to be a researcher.
"I remember in primary school a teacher turning water with different colours with dye. It basically set me on the path from there."
After completing her PhD in Cork, Leahy arrived in New Zealand in 2006, for what she told family and friends was part of a two year adventure around the world. After landing the job at AgResearch, and becoming attached to the work, her team, and the lifestyle, she decided to stay.
"I think my family always knew I was going to go off and see the world and do something more."
While retaining her position at AgResearch, Leahy has recently taken up a new role of International Capability and Training Co-ordinator for the Government-funded New Zealand Agricultural Greenhouse Gas Research Centre (NZAGRC).
The role will support the goals of the Global Research Alliance on Agricultural Greenhouse Gases, an initiative supported by the New Zealand Government to increase collaboration between countries to reduce the emissions intensity of food production. One of the objectives of Leahy's role is to engage scientists and policy audiences in the developing world on why lowering agricultural greenhouse gas emissions intensity (the emissions per kilogram of meat, milk, vegetables or grains) is important for their agricultural production.
"It's something I haven't done before, working on that interface between governments and the science, and the area of developing policy," Leahy says.
"It's vital to have that policy in place if you want to make real change, and for that policy to be built on quality science."
- Sinead Leahy is the International Capability and Training Co-ordinator at the NZAGRAC. Read her profile
Decreasing methane emissions by feeding grazing ruminants: a fit with productive and financial realities?
Pacheco, D., G. Waghorn, et al. (2014). "Decreasing methane emissions from ruminants grazing forages: a fit with productive and financial realities?" Animal Production Science 54(9): 1141-1154.
Ruminants contribute to human food supply and also anthropogenic greenhouse gas (GHG) emissions. An understanding of production systems and information on animal populations has enabled global inventories of ruminant GHG emissions (methane and nitrous oxide), and dietary strategies are being developed to reduce GHG emissions from ruminants. Mitigation strategies need to consider the management/feeding systems used to ensure that these strategies will be readily accepted and adopted by farmers. Housed systems allow diets to be formulated in ways that may reduce GHG production, but the challenge is much greater for systems where animals graze outdoors for long periods. A methane mitigation option in the form of fresh forage would be desirable in livestock production systems with high reliance on grazing. A brief summary of New Zealand research, carried out on fresh grasses, legumes, herbs and crops, suggest that we have an incomplete understanding of the feed characteristics that define a ‘high’ or a ‘low’ methane feed. The variation in methane emissions measured between feeds, individual animals and experiment is large, even in controlled conditions, and the dynamic nature of sward-animal interactions will only exacerbate this variation, creating challenges beyond the identification of mitigants. Furthermore, implementation of knowledge gained from controlled studies requires validation under grazing systems to identify any trade-offs between methane reduction and animal productivity or emission of other pollutants. Therefore, investment and research should be targeted at mitigation options that can and will be adopted on-farm, and the characteristics of temperate grasslands farming suggest that these options may differ from those for intensive (high input/output) or extensive (low input/output) systems.
Report: Monitoring Greenhouse Gas Emissions
Progress over the first year from the Low emissions farm systems for the Maori sector project includes:
- Development of a typology of Maori farming
- The collection of farm and GHG emission profiles on 29 Maori farms from around the country, with 2 more to come. This includes 18 sheep & beef farms, and 11 dairy farms
- The selection of 4 Focus farms; 2 dairy (Bay of Plenty, Taranaki), and 2 S&B (Northland, East Coast)
- The development of Farmax files for each focus farm to allow for farm system modelling, and Overseer files to (a) establish the base GHG emission profile and (b) model the impact of change scenarios
- Data collated to allow for national benchmarking of the emission profiles
- Meetings held with the Trustees of the 4 focus farms and agreement gained re (a) participation in the project and (b) discussion on scenarios for modelling
- Development of priority scenarios for modelling of change in farm systems and subsequent impacts on GHG emissions.
- Development of farm maps to assist with the modelling
- A paper has been produced on the project to date and submitted to an international journal.
Read full report
Collaborative work investigating GHG emissions from dairy farms
During 2015/16, the dairy component of the programme has continued progress towards understanding potential for practical mitigation options to result in lower GHG footprints for dairy farming.
Methane and nitrous oxide measurements on dairy farmlets, testing a range of mitigation options, including high genetic merit cows (Waikato), low N fertilizer input (Waikato) and diverse pastures (Canterbury), have been completed. These data enable mitigation options to be considered within a farming system context.
