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Peer-Review Record

Optimizing Overhead Irrigation Droplet Size for Six Mississippi Soils

Agronomy 2020, 10(4), 574; https://doi.org/10.3390/agronomy10040574

by J. Connor Ferguson^1,*

, L. Jason Krutz², Justin S. Calhoun¹, Drew M. Gholson³

, Luke H. Merritt¹, Michael T. Wesley, Jr.¹, Kayla L. Broster¹ and Zachary R. Treadway¹

Reviewer 1: Anonymous

Reviewer 2:

Farhat Abbas

Reviewer 3: Anonymous

Agronomy 2020, 10(4), 574; https://doi.org/10.3390/agronomy10040574

Submission received: 31 March 2020 / Revised: 10 April 2020 / Accepted: 13 April 2020 / Published: 17 April 2020

(This article belongs to the Special Issue Optimization of Water Usage and Crop Yield Using Precision Irrigation)

Round 1

Reviewer 1 Report

Comments

SUMMARY

The paper addresses the research area related to "Water Use and Irrigation" of the MDPI Agronomy journal. I believe that the target journal is an appropriate forum for this article. The paper aims to (i) Determine the optimal overhead irrigation duration for six common soil types found in row-crop production regions in Mississippi; (ii) Determine the optimal overhead irrigation intensity (defined as unit of water per unit of time) for six Mississippi soil types; (iii) Using a droplet image analysis system in the field, quantify the droplet spectrum for five sprinkler types that are commercially available in Mississippi.

BROAD COMMENT

The Introduction section is well written with recent references. The materials and methods section is well explained and detailed. However, in my point of view, the authors failed to provide detailed information about the preliminary statistical test conducted before the means separations. Besides, another weakness of this study is that the authors failed to put the conclusion of the study in a big picture; it is too specific to the study area and the experiment. Please do include more implications of the results of the study in the conclusion section.

SPECIFIC COMMENTS

Lines 106-107: Please include in the manuscript the methods used to measure the soil parameters such as organic matter, P, K, pH, Ca, Mg, Zn (Table 1).

Lines 291-295: The results presented in Table 3 imply that the authors conducted ANOVA before doing the means separations. I suggest the authors include in the manuscript the detail about the statistical tests they performed on the data before doing the ANOVA. I also recommend them to indicate the method they used for the means separations (least significant difference, etc….).

Author Response

Response to Reviewer 1 Comments

Point 1: The Introduction section is well written with recent references. The materials and methods section is well explained and detailed. However, in my point of view, the authors failed to provide detailed information about the preliminary statistical test conducted before the means separations. Besides, another weakness of this study is that the authors failed to put the conclusion of the study in a big picture; it is too specific to the study area and the experiment. Please do include more implications of the results of the study in the conclusion section.

Response 1: The statistical analysis has been completely re-worked and the part in the manuscript explaining what was done has been re-written. This was a very good point and one that was addressed and fixed.

Point 2: Lines 106-107: Please include in the manuscript the methods used to measure the soil parameters such as organic matter, P, K, pH, Ca, Mg, Zn (Table 1).

Response 2: The methods used to measure the soil parameters has been added and was yet another good point raised by the reviewer.

Point 3 Lines 291-295: The results presented in Table 3 imply that the authors conducted ANOVA before doing the means separations. I suggest the authors include in the manuscript the detail about the statistical tests they performed on the data before doing the ANOVA. I also recommend them to indicate the method they used for the means separations (least significant difference, etc….).

Response 3: As stated with point 1 -the statistical analysis has been completely re-worked and the part in the manuscript explaining what was done has been re-written.

Reviewer 2 Report

Discussion section needs further evidence and material to support the conclusive statements. For example, irrigation water requirements are more related to the type of crop than soil type. How would the researchers balance between the types of crop species on one different types of soil in the region? Additionally, if the study findings lead to the selection of a specific orifice of sprinkler then how the soil and crop types will be related to the orifice type/size? Discussion also needs support from finding of published work if any. If the authors improve the discussion by including crop species matter, the same will have to be the part of introduction. The specific comments include format of presenting numbers and units. Please see the specific comments below in addition to similar points not mentioned here.

Lines 121-122 [and elsewhere]: 2.1 mm, 3.2mm: Why are the units connected with and separated from numbers?

Lines 122, 123, 124: 90 minute, 150 seconds: Why time units are singular and plural?

Line 126: 15cm depth.

Line 126: How was saturation determined?

