Evaluation of Biodegradable Mulch Films on Melon Production and Quality under Mediterranean Field Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This research delves into the effects of biodegradable mulches (such as Mater-Bi and Ecovio) compared to conventional LDPE mulch on watermelon production and quality in a Mediterranean context. The study emphasizes practical applications with a well-designed set of indicators, albeit with insufficient depth in theoretical discussions. Recommendations for enhancement include a substantial revision of the discussion section, particularly focusing on:

In the introduction, the authors mentioned concerns regarding their long-term impact on soil health and productivity, as well as their mechanical properties and costs. This paper selects which issue among these concerns does it primarily address? And did it manage to resolve them? It's unclear if the study addresses widely existing scientific issues beyond this focus.

• In the "Materials and Methods" section, it would be beneficial to include detailed parameters such as the mechanical properties and composition of the different mulches. It should also explain why the conventional mulch has a thickness of 30 micrometers while the others are 15 micrometers; this difference could influence soil temperature.

• In the "Results" section, the first letter of Figure 1 should be capitalized. Additionally, the higher soil temperature under the conventional mulch can potentially be explained through energy balance theory, suggesting that the biodegradable mulches' degradation process might require energy. This explanation should be elaborated upon in the discussion.

• For the "Discussion" part, a thorough examination of how the breakdown products of the biodegradable mulches affect the soil environment is warranted. Considering that the degradation rate is influenced by various factors including temperature, it would be insightful to continue discussing how the structural components and mechanical properties of the mulches impact soil conditions and crop growth.

• Overall, while the conventional mulch leads to higher soil temperatures, the key reasons for increased yields with biodegradable mulches are not clearly identified. There might be a relationship between the residual matter from the mulches and their effectiveness, which should be further explored.

Author Response

Dear Reviewer,

Thank you indeed for reviewing the manuscript.

Below you can find our answers point by point to your valuable comments and, in the manuscript, the suggested modifies as track changes

Kind regards.

Dear Reviewer, please, note each of your comments precedes our answer.

Comments 1: In the introduction, the authors mentioned concerns regarding their long-term impact on soil health and productivity, as well as their mechanical properties and costs. This paper selects which issue among these concerns does it primarily address? And did it manage to resolve them? It's unclear if the study addresses widely existing scientific issues beyond this focus.

Response 1:  Thank you for your valuable feedback. In our manuscript's introduction, we did highlight concerns about biodegradable mulch films, including their potential long-term impacts on soil health, productivity, mechanical properties, and costs. Our study primarily focused on assessing how the use of biodegradable mulches affects melon production in Mediterranean conditions, specifically looking at crop yield and quality, which are closely tied to soil health and productivity. While we did not aim to fully resolve all the issues raised in the introduction, our focus was on immediate agronomic outcomes like regulating soil temperature, enhancing yield, and improving fruit quality. These findings are essential for understanding the viability of biodegradable mulches as alternatives to plastic films in sustainable agriculture. While our study concentrated on agronomic performance and fruit quality, the data gathered contributes to a broader comprehension of biodegradable mulches in sustainable farming. We acknowledge the need for further research to address long-term impacts on soil health, mechanical properties, and cost-effectiveness, which were beyond the scope of this study. To ensure clarity, we have removed the sentence regarding soil health concerns and have refined the introduction accordingly.

Comments 2: In the "Materials and Methods" section, it would be beneficial to include detailed parameters such as the mechanical properties and composition of the different mulches. It should also explain why the conventional mulch has a thickness of 30 micrometers while the others are 15 micrometers; this difference could influence soil temperature.

Response 2:  Thank you for your valuable suggestion. In response to your comment, we have added information on the composition of the different mulches has been included at lines 421-429 of revised manuscript.

The difference in thickness between the conventional LDPE mulch (30 micrometers) and the biodegradable mulches (15 micrometers) comes from the different materials and how they are made. LDPE mulches are made thicker to be strong, resist tearing during the growing season, and keep the soil insulated from temperature changes. The thicker LDPE is also crucial for maintaining its integrity by the end of the growing cycle, allowing for mechanical removal. On the other hand, biodegradable mulches, are made thinner so they can easily break down over time. This thinner design helps balance their strength with their ability to decompose and may also allow heat to move more quickly between the soil and the air. Additionally, the reduced thickness of biodegradable mulches helps lower production costs.

