Weed-Competitive Ability of Teff (Eragrostis tef (Zucc.) Trotter) Varieties

Round 1

Reviewer 1 Report

The paper needs significant revision.  The topic in interesting and novel and the design appears to be robust (although some details are not thoroughly explained).  The logic, organization, and grammar need to be significantly improved.  There are too many vaguely worded sentences and grammatical errors to list or correct them all.   The analysis does not appear to be robust.  The Authors need to provide evidence that the model is partitioning the variance between whole, split, and split-split plots and is not pseudo-replicated.  Providing degrees of freedom for the fixed and error terms in the anova table will allow the reviewers to determine if the analysis is correct.  Also, if there are year and site interactions with treatments, there’s no need to split analyzes by year and site.  Doing so reduces the power and these interactions are interesting (e.g. suggest GxE interactions in crop and weed completion).  The results can be presented by year and site.  The tables and figures are also difficult to read and need improvement.  For example, in figure 1 the post hoc differences (and letter designations) are within site year but use the same letters.  It’s difficult to make the comparisons and interpreted the interactions.  In figure 2, the treatments are not clearly labeled in the legend.  Use something other than with/without (e.g. Weeded/controls). 

Author Response

Dear Reviewer,

Thank you very much for the precious comments that you gave us on our manuscript.

We have recruited an English language editor to this manuscript before we submit it to the MDPI – Agronomy journal. We incorporated thoroughly the comments and suggestions provided by the language the language editor. However, we have tried to do an extensive editing of English language and style on the revised document that we uploaded it on the MDPI-agronomy journal page.

The design that we used during the experiment implementation is split plot design, which contains hand weeding as main plot and the different teff varieties as subplot. It did not have split-split plots and hence did not include such types of plots in our analysis.

We completely agree that if the year and site have significant interaction with the treatments, it is not necessary to present the data by year and location. We have presented the data in figure one without separating year and location and they had significant interaction with varieties. The same letters in the means displayed in figure 1 show their equal ranking. The post-hoc tests were done for the year, location and variety combined and the means connected with the same letter have non-significant difference. In figure 2, we have changed the legend as “weeded” and “unweeded” following your and other reviewers’ comments.

We are very pleased to receive more comments and suggestions if we do not address your questions and suggestions in this reply.

Thank you once again

Author Response File: Author Response.pdf

Reviewer 2 Report

This work provides valuable information regarding the weed-competitive ability of different teff varieties in a two-year experiment carried out in two different locations In Ethiopia under field conditions . The experimental design and methods are in general, comprehensively described. The study, although it is not new for other crops in which the competitive capacity with weeds between cultivars has been evaluated, has novelty for teff cultivation in an region requiring this kind of research. This manuscript is a good contribution to the literature.

However the paper is too long, the most important results expected from both the title of the paper, and its abstract, in which the results and the work is well reflected, are buried in the length. I suggest reviewing the work in order to eliminate redundant parts that appear in the results, in the tables and/or figures and even in the discussion, in which results are sometimes included. If these could be deleted, the logic of these sections could be strengthened. The paper needs to focus more.

Specific Comments

INTRO

L30: Add scientific name Eragrostis tef (Zucc.) Trotter

L51: Reference

L53-57: Are you talking about the need for alternative (non-chemical) control methods to chemical control options that you say are not used? Rewrite

L66 and 71: Hansen et al. , Wicks et al.

M&M

L110. Where is Table 1 cited in the text? I suggest to delete and include the information in the text, explaining the climatological conditions for each study area.

L100: Average temperature for Axum?

L129: Where is Table 2 cited in the text? I suggest to create the sub-heading: Plant material

L142: Yield is also a data associated with the crop (move L169-181, too long, rewrite)

L154: When were weedings carried out? (Add weeding dates) On what basis were those dates selected?

L162: Put “Weeds species identification” before density and biomass

L166: Here and in general, too many references, and in some cases not appropriate.

L182-187 It is a rough estimation. Not well explained (the total weeding time of the three weedings?. According to your results, could be as high as 81 full days per hectare for a teff variety?(1,950 hours/ha in 2015) Do you agree? Is it real?

RESULTS

318  After the first citation  P. lanceolata

 DISCUSSION

Rewite and reduce the discussion eliminating all redundant (resultas) or unnecessary information (L456-461). Subheadings can also be deleted.

Author Response

Dear Reviewer,

Thank you very much for the precious comments that you gave us on our manuscript.

In the newly revised manuscript, we have tried to avoid redundant statements and make it more focused.