Author Response

Response to Reviewer 2 Comments

Point 1: Discussion section needs further evidence and material to support the conclusive statements. For example, irrigation water requirements are more related to the type of crop than soil type. How would the researchers balance between the types of crop species on one different types of soil in the region? Additionally, if the study findings lead to the selection of a specific orifice of sprinkler then how the soil and crop types will be related to the orifice type/size? Discussion also needs support from finding of published work if any. If the authors improve the discussion by including crop species matter, the same will have to be the part of introduction. The specific comments include format of presenting numbers and units. Please see the specific comments below in addition to similar points not mentioned here.

Response 1: The discussion section has been completely re-worked. As to the point about specific crop types, the authors did not feel that was needed as that could muddle the points raised in the manuscript and be too specific for the aim of the impact sought by the manuscript.

Point 2: Lines 121-122 [and elsewhere]: 2.1 mm, 3.2mm: Why are the units connected with and separated from numbers?

Response 2: This was a definite miss. All of these have been changed. Thanks for catching that!

Point 3 Lines 122, 123, 124: 90 minute, 150 seconds: Why time units are singular and plural?

Response 3: Again – another clear thing needing changing. Great catch – all of these have been standardized.

Point 4 Line 126: 15cm depth.

Response 4: This comment was not entirely clear to the authors, but this has been addressed and hopefully edited as the reviewer had hoped it would be.

Point 5 Line 126: How was saturation determined?

Response 5: This was a very good point and has been readdressed and clarified in the materials and methods section.

Reviewer 3 Report

The manuscript entitled “Optimizing overhead irrigation droplet size for six Mississippi soils” by J.C. Ferguson, L.J. Krutz, J.S. Calhoun, D.M. Gholson, L.H. Merritt, M.T. Wesley Jr., K.L. Broster and Z.R. Treadway (Ref. agronomy-776030) presents results from a test conducted under controlled conditions in which several sprinklers were used for irrigating six soil types differing in texture and organic matter content. Authors provided interesting data for optimizing sprinkler irrigation practices and tried to discuss their results on that sense. The experiments seem to be carried out correctly and the results presented are interesting. I think that the manuscript fits within the scope of Agronomy, and within the scope of the Special Issue to which it is intended.

However, this work has several flaws that prevent its publication in its present form because some clarifications are needed in the Materials and Methods section and the Discussion must be improved. Furthermore, the abstract is unclear and needs a deep revision.

Finally, English is rather good but needs slight improvements in order to remove redundancies.

Therefore, I suggest a major revision of this manuscript prior to its eventual acceptance in Agronomy.

Specific comments:

Abstract:

The abstract is not informative in the sense that readers do not know how the experiment was performed and what determinations were carried out. The experimental setup and the treatments are not clear.

Line 16: “by the crop” instead of “at the crop level”.

Lines 16-17: This sentence is confusing. Identical to what? Please, re-phrase.

Lines 20-23: The experiment performed is quite confusing from these sentences. Please, improve.

Lines 25-26: All droplet sizes were appropriate for the six soils? This sentence is unclear.

Lines 26-28: This conclusion is not justified by the results shown in this abstract. As far as I understood, you did not find differences on the use of several sprinklers and you did not mention what were the optimal durations and intensities for any of the six soils studied, which, by the way, we do not know the differences among them.

Keywords:

Please, do not use words that already appear in the title.

Introduction:

This section leads the reader to the objectives of the study and the problem to cope with; however, some parts seem disconnected among them and this could lead to confusion of the readers. From my viewpoint, 47 references for an introduction are too many. Please, consider reducing the number of references.

Line 35: Remove “type”.

Lines 38-39: “is less uniform compared to overhead irrigation” instead of “is a less uniform method of irrigation compared to overhead methods”.

Lines 39-40: This sentence is confusing. I do not see the relation between the first and the second parts of the sentence.

Lines 40-49: Somewhat this seems to be not well organized and some ideas are not linked to what was previously stated in this paragraph. Please, check.

Line 42: Remove “at” before “unsustainable”.

Lines 62-70: This paragraph can be merged with the previous one. Moreover, here you cite 15 articles in 9 lines, are all these citations needed?

Lines 65-66: Check this sentence, please. I do not see what you mean by “can all result”. What do you want to say about soil porosity? It increases or reduces?

Lines 67-70: This seems to repeat the sentence in lines 65-66.

Line 78: Remove “to answer this question. Objectives for the study were”.

