Minimal Necessary Weed Control Does Not Increase Weed-Mediated Biological Pest Control in Romaine Lettuce (Lactuca sativa L., var. Romana)
Round 1
Reviewer 1 Report
Regarding to manuscript titled "Minimal Necessary Weed Control does not Increase Weed-Mediated Biological Pest Control in Romaine Lettuce (Lactuca sativa L., var. Romana)" with Manuscript ID: Horticulturae-1841380.
This study aimed to determine whether it is possible to reconcile the presence of functionally relevant weeds without creating yield losses in Romaine lettuce in open field. This work adequately addresses this issue. The study presented is well designed and carried out at each step. The materials and methods are also well described. The results are encouraging and properly discussed on the basis of the recent scientific literature about this argument. I have only noted two minor errors that need to be corrected:
- L20 define in the abstract the acronym CBC.
- correct numbering 3.5 in the results section.
I recommend acceptance of this work in its present form.
Author Response
Dear Reviewer
thank you for reading and supporting our work. We reply to the comments below.
This study aimed to determine whether it is possible to reconcile the presence of functionally relevant weeds without creating yield losses in Romaine lettuce in open field. This work adequately addresses this issue. The study presented is well designed and carried out at each step. The materials and methods are also well described. The results are encouraging and properly discussed on the basis of the recent scientific literature about this argument. I have only noted two minor errors that need to be corrected:
Thank you!
- L20 define in the abstract the acronym CBC
Done
- correct numbering 3.5 in the results section.
Done.
I recommend acceptance of this work in its present form.
Thank you!
Reviewer 2 Report
There are no reservations to the title of the manuscript, which is suitable for the Horticulturae journal. However, there are a number of deficiencies in the entire manuscript. The authors described the research method very scantily (no mention of the weather conditions, weed calculation formulas, no detailed description of the location of the experiment, no description of the statistical methods). The entire manuscript contains editing errors (different fonts in the descriptions of the figures and tables, diagram 3 – very sloppy descriptions). There are no conclusions from the conducted research. All references fail to comply with the referencing style guide of the Horticulturae journal. The references should also be more up to date. The paper requires a lot of improvements and in its present form, it cannot be accepted for publication in the Horticulturae journal.
Author Response
Dear reviewer
Thanks for reading and commenting our work. We reply in red to your comments below.
There are no reservations to the title of the manuscript, which is suitable for the Horticulturae journal.
Thank you.
However, there are a number of deficiencies in the entire manuscript. The authors described the research method very scantily
no mention of the weather conditions,
We added a sentence in line 112 indicating average Tmin, Tmax and total precipitation during the lettuce growing period for both years.
weed calculation formulas,
We are not quite sure to which ‘weed calculation’ formulas you refer. If you refer to the formulas used to calculate the critical weed-free period, we used four parameter log-logistic models to obtain both the weed-free and weedy curves. Since the formula are well described in Knezevic & Datta (2015) we cited this paper and decided not to render the Materials & Methods section longer by repeating. A standard ‘R’ package was used to create the yield curves and determine the critical period of weed interference: the “drm” function in the “drc” package (Ritz, et al., 2015), which has been cited in the paper (referecen nr 22).
Knezevic, S. Z., & Datta, A. (2015). The Critical Period for Weed Control: Revisiting Data Analysis. Weed Science, 63(SP1), 188–202. https://doi.org/10.1614/ws-d-14-00035.1
Furthermore, we add the weed frequency and cover categories in lines 83-85 as follows:
“Weed species were classified based on their frequency of occurrence (<10%; 10-30% and >30%) and their local cover (<5%; 5-10%; >10%) and the species falling in the highest frequency and local cover category were considered as dominant species.”
no detailed description of the location of the experiment,
In lines 106-112 we describe where the trial was carried out and indicate the exact position of the field (latitude and longitude provided in decimal format). In lines 128-136 we describe exactly the soil conditions and the lettuce management. If you would like to have additional information, please let us know which information is needed.
no description of the statistical methods.
In line 113-120 we describe in detail the experimental layout of the trial, and in section 2.3, lines 162-203 we describe in detail the statistical analyses that have been performed and the R packages used. We think this is the level of detail that is normally provided for the statistical analyses. However, if you have any specific questions about the methods, please let us know which type of information you would like us to present in more detail.
The entire manuscript contains editing errors (different fonts in the descriptions of the figures and tables, diagram 3 – very sloppy descriptions).
Noted. We checked fonts and adjusted them. We have rewritten the heading of figure 3. A colleague, native speaker, has read the paper.
There are no conclusions from the conducted research.
