Reducing N loss from fertilisers

This field lab is trial into the efficiency of different nitrogen fertilisers on grassland productivity.

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Field Lab Timeline

    2/6/2017 12:00:00 AM
  • Start of project

    Start of project
  • 3/1/2017 12:00:00 AM
  • Methods finalised

    Methods finalised
  • 3/6/2017 12:00:00 AM
  • Trial begins

    Trial begins
  • 3/15/2017 12:00:00 AM
  • First application

    First application
  • 4/30/2017 11:00:00 PM
  • Start of data collection

    Start of data collection
  • 7/30/2017 11:00:00 PM
  • Monitoring

  • 8/31/2017 11:00:00 PM
  • Plate meter readings

    Plate meter readings
  • 11/24/2017 12:00:00 AM
  • End of data collection

    End of data collection
  • 12/15/2017 12:00:00 AM
  • Results meeting

    Results meeting
  • 12/18/2017 12:00:00 AM
  • Progress meeting

    Progress meeting
  • 3/12/2018 12:00:00 AM
  • Next steps meeting

    Next steps meeting
For further information hover over the above milestone marks
  • Discussion

    To see the latest activity please log-in (group members only).

  • Achievements

    September 2018

    Research paper on the benefits of different N fertilisers

    The field lab researcher for this trial has recently published a paper assessing the benefits of the different fertilisers used in the trial. The research paper uses different trial sites, however comes to similar results as this trial. Importantly, there are environmental and consequently social benefits such as greenhouse gas reduction, to using urea with a urease inhibitor, however the higher cost of this alongside having no greater impact on yields or forage quality currently means that there is little incentive to use them.

    The paper can be found here:

    Milestone: Results meeting

    April 2018

    Results discussion, observations and reflections

    The group met to dicsuss their results with the researcher and coordinator. As the urea inhibitor was not found to be effective in comparison to the ammonium nitrate and urea without inhibitors, and is significantly more expensive, the farmers decided that it was not a good business decision to continue using it. In light of the benefits that the literature suggests, the group felt that it had under-performed. In order for them to continue using it, they felt that it would need to be substantially subsidised to make economically viable.

    The group discussed undertaking the methods and although these took a bit of effort, on reflection they were not difficult and could be done, and possibly further simplfied for another trial. The applications of fertiliser were easy, although there were concerns that with the large bags there may have been some deterioration of the products. There will be a longer lead-up time to the next trial giving the group more time to prepare, and they may plan in some more help from the coordinator in gathering samples.

    The farmers commented that they have a deeper appreciation of the methodological rigour and man-power needed in research trials around sampling, and equally the researcher agreed that she better understands the practicalities involved for the farmers in real-world scenarios. The farmers are keen to go out and see other trials, as well as expressing a need to be able to read more publications of real-world on-farm trials.

    The group are taking their results to the wider Exe Vale Farmers group to discuss in May, and will then outline ideas for another trial. They are also interested in using sulphate added to their fertilisers because of deficiencies in their fields.

    Milestone: Results meeting

    January 2018

    Results analysis

    For complete analysis the aim was to get 3 replicates per site, however the group was only able to get these replicates from 2 of the farms involved.

    From these 2 farms one had much stronger results than the other. The best treatment was the ammonium nitrate, with less effective treatments being urea, urea inhibitors and the control which was least effective.

    The differences found in the two trial sites could be due to environmental variables such as location, rainfall data, ammonia losses etc. A results analysis is underway and will be posted under the Field Lab Documents section soon.

    Milestone: Results meeting

    December 2017

    Progress meeting

    Of the 5 trial farms only 2 managed to follow the protocol throughout the whole trial period due to unforeseen circumstances and practicalities that made this difficult. One farm wasn’t able to continue the trial after putting the fertiliser on due to other work commitments. Another farm was late in applying the 3 mixes (urea, ammonium nitrate and urea inhibitors) and ended up doing 3 applications at higher doses. The third farm did not apply the required 25 kg of N, and instead applied 25 kg of their standard fertiliser product (which would not have had the same concentration of nitrogen as the alternative).

    Milestone: Progress meeting

    August 2017

    Plate meter readings

    Results were taken by the farmers themselves using plate meter readings. Plate meters measure the height and density of the sward and give an estimation of the field cover. The majority of the 5 trial farms had their own plate meter and took measurements every 7-10 days alongside the rest of their farm.

    Milestone: End of data collection

    August 2017

    Triallist update

    The coordinator has been in contact with the participating farmers for an update/ feedback on the trial:

    • One triallist has sent through plate meter data, which under first inspection shows little differences other than reduced growth, (as expected, from the control plot).

    • This farmer has also observed the growth of the control plot dropping off a lot now it’s getting later in the growing season which the coordinator advised should show up over the next few plate meter readings.

