Peat Substitution in Horticulture: Interviews with German Growing Media Producers on the Transformation of the Resource Base
Round 1
Reviewer 1 Report
The paper presented for review concerns a very current problem of replacing peat in horticultural production with renewable materials. The problem raised in the publication also concerns container forest nursery, which in Poland is mostly based on substrates produced on the basis of peat. For 2 years now in Poland we have been facing the problem of the availability of peat substrates and a rapid increase in prices for peat. The substrate used in Poland came mainly from Scandinavia, but also from the Belarusian market, a location that is increasingly difficult to access in the current geopolitical situation. The conducted discussion is consistent with the conclusions regarding the market of buyers of peat substrates for container nurseries in Poland. The publication is well written, and definitely worth printing..It also seems to me that the publication is a bit too detailed, and too long, I suggest you think about making some shortcuts
Author Response
Thank you very much for your positive comments. On the length: the text was shortened of around 1 page, especially by removing some paragraphs of the section 3.3 which presented redundancies. Some elements were transferred to the previous section 3.2, no information was lost.
Reviewer 2 Report
It is a very well written paper. To me as regards growing media materials there is nothing new here. In the Introduction section to set the scene for the reader, the following points given below should be included . The four well known non peat materials materials were considered, that is woodfiber, bark, composted greenwaste(CGW), and coir. It would have been good if problems and properties with these materials. e,g N immobilization with woodfiber, high bulk density and EC with composted greenwaste and composted bark, nutrients present in these materials in contrast to peat, were highlighted Regarding pine bark does it need “composting” ?. Even with coir there is ordinary washed coir and buffered coir with different properties should have been mentioned. It should be made clear that some materials can be used as an ingredients e.g woodfiber, and others as complete replacement e.g composted bark and coir. The emerging materials, biochar etc should have been not only mentioned but their future potential discussed .There is little or no mention of EU dimension to the policy of peat harvesting. In Germany if peat harvesting ceases peat would still come to Germany for the professional grower from Northern Europe e.g. Baltic states. Will peat harvesting in EU countries continue in these states in the foreseeable future? A very informative table or something similar which one of the authors presented in a Working Paper should be included in the "Introduction" section to set the scene. In other words their excellent working paper (reference 37, Thunen Working Paper 190) in which has almost all the above points mentioned by me and discussed, could be summarized and briefly elaborated in the "Introduction" Section. In my opinion this will improve the paper.
One question that was not put to the growing media producer was their opinion/ view, that peat importing from distant countries even in Europe with the attendant road and ship miles is better from environmental point of view than local peat production over the transition period.
One question: Table 1.. Total number of companies were 9 and the media production was 350,550 M3 while production from 81 companies was 97,690 M3, less than the 9 companies.It appears that the whole German industry produces less than the 9 companies. Is the shortfall covered by imports. Please clarify.
In Fig 6, the high pH of composted green waste was considered a negative point by some of the respondents. In fact is often a positive point when mixed with peat, as lower rates of dolomitic lime e.g 1 kg/M3 is sufficient. It also contains sufficient K and micronutrients, thus saving on lime and micronutrients. Similarly composted bark has nutrients e.g P and K. Need for education and research! Should the authors make such critical comments in the paper to the answers from the growing media producers in this paper I do not know!!!It is okay from me for the authors to decide!
Author Response
Thank you very much for the positive feedback as well as for the detailed review which lead to significant improvements on the manuscript. We structured your comments using numbers and answered accordingly.
(1) It would have been good if problems and properties with these materials. e,g N immobilization with woodfiber, high bulk density and EC with composted greenwaste and composted bark, nutrients present in these materials in contrast to peat, were highlighted. Regarding pine bark does it need “composting” ? Even with coir there is ordinary washed coir and buffered coir with different properties should have been mentioned. It should be made clear that some materials can be used as an ingredients e.g woodfiber, and others as complete replacement e.g composted bark and coir.
Answer: Thank you for these suggestions. A paragraph with more information and literature on the properties and the use of alternative growing media constituents have been included in the introduction (lines 106-134). Especially, the aspects mentioned in the review have been addressed.
(2) The emerging materials, biochar etc should have been not only mentioned but their future potential discussed.
Answer: Thank you for this comment which led to improve the discussion part. We added a commentary in paragraph 3.3, line 500, and in 4.2, line 650.