Since the Journal guidelines indicate that a section ‘Conclusions’ is not obligatory, and required only in case the discussion is long and complex, which is not our case, we preferred to keep the discussion and conclusion section together. We have now changed the section nam to ‘Discussion and Conclusions’. Based on a questions from reviewer 3, we have revised part of the Discussion and Conclusions. We hope this has improved clarity also regarding the conclusions from our research.
All references fail to comply with the referencing style guide of the Horticulturae journal.
Sorry, we erroneously used the unformatted reference list. This has now been replaced with the correctly formatted version.
The references should also be more up to date.
To the best of our knowledge, we have cited the latest and most relevant papers in relation to our work regarding functional weed traits analysis (non-existent in horticultural systems). In the introduction and in the discussion, we refer to some important papers on field margin management and ecology, and the interaction between field margins and ecosystem services. Again, this is mostly referring to arable cropping systems since not much work has been done in open-field horticultural cropping systems. We cited both older and the latest work on critical period of weed interference in lettuce (there is not much work on this, and these papers only calculated one side of the curve whereas we calculated both the increasingly weedy and the increasing weed-free curves).
A Scopus search on the subject was also conducted to verify this. We provide the search terms and the latest published articles below:
Leafy AND vegetables AND weed AND competition. Latest published article from 2017 (https://doi.org/10.1016/j.cropro.2016.07.007)
critical AND period AND of AND weed AND interference AND vegetables. Latest published article from 2013 (doi:10.1614/WS-D-12-00107.1)
functional AND trait AND ecosystem AND services AND vegetables. No relevant articles.
We added three more recent papers in the discussion. If there are specific papers you deem relevant, we would be very happy to receive your suggestions.
The paper requires a lot of improvements and in its present form, it cannot be accepted for publication in the Horticulturae journal.
We hope our revisions are in line with what you meant. If there are still issues, we would much appreciate to hear them and in that case please indicate line numbers so we can address the issues.
Reviewer 3 Report
Comments to the Author
In this research article, Virili1 and Moonen investigated the weed and pest control in Romaine Lactuca sativa L. The present experiments are well-designed, and the Authors obtained average results which be convincible. It is well written in most parts, and there is some redundancy in the information throughout. This article is of great interest to researchers in agriculture development. So, the manuscript can be recommended for publication at the Horticulture after minor revisions.
Materials and methods
Page 3, Line no: 130 – 132 “Each year, two weeks before transplanting, we applied 1 kg m-2 of an organic fertilizer derived from a mix of bovine and equine manure”.
The authors should have explained the percentage of manure mixture bovine: equine?
Page 3, Line no: 134 – 136 “Water was provided to the plots with an overhead irrigation system made of six sprinkler heads, each providing 200 L ha-1 of water for about two hours nearly every day”.
Water irrigation depends on weather conditions and soil type, and the authors should justify the statement.
Results
Table 1 & 2. There is not much difference in the data.
Discussion
The authors should have discussed the statements in the discussion part.
Organic manure may contain grasses and tiny seeds; in addition, it promotes weed germination. Can you justify the statement?
Bluegrass is widespread; shade adaption, low-growing turfgrass in temperate climates, and canary grass adversely affect Lettuces cultivation.
Author Response
Dear reviewer
Thanks for reading and commenting our manuscript. We reply to your comments in the text below.
In this research article, Virili1 and Moonen investigated the weed and pest control in Romaine Lactuca sativa L. The present experiments are well-designed, and the Authors obtained average results which be convincible. It is well written in most parts, and there is some redundancy in the information throughout. This article is of great interest to researchers in agriculture development. So, the manuscript can be recommended for publication at the Horticulture after minor revisions.
Thank you for reading our paper and for supporting our work.
Materials and methods
Page 3, Line no: 130 – 132 “Each year, two weeks before transplanting, we applied 1 kg m-2 of an organic fertilizer derived from a mix of bovine and equine manure”.
The authors should have explained the percentage of manure mixture bovine: equine?
The percentages of bovine and equine manure are not specified in the vermicompost we used (for reference “HORTUS CLT®” produced by Centro Lombricoltura Toscana) (https://www.lombricolturaclt.it/cms/hortus). We have added the product and company names in the text, together with information about the C to N ratio and the percentage of Organic Matter (% calculated based on dry matter) which were provided upon request by the company in a technical fact sheet (in italian).
Page 3, Line no: 134 – 136 “Water was provided to the plots with an overhead irrigation system made of six sprinkler heads, each providing 200 L ha-1 of water for about two hours nearly every day”.
Water irrigation depends on weather conditions and soil type, and the authors should justify the statement.
