Technological Advancements and the Changing Face of Crop Yield Stability in Asia

Round 1

Reviewer 1 Report

The authors computed the Yield Stability Index (YSI) for major food crops for key Asian countries for two distinct time segments (1961-1994 and 1995-2020). The YSI indicates the degree to which crop yield response to weather fluctuations in the context of technology development. While I found this topic interesting, I do not believe this manuscript is ready for publication due to lack of rigor, significance and content.

1. What is the objective of this study? I understand the authors computed the indices and showed the results, but what prompted the authors to conduct such study?

2. The authors chose 1994 as a cutoff year for the two distinct time segment because the two fitted line for temperature anomalies in 24N-44N region versus equator-to-24N region meets (L129-130). This is not a rigorous way to determine the cutoff year.

A. What is the basis of choosing 24N latitude for temperature trend?

B. How was anomalies in regions in these two geographic zones being aggregated? Did you pick the centroid of the two regions (24N-44N vs equator-to-24N) to extract the anomalies?

3. Regarding computation of YSI,is there any calculations for step 2, “The next step is to assess the 153 magnitude of fluctuations in comparison to the mean yield.” (L153-154). If not, Consider avoiding the “first step, next step and third step” sequencing in your manuscript.

4. For figures, 

1. in the result section, consider splitting by crops (as opposed to color-code the crops) for Figure 2.

2. Why do some points have yellow highlights? I did not see any pattens of those points/shapes/crops-country combination that are highlighted.

5. The YSI effectively measures the differences in occurrences of “small fluctuation event” vs “large fluctuation event”. Over the course of more than 4 decades, both technology advancement (e.g. better genetics, tractors, fertilizers, etc.) and variations in climate could contribute to such fluctuation. I do not believe this index can separate the influence of climate variations from the influence of technology. Thus, the conclusion that “the YSI is able to indicate changes in the efficiency of production technology 260 over time, with positive index values indicating the technology's ability to respond to year-to- 261 year environmental variations.” is invalid.

5. Most of section 3 (Results and Discussion) focuses on descriptions of the results with a few sentences presenting information outside of the results (L247-248 about China’s intensive farming technology). This type of manuscript does not demonstrate how the authors’ work is compared to the literature and how their work advance science. I suggest having a separate Discussion section that discuss the following questions with referenced and/or additional analysis:

1. What is the advantage and disadvantage of the YSI that the authors used? What are other ways to compute yield stability at a national scale?

2. What are the major technology advances that may have led to much improved crop yield and/or “large fluctuation event”?

3. Why some countries/crops have higher YSI than others?

4. What is the implication of this study?

Author Response

Please find the reply in the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors investigate the appropriateness of current technologies to local environmental conditions and their impact on crop yields. To do so, they use a dispersion measure, the YSI, which can discriminate between rare and large extreme yields, and frequent minor fluctuations. The study applies the YSI to evaluate the yield stability of six crops in seven Asian countries during two periods (1961-1994 and 1995-2020)

Overall, I think the issue is worth investigating and the article is interesting. I also think the investigation is well conducted. In addition, the figures are nice. However, a lot of parts need to be much more clearly explained. And some rewriting is needed. I would encourage the authors to send a revised version of the paper.

I list some broad and specific comments below. Addressing them can improve significantly the paper:

Broad comments:

·       The objective needs to be much better defined. See below for more information.

·       Regarding the contribution, is it the first time the yield stability index is assessed for these 6 major crops in these seven Asian countries? If so, I would suggest saying so (at the end of the introduction).

·       I would like to see a clearer justification for the selection of the two time periods.

·       I would like to see a clearer explanation of the YSI.

·       I would like to see a clearer explanation of the interpretation of the YSI. In all its dimensions and regarding the relation to the use of technology, its efficiency and well technologized crops.

Specific comments:

Introduction:

·       Overall, I would suggest improving the section’s structure. I would first include all the information related to crop yields and environmental conditions. Then, the information related to technology and its impact on yields. Then, the information related to statistics. Finally, the aim. I would also suggest introducing already in this section the concept well technologized crops.

·       The aim needs to be much better defined. The aim is much wider: I would suggest including others such as assessing whether the YSI is a valuable metric for evaluating crop yield stability, comparing it to other measures of dispersion or its relation to efficiency and environmental changes, etc.

·       Lines 34-35: The text reads: “and production technology should be able to respond to environmental features typical for the geographical zone of production”. I would suggest clarifying here that in what way should production technology respond to environmental features.

·       Lines 52-54: The following sentence is not clear enough: “The definition of „reasonably stable” yield, i.e. of the maximum allowed cumulative deviation from the increasing yield trend is an intriguing problem, that has to consider the objective of having low levels of production-related risks”.

Methodology:

·       Line 85: Beans are not included in the analysis. I would suggest removing it.

·       Lines 90-92: The text reads: “Beans make a significant contribution to global production and are a valuable source of protein in many developing nations”. Beans are not included in the analysis. I would suggest removing the sentence.

·       Line 104: The following reference “as (Bacsi et al., 2022) show” should not be between brackets. The authors have done this several times throughout the paper. I would suggest correcting all of them.

·       Table 1: What does the last column show? It is not clear to me. I would suggest explaining it in the body of the text.

·       Table 2: What do the two last columns show? And the last row? I would suggest explaining it in the body of the text.

·       Lines 124-125: The text reads: “which was subsequently divided into two distinct segments”. I would suggest including here the two distinct periods.

·       Lines 125-135: The text reads: “Annual temperature anomaly series published by the Goddard Institute of Space Studies were retrieved for the major geographic zones of Earth”. What for? This part needs to be explained in a clearer manner. I would suggest some rewriting to make it more concise.