Materials and Methods:

This section would improve if essential information needed for a correct understanding of what has been really done in this study is included. The experimental design is correct and the experiment has been carried out with a high degree of care.

Lines 102-104: How were these soil samples collected? From which depth? Did you collect 140 L of each soil to fill up the two 70-L containers per soil? Was soil structure modified when collecting the samples? This would have a large influence on soil response to irrigation and crusting formation.

Table 1: I am not used to see the values of nutrients in kg ha^-1 but Ca concentrations seem very high. Could you provide any information on the previous use of the collected soils?

Lines 113-114: I would use “that” instead of “where it”.

Line 115: Was this for mixing the soils? How did you determine field capacity?

Line 116: This is unclear. Each container had four replications? What were the containers? If you used 8 replications per soil type, did you use 120 L in total for each soil type?

Line 125: What do you mean by “If the core was at any depth”?

Figure 1: In the caption you say that the noozles were calibrated to apply 20 mm per minute, whereas in the text (line 121) you said that they were calibrated to apply 2.1 mm per minute. Which one is correct?

Lines 150-151: Were the six soil types different from those previously described? If so, why stating this again?

Lines 153-155: I do not see how you calculated irrigation intensity from this sentence. Please, complete.

Line 197: “in the down”, do you mean “on the ground”?

Line 203: Which test was used for mean separation?

Lines 203-204: I would remove this sentence. This procedure is better explained in the following line.

Lines 206-207: Remove “except using the model: Intensity = soil type by time by water volume and replication was set at random”.

Lines 208-210: This sentence regarding bias protection seems incomplete. There is no verb!

Lines 213-214: Which test was used for mean separation?

Results and Discussion:

This section describes rather well the results from the study, although some redundancies and inconsistencies appeared. From my viewpoint, discussion is weak. It seems like an introduction in some passages.

Lines 222-224: This is unclear. You mixed two concepts: total irrigation and water holding capacity. Please, re-phrase this sentence.

Lines 230-231: Well, maybe you are right, but the same texture class can be achieved with different combinations of sand, silt and clay percentages, so you can check if one of those components has a relevant influence on soil water holding capacity.

Lines 234-243: Please, consider reducing this part as it is rather repetitive and some statements look hypothetical.

Table 2: Why using capital letters in the title of this table? I feel confused with this table, as duration is in mm and intensity in seconds. The footnote is unclear, particularly the first sentence in which several English mistakes need to be corrected. Besides, could you provide standard deviations or standard errors, please?

Line 249: “among soil types on the time” instead of “across the time”.

Line 251: Sure? The lowest value in Table 2 was 15.88 mm instead of 18.26 mm as you said here. Please, check and correct where necessary.

Lines 253-257: Yes, you did not find significant differences among soil types, so it is difficult to conclude that soil texture “heavily influenced” irrigation intensity.

Lines 257-259: This sentence is confusing. Please, re-phrase it.

Line 260: “in other studies” instead of “with other studies”.

Lines 260-262: This sentence seems to contradict your previous statements in this paragraph.

Lines 271-272: I do not think that this hypothetical statement should be included in the figure caption.

Line 275: “significantly different among soil types” instead of “significant”.

Lines 281-283: This definition of sphericity is neither Results nor Discussion.

Lines 287-290: First, it is difficult to believe that there were no significant differences among sprinklers in RS. Second, since you talk about the meaning of RS, you should indicate why “the evennes of the spray pattern” is relevant for irrigation.

Table 3: This table is rather confusing. I gather that you used a unique generalized linear model for each parameter but I do not see the differences among sprinklers for some of these parameters. It is difficult to believe the absence of differences in RS when existed for all the droplet diameters. As for sphericity, did you transformed the data prior to analysis?

Line 295: “statistical differences” instead of “statistical separations”.

Line 296: This sub-section must be integrated with the rest of the Results and Discussion section, or be an individual section. However, I do not feel that as it is justifies a single section devoted to discussion.

Line 298: “using size classifications developed for particle size classification”, this sounds redundant. Re-phrase. Besides, “ASABE/ANSI” must be defined.

Lines 299-304: I do not see the discussion here.

Line 307: Remove “by the set-up”.

Lines 315-316: “with a greater variety”, variety of what?

Lines 317-319: This sentence is confusing. Please, re-phrase it.

Line 325: I would remove one of those “further”.

Line 329: “Improving water use efficiency is crucial moving forward”, this seems to be incomplete.

