Monitoring Patch Expansion Amends to Evaluate the Effects of Non-Chemical Control on the Creeping Perennial Cirsium arvense (L.) Scop. in a Spring Wheat Crop

Round 1

Reviewer 1 Report

Dear authors,

thank you for this study. I find the non-chemical and UAV-based approach to thistle monitoring/controlling very interesting and see it as a very relevant and important topic this time. 

Nevertheless, the manuscript needs a lot of revision. In the material and methods part, it is not clear how the treatments were carried out. No machines for the treatments are explained. It is not explained how the drone works, only that it was used. It is only known that trials have taken place in wheat but no details are given.

 

In the results section, actual results are completely missing. It is only mentioned that it was higher or lower but not related to what or concrete numbers mentioned. The thistle density (thistels m-2) is not mentioned at all, the input data in 2019 and the output data in 2021 are not known. 

The reader does not know how big the thistle patchs were at the beginning and at the end, one only knows that they have grown or shrunk. This is too imprecise for a scientific publication. 

 

I also see potential for improvements in the discussion. The results of the individual treatments were not/barely compared with the literature and critically discussed. I would also find a critical discussion with a chemical treatment after harvest compared to CC important (Messelhäuser et al. 2022, Exploring the Effects of Different Stubble Tillage Practices and Glyphosate Application Combined with the New Soil Residual Herbicide Cinmethylin against Alopecurus myosuroides Huds. in Winter Wheat. Agronomy 2022, 12, 167). 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

thanks for critical and constructive evaluation of the manuscript. I have carefully considered the comments and have incorporated the suggested changes. I believe that the revision has greatly improved the quality of the manuscript.

Title

In which crops?

New title:

Monitoring patch expansion amends to evaluate the effects of non-chemical control on the creeping perennial Cirsium arvense (L.) Scop. in a spring wheat crop

Abstract

How much?

How much was the control efficacy without ploughing?

 

Line 19

Treatments including disturbance by ploughing (PL, PL+CC, PL+RC, PL+RC+CC) reduced “Density” by the factor 0.15 (-85%) and “Expansion” by 0.25 (-75%) while those without ploughing (CC, RC, RC+CC) only reduced “Density” by the factor 0.68 (-32%) and “Expansion” by 0.71 (-29%)

 

Whats about the results for Coverage and Height? The authors mention this before. Please write 1 sentence about this results

 

Line 26

 “Height” of the shoots was significantly reduced in four treatments (PL, RC+CC, PL+RC) while “Coverage” did not change significantly

Introduction

Why, please explain a bit more detailed

Line 57

Creeping thistles are considered problematic in the temperate regions of the world, causing yield losses in both conventional [17] and organic arable [18,19] cropping systems.

i miss a bigger overview of another concepts. Whats about glyphosate application after harvest? Or general, the chemical control of thistles, why do the authors not consider this strategy in the introduction?

 

Because we only focused on non-chemical treatments. Added in line 58

Chemical weeding in conventional [21] and inversion tillage by ploughing in organic farming [16] have so far been the primary practices to control C. arvense. Chemical weeding will be restricted in the near future [22]. Costly intensive tillage operations increase the risk of soil erosion and leaching [23]. Alternatives in C. arvense control limiting the need for chemical weeding and inversion tillage are therefore needed. We contributed to this effort by utilizing and combining principles of disturbance and competition without the use of herbicides.

the authors should try to avoid such unspecific explanations. Please write that CC can suppress C.arvense up to XX %.

Line 67

When periods of competition were extended by fallow periods composed of e.g. clover grass mixtures, biomass reductions of up to 69% occurred

This section is a bit short and i don't see the connection to the rest of the introduction or the red-line to the hypotheses? If UAVs can already do all that, then UAVs are not an innovation for futher research. The

focus should be more on the fact that UAV technology can be used to investigate the growth patterns of C.arvense, since UAV technology allows it.

 

Information added to include aspect “focus should be more on the fact that UAV technology can be used to investigate the growth patterns of C.arvense, since UAV technology allows it” Line 82

 

UAV thistle patch mapping can therefore potentially be used to investigate the growth pattern of thistles in response to control treatments.

 

until here i did not know that you only use non-chemical weed management practices. Maybe you include it in the title

 

Hypothesis

this is not a good hypotheses... Of course if you let the thistle uncontrolled, the thistle patch will develop more shoots, cover and will expand. otherwise they would control itself!

 

Hypothesis 1 line 94 changed to:

 

We hypothesized (1) that uncontrolled thistle patches develop not only more shoots and more cover, but also expand in size over time

 

Materials and Methods

please, also include the averagly long term temperature

 

Line 107

10-year average temperature was 9.95 °C

This are not the crops of the experiment? Please describe

These crops were not included in the experiment.

Added: In these time period crops were

seed rate?

 

Line 115

 

Seed rate was 65 seeds m^-2

 

before or after?

 

Close to harvest describes an event happening close to the process of harvesting meaning before harvest.

Some of the thistle patchs are colse to each other. Didn't you have any fear that they would affect each other ?

 

How could you verify that they do not affect each other?

 

Info added in line 123

 

Surrounding shoots with a distance of > 2.5 m were considered independent from the given patch. Between neighbouring patches a distance of > 2.5 m was kept.

why two times spring wheat ? was there no crop rotation? 

We deemed it more favourable for our objectives to test monitoring patch sizes and their treatment responses to crop spring wheat in both years

please use the propper writing style

 

kg ha^-1

 

for the complete manuscript!

Fixed

 

Please, describe all the machines the authors used for this experiment in detail. Which ploughing machine ?Company, size, etc. desrice the prototype, working wide etc...

 

Information added in line 149

 

In the treatments with root cutting (RC) a prototype machine “The Kverneland hori-zontal root cutter” developed by (Kverneland, Klepp, Norway). went through the soil be-low ground without inverting. This machine fragments below ground root and shoot parts without inverting the soil. Almost completely flat, wide and inflexible duckfoot blades facilitate this cutting. Ploughing was done by a 6 sheered mouldboard plough (Grégoire-Besson, Montfaucon-Montigné, France)

 

plase take care about the writing style ! --> author guidlines, how to write the company name

 

Company, location, country

Fixed

How was the georeferencing been done to get an propper area with the drone

Drone has an RTK system

how were different flight heights taken into account over the years?

