Study Visit to New Zealand to Investigate Recent and Ongoing Work Relating to the Use Of

Study visit to New Zealand to investigate recent and ongoing work relating to the use of nitrification inhibitors in agriculture

Tom Misselbrook1 and Rachel Thorman2

1Rothamsted Research, North Wyke, Okehampton, Devon EX20 2SB

2ADAS Boxworth, BattlegateRoad, Boxworth, Cambridge CB23 4NN

Conducted as part of Defra Project AC0213

August 2010

1.Objectives of the study tour

The main objective of the visit was to gain a better understanding of the research activity (recent past and ongoing) in New Zealand concerning the use of nitrification inhibitors in agriculture; the types of inhibitor studied and any factors influencing their effectiveness. In particular, we wanted to discuss with the research groups the methodologies and protocols adopted in making their assessments, to inform our approaches to the experiments being conducted as part of Defra project AC0213.

Secondary objectives were to explore what other research was being conducted on GHG emissions from agriculture, to make links with research groups and individual scientists and to gain information on the Global Research Alliance programme.

2.Sites (and people) visited

Tom Misselbrook (Rothamsted Research, North Wyke) and Rachel Thorman (ADAS Boxworth) visited the major research centres involved in nitrification inhibitor research in New Zealand between 9th and 20th August 2010, which included:

Centre / Scientists met
AgResearch, Hamilton / Stewart Ledgard, Jiafa Luo
NZ GHG Research Centre, Palmerston North / Harry Clark
Landcare Research NZ Ltd, Palmerston North / Surinder Saggar (and group)
AgResearch, Palmerston North / Keith Betteridge
PGgRc, Wellington / Mark Aspin
AgResearch, Dunedin / Cecile DeKlein, Tony van derWeerden
Lincoln University / Hong Di, Keith Cameron, Tim Clough

3.Overview of current GHG Research in NZ

Harry Clark, Director of the New Zealand Greenhouse Gas Research Centre, gave an overview of the Centre’s objectives and current research programmes.

The Centre was established in July 2010 with the aims of:

• Injecting additional resource into NZ GHG research ($50M over 10 years)
• Coordinating GHG research – consortium-led, independent research (as compared with much previous industry-funded research) with a strong emphasis on dissemination and publication
• Leading NZ role in the Global Research Alliance

Three science programmes have been funded, covering nitrous oxide, methane and soil carbon.

The nitrous oxide programme will focus on development of the ’next generation’ of nitrification inhibitors (e.g. DMPP), with improved efficiency, effectiveness over a wider temperature range and development of delivery mechanisms being the main goals. Additionally, there will be continued effort on improving models of nitrous oxide emission, particularly for the grazing situation.

The methane programme will build on the PGgRc programme of research (see below), with focus on animal breeding (and strong links here with SAC research), vaccination and rumen microbial genomics/ecology in reducing methane emissions from enteric fermentation. Diet manipulation will not be a major area as systems rely predominantly on grazing, where opportunities are seen to be limited.

The soil carbon programme will focus on understanding changes in soil carbon stocks for New Zealand production systems, where there is little existing knowledge or research. The main effort will be through modelling (based on models such as the Hurley pasture model and DayCent), to assess the potential for carbon sequestration (against a background of high existing soil carbon content), and what management practices might be appropriate within a given land use. Of particular interest are earthworms and how they can incorporate carbon into deeper soil storage, carbon input via grazing and how stable the added carbon pools are, and the interaction between added nitrogen and carbon stabilisation.

Harry also gave an overview of the Global Research Alliance programme and activities. Structures were still developing, but would become clearer at the Banff conference on Greenhouse Gases from Animal Agriculture (October 2010). There would be three research groups: Livestock, Arable and Rice, with lead countries for each. There would also be cross-cutting groups for inventories, measurement, C/N cycling.