Comments 3: In the "Results" section, the first letter of Figure 1 should be capitalized. Additionally, the higher soil temperature under the conventional mulch can potentially be explained through energy balance theory, suggesting that the biodegradable mulches' degradation process might require energy. This explanation should be elaborated upon in the discussion.

Response 3:  Thank you for your valuable suggestion. We have revised the discussion section to include additional information on the influence of mulch thickness on soil temperature. Specifically, we have added details on the thermal insulation properties of LDPE mulch and how biodegradable mulches contribute to soil temperature fluctuations. These enhancements aim to provide a clearer understanding of how different mulch materials affect soil temperature dynamics. Please see the lines 421-429 of revised manuscript.

Comments 4: For the "Discussion" part, a thorough examination of how the breakdown products of the biodegradable mulches affect the soil environment is warranted. Considering that the degradation rate is influenced by various factors including temperature, it would be insightful to continue discussing how the structural components and mechanical properties of the mulches impact soil conditions and crop growth.

Response 4:  Thank you for your helpful feedback. You are right that looking into how the breakdown of biodegradable mulches affects the soil would be important. However, our study focused mainly on how these mulches impact melon production in Mediterranean conditions, especially in terms of crop yield and quality. While understanding the effects on soil and how quickly the mulches break down is important, our research didn’t explore these areas in detail. Our goal was to see how biodegradable mulches influence melon production, but further studies would be needed to look at their impact on soil health and their breakdown.

Reviewer 2 Report

Comments and Suggestions for Authors

In general meaningful study, the organization of the introduction needs improvement and some rewriting; materials and methods lack sufficient details; overly simple description of results for the results; good discussion.

L16: “positively influenced soil temperature” is vague, depends on do you consider increase temperature beneficial or lowering soil temperature? Please change

L20: Ecovio resulted in significantly higher yield than LDPE, but similar yield compared with Mater-Bi. Therefore it is not appropriate to state Ecovio surpassed Mater-B by 8.84% because they are essentially or statistically similar; there are other statements like this throughout the Results and some in the Discussion section, please correct all.

L33-50: this paragraph is actually describing the benefit of mulch in general, like improved moisture and soil temperature in line 48, not much is specifically to biodegradable mulches. Also, the statements are not meaningful by just saying they improved such and such without proper comparison. For example in line 43 “biodegradable films positively impacts crop yield and fruit quality”, is this compared with open field without mulch, or compared with plastic mulch?

L54: please explain potential cost savings; to my knowledge the price of biodegradable mulch is several times more expensive than plastic mulches

L57: The instruction is meant for anyone even without too much background information to understand a study. In L57, the concerns of using biodegradable mulch were well explained, too general and vague

L60-62: again, statement too general and vague; whether biodegradable mulches are feasible alternative is highly species and mulch type dependent.

L70: please explain the positive impact of biodegradable mulch on soil microbial communities? The residue of degrading mulches in the soil may have negative effect on soil quality and microbial communities;

In addition, the entire introduction lacks comparison between biodegradable mulches and traditional PE mulches

L125 2.2 Experimental design, setting, and crop management: please specify the size of each plot and the number of plants in each plot; age of transplant during transplanting; spacing of plants; how was the field prepared; The materials and method section lacks details for the study to be replicable

L165: again, lack details in data collection; there was no information regarding how plant biomass was collected, with how many plants, and when?

Figure 1: Figures and tables need to stand alone; please add maximum, minimum, and average to the Y-axis in each chart

L295: How was the unmarketable yield determined? Any data? Was there any unmarketable yield due to mulch adhesion problems?

Table 2: the meaning of harvest index needs to be discussed somewhere

L351-353: incorrect description of results: mater – bi did not result in higher firmness (materB similar to ldpe), pulp thickness (materB similar to Ecovio), or total soluble solids (materB similar to Ecovio) compared to the other two types of mulch; there are similar incorrect statements like this throughout the manuscript, please correct all

L362-366: Overly simple description of results: the color data including a*, b* were not discussed at all. Besides, are there pictures to back up the color data?

L462-464: again, please avoid incorrect interpretation of data

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English needs moderate improvement

Author Response

Dear Reviewer,

Thank you indeed for reviewing the manuscript.

