Suitable Water–Fertilizer Management and Ozone Synergy Can Enhance Substrate-Based Lettuce Yield and Water–Fertilizer Use Efficiency

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In table 1 the treatments with different concentrations of Hoagland solution are marked with N, but in the results they are represented with F

Line 491 lower lower irrigation ... is this correct?

Explain why the discrepancy in the effect of irrigation frequency is attributed to the effect of the interaction between treatments (irrigation, nutrients and ozone), what arguments are there to think about it?

Could the differences between the two crops lagged in time be due to the optimal temperature for growing lettuce and not to the decomposition of organic matter? since inert substrates were used for cultivation, and the real contribution of nutrients came from the Hoagland solution? Furthermore, the decomposition of organic matter depends on the action of microorganisms that were not detected in the study.

 

 

Author Response

Dear editor and reviewers,

Thank you for your valuable comments and patient feedback on our manuscript. According to your valuable comments, we have revised our previous manuscript. The manuscript with highlighted changes/additions with red word are given in revised version. The detailed corrections in the manuscript and response to your comments are as follows:

Reviewer #1: Comments on manuscript agronomy-3049708:

1. In table 1 the treatments with different concentrations of Hoagland solution are marked with N, but in the results they are represented with F

Response: Thank you for your careful review. We have represented the treatments with Hoagland solution as "F" in Table 4. Please check line 167 in the Materials and Methods section.

2. Line 491 lower lower irrigation ... is this correct?

Response: We apologize for the misunderstanding caused by our previous explanation. Our intention was to clarify that different lower irrigation thresholds affect the irrigation frequency. To make this clearer, we have revised the sentence from "a lower lower irrigation threshold reduces irrigation frequency, leading to water stress in lettuce and a significant decrease in yield" to "when the lower limit of irrigation is low, a smaller irrigation frequency leads to a significant decrease in water stress and yield of lettuce." Please check lines 530-532 of the article.

3. Explain why the discrepancy in the effect of irrigation frequency is attributed to the effect of the interaction between treatments (irrigation, nutrients and ozone), what arguments are there to think about it?

Response: We apologize for the misunderstanding caused by our different expressions. What we described as the irrigation frequency is actually influenced by the lower irrigation threshold set in this study. Different lower irrigation thresholds directly affect the irrigation frequency. When the lower irrigation threshold is high, the irrigation frequency increases, directly enhancing the impact of water, fertilizer, and ozone on lettuce. Previous studies have shown that irrigation frequency can alter the distribution and storage of water and heat in the soil (substrate), thereby affecting crop growth. Most research indicates that some crops respond well to high-frequency irrigation, mainly reflected in increased crop yield and improved water and fertilizer use efficiency (Cheng et al., 2024; Ballester et al., 2021; Lefever et al., 2015; Ertek et al., 2004). To prevent further misunderstandings, we have supplemented and revised the discussion section. Please refer to lines 521-527 in the article.

Lefever, K.; Laubscher, C.; Ndakidemi, P. The Effects of pH and Phosphorus Concentrations on the Growth Potential of Medicinal Salvia Chamelaeagnea in Hydroponic Cultivation. Acta Hortic. 2015, 1104, 29–34.

Ertek, A.; Şensoy, S.; Küçükyumuk, C.; Gedik, İ. Irrigation Frequency and Amount Affect Yield Components of Summer Squash (Cucurbita Pepo L.). Agric. Water Manag. 2004, 67, 63–76.

Ballester, C.; Hornbuckle, J.; Brinkhoff, J.; Quayle, W.C. Effects of Three Frequencies of Irrigation and Nitrogen Rates on Lint Yield, Nitrogen Use Efficiency and Fibre Quality of Cotton under Furrow Irrigation. Agric. Water Manag. 2021, 248, 106783.

Cheng, M.; Wang, H.; Zhang, F.; Wang, X.; Liao, Z.; Zhang, S.; Yang, Q.; Fan, J. Effects of Irrigation and Fertilization Regimes on Tuber Yield, Water-Nutrient Uptake and Productivity of Potato under Drip Fertigation in Sandy Regions of Northern China. Agric. Water Manag. 2023, 287, 108459.