·       Lines 127-130: Why are these series depicted in Figure 1? Do both of them correspond to the analysed regions? If so, I would suggest noting it here.

·       Lines 129-130: The text reads: “for the latitudes of N24°- 129 44° zone”. I would suggest inserting a note saying that these are the specific latitudes of the analysed countries. Please note already here that the N24°- 129 44° zone corresponds to the northern latitudes and the Equator-N24° zone to the equator zone. I think it would be a good idea to include here which countries correspond to each of them.

·       Why are the two fitted curves included? What do they add to the analysis? This needs to be explained.

·       Lines 133-135: Why is the study period partitioned according to temperature? Why this criterium? Why is it important? I would like to know.

·       Lines 142-143: The text reads: “the more stable (i.e. less fluctuating) the crop in the given time period”. It should be the crop yield, shouldn’t it?

·       Lines 142-145: The interpretation of the YSI needs to be more clearly explained. In all its dimensions: Negative/positive and larger/smaller.

·       Line 148: I would suggest completing the following sentence: “For a technical description see these publications”.

·       Lines 150-172: The paragraph needs to be improved. Would including equations make it simpler to understand? The same applies to lines 173-180.

·       Lines 181-186: I would suggest separating the equation into a separate line.

Results and discussion:

·       Lines 189-190: The text reads: “Stable yields mean positive YSI values”. I would rather say: “positive YSI values mean stable yields”.

·       Lines 205: The text reads: “Figure 3 presents the YSI values together with the respective CV% values”. Why is it important to show the relationship between these two variables? What does it add to the analysis?

·       Lines 205-207: The sentence reads: “Large yield fluctuations should show negative YSI values and high CV% values, while stable yields should be associated with large positive YSI and small CV%”. The interpretation of the YSI should be exactly described in lines 142-145. It is now not clear enough. As indicated in a previous comment, this explanation of the interpretation needs to be improved. If it were better, it would be easier to understand these results.

·       Lines 207-208: The text reads: “looking at the figure, this rule does not always prevail”. Why? They are both measures of dispersion. Some more discussion is needed here.

·       Lines 208-209: The text reads: “Small CV-s are associated with both negative, and positive YSI values for rice and bananas in both periods”. I would like to know, are these negative and positive YSI values large or small?

·       Lines 214-217: The text reads: “These values indicate that YSI really separates small fluctuations from large ones, and can provide more finely tuned information regarding yield stability than the traditionally used standard deviations or variances of time series”. This argument needs to be further developed.

·       Figures 3 and 4: I would suggest using the same range of values in the axes. It is easier to compare between time periods.

·       Lines 237-239: The text reads: “Well technologised crops are those with positive YSI values”. This should also be more clearly explained in lines 142-145. Well technologised crops always have positive YSI values? What does this imply for negative values? Negative values correspond to crops which are not well-technologised? What about larger and smaller values?

·       Lines 238-239: The text reads: “crops and countries considerable changed in this respect from the earlier to the later time periods”. Which respect? Please develop this further.

·       Table 3: What do the last two columns show? This should be explained in the body of the text. And the rows named “no. of WT countries” and “proportion of WT countries? What do they show?

Moderate editing needs to be done. 

Author Response

Please find the reply in the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

This is an interesting manuscript.

As the authors note (lines 73-79), ...the present paper applies a “yield risk index” for assessing 6 major crops in Asia for 7 countries being important producers and exporters of these crops. Its novelty is to examine the trend of yield stability change between two time periods, the relationship between the Yield Stability Index (YSI) and average yields, the identification of well-technologized countries and crops, and the correlation between the coefficient of variation and YSI, for the major crops of Asia...

Because there is room for improvements, some comments are next given that help the authors to improve the manuscript.

- In lines 66-67 the authors note: “...The former may create an unacceptable risk for the farmer, while the latter can be handled well, providing little risk”. They should clearly define it, by supporting it also with the proper references.

- In lines 85 - 86 they note: "The chosen crops are: bananas, beans, rice, palm oil, tea, coffee, and cotton seed." The authors should sufficiently explain why the “cotton seed” instead cotton “fibber” has been chosen....

- The discussion that takes place in section 3, does not sufficiently take into account similar results of previous research, in regards the measurement and/or methodology issues.

- The authors should mention the disadvantages or defects of the tool of measurement or/and methodology and give suggestions for further research.

- The authors could further increase the value of the article if they sufficiently enrich the bibliographic review with more (relevant) publications. They should also check if they follow the journal's guidelines in the citations and "References".

- Some elements in the results and discussion section could be moved to an appendix.

- They should make more obvious the generalizations they give in conclusion section, for which the academics abroad are interested.

- The authors should also make more evident the practical usefulness of the findings of the research for farmers, marketing companies and public authorities.

- They should also make the manuscript more friendly to the audience of the journal.

Author Response

Please find the reply in the attached file.

Author Response File: Author Response.pdf

Reviewer 4 Report

The paper is interesting, but it needs further improvements

1. Introduction

-A more complete context of the bibliographic references is recommended.

-You should better highlight the main contributions of your paper

2. Methodology

-L82-84-Describe the data source and the data selection process

-L146-I recommend presenting the index formulae

-L173-186-Try to convert this into a footnote

3. Results and discussion

-No careful discussion of the results is carried out. This needs to be improved 

Author Response

Please find the reply in the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The paper has improved a lot. I would now recommend it for publication. Notwithstanding this, I think its readability could be somewhat improved.

In my opinion, English language needs to be edited. 

Reviewer 4 Report

The authors have improved the paper carefully. It's ready for publication now.