4.Nitrification inhibitor research

Previous research

A large body of research has been conducted in New Zealand, primarily assessing the effectiveness of the nitrification inhibitor DCD at reducing nitrate leaching or nitrous oxide emissions from pastoral systems (urine and urea fertiliser). Much of this work has been funded by commercial companies and not all of the results are in the public domain. Studies generally focussed on nitrate leaching or nitrous oxide emissions, yield and N uptake was measured in a few studies and ammonia volatilisation was almost never measured. In general, DCD proved effective at reducing nitrate leaching and nitrous oxide emissions, but reductions achieved varied across research sites. The main reasons for the variation in effectiveness were considered to be:

• Soil type - suspect a faster DCD breakdown on volcanic soils
• Temperature – period of effectiveness shorter on N Island because of higher temperatures
• Rainfall – less effective under a higher rainfall regime (fairly ineffective at rainfall >1800 mm)

Much of this work has been conducted at a small scale using lysimeters, and further validation at the field scale may be required before scaling to national impacts.

DCD has been included as an option in the nutrient planning model OVERSEER, which is used by 90% of dairy farmers in New Zealand, which includes the influence of rainfall and temperature (but not soil type) on effectiveness at reducing nitrate leaching.

Evidence of a grass yield effect is limited and variable (0-20% increase) across research sites and studies. Individual studies have shown a yield effect for an individual urine patch over a limited time period, but there is considerable uncertainty when scaling this to a field over a year.

Studies have been initiated looking at the befits of combined urease and nitrification inhibitors, with the potential to reduce both direct and indirect nitrous oxide emissions.

New research project

A new programme of research is being jointly funded by government and industry, with a total budget of $10M, and managed by the Pastoral Greenhouse Gas Research Consortium (PGgRc), to assess the effectiveness of DCD in reducing nitrate leaching and nitrous oxide emissions and enhancing pasture growth. A major aim of the new research programme is to improve the understanding of the effectiveness and performance variations which may occur between farms and across regions, due to physical and climatic conditions. Studies are initially being conducted at 4 research sites, representing the major dairying regions of New Zealand: Waikato (near Hamilton), Manawatu (Palmerston North), Canterbury, and Southland (near Dunedin). Further sites may be added as the programme develops. Common protocols are being used across all sites and research outcomes will be in the public domain.

Current use in New Zealand

With a lack of a clear yield effect, there is little incentive for farmers to use DCD (they are not seen as cost effective), and this is borne out by the current lack of uptake – less than 2% of dairy farmers (mostly on the Canterbury plain) are estimated to use DCD (as the commercial product Eco-N). Use in pastoral systems in New Zealand (predominantly rotational grazing for dairy farms) is based on 2 applications per year, one in early autumn and a second in late winter, targeting the period of greatest leaching risk and nitrous oxide emissions; this is generally a contractor operation, with the DCD being sprayed on as a fine suspension. Ideally, DCD is applied within 7-10 days of grazing, but in practice applications will be made to pastures within a window of 2 weeks before to 2 weeks after grazing, to minimise the number of times a contractor is required to visit a farm.

Field application of DCD to beef and sheep grazing farms, where livestock range over much greater areas, is not practical or economic. Alternative delivery mechanisms such as via boluses or inclusion within drinking water are being investigated.

Relevance to our project

From discussions with the New Zealand scientists, there were a number of points relevant to our current project (AC0213):

• Soil type and climatic differences appear to be important factors influencing the effectiveness of DCD in reducing nitrous oxide emissions and nitrate leaching from pastoral system
• Our current protocol for preparation and application of DCD is appropriate
• An application rate for DCD of ≥10 kg ha-1 is recommended
• NZ trials use different plots for different measurements (yield, nitrous oxide, leaching), with different numbers of replicates; within AC0213 we measure everything from a single plot
• Edge effects are important with urine patches, so plot design for the urine measurements within AC0213 needs careful consideration
• Soil mineral N data is very useful for interpretation of nitrification inhibitor effects
• A DCD-only plot is useful (in addition to a zero control) to assess any influence of DCD without a nitrogen amendment
• It is important to use real urine rather than artificial urine in experimental studies because of potential differences in the nitrous oxide emission pattern

5.Inventory improvement programme

An inventory improvement programme continues to be funded at $3M per year. There is an aspiration to move to a spatially-resolved nitrous oxide emission inventory, but data availability issues are challenging.

