Differences in Weed Suppression between Two Modern and Two Old Wheat Cultivars at Different Sowing Densities
Round 1
Reviewer 1 Report
Thankyou for submitting this well written manuscript. This study has been well conducted and the results are valid and well presented. It is however a significant consern that this study was not replicated in oth space or time. Was any additional studies conducted to verify the results at Beijing University??
Specific comments
Line 97. This trial was not replicated by location or time. Whilst there is suficient replication of each teatment. the lack of replication in space and time is conserning. Otherwise this rial design is sound.
Line 209. Response between weed biomass and wheqat biomass presented. Do you have an R2 value to demonstrate the fitting of your predicted trend line?
Line 198. (Same lack of r2)
There was a lot of discussion around the wheat yield components. However the most important parameter is the weed seed production. Was this measured?
Figure 2: Would t be better to provide the mean and an error bqar around that mean to demonstrate the data? Providing the raw data is the most powerful way to present the result, however it is messy.
Author Response
Reviewer #1
1) Thank you for submitting this well written manuscript. This study has been well conducted and the results are valid and well presented. It is however a significant concern that this study was not replicated in other space or time. Were any additional studies conducted to verify the results at Beijing University??
We are planning to test the findings in future study.
2) Line 97. This trial was not replicated by location or time. Whilst there is sufficient replication of each treatment. the lack of replication in space and time is concerning. Otherwise, this rial design is sound.
We realized this weakness of our study. To make a solid conclusion, we are planning to test the generalization of our findings using more cultivars.
3) Line 209. Response between weed biomass and wheat biomass presented. Do you have an R2 value to demonstrate the fitting of your predicted trend line?
Done
4) Line 198. (Same lack of r2)
Done
5) There was a lot of discussion around the wheat yield components. However the most important parameter is the weed seed production. Was this measured?
We measured weed total biomass which included weed seed production. We realized that weed seed could be an important parameter, as it can influence weed invasion in a new growing season. However, in the present study, weed total biomass, especially leaves and stems, could be more important for crop yield declines.
6) Figure 2: Would it be better to provide the mean and an error bar around that mean to demonstrate the data? Providing the raw data is the most powerful way to present the result, however it is messy.
We kept the raw data in the figure, because the fitted lines were performed for raw data (rather than mean values) and crop density. However, we changed the style of this figure to make it be clearer for readers.
Reviewer 2 Report
Dear authors, please find my 21 comments within the attached annotated PDF version of your manuscript to provide all step-by-step responses. Kind regards
Comments for author File: 
Comments.pdf
Author Response
Reviewer #2
1) line 2-3: This title is not sound. For example, starting the title with "Crop sowing density and weed suppression" implies that both density and weed suppression are the investigated traits here. But only weed suppression is a trait here, whereas sowing density is a cultivation factor. I strongly suggest reformulating the title as follows: "Differences in weed suppressiveness between modern and old wheat cultivars as affected by sowing densities."
We have changed the title in the direction of the suggestion. We agree with the point but do not think the specific suggestion sounded good.
2) line 33-34: The authors should come back to this point at the end of this study, and derive conclusions on how the results of this study could impact future uses of herbicide measures and help to improve the development of best management practice.
The aim of the present study is to test whether weeds can be suppressed by increasing crop sowing density which may increase the size-asymmetric competitive advantages of crops. We focused on this aim throughout the manuscript.
3) line 38: Reference missing.
Done
4) line 39-40: Transition from the previous paragraph unclear. And what do the authors mean with "population yield"
We added one sentence to make logic transition from the previous paragraph. We replaced “population yield” using “plot-level yield” which is more easily understood.
5) line 80: I don't agree that there is a size-asymmetric competition visible in Figure 1a, because for both old and modern cultivars, weed is strongest in late growth stage in less dense plant stands. It should be omitted.
In the figure 1a, we aim to show how crop sowing density influences size-asymmetric competition between weeds and crops. In theory, crops cannot effectively suppress weeds when sowing density is very low, thereby leading to large growth of weeds at the late growth stage of crops. We rephrased this sentence to make this point be clearer.
6) line 80: what kind of weeds? thistles? other grasses? Figure caption must be self-explanatory.
We realized that the definition of weeds is vague here. We added one sentence to interpret what we mean by weeds in our study.
7) line 83: provide reference number as well.
Done
8) line 106: How deep were they sown?
Done
9) line 111: I strongly suggest adding a photograph of the arrangement of the mesocosms to improve understandability of the methodology.
It is a shame that we did not record the experimental setup with clear photos. We provided an illustration to show how we assigned mesocosms in blocks (Figure 1c).
10) Figure 3a, figure 4 and figure 5: Nevertheless, I still suggest to colorize the dots differently, according to their respective cultivar.
Done
11) line 266: reformulate
Done
12) line 276-277: This reads like a conclusion. Why isn't this stated within the conclusions section?
We see what the reviewer means here. However, this suggestion for future study is simply based on the findings we discussed in that paragraph (the last paragraph of discussion section). It is better to have the sentence there. Moreover, we have more suggestions for future studies in the conclusion section.
13) line 278: I miss the overall aim of increasing weed resistance, such as a reduction of chemical synthetical herbicide measures, reduced ground water pollution etc.
The aim of the present study is to test whether weeds can be suppressed by increasing crop sowing density which may increase the size-asymmetric competitive advantages of crops. The primary aim of developing high-density crop systems, of course, is to reduce crop yield loss by weed invasion, and the other aims can be reductions of chemical herbicides and increases of cropland sustainability. We have already asserted this in the introduction (the 1st paragraph) and discussion (the 4th paragraph).
14) line 279: I don't understand whether any hypotheses were answered in this study or not, as the authors later state that "further research is needed (to) test these hypotheses". Must be clarified.
1) Please see the 4th paragraph of the introduction section where we presented the hypotheses that we tested in the study. We have already discussed whether our hypotheses were supported by our data (see discussion section).
2) Based on our findings, we also proposed new hypotheses for what type of modern crops are suitable for developing high-density cropping systems (see the 5th paragraph of the discussion section).
15) line 288: Why? To avoid or reduce the use of chemical synthetical herbicide measures?
See comments to Q13.
16) line 289: to test
Done
17) line 289: I suggest to clearly describe other hypotheses, e.g. compare costs of higher sowing densities vs. lower costs for chemical-synthetical herbicide measures, or omit this statement.
We omitted this statement.
Round 2
Reviewer 2 Report
The manuscript was even improved further.