Lines 330-331: This sentence is hypothetical since you did not test what happen with any of those variables.

References:

Please, consider reducing this list of references. They seem too many for a short manuscript like yours. Besides, you used almost all of them in the Introduction section without movilizing any bibliography for the Discussion.

Author Response

Response to Reviewer 3 Comments

Abstract:

This was a very good point and the abstract has been rewritten to hopefully improve this shortcoming of the first draft.

Line 16: “by the crop” instead of “at the crop level”.

Change has been made as recommended.

Lines 16-17: This sentence is confusing. Identical to what? Please, re-phrase.

Change has been made – sentence rewritten.

Lines 20-23: The experiment performed is quite confusing from these sentences. Please, improve.

Change has been noted and this section has been rewritten for clarity.

Lines 25-26: All droplet sizes were appropriate for the six soils? This sentence is unclear.

Absolutely! This was not at all what I meant and have clarified by rewriting the sentence

The conclusion of the abstract has been rewritten

Keywords:

Please, do not use words that already appear in the title.

Change has been made as recommended.

Introduction:

The authors understand the thought that there are too many references. That said, this was one area where we disagreed with your otherwise very helpful suggestions for this manuscript. Especially given that references are bracketed numbers and do not impact the readability of this manuscript, this suggestion has not been an area of change for this manuscript.

Line 35: Remove “type”.

Change has been made as recommended.

Lines 38-39: “is less uniform compared to overhead irrigation” instead of “is a less uniform method of irrigation compared to overhead methods”.

Change has been made as recommended.

Lines 39-40: This sentence is confusing. I do not see the relation between the first and the second parts of the sentence.

Noted – and this has been rewritten in order to clarify.

Lines 40-49: Somewhat this seems to be not well organized and some ideas are not linked to what was previously stated in this paragraph. Please, check.

This has been checked and substantial changes have been made to clarify.

Line 42: Remove “at” before “unsustainable”.

Change has been made as recommended.

Lines 62-70: This paragraph can be merged with the previous one. Moreover, here you cite 15 articles in 9 lines, are all these citations needed?

Lines 65-66: Check this sentence, please. I do not see what you mean by “can all result”. What do you want to say about soil porosity? It increases or reduces?

Lines 67-70: This seems to repeat the sentence in lines 65-66.

These paragraphs have been reorganized in order to clarify what was a bit of a convoluted mess. The citations are all needed, but hopefully these edits make sense in a much more coherent way.

Line 78: Remove “to answer this question. Objectives for the study were”.

Change has been made as recommended.

Materials and Methods:

This section has been substantially overhauled and will hopefully make significantly more sense than before.

This has been clarified.

Table 1: I am not used to see the values of nutrients in kg ha^-1 but Ca concentrations seem very high. Could you provide any information on the previous use of the collected soils?

Change has been made as recommended.

Lines 113-114: I would use “that” instead of “where it”.

Change has been made as recommended.

Line 115: Was this for mixing the soils? How did you determine field capacity?

Field capacity has been clarified in the section.

Line 116: This is unclear. Each container had four replications? What were the containers? If you used 8 replications per soil type, did you use 120 L in total for each soil type?

This section has been clarified.

Line 125: What do you mean by “If the core was at any depth”?

This was definitely confusing and has been rewritten.

Lines 150-151: Were the six soil types different from those previously described? If so, why stating this again?

Sentence has been removed.

Lines 153-155: I do not see how you calculated irrigation intensity from this sentence. Please, complete.

This section has been clarified.

Line 197: “in the down”, do you mean “on the ground”?

Oops. Yes. That one made me laugh

Line 203: Which test was used for mean separation?

The statistics paragraph has been completely reworked in addition to an overhaul of the statistics themselves.

Lines 203-204: I would remove this sentence. This procedure is better explained in the following line.

Sentence was removed.

Lines 206-207: Remove “except using the model: Intensity = soil type by time by water volume and replication was set at random”.

This part of the paragraph has been removed as a result of another reviewer’s recommendations.

Lines 208-210: This sentence regarding bias protection seems incomplete. There is no verb!

This part of the paragraph has been removed as a result of another reviewer’s recommendations.

Lines 213-214: Which test was used for mean separation?

The statistics paragraph has been completely reworked in addition to an overhaul of the statistics themselves.

Results and Discussion:

The entirety of the results and discussion section has been reworked, rewritten and if any of the sentences to which recommendations were made below were retained in the manuscript, they have been edited as recommended.