Reclaimed Wastewater to Irrigate Olive Groves and Vineyards: Effects on Soil Properties

Round 1

Reviewer 1 Report

Dear Autors,

thank you for your work. Please revise the English. It would be good if a professional revised the English style.

Author Response

Point 1: Thank you for your work. Please revise the English. It would be good if a professional revised the English style.

Response 1: Thank you for your comment. A professional translator has reviewed the manuscript and a translation certificate is attached.

Reviewer 2 Report

This paper is interesting and the experimental conditions evaluated are quite comprehensive and adequate. The paper presents original research and the subject treated is of utmost importance due to the water scarcity in several Mediterranean areas.

Abstract – the information given is adequate and concise.

Introduction – The aim of paper is adequately exploited.

Line 87-88 – It is stated “It has also been seen that there may be an increase in soil salinity although this does not necessarily affect crops [16] since each rain event could reduce excess salinity by allowing soil`s ability to self-cleanse [17]”. Lixiviation will cause an increase of salinity in underground water! That may be a huge problem. Was this problema evaluated?

2. Research area, materials and methods

Lines 206-213 – What were the methods used for PAHs, PCBs and metals determination?

Sampling –at what depth and how were soil samples collected?

3. Results and discussion

Adequate discussion, well documented by tables and figures.

Statistics is well explored and clearly presented.

4. Conclusion- Adequate but two questions remain unanswered. First, was the local underground/well water analysed after these experiments with TW? In this study it was concluded that wastewater samples did not pose problems to be used in agricultural, but nevertheless if it occurs soil lixiviation it is possible to alter underground and well waters, with increase of eutrophication and even, due to high contents of chloride and sodium, to saline intrusion.

The second question is if there were any analysis to compare the chemical/nutritional composition of crops (olive oils and grapes) irrigated with well (WW) and TW to check if there were any significantly differences depending on the water used?

Author Response

Comments and Suggestions for Authors

1. This paper is interesting and the experimental conditions evaluated are quite comprehensive and adequate. The paper presents original research and the subject treated is of utmost importance due to the water scarcity in several Mediterranean areas.

Abstract – the information given is adequate and concise.

Introduction – The aim of paper is adequately exploited.

Point 1: Line 87-88 – It is stated “It has also been seen that there may be an increase in soil salinity although this does not necessarily affect crops [16] since each rain event could reduce excess salinity by allowing soil`s ability to self-cleanse [17]”. Lixiviation will cause an increase of salinity in underground water! That may be a huge problem. Was this problema evaluated?

Response 1: This time the problem has not been evaluated but, as the authors are aware of it, we have documented it with references 16 and 17.

2. Research area, materials and methods

Point 2: Lines 206-213 – What were the methods used for PAHs, PCBs and metals determination?

Response 2:

• PAHs and PCBs determination: Gas chromatography mass spectrometry (GC/MS)
• Metals determination: Inductively coupled plasma mass spectrometry (ICP-MS)

These methods are now included in the text.

Point 3: Sampling –at what depth and how were soil samples collected?

Response 3: depth of 0-40 cm with a hand auger. This information is now included in the text.

3. Results and discussion

Adequate discussion, well documented by tables and figures.

Statistics is well explored and clearly presented.

4. Conclusion- Adequate but two questions remain unanswered

Point 4: First, was the local underground/well water analysed after these experiments with TW? In this study it was concluded that wastewater samples did not pose problems to be used in agricultural, but nevertheless if it occurs soil lixiviation it is possible to alter underground and well waters, with increase of eutrophication and even, due to high contents of chloride and sodium, to saline intrusion.

Response 4: Both treated wastewater and well water were analyzed as discussed in the methodology section but not after these experiments.

The risks mentioned by the reviewer are true but, as explained in the manuscript, the studied olive groves and vineyards have been planted in the plots for longer than monitored in this study. The soil analyses reported in this paper correspond to plots that in most cases have been irrigating with TW for more than 10 years. Based on these results, we cannot affirm that TW is, now, the cause of the problems mentioned by the reviewer.