Methane emissions from cows grazing fodder beet during winter and early lactation can lead to a reduction of 10-20% under some conditions. This is an important result as industry uptake of fodder beet as a winter feed option and as a transition feed used on the milking platform in both late and early lactation is increasing. These findings together with data from the FRNL programme on fodder beet will enable farm systems modelling to understand the wider environmental impacts of increased fodder beet usage.
Sheep & Beef work to identifying strategies to reduce GHGs
The NZAGRC team are working with two B+LNZ monitor farms. The farms now have substantial, robust data and baseline farm systems models which demonstrate the extent to which the key management decisions and efficiency drivers impact on current emissions intensity. The farms are at very different points in development cycle, so provide useful perspectives for informing the wider industry.
Practice-change scenarios have been modelled to predict emissions intensity for Onetai station, a coastal sheep and beef farm in the King country. Scenarios incorporating increased fertiliser use and finishing more stock on farm have predicted a 20 to 38% improvement in emissions intensity is possible.
Scenarios modelled for Highlands (South Canterbury) monitor farm demonstrate the potential for a win-win solution when the area sown in Lucerne and Tall Fescue is increased. This enables more lambs to be finished earlier and results in a large a large effect on lowering emissions intensity. This scenario is assessed as being readily adoptable by farmers.
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”.
Life Cycle Assessment - International comparisons
Life Cycle Assessment (LCA) is a tool to account for total greenhouse gas (GHG) emissions, including from energy use and the production of all inputs that go into farm systems, e.g. fertilisers, feeds. It is product focused and can cover a range of stages along a product life cycle including from extraction of raw materials used, through farm and processing stages, to transport, consumer and waste stages. This talk will cover comparison of the carbon footprint (total GHG emissions) of New Zealand milk, lamb and beef products in comparison with those produced overseas. It will focus on studies where valid comparisons are possible using the same methodology. It will also cover current international work on developing internationally-agreed methods through FAO and the European Commission - where New Zealand is playing a key role. Results from recent Product Environmental Footprinting work will be presented, which will include a range of other resource and environmental indicators as well as GHG emissions.
Stewart Ledgard is a Principal Scientist with AgResearch and an adjunct Professor in Life Cycle Management at Massey University. He has worked with agricultural sector and policy groups in the areas of life cycle management and greenhouse gases for over 10 years, and in nutrient management for over 30 years.
Stewart has worked with government and agricultural sector groups in determining and reducing the carbon footprint of agricultural products, and has linked research in use of Life Cycle Assessment (LCA) in agricultural systems in a range of countries internationally. NZ research in this area involved development of methodology for carbon footprinting of dairy, beef, lamb, wool and venison. This methodology was then applied across regional and national farm datasets and used to determine the effectiveness of potential reduction options. International research has included training of researchers and linked research in Australia, Chile, Uruguay, France and the United Kingdom. Stewart is a member of the operations group (representing AgResearch) in the NZ Life Cycle Management Centre, which included co-supervision of a PhD student.
Stewart led a Technical Advisory Group (TAG) of the Livestock Environmental Assessment and Performance (LEAP) partnership associated with the Food and Agriculture Organization (FAO) on developing Guidelines for estimating greenhouse gas emissions from small ruminant supply chains. He is currently co-chairing another LEAP TAG on nutrient accounting and environmental assessment across multiple livestock supply chains.
Stewart has also worked on nutrient management research, covering work on initial development of the OVERSEER® nutrient budget model, nitrogen mitigation on farms, and on developing and evaluating practical nitrogen mitigation options for farmers. He has also worked with NZ policy groups, including several Regional Councils on approaches for landholders to work within limits on nutrient losses from catchments to meet water quality targets.
Stewart has been active in publishing his research. This includes 8 book chapters, 116 scientific journal papers, 108 refereed scientific conference papers and over 350 other general publications and client reports.
Report: Desk-top review of GHG components of OVERSEER
Report prepared for the New Zealand Agricultural Greenhouse Gas Research Centre
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
Global solutions to reduce methane emissions from ruminant animals are feasible, because the microbes causing the emissions are similar around the world
The New Zealand-led “Global Rumen Census” project analysed the microbes responsible for ethane emissions from a wide range of ruminant animals around the world. The project found imilar bacteria and methanogens dominate in nearly all rumens across a wide variety of species and animal diets. This means that new technologies that seek to reduce methane emissions by influencing rumen microbes should have global applications.
The results of the Global Rumen Census were released on 9 October 2015 in the open-access journal Scientific Reports.