Flight altitudes were not different…stable at around 50m

i would also take the coverage of the CC into account because this parameter has an impact of the control efficacy.

 

There was no CC when flights took place

How is it done? was there any image-analysis behind? how did the authors got the thistel coverage value?

 

Thistle were detected through both pixel and object-based image classification from RGB ortho-mosaic and coverage per plot has been calculated in %

did c.arvense already flowered ?

 

This would be a major error value for the CoverageUAV

 

Yes C. arvense did already flower. Flowering is not in issue and did not cause any errors when comparing it to images taking before flowering

What is the key result of this section ?

 

i just get the information that ini the UC the thistle patch almost tripled.

 

Whats about the other treatments? please consider them in a equal way

The key result is the discussed sharp increase in patch size for UC and the discussed differences between Expansion and Density. Individual treatment effects were not in focus. Detailed and discussed treatment differences can be found in Table 2 and Figure 5

I would recommend, creating a table with the measured density and expansion for all three years and each treatment. This way you can see the changes over time.

Please see Materials and methods section (2.3). We did not include all 3 years. Shown values are differences of starting point 2019 till end in 2021.

mean value over all years or one specific year?

Mean values of 2019 and 2021, Please see Materials and Methods (line  170)

We used the measured values of summer 2019 as starting values of each plot for all variables. Thus, relative changes between starting values in 2019 (Xp2019) and end values of 2021 (Xp2021), given per plot (p) were used:

please name the patch size in 2019 in m² and then you can talk about an expansion of 180 %

 

Please see elaboration on why we used relative values instead of absolute values and how representations were adjusted in line 181

Figure 3 selects two plots to illustrate the variable “Expansion”. In example 1 the patch increased in size from 73 m² to 95 m², (“Expansion” = 1.32, absolute difference +22 m²), whereas in example 2 it decreased in size from 85 m² to 21 m² (“Expansion” = 0.25, absolute difference – 64m²). Therefore, example patch 2 got reduced by the factor 0.25.

 

 

was this significantly different from the other treatments ? please compare your single treatment results more with each other

Individual treatment effects are described in table 2.

Anova- Table including treatment effects and interactions was added

 

	“Expansion”		“Density”		“Coverage”		“Height”
Factor	P value		P value		P value		P value
PL	<0.001		<0.001		0.039		0.001
RC	0.005		0.002		0.515		0.431
CC	0.008		0.011		0.959		0.638
PL:RC	0.047		<0.001		0.851		0.372
PL:CC	0.033		0.271		0.952		0.036
RC:CC	0.122		0.848		0.241		0.111
PL:RC:CC	0.145		0.192		0.886		0.081

 

Define

 

Please see next sentence “Plant pathogen interaction”

 

compared to what?

 

Compared to UC. Please see line 254/255, 265/266 for further explanation.

 

In Table 2, the treatments effects on the thistle variables contrasted to the untreated control (UC) are estimated in a linear model

the results in table 2 show someting different. it change compared to UC

 

Line 265

Linear model effects of treatments on thistle variables "Expansion", "Density", “Coverage” and “Height”, Significance codes: * P < 0.05, * * P < 0.01 and * ** P < 0.001. Please see description in section 2.4 to see statistic of Table 2: Linear models were used to estimate the relationship between treatments and each variable with the respective “Density”, “Height”, “Expansion”, “Coverage” as response variables:

Yp = α + β* TRp + ε                  Y = Density | Expansion | Height | Coverage, p = plot 1-32 (2)

with variable of plot p, TR is the effect of the treatment in plot p, epsilon is the error term. Intercept is defined as α (treatment 'Untreated control', UC) and (β) measuring the change for “Density”, ”Expansion”, ”Height” and ”Coverage” in respect to the treatment (TR).

A factorial ANOVA (PL, RR, CC) with all three-way interactions of the applied factors was carried out with the “Density”, “Height”, “Expansion”, “Coverage”.

 

Figure 5 Effect of control on thistle “Expansion” and ”Density”. Given are the effects of single and combined control in the treatments relatively to the maximum reduction effect of treatment PL+RC+CC = 100%. Single treatments (RC, CC, PL) shown in plain colour. Treatment combinations (RC+PL, RC+CC, PL+CC) shown by added hatching

 

write some values

Please see Figure 5

Why is the UC treatment not included?

 

Line 268

The three single factors (plough, root cutter, cover crop) as established in the treatments significantly affected “Expansion” and “Density” (Table A1). Significant interactions between two factors were found when ploughing (PL) was involved. Regardless of the response variable the treatment PL+RC+CC - combining three control measures - reduced the thistle infestation to the highest degree (Table 2). This result does not depend on an interaction as the three factors did not interact (Table A1). Therefore, we calculated the reduction of the other control treatments relative to this most effective treatment. Figure 5 compares the treatment reduction effects estimated in the linear models on the response variables “Expansion” and “Density”.

 

 

it is hard to understand what 80 % expansion mean.

 

so the efficacy of a treatment was an expansion of 80 % of the thistel patch over the years?

 

i would suggest to choose a different visualization. In a table or a simple graph where the reduction of the expansion in "% reduced thistel-area" is compared to the UC. The same for the density 

 

i miss that the possibilities of species identification based on neural networks is not discussed

 

Please see adjusted Figure 5 and Figure description in line

 

Shoot density are plants m-2 and coverage is %

 

How can you compare it ? or how can you get plants m-2 from the coverage value?

 

Please see section 2.3 and 2.4 with adjusted material and methods

The authors forgot to discuss the results for the coverage and height

 

Added in line 291 and 375

 

“Height” was also additively reduced by the combination RC+CC but the effect was still smaller than that of ploughing (see Table 2). Root cutting has been shown to reduce “Expansion” and “Density” without reducing “Height” [29]. When root cutting frequency was increased to more cuttings than required to reduce “Density” and “Expansion”, “Height” was reduced, too [29]. This was attributed to a higher depletion of root reserves by repeated cutting by which thistles first reduced “Expansion” and “Density” before giving up on “Height”. This further strengthens the observation of ploughing being the superior treatment to root cutting in reducing thistle infestations.