Point 5: The second question is if there were any analysis to compare the chemical/nutritional composition of crops (olive oils and grapes) irrigated with well (WW) and TW to check if there were any significantly differences depending on the water used?

Response 5: Thank you for your interest in the results of our research. We can anticipate that no nutritional imbalances were found in the crops, since in this project, indeed, leaf tissue analysis was done in both crops. In this manuscript we decided to focus on the results obtained in soil, even being aware of the soil-plant interaction is important. However, the results obtained in the crops will be presented in a future paper in which we are already working.

Reviewer 3 Report

General Comments
This paper presents a case study which showed the use of treat waste water for irrigation did not cause severe negative impacts on soil. Since the amounts of fertilization and irrigation are interview-base rather than strictly controlled and recorded, and comparison of CW and TW was no carried out for place where the source of the tap water use the same one as WC, what the authors carried out should not be called experiments, but rather survey and analysis. Without any yield evaluation.

Still, I appreciate the efforts and hard work done by the authors. There are wrong wording and inappropriate or questionable interpretation of data.

Specific Comments
L12 There is no such statements in the introduction section. All statements in an abstract should be summary of the text. This should be removed or inserted at the begging of the introduction.
L15 The authors did not carry out experiments, but survey and analysis.
L16, 111 SE --> south east
L25, 431 This level may not cause difficulty even in the long-term for Olive, which is a moderately tolerant crop.
L43, 45, 48 Use upper case for "m3" In L239, L^-3 is used. You should unify the form of denominator either "/" or exponential form.
L75 "sewage" should be removed.
L76 "and" should be removed.
L81 "permitted" should be removed.
L101 been have --> have been
L103 "To confirm this," should be removed.
L135 In Albacete, there is the local steppe climate --> Albacete is located under the local steppe climate.
L155 What is the meaning of "typically" here?
L158, 172, Table 1 The unit of applied water should be in depth rather than m 3 per ha.
L163 Not 3 m between row, 1.5 m between trees in the row? To avoid misunderstanding, such a statement should be like "row distance was [ ] m while tree spacing along each row was [ ] m."
L215 What was the depth of soil taken?
L216 EC of saturated extract? Some researchers state EC of (soil: water = )1:5 suspension. You should clarify what kind of EC.
Figure 1 The classification is too old. The authors should evaluate based on the newer classification in Ayers and Westcot (1985)?
L245 Refer using [24][25].
L258 alkarising --> alkarised
Table 5 I would recommend to add one more column for expressing WC/TW.
Table 6 I would recommend to add one more column for expressing CS/TW.
L301 Erase ":".
L303 development --> development inside the emitters which may cause clogging
L314 metal content --> concentration of metals
L316 should not exceed --> is
L317 30 mg/L is too strict. The authors should not employ older classification [26]. Ayers and Westcot (1985) [24] classified "severe restriction" if Cl- is higher than 10 me/L = 355 mg / L.
L333 The authors should state why hardness and Scott Index are relevant for irrigation.
L337 The study area soils --> The soils in the study area
L339 So, --> Thus,
L346 Why are emitters obstracted by NaCl, not by Calcium?
L354 . On the one hand --> as well as
L361 According --> According to
L364 What does "intensity" mean here?
L370 correct --> appropriate
L372 mitigate --> mitigating
L372-382, 403-419 Statements are too general and well-known facts written in textbooks for students. They can be erased to avoid impression of verbose to readers.
L384, 433 It is too obvious that continuous irrigation with TW did not alter texture, because there is no physical mechanism to change it.
L398 a direct --> there is a direct
L400 potentially hazardous --> potential hazard
L401 there is --> there are
L428 electric --> electrical
L431 electro --> electrical

Author Response

Comments and Suggestions for Authors

General Comments

This paper presents a case study which showed the use of treat wastewater for irrigation did not cause severe negative impacts on soil. Since the amounts of fertilization and irrigation are interview-base rather than strictly controlled and recorded, and comparison of CW and TW was no carried out for place where the source of the tap water use the same one as WC, what the authors carried out should not be called experiments, but rather survey and analysis. Without any yield evaluation.