We found your comments and suggestions more valuable and considered them for the improvement of the manuscript. Thank you once again!

The weeding time that had been calculated was in terms hours a single person could take to hand weed a hectare of land. The highest weeding time indicated that the highest weed intensity (incidence) in the experimental site. We do agree with our result that a person could take 1950 hours to hand weed a hectare of teff field considering that the person may not have the same energy to pick the weeds from the whole field. Of course, this was calculated based on a sample data from a single experiment site and may have different result when studied considering different sites and seasons!    

We are very pleased to receive more comments and suggestions if we do not address your questions and suggestions in this reply.

Thanks once again

Author Response File: Author Response.pdf

Reviewer 3 Report

I found interesting manuscript "Weed-competitive ability of teff varieties" and suitable for Agronomy Open access journal.

Following additional work should be done before publishing. Authors should focus on Material and Methods section which must be supplemented by missing information.

Please add Latin name of teff species on manuscript title

I didn't understand how weed utilization as a forage increase crop yield (row 52). Please rewrite sentence.

All Latin name of species should be written Italic fonts throughout whole manuscript.

Missing references list number at position Wicks and co - researchers (line 71).

Missing references list number at position Bertholdsson (line 77).

My opinion sub-chapter wrong title. Instead "Climate in 2015 and 2016" I suggest Weather condition during experiment. (Row 107). Missing table 1 citation. Data and comments for weather conditions very limited at table and sub-chapter. 

Please check and correct yield gap data at table 2. My opinion few range data are wrong. At sub-chapter 2.2. missing table 2 citation.

Between experimental sites operation data are different. At Axum site for both experimental years fourth ploughing tillage was done. At Mekelle three times experimental field was plow. Please explain differences and effect on weed competition. That remarks base on sentence (rows 51-52) "... many direct and cultural methods used by farmers to reduce weed competition such as frequent tillage...

My opinion days to different teff stages aren't phenology data and crop traits. I suggest exclude iv teff development   

Row 141 data related to weeding time consist third classes not second (ii)

Please more precisely describe how visually weed shoot density was assessed. Commonly Braun Blanquet methodology researcher used for  species coverage and species identification. Firstly I note that shoot density were assess.

Dominant weed species was identify before sowing? Your opinion that species well characterized weed flora of teff species? 

Please used Word Equation formula for yield losses equation.

Few times square meter units used incorrectly. Please use superscript for 2 (f.ex. row 185).  

Comments written at rows 207-208 is addressing to table 2 or 4?

Figure 2. Please change scale for axis y for tiller No. The same proposal for Figure 3 and graph of grain yield. Axis 'y' should be max. 2000 kg. 

Sub-chapter 3.2 is questionable for me. I couldn't imagine methodology description and how visually assessed number of weed shoots.

I didn't understand how weed dry weight data collected (data presented at Table 7 and sub- chapter 3.3.) base on methodology presented in sub-chapter 2.3. ii. Please add methodology of weed weight measurement with separation for mono and dicots.

Rows 316-318 Latin name of weed species please write using Italic fonts.

The time taken for weed control was few folds time longer at Mekelle than in Axum. My opinion very important (information was missing) is different tillage system  and no weed density information on time of identification weed species (before sowing).

Rows 320-321 very limited information about biomass and teff grain yield (table 8). My opinion too strong limited.

Discussion part is well prepared. Few editorial remarks. All Latin name of species (crops and weeds) must be written by Italic fonts. Use correct square meter units throughout discussion part. 

Author Response

Dear Reviewer,

Thank you very much for the precious comments that you gave us on our manuscript.

The experimental sites are located on the same altitude but have different soil types. Teff grows both under sandy loam soil, which was found in Mekelle research site, and under Vertic black soil, which was found in Axum, research site. Farmers plough their land more frequently in a field with Vertic black soil and less frequently in sandy and sandy loam soils. That is why the plough frequency in Axum was 4 times but that in Mekelle was 3 times. Except tillage frequency, the weed management practices are equal for both Axum and Mekelle. Difference in soil types may have differences in weed species composition and hence the varieties are tested for their weed competitive ability under the two major soil types to accommodate a representativeness.

We have assessed the dominant weed species before sowing to assure a good picture of the nature of the weeds in the experimental sites so that we can have a good information about which weed species compete more with teff. It was also possible to assess the dominant weed species after sowing but hand weeding is implemented during the vegetative stage of the weeds, which, we assume to be, difficult for identification. We simply mention the dominant weed species in the experimental site without linking them with the teff competitive ability in order to show the reader the weed species found in the experimental sites.