4. Could the differences between the two crops lagged in time be due to the optimal temperature for growing lettuce and not to the decomposition of organic matter? since inert substrates were used for cultivation, and the real contribution of nutrients came from the Hoagland solution? Furthermore, the decomposition of organic matter depends on the action of microorganisms that were not detected in the study.

Response: As you mentioned, we have discussed the impact of organic matter decomposition on the differences in lettuce growth. Another factor could be temperature. Through literature review, we found that "as the temperature increases, the number of leaves, shoot fresh and dry weight, root fresh and dry weight, and leaf area significantly increase. From both quantitative and qualitative perspectives, 25-30℃ is the optimal temperature for lettuce production" (Yan et al., 2010). This is mainly because the maximum values are reached at 25℃, and the dry matter content is highest. The effect of root zone temperature on lettuce leaf net photosynthetic rate and mineral element content is similar to its effect on yield. However, when the temperature reaches 35℃, root and leaf growth and the accumulation of mineral elements in the shoots are severely hindered, and lettuce leaf nitrate content significantly decreases (Li et al., 2015). Additionally, studies have shown that as temperature increases, plant height, shoot fresh weight, total soluble sugars, caffeine, and oleanolic acid content all first rise and then fall (Chen et al., 2019). These studies all illustrate the relationship between temperature and lettuce growth, indirectly explaining the potential reasons for the seasonal differences in our results. We have supplemented this content in lines 509-521.

Chen, Y.; Yang, L.; He, Z. Effects of Temperature on Growth and Quality of Dormancy-Released Sedum Aizoon L. IOP Conf. Ser. Earth Environ. Sci. 2019, 310, 052020.

We greatly appreciate your second suggestion, which validates our hypothesis. After observing the patterns of lettuce growth, yield, and water-fertilizer use efficiency under different water-fertilizer and ozone treatments, we sought to understand the underlying mechanisms. Therefore, we investigated the role of the nutrient solution by testing its microbial content. Due to space constraints, we cannot present this data in the current article but wish to report our findings here. As shown in the attached figure 1, the nutrient solution, rich in nutrients, potentially accumulates a large number of microorganisms during lettuce growth. We analyzed the relationship between the alpha diversity of bacterial communities in the nutrient solution and lettuce yield and quality indicators. Using a random forest model, we predicted lettuce yield and quality indicators and found that, based on these results, isolating Bosea strains from the nutrient solution on day 20 could be considered to verify if they can act as probiotics for lettuce growth.

 

Figure 1. Analysis of the association between nutrient solution bacterial communities and lettuce quality.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript by Qingqing Zhao and colleagues is well written and describes a carefully planned experiment to address the stated objectives. I have just a few minor recommendations.

In the sentence beginning on line 39, the authors mention the environmental sustainability of soilless cultivation methods. While it is true that such controlled production systems can achieve much higher yields with more efficient use of inputs like water and fertilizers, the carbon emissions per unit of product is still typically higher, often much higher, than open field production. Thus, the environmental sustainability is not necessarily improved across all variables, and greenhouse gas emissions is certainly a vitally important one.

In Table 4, the heading of the column furthest to the right of the page should be “pH” rather than “PH.”

In Table 5, the column headings can just be First, Second, Third, Fourth, and Fifth. The words “The” and “time” are redundant and unnecessary.

The caption for Figure 2 should be on the same page as the diagram and photograph it descibes.

Beginning in line 249 the authors write that Duncan’s multiple range test was used to separate means while Tukey’s was used to determine interactions. Why were two different tests used rather than one? Tukey’s test is a more conservative test than Duncan’s, and less likely to find significant differences.

In Table 6 and 7, the authors put the maximum value in bold font, which is helpful to the reader. This should be stated in the figure captions or footnotes. It would also be helpful to do this in Table 8.

The word “Tukey” is missing the “y” in caption for Table 9.

Add labels and units to the Y axes (or headings) to the three graphs shown in Figure 11.

Author Response

Dear editor and reviewers,

Thank you for your valuable comments and patient feedback on our manuscript. According to your valuable comments, we have revised our previous manuscript. The manuscript with highlighted changes/additions with red word are given in revised version. The detailed corrections in the manuscript and response to your comments are as follows:

Reviewer #2: Comments on manuscript agronomy-3049708:

1. The manuscript by Qingqing Zhao and colleagues is well written and describes a carefully planned experiment to address the stated objectives. I have just a few minor recommendations.