Specific work on improving nitrous oxide emission estimates includes (Cecile de Klein, Dunedin):

• Emission factor for grazing returns (EF3) – in 1997 NZ changed from the IPCC default of 2% to a country-specific value of 1%. Since then 4 studies have been conducted in different regions and seasons measuring emissions from urine and dung. Spring and autumn applications gave the greatest emissions, and emissions were lower for freely draining soils. Emissions were in the order: cow urine > cow dung > sheep urine > sheep dung. For urine this was due to the loading effect (higher volume of cattle urine per event).
• EF3 for grazing in the hill country (accounts for c. 60% of NZ agricultural land) – there is high spatial variability in N deposition and in the EF. Land can be categorised according to drainage, aspect and slope and specific EF3 values associated with each category. N excretion can be modelled according to animal behaviour. Work continues to assess whether this can be incorporated into the inventory model.
• Effect of fertility on EF3 – a relationship has been determined between soil Olsen P concentration (i.e. effect of fertility) and EF3. A higher concentration of P (i.e. more fertile) results in higher EFs. Would like to link soil Olsen P to the P status of vegetation and use satellite imagery to map areas of higher and lower emissions.
• Revision of FRACleach – Since 2001, NZ have used a country-specific value of 0.07 (cf IPCC 0.3), based on OVERSEER modelling. They are now assessing a refinement based on the intensity level of a farming enterprise, suggesting 0.07 for dairy sheep and 0.3-0.55 for cropping (only 4% of agricultural land).
• Emission factor for fertiliser applications (EF1) – NZ use a country-specific value of 1% (IPCC default is 1.25%), arguing that the EF for urea fertiliser will be the same as for urine (EF3). Nitrification inhibitors have been included in the inventory as a mitigation option.
• Spatial integration of EF3 – deriving a relationship between EF3 and soil water content, and combining this with a water balance model at 250 x 250 m resolution using spatial data from NIWA.
• FRACgasfand FRACgasm – Rob Sherlock is publishing a review of national and international data.

In addition, Donna Giltrap (Surinder Saggar’s group) is working with Chang-Sheng Li on developing the mechanistic DNDC model for use in New Zealand, adapting it for grazing situations, including nitrification inhibitors and developing regional scale EFs.

6.Methane research

Research on methane from enteric fermentation managed by PGgRc includes animal selection for low emissions, development of a methane vaccination and more fundamental molecular work aimed at developing methanogen inhibitors for ruminants.

Animal selection work combines measuring emissions from individual animals, using chambers or SF6 techniques, with genetic studies to identify candidate genes andquantitative trait loci (QTLs). The ongoing programme will screen 1000 sheep over three years and use selective breeding to develop a generation of low methane sheep. This will be linked with productivity measurements.

The methane vaccination work is into its 4th year, where the work has been to identify specific antigens, enhance their activity and develop a delivery mechanism. The aim is a prototype vaccine by 2012.

Surinder Saggar has a project on methane oxidation in soils, including microbial work to identify appropriate methanotroph populations and developing soil filter systems for treatment of air from effluent ponds.

7.Other activities of interest

Urine deposition – Keith Betteridge of AgResearch, Palmerston North, is developing urine sensors for use with cows which will give information on the volume of a urination event and the urine N concentration. This can be combined with GPS sensors on the cattle to give spatial and temporal information.

Chris Jones and John Caradus of AgResearch and GrasslandzTechnology ,Palmerston North, are looking to develop forages with environmental benefits. Current work is focussing on condensed tannins, but future developments will look at sugars, lipids and lignins in forages.

Environmental aspects associated with intensification – herd homes; ammonia; odour; effluent management. These are all areas where NZ researchers are looking to us for a lead.

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