It was a type error but we do not estimate weed density visually. We visually determine the weed cover. We have corrected the type error in the newly revised manuscript.

We have now clearly put the method used to determine the weed dry weight on the materials and methods section of the revised version.

Table 8 contains the biomass yield and gain yield of the varieties from plots with and without hand weeding to calculate the yield loss due to weed competition.

We are very pleased to receive more comments and suggestions if we do not address your questions and suggestions in this reply.

Thanks once again!

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The main concerns in my previous review (below) have not been addressed.

The paper needs significant revision.  The topic in interesting and novel and the design appears to be robust (although some details are not thoroughly explained).  The logic, organization, and grammar need to be significantly improved.  There are too many vaguely worded sentences and grammatical errors to list or correct them all.   The analysis does not appear to be robust.  The Authors need to provide evidence that the model is partitioning the variance between whole, split, and split-split plots and is not pseudo-replicated.  Providing degrees of freedom for the fixed and error terms in the anova table will allow the reviewers to determine if the analysis is correct.  Also, if there are year and site interactions with treatments, there’s no need to split analyzes by year and site.  Doing so reduces the power and these interactions are interesting (e.g. suggest GxE interactions in crop and weed completion).  The results can be presented by year and site.  The tables and figures are also difficult to read and need improvement.  For example, in figure 1 the post hoc differences (and letter designations) are within site year but use the same letters.  It’s difficult to make the comparisons and interpreted the interactions.  In figure 2, the treatments are not clearly labeled in the legend.  Use something other than with/without (e.g. Weeded/controls). 

Agronomy Review 12.10.19

Abstract: needs to be improved for clarity and accuracy

L15: poorly written.  Improve grammar, add articles.  E.g. “Teff is a staple and well-adapted crop in Ethiopa.  In the region, weed competition and control have major impacts on yields and economic returns.”  Add statement that emphasizes the importance of crop competitive ability in the integrated weed management for teff. 

L16-20:  explanation of experimental design should be more concise.  E.g. “Treatments were applied using a randomized complete block design with three blocks at each site.  Hand weeding and non-weeded treatments were applied to whole plot treatments with teff varieties assigned as split plots within whole plots.”  Also need to include a line on what was measured and logic of how you estimated competitive ability. 

L15-16. Remove years and names of locations.  Not important enough to include in abstract.  It’s enough to state that trials occurred at two locations for two growing seasons at each location. 

L20-27: The main objective is to determine relative competitive ability among teff varieties.  Put more emphasis on this, rather than starting with the main effects (average effects of hand weeding across all varieties.) That weeding reduced weed biomass and increased yields is not surprising or important.  The grammar and writing needs to be more clear and accurate.  E.g. line 21-22, “Varietal differences resulted in significant variation in teff and weed responses” is so vague that it’s almost meaningless. Better as, Teff varieties differed in competitive ability (i.e. weed suppression and response to weed competition).  The alpha numeric codes for the lines do not provide added info.  Consider dropping these codes and discussion of specific varietal difference and, instead, focusing in the variation in competitive ability and the importance/mechanisms of the results.

Introduction:  The introduction needs to be significantly revised for clarity and brevity.  There’s too much focus on adaptation to different environments.  This is not a focus of the paper and the terminology used is not accurate.  Crop traits are selected by growers and/or breeders (artificial selection), thus do not adapt on their own, as suggested by the first line (L31).  I suggest a more focused structure to the introduction with the following topic sentences.

Teff is an important (e.g. well-adapted, widely grown, staple) crop in the region (and else where). Weed control/competition has major impacts on teff yields in these production systems. Crop competition/ competitive ability is an important tool in low-input, integrated weed management systems. Competitive ability has been defined and measured as… Certain crop traits have been associated with crop competitive ability in cereals. Include if this has been studied in teff (i.e. clearly emphasize novelty of this work).

L43-51:  This paragraph may not be needed.  It is vague, confusing, and tangential.  It’s not clear if traits are a product of the growing conditions, genetic differences, or interactions between those two factors (genotype by environment interactions).   These traits are not clearly linked to the main topic.  The last sentence does not make sense.  The broad adaption does NOT cause the weed pressure.  It’s sufficient to make the case that weed control is major constraint on teff production in low-input systems. 

L60: provide citation or more detailed evidence.  Especially for claim of health risks, a citation is needed. 

L88: include rational for identifying traits associated with competitive ability (e.g. may be able to predict or select for competitive ability). 

L89: vague topic sentence.  Aspect of what?  To competitive ability?  Isn’t this the same as tolerance ability that is discussed earlier.  You should also discuss how these aspects of competitive ability are linked.  If a variety reduces weed biomass (suppressive ability), that may increase its tolerance ability.