 

This also explains why Table 2 did not show any significant differences between treatments for “Coverage” while “Density” did. 

 

I miss that the possibilities of species identification based on neural networks is not discussed

 

As we have no experience on species identification based on neural networks we focused the methods described

Author Response File: Author Response.pdf

Reviewer 2 Report

Review of

 Monitoring patch expansion of the creeping perennial Cirsium 2 arvense (L.) Scop. to evaluate the efficacy of control treatments

 

General impression

The study includes three new and therefore interesting aspects: (1) the root cutter, (2) interactions between three different control tactics (root cutter, ploughing and cover crops) and (3) a new spatial evaluation method: expansion of patches.

The description of the root cutter and the treatments with the root cutter has to be improved and elaborated. The ideas behind the new implement and the way it is used have to be explained. It is not clear what to expect based on previous experiences and knowledge.

The experiment includes three factors (ploughing, root cutter and cover crops) which makes it possible to investigate how these factors interact. What is expected and what does the statistical test show?  The structure in data (factorial design) should be utilized.

Expansion of patches is a new and relevant evaluation parameter. However, there is no definition of how a patch is delimited.  According to previous research, it seems not to be trivial to delimit a patch.

There exist several studies with ploughing and cover crops. Therefore, the manuscript should be focused on the new aspects (mentioned earlier).

Under the conditions that the new aspects are emphasized, the study deserves to be published. However, it requires a major revision of the manuscript.

 

Comments to the introduction

The introduction is too general.

It would improve the introduction if it was clearly stated why the control strategies (competition and disturbance) were chosen and what kind of results the authors expected to achieve based on previous knowledge. There exists plenty of results related to competition and disturbance. Root cutting seems to be a new approach. What has been achieved previously with root cutting and what is expected compared to inversion tillage – and how do they interact?

The growth of weed patches is a new aspect. However, it is not new in population dynamics. Therefore, I would suggest drawing on the knowledge from weed population dynamic studies emphasizing dispersal rates and invasion from high to low weed density areas. What do we know about dispersal rates of C. arvense and how has it been studied? It would improve the introduction if theoretical aspects related to population dynamics were integrated. To give an example how theoretical aspects could be integrated in relation to C. arvense dispersal, look at Blumenthal and Jordan (2001) (Weed Science, 49:509-519). If the authors do not think population models and knowledge generated from such modes are useful, it would be helpful to know why.

 Hypotheses are not clear and justified in the introduction. Hypothesis 1 seems to be justified based on reference 28, but there is no indication of the content of this reference.  The introduction should give the background and the understanding behind the hypotheses - not just a reference. Please reconsider whether hypothesis 1 is trivial. If the opposite hypothesis (uncontrolled thistle patches do not develop over time) makes no sense, it is a strong indication that hypothesis 1 is trivial and not based on existing knowledge and/or expectations

In conclusion. The introduction needs to be improved.

Detailed comments

35 : delete:  “with clonal shoots and stems above – ground”

 

36: substitute “allow patches to increase the covered area while safeguarding their persistence” with “allow patches to increase in size”

 

43: reformulate. C. arvense does not threaten the existence of conventional farming

 69: please reformulate hypothesis 2, it is not clear what is meant

 72: What does “relatively monitored” mean? It has to be clarified.

 

73 and 74: Delete

 Comments to Materials and Methods

 This section has to be elaborated.

 Details have to be given about how thistle patches were monitored. It is not enough to write  “(i) UAV (DJI P4 RTK, image sensor 1" CMOS, 20 MP, 94 objective 8.8mm) and (ii) GPS (Pentax-GNSS, Getac-PocketPC) on the ground”. This information is not sufficient for reproducibility.

 The experimental treatments are presented as unstructured but there is a structure. It is a three-factorial design with Ploughing (+/-), Root cutting ((+/-) and Cover crop (+/-).

 144: relative values are used in statistical analyses. I think it would be better to use pre-treatment values as co-variates in co-variance models.

 Figure 3. Please clarify how borders were defined. Was a threshold used, or were there simply no thistles outside the patches?

 Statistics

I am not able to follow that statistics. The presented model does not include treatment, and the data structure seems to be ignored. Please elaborate on the statistics. It is not possible to reproduce the calculations based on the description.

 

Comments to Results and Discussion

 191-195: This is an explanation belonging to Materials and Methods

 

196: “In quantity the patches in untreated (UC) increased in their “Expansion” by 180 % in 196 the two-year experimental period (2019 - 2021).” This is contrasting the information given in Fig. 3. Explain.

 

Table 2. It is unclear what the significance codes denote. The interesting part here is if the treatments differ in efficacy but I cannot see any tests showing that.

 231: “treatment PL+RC+CC - combining three control measures - reduced the thistle infestation to the highest degree”. Please “translate” the estimates into easy understandable information. For example, when it comes to expansion, the estimate for PLRC is -2.63 and -2.76 for PLRCCC.  What does it mean in terms of expansion – and is the difference statistically significant?

 

Are there any interactions between treatments? (not tested) og would the author expect interactions?

 

Figure 4: Please give effects relative to untreated. How is Figs 3 and 4 related? I think it is a double presentation.

 

Comments to Conclusions

Please delete discussion from the conclusion. The conclusion should be related to the objectives /hypotheses of the study only – not including new aspects such as testing herbicides.

 

The conclusion needs to be rewritten.

 

 

  

 

 

Improvements needed

Author Response

Dear Reviewer,

thanks for critical and constructive evaluation of the manuscript. I have carefully considered the comments and have incorporated the suggested changes. I believe that the revision has greatly improved the quality of the manuscript.