(3) There is little or no mention of EU dimension to the policy of peat harvesting. In Germany if peat harvesting ceases peat would still come to Germany for the professional grower from Northern Europe e.g. Baltic states. Will peat harvesting in EU countries continue in these states in the foreseeable future? A very informative table or something similar which one of the authors presented in a Working Paper should be included in the "Introduction" section to set the scene. In other words their excellent working paper (reference 37, Thunen Working Paper 190) in which has almost all the above points mentioned by me and discussed, could be summarized and briefly elaborated in the "Introduction" Section. In my opinion this will improve the paper.
Answer: We included the countries in which political goals were formulated (line 65). We also included a commentary on political action concerning peat extraction (non-existent) and our appreciation on the future of imports and peat extraction in the EU (line 72). We decided not to include the detailed table on political initiatives presented in the Thünen Working Paper 190 in order to limit the length of the paper, which we tried to reduce following the advice of another reviewer, but added a reference to it for further information (line 66).
(4) One question that was not put to the growing media producer was their opinion/ view, that peat importing from distant countries even in Europe with the attendant road and ship miles is better from environmental point of view than local peat production over the transition period.
Answer: Thank you for this remark. This aspect was mentioned although not directly asked. We mentioned the idea in the text in the paragraph 3.2.3, line 382.
(5) One question: Table 1.. Total number of companies were 9 and the media production was 350,550 M3 while production from 81 companies was 97,690 M3, less than the 9 companies.It appears that the whole German industry produces less than the 9 companies. Is the shortfall covered by imports. Please clarify.
Answer: Thank you for bringing this misunderstanding to our attention. 97,690 M³ is the average production per company. Only the activity within Germany was considered. We modified the Table to make it clearer.
(6) In Fig 6, the high pH of composted green waste was considered a negative point by some of the respondents. In fact is often a positive point when mixed with peat, as lower rates of dolomitic lime e.g 1 kg/M3 is sufficient. It also contains sufficient K and micronutrients, thus saving on lime and micronutrients. Similarly composted bark has nutrients e.g P and K. Need for education and research!
Answer: Thank you for this indication. These aspects are probably seen as disadvantages due to the history of peat-based growing media and the structure of large-scale horticulture production. Unfortunately, the expertise of the authors is not sufficient to assess the statements of the interviewees on the properties of constituents. But the need for education and information is worth discussing and was included as a potential transformation factor in the discussion 4.2., line 648.
(7) Should the authors make such critical comments in the paper to the answers from the growing media producers in this paper I do not know!!!It is okay from me for the authors to decide!
Answer: Thank you for notifying this. We would be glad to know what comments you considered critical to the answers of the interviewees and, if necessary, to modify them. Actually, we considered the answers from the interviewees the base of our interpretations and did not mean to contradict them with our conclusions.
Reviewer 3 Report
Well written manuscript and quite usefull for all those involved in managing a valuable natural resource a is peat.
Only a few points on english.
Comments for author File: 
Comments.pdf
Author Response
Thank you very much for the attention paid to our manuscript. We followed most of your suggestions. We only kept the term “constituent” due the context of growing media production in the sentence and as used in literature, for example Schmilewski 2017 “Growing media constituents used in the EU in 2013”. The apparent mistake in Table 1 was a misunderstanding which was also noticed by another reviewer, thank you for bringing our attention to it. We hope that the modifications provide clarity.
Reviewer 4 Report
Reviewer comment to manuscript horticulturae-2500438
[Peat substitution in horticultural growing media: Interviews with the German industry on the transformation of the resource base]
The subject of the work is interesting about the high practical use, because peat has been the main component of rooting media for plant production for many years. However, it should be noted that peat is one of the non-renewable environmental resources, and its consumption causes the exploitation and degradation of valuable and endangered ecosystems such as peatlands. Therefore, further research on the use of alternatives to peat additives to growing media is necessary.
Research was conducted on the replacement of peat in the construction of growing substrates, through the use of e.g. vermicompost or compost. But here the problem is the unstable content of macro-, microelements and heavy metals in different batches of the produced biofertilizer - it depends on the characteristics of the initial biomass. Therefore, it is recommended to use substitutes for peat in the production of growing media, but on a small scale, locally, where, on the site of production of these media, e.g. vermicompost or compost from homogeneous initial biomass will be produced.
MS was prepared really well. The purpose of the work was properly implemented and presented.
Author Response
Thank you very much for your input. The aspects that your mentioned – environmental impacts of peat, quality challenges and local resources – were largely and hopefully sufficiently mentioned in our work. Thanks you for the positive comments on the manuscript.