L90: These trade-offs need to be more clearly explained and supported.  The language and grammar is vague.  It’s documented in cereals that the highest yielding varieties in weed-free conditions are not always the same as those in low-input, organically-managed systems, but this is not direct evidence of a trade-off.  The paper you cite here (Andrew et al. 2014) has a much more clear discussion of this topic and make the important distinction that yield potential in weed free environments often drives breeding and the farmers’ selection of varieties.  This process can select for reduced weed competitive ability (e.g. short statured wheats). 

Methods: In general, headings are over used and all but the numbered headings should be removed and that information can be added to the topic sentence.   Grammar, logic, and word use still needs to be improved. 

Sites:  Remove added headings.  Add an introduction/summary statement that states the two sites separated by 245 km and have similar elevation and climate, but differ in soil type.  There’s a lot of unnecessary or redundant information.  

L103: cut (capital of Tigray region).  This info in not needed. 

L104: Cut distance relative to Axum.  You already provide the coordinates. 

L107: The agroecological classification system is not cited or widely used.  Just describe the climate, etc. 

L111: Cut main campus.  This info is not relevant. 

L117: cut out this heading.  Include in the topic sentence.

L119: Table 1 is referenced but does not show these data or support these statements.   Include some discussion of climate during the trials as it relates to the results.  Where these years about average or anomalous in any climate variable?

L127: more clear to describe design as RCBD with three blocks with split plots.  Clarify in each location if trials were in the same or new locations each year. 

L133: Another example of poor grammar and vague use of terminology. “Teff farmers” is redundant since teff is the subject of the sentence.  If something is adapted to every climate/soil, is it adapted?  Adaptation implies that selection for a given environment has occurred.   I think what you might be trying to say is, The varieties used in this trial are commonly grown teff varieties across wide climate ranges in Ethiopia.  More info on varieties should be added here. Explain origin of the DZ-lines.  Are these experimental or publically available?  If available, why aren’t they named?  Include the explanation of the “local” landrace in the text rather in Table 2.  If seed color is important to this research, explain why.

This paragraph doesn’t have a clear topic and this sentence does not describe that topic as it should.  The main topic is the general management of the plots.  Remove the long table caption on Table 3 and include this info in the text.  There’s other info from Table 3 that could be moved here (see comment on table 3 below). 

Table 2:  Condense.  I don’t see a reason to include year of release, seed color.  Maturity and heights ranges overlap among varieties that make the differences less apparent.  Where do these ranges come from? Provide that information of the data source.   Could you categorize varieties at early, mid, late maturing or short, med, tall? 

Also in Table 2: you must use a consistent methodology to calculate yield gap range.  Or better yet, cut this column out completely.  Why is it needed?  Is this an estimate of the yield reduction due to weed competition?   

L135: capitalilze Table 3. 

Table 3: needs to be condensed by 50% or more. There’s a lot of unnecessary detail provided here that detract from the main information, weeding frequency and timing and how this varied between sites and years.  Multiple ploughing dates for field prep are not needed in the table, just mention that prior to seeding, fields were keep weed free with tillage.  Do you actually mean ploughing as in inversion tillage or do you mean tillage?  Describe the type of tillage in the text.   Crop assessment date ranges can be cut and state in text that crop assessment occurred from 7 days after planting (DAP) to harvest.  Move the crop and weed biomass measures to the text, emphasizing that the weed biomass data collected at the end of the season, after grain harvest. 

L153: Cut the unneeded headings throughout.  Just use topic sentences.  None of the current headings are needed.  The methods section starts with simple, numbered headings (i.e. 2.2 Experimental Design and treatments on L126).  These are the only headings that are needed.  On Lines 164-165, you used a sub heading with an additional sub-sub headings that are each formatted differently.    As a general rule, if you have a heading between each paragraph, you are over using headings. 

L161: add information of if biomass was wet or dry weights and if samples were oven dried.

L166: Weed shoot density is not standard terminology for weed density.  Should be weed or weedly plant density.  Include that weeds were sorted into monocot and dicot functional groups. 

L174: Add objective of this measure to the topic sentence. Determining dominant weed species is not part of the experiment, rather its purpose is to determine the dominant weeds species in the experimental fields or background weed population prior to planting. 

L182: Use more direct and clear language.  Rather than posing a question, state, To determine the effect of weed competition on teff yields (tolerance ability)…

L185: use consistent terminology for the aspects of crop competitive ability.  This is weed suppression or suppressive ability.  Also separate this metric into a separate paragraph. Keep this paragraph focused on tolerance or effects of weed competition on yield. 

