Catch Crops in Lower Saxony—More Than 30 Years of Action against Water Pollution with Nitrates: All in Vain?

Comments of reviewer 1

Answers

Really interesting study overall. Difficult for me to review as I’m not familiar with these programs. To make the study accessible to those in the US, authors need to continually remind us of the nature of various programs, and carefully define acronyms in first use. Table 2 provides very useful comparison but requires quite a bit of study.

Thank you for your comment from the viewpoint of an oversea’s reader. We are used that readers are familiar with the situation in Europe, but have to keep in mind the international viewpoint.

The English needs a thorough read through yet, there are quite a few typos throughout.

There will be a proofreading now.

L 16 I’m unfamiliar with the term “document analysis”- sort of a meta-analysis or lit search?

Document analysis should imply a research including all kind of documents, revised literature, “grey” literature, e.g., reports and statistics

L 18-19- fascinating incr in subsidized/decrease in non subs! What’s the total acreage of the area?

We added the acreage of total arable land: 1,880,000 ha; we also added total acreage and total acreage of agricultural land.

L43 what are “cooperation areas”?

We inserted the definition: cooperation areas are water protection and abstraction areas, where water suppliers subsidize farmers to apply measures against (ground)water pollution

L 44 what is UAA?

Utilized agricultural area

L 43-47- interesting background essentially showing lightly more manure than mineral N over time. But the two reporting windows are confusing. Are you comparing 1998 to 2018 and then 2009 to 2018? Or are these rolling averages? And why focus in on 2009-2018? Did more of the reduction happen 1998-2009?

The reporting windows are due to the availability of data reported: we’ve compiled and mixed data which are usually reported separately. The focus is on the period 2009-2018, because there exist this evaluation of again increasing concentrations of nitrate in groundwaters

L 62 would like to see clarity about this “estimate”- based on a model or back-of the envelop or ?

Estimate in the sense of expert’s opinion; possibly “assess” is the better word in this context

3.1 Interesting definitions. This is not how these terms are used in the states, so it’s very helpful to have them defined here. However I do think farmers are often interested in multiple benefits, even if policy-makers are focused on one or another of these functions of the c&c practice.

I agree, farmers want all effects of c&cs at once, but high gains in large biomass on top and below soil surface are gained at the expenses of water protection against nitrate leaching; this is the reason a farmer is paid for implementing catch crops

L 111-112 prove not proof, other grammatical issues in this sentence

Thanks!

L 113 not clear why this idea about ET “therefor” follows the previous idea on N leaching and legumes.

See also comment under 3.1: if c&cs are grown to prevent leaching, fertilization would reduce efficiency, as cited literature show

L 120 “protect” not prevent?

Indeed, thanks!

L 143-144 the harvest doesn’t seem to me to be essential to the definition, but perhaps you want to make it clear that’s a local practice of interest?

The definition is necessary in the legal context, as fertilization is only allowed in case plant biomass is removed from the field

L 162- this advisory service is the farmer advising? To implement c&cs?

The implementation of c&cs is included in the advice, but farm advice covers many aspects of s.c. good agricultural practice

3.2 This section is a bit hard to read. I like the timeline of programs, and the table. What can the narrative add to this? What is the most important aspect of each program for the reader to understand?  

Thanks, we transferred the timeline further up, we hope it is better to read now.

L 196-202: I don’t think it’s necessary to repeat these pieces of info from the table in the text.

True, but it gives a good overview of what in presented on the next pages

L 204: what is “IE”?

This abbreviation is the “name” of the program

L 250: what is “EFA”? used multiple times and not defined.

Thanks, now explained in line 178

Fig 3: “cooperation areas” don’t show up on map in turquoise but blue.

This I think is the influence of your monitor

L 375 does this mean that each farmer negotiates an individual subsidy for the c&c practice?

Almost, not each farmer by himself but farmers of one cooperation area with the water supplier responsible

Fig 6 the second box is very confusing.

Thanks, we redesigned the figure and merged it with Fig 7

L499 typo winter_hardiness

Thanks!

L502 typo period not perion

Thanks!

Sect 4.1 I think this section might be more clearly organized. There is interesting discussion of fertilization regulations, but it should proceed more promptly to this idea of the windfall effect, and farmers choosing the c&c program with the loosest regulations- those are the key ideas here.

We reorganised the conclusion part, thanks!

L 494: Why is it a problem to dispose of manure on c&cs? Don’t the c&cs take up the N and P in manure?

See also comment under 3.1: if c&cs are grown to prevent leaching, fertilization would reduce efficiency, as cited literature show

L 505-508: this is a really striking point. I think it should be highlighted, perhaps earlier in the discussion.

We reorganised the conclusion part, thanks

L 532 typo subsides

Thanks!

L 540 I need some more detail on the results-based scheme. Do farmers get paid after water quality improves? Is the c&c required, and once water quality improves, the payment is a bonus? How to manage the time lag?