    • The coordinator is hoping to visit some of the trial sites soon when they hopefully have a lot of cover which should make visual differences most obvious.

    Milestone: Monitoring

    May 2017

    Trial check

    Jack from Creedy Associates has visited the trial sites to check on progress.

    The trial is progressing well so far, despite it being an unusually dry for the time of year, with very little rainfall last month (April). A heavy dew has been sufficient enough to start breaking down the treatment fertiliser however. Jack has started plate metering the trial plots and took photos (see the activity feed - requires log-in). Currently the grass is short due to grazing so differences are not visible yet, however, with the visit later in the year the grass will be longer and effects should become more apparent.

    Milestone: Start of data collection

    March 2017

    Starting the treatments

    There has been a delay on the fertiliser getting to trial farms (delivered late March) and the farmers will have started applying on the 1st April with the first 50 kg target application. This means that the original timeline of application in February/March has been delayed.

    This delay may mean that the trial farms may not be able to reach their target application in September and be 50 kg off. This is not expected to significantly effect the trial and the group will monitor and adapt through the season where possible.

    Milestone: First application

    January 2017


    Comparisons will be made between:

    • UREA

    The trial has been kept simple in design so that a robust small set of data can be analysed.

    - Four treatments in minimum 12 m bands, depending on fertiliser spreading width.
    - Strips will incorporate effect of slope in the field. The trial field will be split into 4 strips, one for each treatment.
    - Between these strips boundaries will be incorporated to avoid cross-contamination of treatments.

    Milestone: Methods finalised

    January 2017

    Aim of the field lab

    To improve knowledge of which fertiliser increases nitrogen capture on grassland (resulting in improved grass growth) and minimises nitrogen losses to the environment via ammonia losses and nitrate leaching.

    To conduct a robust and practical research trial into the efficiency of different grassland fertilisers to determine which type of product is taken up by the grass more efficiently. This would be measured by looking at the grass response to nitrogen applications by measuring grass yield (DMt/ha/yr).

    The group ultimately want to reduce their artificial fertiliser use and reliance in the long term, and reduce their environmental impact, through greater precision and much more efficient use of inputs when they are needed. This is a whole farm approach where (as mentioned in the group description above) the farmers are already knowledgeable on alternative sources of nitrogen. This group specifically are keen to have a field lab to identify how to fertilise better in a much more efficient way. This is stage one of a process where grassland management will be investigated in different field labs over time.

    Milestone: Start of project

  • Findings

    May 2018

    Trial results

    Five farmers from the Exe Vale cooperative group were interested in trialling the differences in grass growth between their standard practice of ammonium nitrate, used to top-up their grassland nitrogen levels, against urea and urea + urease inhibitor. Research has shown that there can be greater grassland yields from the latter fertilisers if applied prior to rain, and that greenhouse gas emissions are lowered when using the inhibitor, which is being recommended as best practice. This presented an opportunity for the farmers to trial these different fertilisers and see the effect on their own fields.

    The three fertiliser amendments were applied in strips across each farmer's field, these were control (no fertiliser), urea, ammonium nitrate (AN) and urea + urease inhibitor. A plate meter was used to measure the grass growth in each strip before application, before grazing and after grazing, repeated weekly. Variable fertiliser rates were used by four farmers (ranging from 25 – 62.5 kg N / ha-1) and a set rate by two (one at 55 kg N / ha-1 and the other 125 kg N / ha-1) across the season from May – October.

    The results show that generally there was little difference in the performance on grass growth of the three nitrogen fertilisers examined, with results varying across the four sites and across the growing season at each of the sites.

    On Farm E, a general trend of greater dry matter yield earlier on in the growing season (April – May) was observed under the AN and urea + inhibitor treatments relative to the urea alone treatment. On Farm C after grazing periods the urea + urease inhibitor and subsequently the urea treatment gave highest yields. The other two farms did not show any significant difference in grass yield between treatments at any measurement points through the season.

    As the urea + inhibitor was more expensive than their usual application of AN and comparatively didn’t increase grassland yields, the farmers feel there is little incentive to use this fertiliser. Other research since carried about by the field lab researcher has shown that greenhouse gas emissions are significantly reduced by the inhibitor, and the farmers are positive about using it if it becomes more economically viable.

    The farmers feel that this was a very worthwhile trial to carry out and commented that they have a deeper appreciation of the methodological rigour and man-power needed in research trials around sampling. Equally, the researcher agreed that she better understands the practicalities involved for the farmers in real-world scenarios. The farmers are keen to go out and see other trials, as well as expressing a need for there to be more publications of real-world on-farm trials to read.

    Please log in for free and download the full results in the ‘field lab documents’ section.

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