Comments to the introduction

“It would improve the introduction if it was clearly stated why the control strategies (competition and disturbance) were chosen and what kind of results the authors expected to achieve based on previous knowledge”

Added in Line 57-65

Creeping thistles are considered problematic in the temperate regions of the world, causing yield losses in both conventional [17] and organic arable [18,19] cropping systems. Chemical weeding will be restricted in the near future [21]. Costly intensive tillage operations increase the risk of soil erosion and leaching [22]. Alternatives in C. arvense control limiting the need for chemical weeding and inversion tillage are therefore needed. We contributed to this effort by utilizing and combining principles of disturbance and competition without the use of herbicides

“There exists plenty of results related to competition and disturbance. Root cutting seems to be a new approach. What has been achieved previously with root cutting and what is expected compared to inversion tillage – and how do they interact?”

Information on root cutting is added in Line 72

Root cutting showed first promising results in a two-year field study without a crop [26] by significantly reducing C. arvense shoot numbers and patch sizes if applied at least twice per year. Nevertheless, the root cutting concept remains to be tested in field experiments and practical

Expectations in comparing cutting with inversion tillage are not given as there were no studies comparing these two approaches

The growth of weed patches is a new aspect. However, it is not new in population dynamics. Therefore, I would suggest drawing on the knowledge from weed population dynamic studies emphasizing dispersal rates and invasion from high to low weed density areas. What do we know about dispersal rates of C. arvense and how has it been studied? It would improve the introduction if theoretical aspects related to population dynamics were integrated. To give an example how theoretical aspects could be integrated in relation to C. arvense dispersal, look at Blumenthal and Jordan (2001) (Weed Science, 49:509-519). If the authors do not think population models and knowledge generated from such modes are useful, it would be helpful to know why.

Added in Line 44

1. arvense produces seeds, however, under arable and ruderal conditions dispersal via clonal propagules is often described as prevalent [7,8]. Genetic diversity within fields and patches is proven [9].Therefore, patches can potentially grow with generatively and vegetatively reproduced units. While long and medium distance dispersal on a landscape scale, e.g., from field margins into fields demands for modelling the full population dynamics [10], short distance growth of small existing patches on a field scale are reasonably addressed by repeated monitoring.

Hypotheses are not clear and justified in the introduction. Hypothesis 1 seems to be justified based on reference 28, but there is no indication of the content of this reference.  The introduction should give the background and the understanding behind the hypotheses - not just a reference. Please reconsider whether hypothesis 1 is trivial. If the opposite hypothesis (uncontrolled thistle patches do not develop over time) makes no sense, it is a strong indication that hypothesis 1 is trivial and not based on existing knowledge and/or expectations

Hypothesis 1 was adjusted and is now justified on the bases of the introduction: We hypothesized (1) that uncontrolled thistle patches develop not only more shoots and more cover, but also expand in size over time (line 94). Key information given in line 50-56: Despite the prominent and visible field establishment of thistle patches, field trials are standardly designed with systematically located treatment plots, not accounting for existing patches [11–13]. In these plots mainly shoot numbers and shoot biomass are assessed to evaluate the effectiveness of control treatments [11,13–16], regardless of the fact that patches also change in size [17]. The drawback of this method is that expanded or downsized patches are not accounted for, and thus, may be overlooked in evaluating treatment effects.

35 : delete:  “with clonal shoots and stems above – ground”

Deleted

36: substitute “allow patches to increase the covered area while safeguarding their persistence” with “allow patches to increase in size”

Line 41

Expanding creeping roots allow patches to increase in size while safeguarding their persistence [6].

43: reformulate. C. arvense does not threaten the existence of conventional farming

Line 57

Creeping thistles are considered problematic in the temperate regions of the world, causing yield losses in both conventional [18] and organic arable [19,20] cropping systems.

 69: please reformulate hypothesis 2, it is not clear what is meant

Hypothesis changed, line 95

(2). Evaluating both, patch size and thistle characteristics within patches changes the rating of non–chemical control treatments effects

 72: What does “relatively monitored” mean? It has to be clarified. 

I think you meant “reliably”. Changed to “accurately enough” (line 98)

73 and 74: Delete

Done

Comments to Materials and Methods

This section has to be elaborated

More info was added, please see line 115

Individual thistle patches were mapped by (i) UAV (DJI P4 RTK, image sensor 1" CMOS, 20 MP, objective 8.8mm) and (ii) GPS (Pentax-GNSS, Getac-PocketPC) on the ground. GPS measurements were obtained by physically surrounding each patch in the field and setting the signal manually.

144: relative values are used in statistical analyses. I think it would be better to use pre-treatment values as co-variates in co-variance models.

We prefer not to use pre-treatment values as a co-variate because we target to explain the occurring differences in the treatments.   

Figure 3. Please clarify how borders were defined. Was a threshold used, or were there simply no thistles outside the patches?

Explanation added in line 123

Surrounding shoots with a distance of > 2.5 m were considered independent from the given patch. Between neighbouring patches a distance of > 2.5 m was kept

Statistics

I am not able to follow that statistics. The presented model does not include treatment, and the data structure seems to be ignored. Please elaborate on the statistics. It is not possible to reproduce the calculations based on the description.

Description of statistics renewed (line 199): with variable of plot p, TR is the effect of the treatment in plot p, epsilon is the error term. Intercept is defined as α (treatment 'Untreated control', UC) and (β) measuring the change for “Density”, ”Expansion”, ”Height” and ”Coverage” in respect to the treatment (TR).

Comments to Results and Discussion

 191-195: This is an explanation belonging to Materials and Methods

The flexible plot size is technically described in Material and Methods. In L-L we discuss this characteristic of the experiment. Therefore, we prefer to keep it in “Results + Discussion

196: “In quantity the patches in untreated (UC) increased in their “Expansion” by 180 % in 196 the two-year experimental period (2019 - 2021).” This is contrasting the information given in Fig. 3. Explain.

In Figure the initial infestation base line is set at 1. UC is set at 2.8 meaning an increase of 1.8 or 180%. We added increase by factor to make results more clear (line 225)

In quantity the patches in untreated (UC) increased in their “Expansion” by the factor 2.83 in the two - year experimental period (2019 - 2021)

Table 2. It is unclear what the significance codes denote. The interesting part here is if the treatments differ in efficacy but I cannot see any tests showing that.