Global press release
GRC Global Release (0.31MB)
New Zealand press release
GRC New Zealand Release (0.34MB)
GRC Q&A (0.29MB)
Rumen microbial community composition varies with diet and host, but a core microbiome is found across a wide geographical range
G. Henderson, F. Cox, S. Ganesh, A. Jonker, W. Young, P.H. Janssen. 2015.
Scientific Reports 5: 14567.
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”.
Reducing New Zealand's agricultural emissions: Efficiency in the whole farm system
This publication provides an overview of how the NZAGRC is working with other organisations to understand what efficiencies can be gained on New Zealand's sheep and beef farms.
Delving into rumen 'soup': identifying targets to mitigate methane
What's really in a rumen? It's probably something that most people haven't given much thought to. However, in the search for methods and technologies to mitigate methane produced from ruminant animals, this is a key question.
The rumen of a typical NZ ruminant animal contains a complex ‘soup' of chewed-up plant material, saliva, drinking water, plus a vast array of microbial species. Methane, the potent greenhouse gas, is produced in the rumen by microbes known as methanogens. They use hydrogen, another gas that is produced by other microbes like bacteria that break down ingested feed. By converting hydrogen to methane, the methanogens get the energy they need to grow.
Sandra Kittelmann and Henning Seedorf, along with the rest of the rumen microbiology team at AgResearch, have been delving into the rumen contents of a wide range of NZ sheep and cattle to investigate the microbial communities that live there. By accurately identifying and classifying rumen microbes, and looking for similarities and differences in types and abundances between animals, the search for targets and strategies to reduce agricultural methane is being advanced.
A key outcome of the team's work has been the development of a taxonomic framework to enable classification of the methanogens from the rumen, and from other animal and human intestinal tracts. This work has been recently published in PeerJ (http://dx.doi.org/10.7717/peerj.494). Setting up the framework was a long, and sometimes tedious process, with many of the organisms initially unclassified and most requiring new names. However, the completed classification provides a map that allows researchers to identify the methanogen species that are present in a sample from a rumen. "We may not know what they all do yet", says Sandra, "but we can identify what we've got and what we don't have. Sometimes it's incredibly useful to know what we don't know".
The first use of the new classification was to identify the major methanogens present in NZ ruminants. Surprisingly, regardless of species and diet, there turned out to be a limited diversity of methanogens present. This has big implications for vaccine and inhibitor development. If a new vaccine or inhibitor targets and knocks out the major methanogen groups, it has a high likelihood of working across all NZ species. Currently a Global Rumen Census project (funded by the Global Research Alliance) is underway. Led by Gemma Henderson and Peter Janssen, it aims to survey the diversity of microbes present in rumen samples obtained from a range of locations and farming situations around the world. If the same major methanogens turn out to be globally common to ruminants, any new technologies developed in NZ could be used internationally to help make a real impact on agricultural GHGs.
New taxonomic frameworks for rumen microbes have also been instrumental in a recently published study investigating the microbes present in the rumens of naturally high- and low-methane emitting sheep (http://dx.doi.org/10.1371/journal.pone.0103171). The team were hoping to find differences in the communities present, with the expectation that there was something special about the high-emitters. However, unexpectedly the results showed that it was the low-emitters that had additional, different strains of bacteria present.
After some time spent examining the results of the study, it was deduced that there are actually two types of low-emitting sheep. In the more abundant type, bacteria which don't seem to produce hydrogen have muscled their way into the rumen. Less hydrogen means less methane. The animal breeding team, led by John McEwan, have found that the low-emitting sheep tend to have physically smaller rumens, so current thinking suggests that feed passes through the smaller rumens faster, and the non-hydrogen producing species can establish themselves better under these conditions.
As for the second type of low-emitting sheep (as classified by their rumen microbes), the team are still working on an explanation for this. Sandeep Kumar, a PhD student funded jointly by the NZAGRC in NZ and Teagasc in Ireland, is currently unravelling this issue.
Investigation of rumen samples is a pivotal, underpinning part of the NZAGRC-PGgRc methane programme. With major vaccine and inhibitor trials planned during the next year, understanding the effects that these are having on the methanogens present is very important. So Sandra and her team will continue to receive and study as many rumen samples as they can handle for the foreseeable future, feeding back their valuable results and insights to the rest of the methane team.
Low GHG feeds: latest research shows that forage rape can make a real impact
Could forage rape, a brassica crop, hold the key to understanding what and how to feed animals to reduce their greenhouse gas emissions?
