Effects of Drainage Water Management in a Corn–Soy Rotation on Soil N2O and CH4 Fluxes
, Thomas R. Fisher 3, Rebecca J. Fox 3,4, Qiurui Zhu 1, Anne B. Gustafson 3, Erika Koontz 3,5, Mark S. Castro 1 and James Lewis 6Round 1
Reviewer 1 Report
1) Using a list of lumped references is not helpful to the readers. At least a short justification should be provided - individually. See "Both nitrification and denitrification can contribute to large N2O emission spikes, especially when high soil nitrate concentrations co-occur with high soil moisture conditions [23-25]." etc.
2) It is necessary to describe the novelty of the work more in relation to the existing articles. There is a need to comment more on the benefits and weaknesses in existing publications. The contribution of the work needs to be described more.
3) 2.1. Study Site Location: Does the choice of the site have any justification in light of previous studies?
4) Figure S4: The results for R2 on figure S4 look very debatable. In addition, the significance of the model seems to be due to outliers. Try to omit values above 40. I dare to estimate that the p-value will increase and the model may even be statistically insignificant. And the coefficient R2, which is already so negligible, will decrease.
5) Fig. 6: After visual inspection, the resulting model appears to identify a small proportion of measurements that are remote from most observations. From this point of view, the statistical results seem questionable. Low R2 supports this thesis. It would be interesting to look in detail at the outliers. Unless they have something similar. The results could be subjected to cluster analysis. Maybe there is some interesting information in the results. The presented regression models seem very debatable and do not provide an answer to the main motivation for the creation of this article. See L73: "While some of these studies did not directly evaluate DWM manipulations, rather just drainage in general, the variability in conclusions means that further research is needed to understand the impacts of this particular BMP on the potential for increased GHGs."
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript “Effects of Drainage Water Management in a Corn-Soy Rotation on Soil N2O and CH4 Fluxes” presented three years of static chamber measurements of greenhouse gas emissions (N2O and CH4) from the soil surface in farm plots with and without drainage water management in a corn-soybean rotation on the Delmarva Peninsula. Drainage water management is the best management practice designed to slow nitrate movement and thereby reduce reactive N loss from agricultural fields that have drainage ditches. The authors investigated the effect of drainage water management on soil greenhouse gas emissions.
The topic is within the scope of the journal.
Due to enormous difficulties in quantifying N2O and CH4 fluxes from a farm plot with and without drainage water management in a corn-soybean rotation, there are very few studies that provide detailed and reliable information. Therefore, these information and new measurements are important to demonstrate the applicability of drainage water management as the best management practice. The manuscript, therefore, deals with an interesting and important topic.
General comments
The paper is well written, easy to follow and comprehensive. The demand for this kind of studies is well indicated and conclusive. There are just some minor concerns about how the study is applied and presented.
- The graphical resolution of several figures is low.
Specific comments
Line 119-120: Please, change the order of DWM and non-DWM in the sentence (A and B should be the first)
Line 133-134: I would extend the sentence with the description of the instrument. Maybe not all the reader knows the piezometers and the reason of the application.
Line 412: Figure 4: quality is low
Line 417: Figure 5: “Red squares represent means”. What are the black lines in the boxes? Median?
Line 470: subscript: N2O and NO3-N.
Line 606: “91-139 kg N ha-1” I got 141 kg N ha-1 instead of 139 kg N ha-1
Line 609: “97 ± 20 kg N ha-1”. It is correct, if we calculate with 141 kg N ha-1 N removal
Supplementary material:
Line 695: Figure S2: quality is very low
Line 698: Figure S3: quality is low
Line 704: Figure S5: quality is low and please use on the y-axis “N2O-N kg ha-1” instead of “N2O-N kg/ha”
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have answered comments sufficiently and in great detail. I consider the revision of the text to be sufficient.