Still, I appreciate the efforts and hard work done by the authors. There are wrong wording and inappropriate or questionable interpretation of data.

Point 1: L12 There is no such statements in the introduction section. All statements in an abstract should be summary of the text. This should be removed or inserted at the begging of the introduction.

Response 1: The statement is now included in the first paragraph of the introduction

Point 2: L15 The authors did not carry out experiments, but survey and analysis.

Response 2: “to conduct experiments” has been removed.

Point 3: L16, 111 SE --> south east.

Response 3: Done

Point 4: L25, 431 This level may not cause difficulty even in the long-term for Olive, which is a moderately tolerant crop.

Response 4: It could be, but we wanted to know what happens in soil.

Point 5: L43, 45, 48 Use upper case for "m3" In L239, L^-3 is used. You should unify the form of denominator either "/" or exponential form.

Response 5: Ok. It was a format mistake. Now is corrected.

Point 6: L75 "sewage" should be removed.

Response 6: Now is removed

Point 7: L76 "and" should be removed.

Response 7: Done

Point 8: L81 "permitted" should be removed.

Response 8: Done

Point 9: L101 been have --> have been

Response 9: Done

Point 10: L103 "To confirm this," should be removed.

Response 10: Done

Point 11: L135 In Albacete, there is the local steppe climate --> Albacete is located under the local steppe climate.

Response 11: This sentence is now included

Point 12: L155 What is the meaning of "typically" here?

Response 12: The meaning is Usually. We have changed the word in the text.

Point 13: L158, 172, Table 1 The unit of applied water should be in depth rather than m 3 per ha.

Response 13: Units are now expressed in mm.

Point 14: L163 Not 3 m between row, 1.5 m between trees in the row? To avoid misunderstanding, such a statement should be like "row distance was [ ] m while tree spacing along each row was [ ] m."

Response 14: Ok. Plantation framework is now described in this way.

Point 15: L215 What was the depth of soil taken?

Response 15: 0-40 cm. This information is now included in the text.

Point 16: L216 EC of saturated extract? Some researchers state EC of (soil: water = )1:5 suspension. You should clarify what kind of EC.

Response 16: It was 1:5. This information is now included in Table 2

Point 17: Figure 1 The classification is too old. The authors should evaluate based on the newer classification in Ayers and Westcot (1985)?

Response 17: Although the reference “USSL diagram for classification of irrigation waters (US Salinity Laboratory Staff, 1954)” is old, it is still in force and is still cited in current publications:

• Example 1: Singh, K.R., Goswami, A.P., Kalamdhad, A.S. et al. (2020). Development of irrigation water quality index incorporating information entropy. Environ Dev Sustain 22, 3119–3132. https://doi.org/10.1007/s10668-019-00338-z
• Example 2: Khalil, M., El-Sherbieny, A., Dahdouh, S., Sherif, M. (2019). Evaluation of belbais drain water quality and the possibility of using in agricultural irrigation purposes in Sharkia governorate, Egypt. Zagazig Journal of Agricultural Research, 2019; 46(6): 2297-2306. doi: 10.21608/zjar.2019.65092
• Example 3: Song Heab PeiyueLi (2019). A MATLAB based graphical user interface (GUI) for quickly producing widely used hydrogeochemical diagrams. Geochemistry, 125550. https://doi.org/10.1016/j.chemer.2019.125550

Point 18: L245 Refer using [24][25].

Response 18: Ok. Changes have been made.

Point 19: L258 alkarising --> alkarised.

Response 19: We have corrected it.

Point 20: Table 5 I would recommend to add one more column for expressing WC/TW..

Response 20: Sorry, but we don't understand what WC / TW means. If you clarify it, no objection to doing so..

Point 21: Table 6 I would recommend to add one more column for expressing CS/TW.