A wide search has been carried out to date for animal feeds that reduce GHGs. For a long time everything studied either had no effect or contained some sort of inhibitory compound, but was impractical as an animal feed. For example, garlic has been shown to reduce methane emissions, but is not an agronomically viable forage crop. Grain is known to lead to reduced emissions, but a large proportion of the diet needs to be grain (>65%) to see a reduction. Not a viable option for NZ farmers. Some fresh forages evaluated in New Zealand, such as white clover, have given inconsistent responses when fed to sheep.
Researchers had begun to think that any type of fresh animal feed would result in the same amount of methane for the same amount of dry matter. That was until some species of brassicas were studied and gave a surprising result.
Field trials have shown that diets based on 100% forage rape, a type of brassica, can reduce methane emissions per unit of feed from sheep by as much as 30%. Currently the reason for this is not fully understood. Brassicas contain compounds that could act as potential inhibitors of methanogenesis, but all the data so far suggest they are not causing the reduction in methane. It seems that the reduction is due to the way that the feed is being fermented in the rumen.
David Pacheco and Sunny Sun, with their team, have been following up on this observation with the aim of working out what it is about the brassicas that leads to a drop in methane. Once this piece of the puzzle has been solved, the goal is to be able to identify and develop feeds and feeding practices that result in reduced GHG emissions and can be counted in the national greenhouse gas inventory.
The research team has been investigating how increasing levels of forage rape in the diet affects methane production. In contrast to grain, preliminary observations from indoor trials with forage rape suggest a linear reduction in methane yield as the proportion of forage rape in the diet increases. If confirmed, this result would mean that feeding of forage brassicas can lead to a reduction in methane emissions at a larger range of dietary inclusion levels than previously thought. The results also suggest that reductions in methane observed in brassicas may occur through a different mechanism to those elicited by feeding grains.
The research is being extended to include more brassica species, as all those studied to date appear to have reduced methane emissions to some degree. One prediction is that the decrease is due to readily fermentable carbohydrates present in the brassicas. This suggests that researchers should look at other forage crops with this characteristic. Therefore, one of the next feeds to be studied more closely is fodder beet. This crop has been growing in popularity in recent years and the results of any GHG trials will be of interest to NZ livestock industries. Results will also help to inform the search for new feeds and feeding strategies that can be included in the NZ inventory.
While the team expertise is focused on methane, the project team is linking with other experts to have an integrated, wider view of what the impact is for whole GHGs. For example, Pacheco's team has also been looking at the impacts of brassica feeds on nitrous oxide emissions from urine deposited onto soil by grazing animals. This is being done in conjunction with the nitrous oxide experts in AgResearch and funded by MPI through its Sustainable Land Management and Climate Change (SLMACC) programme. To bring all these findings together a parallel project led by Stewart Ledgard, also part of the SLMACC research fund is using the data generated to do a full life cycle analysis of alternative feeds, like brassicas, that require cultivation and application of fertilisers. These processes can also produce GHGs, and their impacts need to be known as well.
The search for plant species to reduce nitrous oxide emissions
Could plants be used to reduce nitrification rates in soils and hence reduce nitrate leaching and emissions of nitrous oxide? Results of screening experiments conducted by Dr Saman Bowatte and his team at AgResearch Grasslands campus in Palmerston North suggest that they could. Plus, the variability of nitrification activity detected presents an opportunity to explore alternatives to synthetic inhibitors such as DCD.
The screening experiment measured the potential nitrification rate in soil associated with 126 cultivars of 26 species representing three functional groups used in temperate managed grassland. The team found little difference between the average nitrification values for grasses, legumes and fodder crops, but there was a 71% difference between the lowest and highest nitrification values. Fortuitously, several cases were found where a low nitrification rate was coupled with an above average biomass, suggesting that some currently available cultivars may have lower N emissions - a possibility that is now being tested out in the field.
Over the past New Zealand winter, 18 plant species/cultivars carefully selected from the screening experiment have been quietly growing away in a paddock at Grasslands. The team sowed the experimental plot trial back in mid-April and have been busy weeding, fertilising and watering as required to ensure good growth ready for the next stage of the work. This will involve adding urine to each species/cultivar and then measuring the nitrous oxide emitted.
The hypothesis is that the results seen in the glasshouse experiments will be repeated in the field and that some species will have lower emissions than others. Ideally, the reduction will be of a sufficient magnitude to warrant further investigation and lead on to potential options for low N emitting plant species for use in NZ pastoral settings and beyond.
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.