L186: clarify that reference treatment used to calculate the reduction in weed metrics.  Is this measured relative to plots where no crop was planted?   Is it calculated among varieties in the unweeded reference plots?  It needs to be clarified. 

L203-218:  The authors must show that the analysis is not pseudoreplicated (https://en.wikipedia.org/wiki/Pseudoreplication).  With a split plot and repeated measures with the split plots (a split-split plot), there is a high risk of this occurring in this analysis.  As I emphasized in the previous review, the best way to demonstrate this is to provide information how the variance was partitioned among the various plot levels by showing the degrees of freedom in the ANOVA tables.  As I cannot determine if the analysis is robust, I cannot determine if the results are robust and will not review this manuscript further.  I will note that the tables and figures need further editing for clarity.  The ANOVA tables need to be organized by whole, split, and, where needed, split-split plot levels.  The use of four digit p-values and codes for p-values is redundant and makes the tables difficult to read.  Use only the codes or symbols for the p-value categories.  The figures are sloppy and need revision.  The fonts should be consistent.  Some figures do not match the title.  For example Figure 2 title is tiller number but has grain yield results. Some figures do not fit the page.  In general, there are too many figures. 

Author Response

Comments from Lars Olav, Ole Martin and Torfinn Torp (Statistician)

Rev. 1 – Main concerns – Round 2

General

“The paper needs significant revision. The topic in interesting and novel and the design appears to be robust (although some details are not thoroughly explained). The logic, organization, and grammar need to be significantly improved.  There are too many vaguely worded sentences and grammatical errors to list or correct them all”.  Comments (grammar and vaguely worded sentences: The journal (Agronomy) has a language editing service and we will order that service from the journal for improving the language.

Statistics

“The analysis does not appear to be robust”.  Comments: In general, we have invested considerable resources in the choice of statistical models and methods. We will also mention that a statistical expert, who works exclusively with statistics, is one of the authors. As remarked and suggested below, by Reviewer 1, we have also in the past discussed to base all results and discussions directly on the fitted model including all the factors weeding, genotype, year, and site. Although the degrees of freedom will then be increased, we considered it that not splitting will make the results and presentations unnecessary complicated for the readers. Even when splitting by year and site the degrees of freedom is considered to be satisfactory high because there are 3 replications, 10 genotypes, and 2 levels of the main plot factor weeding (performed or not). In contrast to the comment, we consider the analysis to be robust even when splitting by year and site.   

“The Authors need to provide evidence that the model is partitioning the variance between whole, split, and split-split plots and is not pseudo-replicated”. Comments: (i) We believe, as described in ‘2.2 Experimental design and treatments’ and ‘2.3 Data collection’, that we provide clear evidence that this experiments is clearly not ‘pseudo-replicated”. (ii) It is not a split-split-plot design, see ‘2.2 Experimental design and treatments’. It as a split-plot with weeding on main-plots and genotypes on sub-plots.  

“Providing degrees of freedom for the fixed and error terms in the anova table will allow the reviewers to determine if the analysis is correct”.  Comments: Degrees of freedom is now included in Anova tables. Because we fit a mixed model the Satterthwaite approximation for the denominator degrees of freedom was used for the tests of fixed effects.

“Also, if there are year and site interactions with treatments, there’s no need to split analyzes by year and site.  Doing so reduces the power and these interactions are interesting (e.g. suggest GxE interactions in crop and weed completion).  The results can be presented by year and site.” Comments: See our comments above.  

The tables and figures are also difficult to read and need improvement.  For example, in figure 1 the post hoc differences (and letter designations) are within site year but use the same letters.  It’s difficult to make the comparisons and interpreted the interactions.  In figure 2, the treatments are not clearly labeled in the legend.  Comments:  Fig. 1-2-3, different letters are used between years; small letters the first year versus big letters the second year

Use something other than with/without (e.g. Weeded/controls). Comments: We agree, it is changed.

Author Response File: Author Response.docx

Reviewer 3 Report

Manuscript has been significantly improved but still some remarks not accept (f.ex. at table 2). Also I'm not satisfy on weed shoot number measurement explanation. By editor decision I leave the manuscript acceptance for next processing steep.

Author Response

Dear Reviewer, 

Thank you very much for your tireless contribution to the improvement of our paper.

Regarding the weed density measurement, we simply count the number of weed plants using 25cm X 25 cm Quadrate before each hand weeding from each treatments and plots.