Response 21: Sorry, but we don't understand what CS/TW means. If you clarify it, no objection to doing so.

Point 22: L301 Erase ":".

Response 22: Done

Point 23: L303 development --> development inside the emitters which may cause clogging.

Response 23: Done

Point 24: L314 metal content --> concentration of metals

Response 24: Done

Point 25: L316 should not exceed --> is

Response 25: Done

Point 26: L317 30 mg/L is too strict. The authors should not employ older classification [26]. Ayers and Westcot (1985) [24] classified "severe restriction" if Cl- is higher than 10 me/L = 355 mg / L.

Response 26: Thank you. There was a mistake in the units (me/L instead of mg/L). We have referenced Ayers and Westcot (1994) http://www.fao.org/3/t0234e/T0234E01.htm#note4

Point 27: L333 The authors should state why hardness and Scott Index are relevant for irrigation.

Response 27: This information is now included in the text (L336-341)

Point 28: L337 The study area soils --> The soils in the study area

Response 28: Done

Point 29: L339 So, --> Thus,

Response 29: Done

Point 30: L346 Why are emitters obstracted by NaCl, not by Calcium?

Response 30: Calcium is considered a macronutrient. Its absence is more problematic than its excess in crops. Although it can also obstruct irrigation equipment, in these lines we do not name it because we only want to refer to Na and Cl^- since them can damage both equipment and crops.

Point 31: L354 . On the one hand --> as well as

Response 31: Done

Point 32: L361 According --> According to

Response 32: Done

Point 33: L364 What does "intensity" mean here?

Response 33: It means “concentration”. The word has been replaced.

Point 34: L370 correct --> appropriate

Response 34: Done

Point 35: L372 mitigate --> mitigating

Response 35: Done

Point 36: L372-382, 403-419 Statements are too general and well-known facts written in textbooks for students. They can be erased to avoid impression of verbose to readers.

Response 36: Most of suggested lines with statements too general have been removed. Therefore, the numbering of the references had to be revised and partially restructured.

Point 37: L384, 433 It is too obvious that continuous irrigation with TW did not alter texture, because there is no physical mechanism to change it.

Response 37: The sentence has been removed

Point 38: L398 a direct --> there is a direct

Response 38: Mistake corrected

Point 39: L400 potentially hazardous --> potential Hazard

Response 39: Done

Point 40: L401 there is --> there are

Response 40: Mistake corrected

Point 41: L428 electric --> electrical

Response 41: Mistake corrected

Point 42: L431 electro --> electrical

Response 42: Mistake corrected

Round 2

Reviewer 3 Report

General Comments
The manuscript has now been remarkably improved.

Still, I wonder why the authors stick to the old classification when new one is available.
New one may have been presented considering "recent" studies at that time.

Specific Comments
Point 20 and 21. For example, EC of WC is 1.56 and that of TW is 2.11, then WC/TW = 1.56/2.11=0.74. Actually, TW/WC and TW/CS would be better.

Author Response

Comments and Suggestions for Authors

General Comments

The manuscript has now been remarkably improved.

Point 1: Still, I wonder why the authors stick to the old classification when new one is available.

New one may have been presented considering "recent" studies at that time.

Response 1: I want to thank the reviewer for this comment. Thanks to it, I have searched for information in this regard.

I must admit that I did not know that this widely used reference contains misconceptions (http://rabida.uhu.es/dspace/bitstream/handle/10272/8899/Sobre-la.pdf?sequence=2).

I will keep it in mind for this and future manuscripts.

Now, in the text of the manuscript, Ayers and Westcot (1994) is referenced (L232-234).

Moreover, Figure 1 has been removed to avoid misinterpretations.

Point 2: Specific Comments

Point 20 and 21. For example, EC of WC is 1.56 and that of TW is 2.11, then WC/TW = 1.56/2.11=0.74. Actually, TW/WC and TW/CS would be better.

Response 2: Thank you for your clarification. Now Tables 5 and 6 have a new column with the relations TW/WC and TW/CS respectively.