Table 2 shows the results of the Linear Mixed Models. Linear models were used to estimate the relationship between treatments and each variable with the respective “Density”, “Height”, “Expansion”, “Coverage” as response variables. The significance values denote statistical significance at the P-value < 0.05 level.

 231: “treatment PL+RC+CC - combining three control measures - reduced the thistle infestation to the highest degree”. Please “translate” the estimates into easy understandable information. For example, when it comes to expansion, the estimate for PLRC is -2.63 and -2.76 for PLRCCC.  What does it mean in terms of expansion – and is the difference statistically significant?

Translation of estimates was fixed. Shown values are changes in the given variable compared to UC. -2.63 means 2.63 less than UC. UC (2.83), PLRC -2.63, meaning Expansion is at 0.2. As initial baseline is always set at 1, 0.2 meaning a reduction of 80% to baseline while UC increased 180%

PLRC and PLRCC are significant compared to intercept: UC. Please see table 2

Figure 5 axis labeling adjusted: Figure 5 Effect of control on thistle “Expansion” and ”Density”. Given are the reduction effects of single and combined control treatments relatively to the maximum reduction effect of treatment PL+RC+CC = 100%. Single treatments (RC, CC, PL) shown in plain colour. Treatment combinations (RC+PL, RC+CC, PL+CC) shown by added hatching. (Line 280)

Are there any interactions between treatments? (not tested) og would the author expect interactions?

 Interactions were calculated and now included in cv. As we focused on the treatment combinations as a whole, we did not see the need to specifically discuss treatment interactions

Table A1 Factorial ANOVA (PL, RC, CC) for thistle variables. The P-value column shows the p-value for each individual factor and the interactions between the factors. Bold values denote statistical significance at the P-value < 0.05 level.

	“Expansion”		“Density”		“Coverage”		“Height”
Factor	P value		P value		P value		P value
PL	<0.001		<0.001		0.039		0.001
RC	0.005		0.002		0.515		0.431
CC	0.008		0.011		0.959		0.638
PL:RC	0.047		<0.001		0.851		0.372
PL:CC	0.033		0.271		0.952		0.036
RC:CC	0.122		0.848		0.241		0.111
PL:RC:CC	0.145		0.192		0.886		0.081

 

Figure 4: Please give effects relative to untreated. How is Figs 3 and 4 related? I think it is a double presentation.

We added further explanation and slightly adjusted the figure description. Please see line 280

Figure 5 Effect of control on thistle “Expansion” and ”Density”. Given are the reduction effects of single and combined control treatments relatively to the maximum reduction effect of treatment PL+RC+CC = 100%. Single treatments (RC, CC, PL) shown in plain colour. Treatment combinations (RC+PL, RC+CC, PL+CC) shown by added hatching. (Line 280)

 

Comments to Conclusions

Please delete discussion from the conclusion. The conclusion should be related to the objectives /hypotheses of the study only – not including new aspects such as testing herbicides.

 The conclusion needs to be rewritten.

Conclusion part is now without references

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

 

thank you for revising the manuscript. It becomes clear that you have made an effort. There are only small things that need to be added. Please have a look at the report 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thanks again for your evaluation of the manuscript. I am glad that I was already able to incorporate most of your suggestions after your first review and I am hoping the second revised version which was sent today addresses all your suggestions and recommendations you made after the first revision.

 

1. three?

 

Thanks for this comment. We forgot to include the treatment PL+RC+CC (line 26)

2. As i mentioned last time the section on the UAV is too short. This is the main part of the paper and you only write 6 lines.

the section needs to be better integrated into the text. you reader get the feeling that it does not belong to the introduction and stands alone.

 

Added information in order to incorporate it better into the introduction in line 78

Monitoring patches manually is time consuming and labor intensive, because patches can be large and rapidly expand over time. Using UAV (Unmanned Aerial Vehicle) has become a wide-spread technology in arable farming [34]. UAV based weed monitoring is described as being accurate, flexible and cost effective [35–37]. As thistles occur in patches, mapping them with UAV based cameras is promoted in research [11,34,38] and considered suitable for practical applications [11]. In cereals, off-the-shelf UAVs with RGB cameras pre-harvest detected patch sizes and the coverage with approximately 90 % ac-curacy compared to visual observations - as long as the green vegetation mainly consisted of C. arvense [11,34,39]. UAV thistle patch mapping can therefore potentially be used to investigate the growth pattern of thistles accurately and time efficient in response to control treatments.

 

3. are there coverage values for CC too ? as an parameter for the CC establishment

 

Coverage data of thistles presented were generated when there was no CC: However, there were additional flights done (In October after canopy closure) when cover crops were present. This information was added in line 310.

Cover crops were dense reaching more than 90% coverage six weeks after sowing. C. arvense plants were in late summer/autumn quickly overgrown by the closing canopy

 

4. include the flight high and the image size in the text

 

Added in line 171

“CoverageUAV” was assessed based on RGB and multispectral images [34]. The flight altitude was approximately 50 m, resulting in a ground resolution of 1 cm for the RGB images and 5 cm for the multispectral images

4. What does reduced the thistle infestation mean? from XX to XX plants m-2?

In terms of “Density”…Yes from XX to XX plants m-2?

Please keep in mind that the shown reductions are based on relative changes.

We added further explanations in line 179

These relative changes have no dimension because units are cancelled out.

5. Again, i would suggest to choose a different visualization. In a table or a simple graph where the reduction of the expansion in "% reduced thistel-area" is compared to the most effective treatment. The same for the density the reader can only appreciate the value

how much %

Added in line 296

Root cutting alone (RC) reduced both “Density” (50.4%) and “Expansion” (70.7%) only moderately

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript has been improved but there are still major issues that have to be addressed before acceptance.