Below you can find our answers point by point to your valuable comments and, in the manuscript, the suggested modifies as track changes

Kind regards.

Dear Reviewer, please, note each of your comments precedes our answer.

Comments 1: L16: “positively influenced soil temperature” is vague, depends on do you consider increase temperature beneficial or lowering soil temperature? Please change

Response 1:  Thank you for pointing out the need for clarity in our wording. We agree that the phrase "positively influenced soil temperature" could be more specific. We have revised the sentence to clearly state whether the increase or decrease in soil temperature is beneficial depending on the context. The updated sentence now reads:

“Biodegradable mulches influenced soil temperature, with Mater-Bi maintaining higher maximum soil temperatures conducive to crop growth, while Ecovio exhibited lower maximum temperatures beneficial in hot summer months.”

Comments 2: Therefore it is not appropriate to state Ecovio surpassed Mater-B by 8.84% because they are essentially or statistically similar; there are other statements like this throughout the Results and some in the Discussion section, please correct all.

Response 2:  Thank you for your careful review and for pointing out the need for clarification regarding the comparison of yields between the biodegradable mulch films. We acknowledge that the statistical analysis indicated no significant difference between the yields of Ecovio® and Mater-Bi® mulches. Therefore, it is indeed more accurate to state that both biodegradable mulches, Ecovio® and Mater-Bi®, demonstrated a notable advantage in terms of marketable yield compared to LDPE, with an increase of approximately 23.4%. Please see the lines 19-20 of modified manuscript.

Comments 3: L33-50: this paragraph is actually describing the benefit of mulch in general, like improved moisture and soil temperature in line 48, not much is specifically to biodegradable mulches. Also, the statements are not meaningful by just saying they improved such and such without proper comparison. For example in line 43 “biodegradable films positively impacts crop yield and fruit quality”, is this compared with open field without mulch, or compared with plastic mulch?

Response 3:  Thank you for your insightful feedback on the Introduction section of the manuscript. We appreciate the opportunity to address your concerns and clarify the points raised. In response to your comments on lines 33-50, we acknowledge the need for more specific distinctions when discussing the benefits of mulch, particularly focusing on biodegradable mulches. We will revise the paragraph to emphasize the unique advantages of biodegradable mulches over traditional mulching techniques. This revision includes now more direct comparisons between the effects of biodegradable mulch films and other types of mulch, such as LDPE or bare soil (lines 44-70).

Comments 4: L53: please explain potential cost savings; to my knowledge the price of biodegradable mulch is several times more expensive than plastic mulches

Response 4:  In response to the reviewer's comment regarding the potential cost savings associated with biodegradable mulch films compared to traditional plastic mulches, it is crucial to consider a comprehensive analysis of the overall costs involved. While it is true that the upfront cost of biodegradable mulches may be higher than that of plastic mulches, the long-term economic benefits and environmental advantages need to be taken into account. Biodegradable mulches can contribute to reduced waste management costs, decreased environmental pollution, and potential savings in terms of soil health and productivity in the long run. Additionally, factors such as regulatory incentives, market demand for sustainable practices, and potential crop yield improvements facilitated by biodegradable mulches can also influence the cost-effectiveness of their use over time, and moreover the biodegradable sheets benefit from a reduced VAT of 4% compared to 22% for LDPE. Therefore, a holistic assessment considering not just the initial price but also the long-term benefits and externalities is necessary to fully evaluate the cost-effectiveness of biodegradable mulch films in agricultural practices.

Comments 5: L57: The instruction is meant for anyone even without too much background information to understand a study. In L57, the concerns of using biodegradable mulch were well explained, too general and vague.

Response 5:  To ensure clarity, we have removed the sentence regarding soil health concerns in line 57 and have refined the introduction accordingly.

Comments 6: L60-62: again, statement too general and vague; whether biodegradable mulches are feasible alternative is highly species and mulch type dependent.

Response 6:  We have removed this paragraph because it reiterates an argument that was previously discussed.

Comments 7: L70: please explain the positive impact of biodegradable mulch on soil microbial communities? The residue of degrading mulches in the soil may have negative effect on soil quality and microbial communities; In addition, the entire introduction lacks comparison between biodegradable mulches and traditional PE mulches.

