Thu 18 Oct 2018 8:06PM

Adding urease inhibitors to Overseer

AW Antony Williams Public Seen by 198

This discussion thread has been created to discuss the attached plan for adding urease inhibitors to Overseer.

We have invited experts or companies known to be involved in the supply of urease inhibitors, or have undertaken research or have expertise in the use of urease inhibitors (the group). Please advise of additional people who should be part of this group.

We are asking that you review this plan and add any comments to this discussion, particularly any that relate to errors or additional information that would materially change the implementation. Others in the group can see these comments and additional responses added so that a consensus is arrived before voting on the plan.

If you are not an invited reviewer but have comments that may materially affect the implementation plan, please leave a comment.

Once you are ready to vote please review the proposal on the right of this discussion and vote accordingly.


Poll Created Thu 18 Oct 2018 8:09PM

The proposed plan for adding urease inhibitors is acceptable Closed Fri 2 Nov 2018 4:02AM

We ask that you vote on whether the implementation plan, as outlined in the implementation section of the attached document, is acceptable for inclusion in Overseer.

If the majority find it acceptable, the implementation plan will be actioned, taking into account any comments made. If the majority find it unacceptable, the implementation plan will be re-worked based on comments received.

Note that additional questions are highlighted within each section of the document, in summary we are asking for the following:
• That the way products are proposed to be entered into the software is sensible and understandable in relation to practical management activities
• Confirm that given the research findings it is acceptable to set the effectiveness of urea treated with nBTPT at a rate of 250 ppm or more as 0.45
• Confirm that given the previous research scope and lack of supporting data, it is not possible to implement a site-specific approach
• To identify if there are any errors or additional information that would materially change the


Results Option % of points Voters
Agree 100.0% 3 AR ME IP
Abstain 0.0% 0  
Disagree 0.0% 0  
Block 0.0% 0  
Undecided 0% 8 GR AW CR AM NM

3 of 11 people have voted (27%)


Ants Roberts
Thu 25 Oct 2018 12:24AM

See my comments in discussion.


Joel Gibbs
Sun 28 Oct 2018 8:33PM

I agree with the proposal. The planned implementation is consistent with the current inventory methodology. The inventory also makes use of the same research that is referenced in the methodology research.


Surinder Saggar Tue 23 Oct 2018 9:25PM

I support this proposal plan of adding UIs and support further research to assess the UIs impacts on reducing ammonia emissions. Using a excreta-N deposition rate of 119.5 kg N head-1 yr-1 for dairy cattle (Ministry for the Environment, 2018), the annual losses of NH3 from deposited excreta in NZ dairy pastures is estimated to have a value of about $94 million, of which urine accounts for about 60–70%. Similarly, a press release by Ballance Agri-Nutrients (2015) reported that $30 million of urea fertiliser is lost annually as NH3 in NZ and most of which is from dairy farms.


TerraCare Fertilisers Sun 28 Oct 2018 11:04PM

I support this proposal. I think its very important to include mitigation methodology around different nutrient forms and inhibitors into the model as much as possible so the industry can clearly project the mitigation's possible in each agricultural enterprise. I am not an expert in the assessment of this particular method but the approach seems logical in its assumptions of requiring a 'buffer', and the methods effectiveness across variable situations. Until more information comes to hand via research (perhaps particularly on different soils), the current methodology appears well thought out and applicable.
I would like to see a less biased language used for these mitigation's. For example Agrotain is a trade mark for only one company and the use of language outlining it as the pseudonym for nBTPT could cause unintended exclusion of other companies products using the same methodology

Other questions we have:
1) Does the question around nitrogen application center more around factors such as application type (incorporation vs surface).
2) The use of urease inhibitors infers that the climate and growth conditions are sub optimal for the use of urea without an attached inhibitor. Hence if an inhibited urea is used in conditions where urea is optimal, there is no actual benefit to using an inhibitor and therefore it should not then be modeled as a benefit.


David Wheeler Tue 30 Oct 2018 8:17AM

Fair comment about bias. We will update the document to reduce this.
The question around nitrogen application is whether their are factors related to application (e.g. rate, method) that should be considered. Incorporation v surface application is an options for cropping systems, and information was found to indicate that incorporation reduces effectiveness.
Note sure about point 2. In the model the use of urease inhibitor simply implies they are used - the data didn't indicate that conditions had any effect on its effectiveness. In sub-optimal conditions I would expect that plant growth and hence uptake would be less, and hence there would be more N in the soil that could potentially be denitrified or leached.


Alister Metherell Wed 31 Oct 2018 10:15PM

Can you confirm that there is an error in the opening paragraph " In the agricultural inventory method, emission factor for volatilisation from N fertiliser treated with a urease inhibitor is 0.55 (FracGASFnFert(UI)), and 0.1 otherwise (FracGASFnFert(non-UI))."?
Surely the emission factor for an N fertiliser treated with a urease inhibitor should be 0.055, not 0.55


Alister Metherell Thu 1 Nov 2018 12:16AM

I was looking for more information on the Overseer N volatisation model, so I looked in the Overseer Technical Manual for Fertilisers July 2018. There is a description there with many references to Woodward 2008. However Woodward 2008 is not listed in the references in that document. It looks like Woodward 2001 was mistakenly included in the references instead. What is the Woodward 2008 paper that is referenced in the Characteristics of Fertiliser Technical Manual?


Alister Metherell Thu 1 Nov 2018 12:22AM

Perhaps it was meant to be "Wheeler , D.M. ; Ledgard , S.F. ; Deklein , C.A.M. (2008) Using the OVERSEER nutrient budget model to estimate on-farm greenhouse gas emissions. Australian journal of experimental agriculture, 2008, Issue 1, pp.99-103"
Can you please upload this paper.


Caroline Read Thu 1 Nov 2018 11:40PM

Thanks Alister - David is on the road today and so has let me know a couple of points to follow up as the thread expires today. He will check the unit (though it doesn't impact on the implementation methodology) - Joel if you could also check the inventory that would be good. He will also follow up the reference in the manual (he suspects its a Woodward 2008 paper) to make sure the right one is referenced - though this is outside the scope of the methodology being considered in this thread - so will take that offline.


Caroline Read Sun 4 Nov 2018 8:09PM

Hi Everyone - thank you so much for your input and comments and for those of you who clicked on the green Agree decision button. We have been able to capture a couple of updates/checks through this process and will post the updated implementation methodology document shortly. Given we didn't have any disagree votes we will now progress with implementing this solution. Thank you and please let me know how you found this process as we look for ways to enable involvement in the modelling.


Joel Gibbs Mon 5 Nov 2018 1:45AM

Looking through the paragraph that Alister commented on (the second in the document, starting with "The effect of urease inhibitors in..." ):

1: FracGASFnFert(UI) should be 0.055 rather than 0.55.
2. We probably shouldn't refer to FracGASFnFert(UI) and FracGASFnFert(non-UI) as emission factors, as these only calculate the fraction of fertiliser N that volatilises as NH3 or NOx. The N volatilised in these gasses is later multiplied by EF4 (which is the ef for N2O emissions from volatilised N, which is 0.01) to calculate N2O emissions.

Equations one and two in the document are still consistent with the inventory approach.


Caroline Read Fri 9 Nov 2018 9:40PM

Again - thank you all for your input into the development and confirmation of the methodology to implement urease inhibitors in Overseer.
David has revised the document to capture the corrections and amendments identified (attached). This has now been provided to the Dev team and they will work with the science team to implement and test this in Overseer. We will keep you posted on progress.