 In general, the manuscript has to be improved with a sharper and more consistent focus. From a non-chemical weed control perspective, the root cutter and its interaction with ploughing and the cover crop is “the thing to emphasize” because the root cutter represents a new weed control method. However, the root cutter is not highlighted in particular in the manuscript when it comes to Results, Discussion, and Conclusion. In the introduction, it is explained that the root cutter showed promising results in a previous study (without being specific about the results) but it is not clear if the current study supported the “promising results” found earlier. The main effects of the root cutter are not presented and it is not made clear what the interactions between ploughing and root cutting mean. In the conclusion, there is nothing about the root cutter. Hence, do the authors think that the root cutter is a promising tool and is it worthwhile to do more experiments?

From a methodological perspective, the patch approach including patch expansion represents a new way to conduct experiments. This aspect is highlighted in the title, in the hypotheses, and in the conclusion, which is exclusively about the methodological perspective. The abstract, however, is mainly focusing on the mechanical weed control treatments

In summary, it would improve the manuscript, if the objective was clearly stated and reflected in the priorities taken in the presentation. Now there are no formulated objectives and the focus appears to be shifting throughout the manuscript.

 

More specific comments are:

Introduction

The introduction is still too general and vague when it comes to root cutting (if the authors want to emphasize on the new tool). The reader should have a clear picture of how and when root cutting is carried out, and the effects achieved so far. What does the root cutter implement look like? When and how is it used? What is the idea behind and does it match the biology? Is there only one reference with control effects? If yes, are the results promising? If yes, give the reasons.

67-68. “When periods of competition were extended by fallow periods composed of e.g. clover grass mixtures, biomass reductions of up to 69% occurred [12]. This is the first time an exact weed control effect is mentioned but “69%” is not interpreted (is it a satisfactory effect?) and the “treatment” (competition + fallow) is not described in detail. Hence, the reader does not get much information.

68: “Another concept is disturbing the soil belowground”. Please clarify. Is stubble cultivation in this category?

72: “…but also by cutting roots with minimal soil inversion”. Does this include stubble cultivation?

72-73: “Root cutting showed first promising results in a two-year field study without a crop….” I would improve the text considerably if control effects were mentioned and compared with well-known control methods. To say that the effects were “significant” is too vague.

86: “non-inversion cutting” If this is root cutting, then call it root cutting.

89-90. “Hence, instead of fixed plots with the same size, we established individual plots each on one individual patch” could it be “Hence, instead of fixed plots with the same size, patches with variable size constituted plots”

 

Methods and Results

“Untreated” is not explained (does it mean direct seeding?) and used as a reference in Table 2. Why? It gets more complicated than necessary to make estimates based on relative measures (changes) and make these changes relative to a specific treatment (relative measures to relative measures).

The linear model presented in line 197 is a simple one-way ANOVA on relative changes.  In line 202, however, it is explained that a three-way ANOVA with interactions was carried out. Why is only the one-way analysis described in detail? The normal procedure is to start with a full model (with interactions).

Data presentation should be shortened and double presentation should be avoided. The presentation of the results is unnecessarily complicated because treatment effects are presented in three different ways; (1) as estimated parameters (table 2), (2) as factors (text), and (2) as percentages (text). Table 2 presents the estimated parameters “contrasted to the untreated control (UC)” from the one-way ANOVA but it would be much more straightforward to present the changes directly. For example, if the reader wants to know if the coot cutter changed the expansion of the thistles, he or she has to do some calculations to find out how the root cutter affected the expansion: 2.82-1.95= 0.88, which corresponds to a 22% decline of the area covered with thistles. The calculations are based on factors, so I think it would make sense to present the factors in a Table – and refer to factors in the text as well.

Fig. 4, Table 2, and Fig 5 present the same results in different ways.  This is a no-go. Please choose ONE way to present data and stick to that throughout the manuscript.

Table 2. Add units

 259: It makes it unnecessary hard to understand that treatments reducing thistles by a small factor (e.g. 0.15) have a great effect (85%) on thistles. It underlines the inappropriate way of presenting results.

269: “Significant interactions between two factors were found when plowing (PL) was involved.” Explain what it means.  Positive or negative interactions?

.

Conclusion

 

This is not a conclusion. The section is “Discussion and perspectives”. The easiest way to conclude is to look up the objectives and/or hypotheses and the concluded on that. Due to a lack of objectives and hypotheses that only relates to the methodological part of the study, the procedure is not possible. I will recommend reconsidering whether hypotheses should be related to both non-chemical treatments (mainly focusing on the root cutter) and the path expansion issue.

Author Response

Dear Reviewer,

Thanks again for your evaluation of the manuscript. I am glad that I was already able to incorporate most of your suggestions after your first review and I am hoping the second revised version which was sent today addresses all your suggestions and recommendations you made after the first revision.

 

1. The introduction is still too general and vague when it comes to root cutting (if the authors want to emphasize on the new tool)

The main emphasize is on the new methodological concept of using whole patches as plots and monitoring them. For this reason, we did not highlight the root cutting treatment.

2. What does the root cutter implement look like?

When and how is it used?

In general, root cutting treatments can be implemented between two crops, often called the stubble period Added in line 76

3. What is the idea behind and does it match the biology?

Principle of control information added in line 155

This machine fragments root and below ground shoot parts of thistles without inverting the soil

Yes, it does match the biology as it targets the root system as described in line 71

Creeping roots in the soil of arable fields are not only disturbed by ploughing which fully inverts the soil but also by cutting roots with minimal soil inversion [17,31–33]

4. Is there only one reference with control effects?

Yes

5. If yes, are the results promising?

Yes, because Thistle infestations were reduced even without a field crop (line 73)

If yes, give the reasons

Thistle infestations were reduced even without a field crop by using the cutter just twice per year (line 73) We added values

1. arvense shoot numbers were reduced by 75% and patch sizes by 90%. These effects were similar to those of ploughing [17,22]
2. 67-68. “When periods of competition were extended by fallow periods composed of e.g. clover grass mixtures, biomass reductions of up to 69% occurred [12]. This is the first time an exact weed control effect is mentioned but “69%” is not interpreted (is it a satisfactory effect?) and the “treatment” (competition + fallow) is not described in detail. Hence, the reader does not get much information.

