Crop Residue Management Strategies to Reduce Nitrogen Losses during the Winter Leaching Period after Autumn Spinach Harvest

Round 1

Reviewer 1 Report

The manuscript shows a lot of work done in an specific area.

During the reading the trials and treatments explantion for whiles is confusing. Is it possible to add a capture of the trials and design?

I´m assuming that the crops used and mixture is the way most of the farmers use to work.

I recommend to add more supplementary infomation related with ammonium and nitrate analysis results.

In line 282, do you have any information from other trials or just supposing? 

Some specific details:

Line176: why twice? Wasn not possible only installed the columns after postponed tillage and drilling in late summer ? (line 178-179)

Line 186: m2

Line 335 and 336: the phrase is confusing.

Author Response

Thank you for your valuable comments and suggestions. We used most of the points you mentioned to clarify methodical aspects and to improve the presentation of the results in our manuscript. In the following we would like to respond to your mentioned points in more detail:

During the reading the trials and treatments explanation for whiles is confusing. Is it possible to add a capture of the trials and design?

We think, that using a capture instead of trial 1, trial 2, … will not improve the clarity of the text. Furthermore, the use of abbreviations such as T1 to designate the trials can lead to confusion with the treatments (treatment 1, treatment 2, …).

I´m assuming that the crops used and mixture is the way most of the farmers use to work.

As mentioned at the beginning of sections 2.2 and 4.1, only treatments 1 and 3 are presenting the common practice in the region Borken following autumn-grown vegetables like spinach.

I recommend to add more supplementary information related with ammonium and nitrate analysis results.

With the exception of treatments 2 and 6 only nitrate was detected in the soil samples (see section 3.4). Therefore, in Figures 3-5 only the nitrate concentration is provided. We now add this information also into the text of the section 3.2.

In line 282, do you have any information from other trials or just supposing?

Yes, the results are “described below” (section 3.3). We have now clarified the theorem somewhat.

Some specific details:

Line 176: why twice? Was not possible only installed the columns after postponed tillage and drilling in late summer? (line 178-179)

In treatments 5 and 6, the soil was tilled in late autumn. In order to detect the mineralization between spinach harvest (early autumn) and late tillage (late autumn) as well as from late tillage to early spring we had to install the columns twice. Before and after tillage. We now add a further sentence into the section 2.3 in order to clarify the procedure.

Line 186: m2

0.25 spare meter = 0.25 m^-2 (according to SI units)

Line 335 and 336: the phrase is confusing.

We now clarified this point in sections 3.2 and 3.4 by the explanation, that no NH₄⁺ was detectable in treatments without DMPP application.

Reviewer 2 Report

Dear Colleagues,

your manuscript reports interesting results about the crop residues management in autumn spinach harvest in order to reduce the presence of nitrates onto soil.

In my opinion the title exceeds the limits of the research: the study is focused on organic nitrogen mineralization and nitrates concentration onto soil, others forms of nitrogen losses are not calculated.

The experimental design is well developed, and structured, three years of study with seven different thesis. In my opinion, the experimental approach is adeguate to the purpose of the research. I have only few point to underline:

• row 103: "loamy sand texture", do you mean the USDA classification?
• row 144-149: in the scientific name of plants species, introduce the code of the classifier.
• row 213: the data of nitrates concentration in soil (figures 3-5 and table 3) are in kg/ha. How have you derivate these results starting from N concentrations in soil samples? (How have you calculated the soil bulk density?)

The results and discussion chapters are well organized and I have not comments about these parts.

Best regards.

 

 

Author Response

Thank you for your valuable comments and suggestions. We used most of the points you mentioned to clarify methodical aspects in our manuscript. In the following we would like to respond to your mentioned points in more detail:

In my opinion the title exceeds the limits of the research: the study is focused on organic nitrogen mineralization and nitrates concentration onto soil, others forms of nitrogen losses are not calculated.

In sections 2.3 and 2.4, we describe our measurements and calculations. Indeed, we only determined the NO₃^- and NH₄⁺ concentration in the soil. However, by using the balance approach we were able to calculate the potential N losses during the autumn and winter seasons. This approach was appropriate to distinguish the overall N losses in the treatments.

row 103: "loamy sand texture", do you mean the USDA classification?

We used the classification according to the German DIN 4220. This classification is also described by the German VDLUFA [51]. We now add this information into the section 2.1.

row 144-149: in the scientific name of plants species, introduce the code of the classifier.

Now, we add the taxonomy ID to the botanical name of each species. If you mean another code of classifier, please give us an example.

row 213: the data of nitrates concentration in soil (figures 3-5 and table 3) are in kg/ha. How have you derivate these results starting from N concentrations in soil samples? (How have you calculated the soil bulk density?)

The nitrate and ammonium concentration as well as the bulk density was measured by the soil lab according to VDLUFA [51]. See chapter 2.3

Reviewer 3 Report

Dear Authors,

This manuscript could be suitable for the publication in MDPI Agronomy Journal, however, authors are requested to address the following suggestions while revising the manuscript.

Authors need to state research questions (RQs) and thoroughly revise the introduction section in line with the research objectives

The article is quite long and I suggest that you shorten the introduction and discussion section especially. 

Conclusions
1. The conclusion should be presented in line with RQs.

Author Response

Thank you for your valuable suggestions. The research questions are mentioned at the end of the introduction section. In order to make the conclusion clearer, we now add the research questions also to the conclusion section. However, in the introduction and discussion sections, we want to give the reader a brighter view on recent investigations focusing on the crop residues management of field-grown vegetables. Therefore, we only slightly shorted the discussion section.

Round 2

Reviewer 1 Report

The explanation and small changes made clarified the overall manuscript.