The soil is a sandy soil (soil analysis reported in line 128-130) and the weather conditions were typically Mediterranean. Weather data have now been added in the Materials and Methods section. Considering these factors and the water requirements of lettuce (around 2340 m3 ha-1) the sprinklers were activated accordingly. Each sprinkler had a water flow capacity of 200 L ha-1 hr-1, we acknowledge that the way the sentence was written was unclear and hope the statement is clear now.
Results
Table 1 & 2. There is not much difference in the data.
Sorry, we are not quite sure what we understand what you want us to do. We thought it would be useful to provide the means and standard deviations of the three variables describing lettuce growth and development as a response to the various weeding regimes. Regarding SPAD-values, for example, the range is quite small, but there still is a significant difference between the weed-free control and the weedy-control. Small but significant effect have also been identified for lettuce head circumference and most importantly for crop yield. The differences at the extreme ends of the weeding regime scales are clear. Unfortunately the intermediate levels of weeding did not results in clear differences. In the case of lettuce yield this was due to a relatively high variability within the same treatments. We have now added a paragraph at the start of the discussion.
Discussion
The authors should have discussed the statements in the discussion part.
We have revised the discussion and we hope to have clarified the links between the research hypothesis, results and the discussion and conclusions.
The discussion has been written to elaborate on the agronomical and ecological aspects of reduced weeding in relation to the Agro-Ecosystem Service of interest. Our research question was the following: “Can the weed community that develops after the necessary critical weed-free period potentially support Conservation Biological Control (CBC)?”.
To answer this question, we first had to find the critical period of weed interference in romaine lettuce in our climatic conditions. We elaborate on this result in lines 341-362.
Secondly, we investigated whether the weed community which developed after the critical weed-free period could support CBC based on the functional traits of the weed species present at that time. We concluded that this was not possible, and we discuss the possible reasons: 1) after the necessary weed-free period had ended, Cyperus spp. was the only weed able to quickly germinate and occupy soil cover in all plots; 2) weeds associated to CBC were found in these plots as well, but they could not develop fast enough and did not have enough ground cover to potentially deliver the service.
Lastly, we investigated whether the weed community we found in the weedy control plots could provide CBC. In this case, the functional trait analysis showed a positive association between the weed species traits and the service of interest. Despite this, the timing of the cropping season did not favour flowering of some useful species, while less interesting and more competitive species developed very quickly. In this case we concluded that the potential service provisioning was only partially feasibile. We selected the May-July growing period because we expected the highest number of flowering weeds in this time of the year. However, future research could focus on the comparison of weed communities that develop in lettuce when earlier transplanting periods are chosen. From the end of March onwards the risk of night frost are low and daily temperatures can allow lettuce to grow outdoors.
Organic manure may contain grasses and tiny seeds; in addition, it promotes weed germination. Can you justify the statement?
As mentioned in lines 129-132, we applied vermicompost derived from organic manure. The composting process is effective in killing most weed seeds. Furthermore, the soil amendment was applied almost two weeks prior to crop transplanting, and all weeds were removed during the soil preparation process. We performed this trial in a part of a much larger field, where other trials were set up contemporarilty. The weed species composition in this area is faily homogenous and each trial was set up in a part of the field with an as homogenous as possible weed community and this was based on our knowledge of the experimental area and the observations prior to field selection. Therefore, within each experimental year, the weed community was homogeneous, whereas between the year we found only one dominant species more in 2020 (Solanum nigrum), and some differences in the less frequent species (please see the supplementary tables S1, 2 and 3). We are therefore confident that the application of vermicompost did not affect the trial, and if it did, it was in a homogenous way throughtout the trial, and should therefore not have affected the results.
Bluegrass is widespread; shade adaption, low-growing turfgrass in temperate climates, and canary grass adversely affect Lettuces cultivation.
Indeed, we found a strong negative correlation between grasses and lettuce yield (table 4, line 326). We found some bluegrass (Poa pratensis) in our plots but canary grass (Phalaris arundinacea) was not recorded. Poa spp. was not a dominant species in the weed community. We are not quite sure how to improve the manuscript based on this comment. If you would like to explain this further, we would be glad to add information about the influence of grasses and broadleaf weeds on lettuce yield and growth. Based on your comments we decided to include a new table, table 4, that shows how different weed groups affect lettuce yield. We also enriched the discussion.
Round 2
Reviewer 2 Report
Almost all of the reviewer's comments have been corrected, however, I believe that the conclusions should be written separately. After this amendment, the work can be published in a journal Horticulturae.
Author Response
Dear Reviewer
thanks for your comments. We have added the Conclusions section to the paper.
Regards
Camilla Moonen
Alessandra Virili
Author Response File: 
Author Response.docx