We added satisfactory and also clarified that we are talking about thistle biomass reductions (line 66)

When periods of crop competition were extended by cover crops e.g., clover grass mixtures, reduction of thistle biomass up to 69% indicate a satisfactory control

7. 68: “Another concept is disturbing the soil belowground”. Please clarify. Is stubble cultivation in this category?

Belowground disturbance in agriculture describes the process of disturbing the soil belowground by a form of tillage, meaning stubble cultivation is in this category

8. 72: “…but also by cutting roots with minimal soil inversion”. Does this include stubble cultivation?

Yes…Please see added information in line 77

In general, root cutting treatments can be implemented between two crops, often called the stubble period

9. 72-73: “Root cutting showed first promising results in a two-year field study without a crop….” I would improve the text considerably if control effects were mentioned and compared with well-known control methods. To say that the effects were “significant” is too vague.

Adjusted and compared to ploughing line74/75

1. arvense shoot numbers were reduced by 75% and patch sizes by 90%. These effects were similar to those of ploughing [17,22]
2. 86: “non-inversion cutting” If this is root cutting, then call it root cutting.

Yes, it is. Changed to “root cutting” (line 91)

We established cover crops for competition, disturbed plots by either inversion tillage or root cutting and combined the methods in seven treatments.

11. 89-90. “Hence, instead of fixed plots with the same size, we established individual plots each on one individual patch” could it be “Hence, instead of fixed plots with the same size, patches with variable size constituted plots”

Yes, changed to your suggestion in line 94

Hence, instead of fixed plots with the same size, patches with variable size constituted plots

12. “Untreated” is not explained (does it mean direct seeding?) and used as a reference in Table 2 Why?

Untreated contains the field crop but no further treatments (PL, RC, CC)

Seedbed preparation. Info added in line 132

The seedbed to sow the wheat was prepared by a single run of a field cultivator (10 cm depth).

It is used as a reference in table 2 as you need a control treatment as a baseline in order to assess the efficacy of your treatments. As there is no “negative control” by the mentioned missing form of chemical weeding it makes sense to use a “positive control” by untreated as a baseline.

13. It gets more complicated than necessary to make estimates based on relative measures (changes) and make these changes relative to a specific treatment (relative measures to relative measures).

Initial infestation levels differed (see section 2.2). Making estimates based on absolute values changes efficacy ranking of treatments. It may seem complicated from a methodological perspective, however in our opinion, this is the most precise way in creating an accurate treatment ranking as seen in table 2.

14. The linear model presented in line 200 is a simple one-way ANOVA on relative changes.  In line 208, however, it is explained that a three-way ANOVA with interactions was carried out. Why is only the one-way analysis described in detail? The normal procedure is to start with a full model (with interactions).

Because our focus was not on interactions. We felt that interactions are not necessary to evaluate treatment rankings and the implementation of using whole patches as plots. Interaction do not give information about additive effects of treatments for example. It is therefore only shown in the appendix. The model presented in line 203 is in focus and the bases for table 2.

15. Data presentation should be shortened and double presentation should be avoided. The presentation of the results is unnecessarily complicated because treatment effects are presented in three different ways; (1) as estimated parameters (table 2), (2) as factors (text), and (2) as percentages (text).

We excluded % and just used factors in order to make it more streamlined and clearer like you suggested

16. Table 2 presents the estimated parameters “contrasted to the untreated control (UC)” from the one-way ANOVA but it would be much more straightforward to present the changes directly. For example, if the reader wants to know if the coot cutter changed the expansion of the thistles, he or she has to do some calculations to find out how the root cutter affected the expansion: 2.82-1.95= 0.88, which corresponds to a 22% decline of the area covered with thistles. The calculations are based on factors, so I think it would make sense to present the factors in a Table – and refer to factors in the text as well.

You are absolutely right.

Additional info added in line 265

Comparing estimates of the treatments with UC reveals that after disturbance by plough-ing (PL, PL+CC, PL+RC, PL+RC+CC) “Density” is reduced by the factor 0.15 and “Expan-sion” by 0.25, while treatments without ploughing (CC, RC, RC+CC) had smaller effects with 0.68 for "Density" and 0.71 for “Expansion

What you are asking for is presented in Figure 4 and 5. Both figures show RC effects on Expansion. They do highlight different results however. Table 2 is the bases of our results representing all described variables and their corresponding treatment effects compared UC. Figure 5 highlights treatment effects and additive effects of stacking treatments in comparison to the most effective treatment (PLRCCC).

Figures and table are based on similar values but highlight different things. Figure 4 highlights differences of “Expansion” and “Density” for UC: Table 2 is the bases of our results representing all described variables and their corresponding treatment effects. Figure 5 highlights treatment effects and additive effects of stacking treatments in comparison to the most effective treatment (PLRCCC).

17. Table 2. Add units

Table is based on relative changes, meaning they have no dimension and no units can be added.

Please see added information in section 2.3 in line 179

These relative changes have no dimension and units are cancelled out.

18.  259: It makes it unnecessary hard to understand that treatments reducing thistles by a small factor (e.g. 0.15) have a great effect (85%) on thistles. It underlines the inappropriate way of presenting results.

Deleted % in order to make it appropriate. Only factors are used.

19. 269: “Significant interactions between two factors were found when ploughing (PL) was involved.” Explain what it means.  Positive or negative interactions?

Added in line 275

Significant interactions between two factors were found when ploughing was involved. PL reduced “Expansion”, “Density”, “Coverage” and “Height” significantly. Combining RC and CC with ploughing (treatments PL+RC and PL+CC) increased the effects. However, the values are lower than the summed effect of the two factors. In the combined treatment RC+CC the effects of RC and CC are roughly added, thus, no interaction occurred

20. Conclusion

This is not a conclusion. The section is “Discussion and perspectives”. The easiest way to conclude is to look up the objectives and/or hypotheses and the concluded on that. Due to a lack of objectives and hypotheses that only relates to the methodological part of the study, the procedure is not possible. I will recommend reconsidering whether hypotheses should be related to both non-chemical treatments (mainly focusing on the root cutter) and the path expansion issue.