Response 7:  Thank you for your valuable feedback. In response to the reviewer's comments, we have revised the manuscript accordingly. We have added some information about the positive impact of biodegradable mulch on soil microbial communities at lines 90-105 in the revised manuscript

Comments 8: L125 2.2 Experimental design, setting, and crop management: please specify the size of each plot and the number of plants in each plot; age of transplant during transplanting; spacing of plants; how was the field prepared; The materials and method section lacks details for the study to be replicable

Response 8:  In response to the reviewer's request for more detailed information in the Materials and Methods section, we have provided the following specifics to ensure the study's replicability:

Each plot measured 6 m x 7 m, consisting of 3 rows, with a planting density of 5000 plants per hectare. The spacing between the plants was 2 m between rows and 1 m between plants within each row. For each mulch treatment, the central row was harvested, excluding the first and last plants as borders, resulting in 5 plants per plot. The experiment included three replicates for each treatment, totaling 9 plots, with an overall field size of approximately 400 m². At the time of transplanting, the plants had 4 leaves. The field was prepared through superficial plowing to a depth of 25 cm, followed by subsoiling to a depth of 60 cm.

These details have been added in the 2.2 and 2.3 Materials and Methods section to improve the clarity and replicability of the study.

Comments 9: L165: again, lack details in data collection; there was no information regarding how plant biomass was collected, with how many plants, and when?

Response 9:  In the lines 200-205 of modified manuscript, we provided a detailed description of how plant biomass was collected, including the number of plants and the timing of the collection. Specifically, we reported: 'At the last harvest, three plants per replicate were sampled, weighed, and a sample was oven-dried to determine the dry matter percentage (dry AGB). Finally, the harvest index (HI) was calculated as the ratio between yield and plant biomass (dry AGB).”

Comments 10: Figure 1: Figures and tables need to stand alone; please add maximum, minimum, and average to the Y-axis in each chart

Response 10:  In response to the reviewer's suggestion, we have revised Figure 1.

Comments 11: L295: How was the unmarketable yield determined? Any data? Was there any unmarketable yield due to mulch adhesion problems?

Response 11:  unmarketable fruits were those that were deformed, decaying, or weighed below 700 g. we haven’t recorded the unmarketable yield. Please see the lines 199-200 of modified manuscript.

Comments 12: Table 2: the meaning of harvest index needs to be discussed somewhere

Response 12:  we improved the discussion section and we added some information about how does the use of biodegradable mulch (BDM) influence the harvest index of crops compared to plastic mulch?  Please see the lines 451-458 of modified manuscript.

Comments 13: L351-353: incorrect description of results: mater – bi did not result in higher firmness (materB similar to ldpe), pulp thickness (materB similar to Ecovio), or total soluble solids (materB similar to Ecovio) compared to the other two types of mulch; there are similar incorrect statements like this throughout the manuscript, please correct all.

Response 13:  Thank you for your observation. In response to the reviewer's comments, we have revised the manuscript accordingly. We have added the following paragraph at lines 360-363 in the revised manuscript: "Specifically, the Mater-Bi treatment exhibited significantly thicker pulp and higher levels of dissolved solids compared to LDPE, with notable increases of 19.47% and 14.22%, respectively. Furthermore, Mater-Bi significantly enhanced the fruit's firmness, showing a remarkable 42.22% increase compared to Ecovio."

Comments 14: L362-366: Overly simple description of results: the color data including a*, b* were not discussed at all. Besides, are there pictures to back up the color data?

Response 14:  We have included additional comments in the discussion section regarding the effects of mulch treatment on the color of muskmelon fruits, specifically focusing on the a* (red-green) and b* (yellow-blue) color coordinates. Please see the lines 511-524 of modified manuscript. Regrettably, we do not have accompanying pictures to support the color data.

Comments 15: L462-464: again, please avoid incorrect interpretation of data

Response 15:  Thank you for your valuable feedback. In response to the reviewer's comments, we have revised the manuscript accordingly. We have added the following paragraph at lines 394-397 in the revised manuscript: " Particularly, the Mater-Bi treatment led to a significant 41.6% increase in LAA compared to LDPE. While Mater-Bi showed a 15.9% higher LAA than Ecovio, this difference was not statistically significant, suggesting that Mater-Bi and Ecovio have comparable performance from a statistical perspective."