Nitrogen use efficiency and N<sub>2</sub>O and NH<sub>3</sub> losses attributed to three fertiliser types applied to an intensively managed silage crop

Cowan, Nicholas; Levy, Peter; Moring, Andrea; Simmons, Ivan; Bache, Colin; Stephens, Amy; Marinheiro, Joana; Brichet, Jocelyn; Song, Ling; Pickard, Amy; McNeill, Connie; McDonald, Roseanne; Maire, Juliette; Loubet, Benjamin; Voylokov, Polina; Sutton, Mark; Skiba, Ute

doi:https://doi.org/10.5194/bg-16-4731-2019

Articles | Volume 16, issue 23

https://doi.org/10.5194/bg-16-4731-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-16-4731-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 23

Research article

|

13 Dec 2019

Research article |

| 13 Dec 2019

Nitrogen use efficiency and N₂O and NH₃ losses attributed to three fertiliser types applied to an intensively managed silage crop

Nicholas Cowan, Peter Levy, Andrea Moring, Ivan Simmons, Colin Bache, Amy Stephens, Joana Marinheiro, Jocelyn Brichet, Ling Song, Amy Pickard, Connie McNeill, Roseanne McDonald, Juliette Maire, Benjamin Loubet, Polina Voylokov, Mark Sutton, and Ute Skiba

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Final revised paper (published on 13 Dec 2019)
Preprint (discussion started on 10 Apr 2019)

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Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Referee comments', Anonymous Referee #1, 24 Apr 2019
- AC1: 'Response to reviewer 1', Nicholas Cowan, 13 Jul 2019
RC2: 'Referee Comment', Anonymous Referee #2, 01 May 2019
- AC2: 'Reply to Reviewer 2', Nicholas Cowan, 13 Jul 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (24 Jul 2019) by Andreas Richter

AR by Nicholas Cowan on behalf of the Authors (15 Aug 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Aug 2019) by Andreas Richter

RR by Anonymous Referee #2 (21 Aug 2019)

Suggestions for revision or reasons for rejection

I appreciate that the authors took the time to revise the manuscript. However, a few of my comments have not fully been addressed by the authors. Therefore, I would like to reiterate a few minor points, which only concerns data presentation and statistical analyses.

In my previous review I pointed out that there was an interesting pattern in the yield data and suggested that it might be worth to explore other statistical approaches. I understand that separating the data set is not the right way but the analyses need to take into account the variability between fields. For example, it might be worth to work with response ratios, a way to make data comparable between fields, or do a mixed effect model including “field” as a random effect. Maybe the authors did that but I just don’t know because the statistical analyses are not described. This brings me to my next point. The authors agree that the description and reporting of the statistical analyses is missing, arguing that it has little relevance to the study. Well, it is somewhat important, as, hopefully, I’ve made my point above. At least, the authors need to mention somewhere the type of analysis applied.

Regarding Figure 4, I was asking if there are no error bars and suggesting that there might be an outlier in their data set, making it impossible to compare 2016 Event 2 to the others. 500 mg N/kg for ammonium just seems a lot. Doing a back-of-the-envelope calculation: The fertilizer application of 70 kg N/ha equals roughly 30 mg N/kg, assuming a bulk density of 0.7 g/cm3 and 30 cm soil depth. This means that the ammonium concentration at that one time point is approximately 15-fold higher than the fertilizer added. Anyway, it would have been easier to assess this if there would be some sort of measure of the variability of the replicated plots displayed in the figure. The authors argue that it is exceptionally difficult to display meaningful error bars. In my opinion, showing the mean and the standard deviation of the four replicates is meaningful. Figure 3 shows each plot, which helps to assess the variability of the replicated plots. Figure 4 also needs to show somehow the variability of the replicated plots.

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ED: Publish subject to minor revisions (review by editor) (06 Oct 2019) by Andreas Richter

AR by Nicholas Cowan on behalf of the Authors (09 Oct 2019) Author's response Manuscript

ED: Publish as is (18 Nov 2019) by Andreas Richter

AR by Nicholas Cowan on behalf of the Authors (18 Nov 2019) Manuscript

Short summary

Commonly used nitrogen fertilisers, ammonium nitrate, urea and urea coated with a urease inhibitor, were applied to experimental plots. Fertilisation with ammonium nitrate supported the largest yields but also resulted in the largest nitrous oxide emissions. Urea was the largest emitter of ammonia. The coated urea did not significantly increase yields; however, ammonia emissions were substantially smaller than urea. The coated urea was the best environmentally but is economically unattractive.

Nitrogen use efficiency and N2O and NH3 losses attributed to three fertiliser types applied to an intensively managed silage crop

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Nitrogen use efficiency and N₂O and NH₃ losses attributed to three fertiliser types applied to an intensively managed silage crop