They Hypothesis have been discussed and have been answered accordingly. Main parts explaining hypothesis are listed below:

(1) Uncontrolled thistle patches develop not only more shoots and more cover, but also expand in size over time.

Figure 4 (line 225)

When illustrating mean values of the response variables “Expansion” and “Density” in a radar plot (Figure 4), the different shape and spike for “Expansion” becomes immediately obvious. When untreated (UC in Figure 4), the thistle patch “Expansion” almost tri-pled in two years, while the “Density” within the patch changed to a much smaller extent. (line 219-223)

In quantity the patches in untreated (UC) increased in their “Expansion” by the factor 2.83 in the two - year experimental period (2019 - 2021) (line 234)

We answered Hypothesis 1 in line 236

Therefore, we confirm our first hypothesis that uncontrolled thistle patches develop not only more shoots and more cover, but also expand in size over time.  

Table 2 (line 272)

In Table 2, the treatments effects on the thistle variables contrasted to the untreated control (UC) are estimated in a linear model. All treatments reduced the “Expansion” of the patches and the “Density” of shoots within the patches significantly compared to UC (Table 2).

The “Height” of the shoots was also reduced in all treatments, significantly in four of them (PL, RC+CC, PL+RC, PL+RC+CC). The “Coverage” of thistles within the patches did not change significantly.

(2) Evaluating both, patch size and thistle characteristics within patches changes the rating of non–chemical control treatments effects.

Table 2 line 272

In Table 2, the treatments effects on the thistle variables contrasted to the untreated control (UC) are estimated in a linear model. All treatments reduced the “Expansion” of the patches and the “Density” of shoots within the patches significantly compared to UC (Table 2). Estimate subtraction (Table 2) of treatments from UC revealed that disturbance by ploughing (PL, PL+CC, PL+RC, PL+RC+CC) reduced “Density” by the factor 0.15 and “Expansion” by 0.25 while treatments without ploughing (CC, RC, RC+CC) reduced “Density” by the factor 0.68 and “Expansion” by 0.71. The “Height” of the shoots was al-so reduced in all treatments, significantly in four of them (PL, RC+CC, PL+RC, PL+RC+CC). The “Coverage” of thistles within the patches did not change significantly.

Figure 5 line 288

Treatments including ploughing (PL, PL+CC, PL+RC) reduced “Density” and “Expansion” more than those without ploughing (Figure 5). Adding root cutting or cover crops did not further increase the reduction effect of ploughing. Root cutting alone (RC) reduced both “Density” (50.4%) and “Expansion” (70.7%) only moderately. Treatments with competition by cover crop (CC) impacted “Expansion” more clearly than “Density”. When cover crops were combined with root cutting (RC+CC) “Expansion” was almost additively reduced, resulting in a reduction comparable to that in the ploughed treatments. “Height” was also additively reduced by the combination RC+CC but the effect was still smaller than that of ploughing (see Table 2). Root cutting has been shown to reduce “Expansion” and “Density” without reducing “Height” [29]. When root cutting frequency was increased to more cuttings than required to reduce “Density” and “Expansion”, “Height” was reduced, too [29]. This was attributed to a higher depletion of root reserves by repeated cutting by which thistles first reduced “Expansion” and “Density” be-fore giving up on “Height”. This further strengthens the observation of ploughing being the superior treatment to root cutting in reducing thistle infestations. The effect of the combined treatment (RC+CC) on “Density” was much smaller than on “Expansion”.

Using shoot “Density” measurements to rank the effectiveness of thistle control treatments is common [14,52]. Nevertheless, without measuring “Expansion” the treatment effects would have been evaluated differently,

Here we answered hypothesis 2 specifically in line 330

what confirms out second hypothesis: Evaluating both, patch size and thistle characteristics within patched changes the rating of non–chemical control treatments effects.

Especially the effects of cover crop alone and in combination with other treatments would have been severely underestimated, without the effort to measure “Expansion”. Combinations of competitive cover crops and disturbance treatments were proven to suppress C. arvense shoot densities [32,52]. Our results indicate that these effects can be even more pronounced when including “Expansion” measurements.

(3) Thistle patch sizes and thistle characteristics within patches can be monitored accurately enough using UAV-based cameras.

Section 3.3

Table 3 in line 399

Replacing reference data traditionally collected on the ground with data from aerial observations requires the so-called ground truthing of the latter [56]. The third hypothesis is linked to this requirement. Based on our results, we confirm that patch size was reliably monitored using UAV-based cameras, but not intensity (“Shoot density”, “CoverageUAV”) within patches. However, the presented ground truthing is promising for future ap-plications. Patch size monitoring is ideal for UAV-imaging. Monitoring thistle intensities within the patches presupposes a much more precise thistle identification. Higher resolutions in the camera, lower flight height or more time over a patch may assist to overcome the current limits we experienced in our experiments.

The conclusion is based on the discussion in section 3. In section 3 results are presented, interpreted and discussed. A conclusion is not a one-on-one summary of what has already discussed previously. Our conclusion aims to describe future ways on how to incorporate our innovative approaches of using whole patches as plots and their surrounding methodology into research and practical applications. You are correct that presented hypothesis relate to the methodological part, but this is exactly what our presented research is about. It focuses the methodological part and not root cutting.

As your understanding of a conclusion definitely demands a brief summary of previously discussed research questions and hypothesis and the fact that you brought up the root cutter, we addressed your concerns by adding line 403

Uncontrolled thistle patches developed not only more shoots and more cover, but also expanded in size over time. Evaluating both, patch size and thistle characteristics within patches changed the rating of non–chemical control treatments effects. Root cutting in combination with cover crops was as effective as ploughing in reducing patch sizes. Therefore, monitoring patch size changes proved to be vital in order to accurately determining infestation levels and treatment efficacies on C. arvense. Thistle patch sizes could be monitored accurately enough using UAV-based cameras while monitoring thistle characteristics within patches has to improved. 

Author Response File: Author Response.pdf