Interesting questions from your side: For the result-based approaches, farmers get paid if certain indicators are reached, e.g., autumn/after harvest mineral N concentration in soil. This is an instant indicator (almost) no time lag, but may fail due to irregularities in weather conditions. In this case a sort of correction factor could help to adjust the target value applicable

The details are quoted in the cited literature

Fig 8: could include this just once as Fig 6, with the dotted red line

True, we try to also improve Fig. 6.

L 562 typo stronger

Thanks, more strongly?

L 567: Delete preface of this statement, the powerful conclusion that C&C did not contribute to water protection should lead.

We rearranged the whole chapter, thanks!

L 579 I don’t understand this sentence. If the results-based measure is mandatory, why would subsidy level matter?

In addition, or on top, result-based measures could be applied, as the mandatory application of c&cs will not be sufficient to reach target qualities of ground water

Line 20: replaced dot at thousands digit with comma

Thanks, I did so.

Line 37: replace 90ies with the 90s

Thanks!

Line 44: the abbreviation UAA is not yet explained here

Thanks!

Line 52: insert according to EC Groundwater Directive

Thanks!

Line 102-144: part of the definition could be transferred to the M&M section

Thanks for your viewpoint. Indeed, the definitions were first part of the M&M section but we transferred it, as there is quite some interpretation linked to the definitions. Only transferring part of the definitions would reduce the comprehensibility.

Line 250, Figure1: the abbreviation EFA is not defined until line 337 and is already used here for the first time

Thanks, we now defined EFA in line 178

Line 252: undersawn

Thanks!

Table 2a-d: the date format is inconsistent, e.g., 15^th, 15 th, 15^thSept., 15th February

Thanks, I checked the data format, hope it is consistent now: 15^th September

Table 2a: line2 C&c lowercase; line 14 fertilization

Thanks!

Table 2b: line 14 fertilization; line 16 destruction

Thanks!

Table 2c: line 14 fertilization; Ntot under the table, subscript

Thanks!

Table 2d: line 14 fertilization

Thanks!

Figure 4: stars in the figure label are not explained

Data sources are in the table which has been transferred to the Appendix, I will refer to it

Line 305/309/311: replace 1990ies with the 1990s

Thanks!

Line 313/319/333: replaced dot at thousands digit with comma

Thanks!

Figure 5: the unit ha in the figure labeling is not necessary

Yes, I removed them!

Table 3: replaced dot at thousands/million digit with a comma; specification

Thanks!

Figure 6: the figure is not referenced in the text and does not provide any new or summarizing insights, should be omitted

We merged figure 6 and 8 and improved the lay-out

Line 512: the abbreviation ND is used here for the first time and is not explained

Thanks, we inserted the full text

Figure 7: the figure provides new information and should be included in the results section

We followed your advice, thanks!

Figure 8: the figure is not referenced in the text and does not provide any new or summarizing insights, should be omitted

We merged it with figure 6

Line 20: replaced dot at thousands digit with comma

Thanks, I did so.

Line 37: replace 90ies with the 90s

Thanks!

Line 44: the abbreviation UAA is not yet explained here

Thanks!

Line 52: insert according to EC Groundwater Directive

Thanks!

Line 102-144: part of the definition could be transferred to the M&M section

Thanks for your viewpoint. Indeed, the definitions were first part of the M&M section but we transferred it, as there is quite some interpretation linked to the definitions. Only transferring part of the definitions would reduce the comprehensibility.

Line 250, Figure1: the abbreviation EFA is not defined until line 337 and is already used here for the first time

Thanks, we now defined EFA in line 178

Line 252: undersawn

Thanks!

Table 2a-d: the date format is inconsistent, e.g., 15^th, 15 th, 15^thSept., 15th February

Thanks, I checked the data format, hope it is consistent now: 15^th September

Table 2a: line2 C&c lowercase; line 14 fertilization

Thanks!

Table 2b: line 14 fertilization; line 16 destruction

Thanks!

Table 2c: line 14 fertilization; Ntot under the table, subscript

Thanks!

Table 2d: line 14 fertilization

Thanks!

Figure 4: stars in the figure label are not explained

Data sources are in the table which has been transferred to the Appendix, I will refer to it

Line 305/309/311: replace 1990ies with the 1990s

Thanks!

Line 313/319/333: replaced dot at thousands digit with comma

Thanks!

Figure 5: the unit ha in the figure labeling is not necessary

Yes, I removed them!

Table 3: replaced dot at thousands/million digit with a comma; specification

Thanks!

Figure 6: the figure is not referenced in the text and does not provide any new or summarizing insights, should be omitted

We merged figure 6 and 8 and improved the lay-out

Line 512: the abbreviation ND is used here for the first time and is not explained

Thanks, we inserted the full text

Figure 7: the figure provides new information and should be included in the results section

We followed your advice, thanks!

Figure 8: the figure is not referenced in the text and does not provide any new or summarizing insights, should be omitted

We merged it with figure 6