Response: Thank you for your recognition!

2. In the sentence beginning on line 39, the authors mention the environmental sustainability of soilless cultivation methods. While it is true that such controlled production systems can achieve much higher yields with more efficient use of inputs like water and fertilizers, the carbon emissions per unit of product is still typically higher, often much higher, than open field production. Thus, the environmental sustainability is not necessarily improved across all variables, and greenhouse gas emissions is certainly a vitally important one.

Response: Thank you for your feedback, which has enabled us to delve deeper into our research. We understand that greenhouse gas emissions from hydroponic cultivation primarily originate from carbon dioxide released during crop growth, water and nutrient inputs in agricultural production, improper treatment of nutrient solution wastewater, and soil management issues. Although we did not specifically analyze carbon emissions and focused instead on the relationship between water and nutrient management and lettuce yield and efficiency, our results indicated that the most suitable outcome was not achieved with high nutrient solution concentration treatments. Studies by Guo et al. (2024), Dejie et al. (2020), and Hu et al. (2013) demonstrate that appropriate water and nutrient management is an effective measure to reduce carbon emissions, suggesting that we may have inadvertently reduced emission risks as well. Furthermore, research by Sharma et al. (2023) and Pan et al. (2024) confirms that the treatment of nutrient solution wastewater is also a crucial step in reducing carbon emissions. The ozone disinfection treatment used in our hydroponic cultivation may have also contributed to reducing carbon emissions. Our final research results indicate that the F3W4O2 treatment may not only enhance yield and efficiency but also reduce the risk of carbon emissions. We have included the corresponding explanation in the discussion; please refer to lines 599-612 for the relevant supplementary details. 

Guo, G.; Li, X.; Kuai, J.; Zhang, X.; Peng, X.; Xu, Y.; Zeng, G.; Liu, J.; Zhang, C.; Lin, J. Estimation of Annual Soil CO₂ Efflux under the Erosion and Deposition Conditions by Measuring and Modeling Its Respiration Rate in Southern China. J. Environ. Manage. 2024, 351, 119686.

Dejie, K.; Liu, N.; Li, H.; Wang, W.; Li, N.; Ren, G.; Yang, G. Effect of Nitrogen Fertilizer on Soil CO2 Emission Depends on Crop Rotation Strategy. Sustainability 2020, 12, 5271.

Hu, H.; Zhang, L.; Dai, Y.; Di, H.-J.; He, J.-Z. pH-Dependent Distribution of Soil Ammonia Oxidizers across a Large Geographical Scale as Revealed by High-Throughput Pyrosequencing. J. Soils Sediments 2013, 13.

Sharma, A.; Sepehya, S.; Sharma, R.; Kumar, A. Impact of Various Cropping Systems on the Status and Distribution of Selected Micronutrients in Subtropical Region of Himachal Pradesh, India. Int. J. Plant Soil Sci. 2023, 35, 454–463.

Pan, Z.; He, P.; Fan, D.; Jiang, R.; Song, D.; Song, L.; Zhou, W.; He, W. Global Impact of Enhanced-Efficiency Fertilizers on Vegetable Productivity and Reactive Nitrogen Losses. Sci. Total Environ. 2024, 926, 172016.

3. In Table 4, the heading of the column furthest to the right of the page should be “pH” rather than “PH.”

Response: Thank you for your careful review. We have changed "PH" to "pH" in Table 4. Please check line 167.

4. In Table 5, the column headings can just be First, Second, Third, Fourth, and Fifth. The words “The” and “time” are redundant and unnecessary.

Response: We have deleted the redundant parts in Table 5. Please check line 217.

5. The caption for Figure 2 should be on the same page as the diagram and photograph it descibes.

Response: We have adjusted the caption of Figure 2 and ensured that the corresponding photo is on the same page. Thank you for your suggestion. Please check lines 183-185.

6. Beginning in line 249 the authors write that Duncan’s multiple range test was used to separate means while Tukey’s was used to determine interactions. Why were two different tests used rather than one? Tukey’s test is a more conservative test than Duncan’s, and less likely to find significant differences.

Response: Thank you for your inquiry. We used the Tukey test in our multifactorial analysis primarily to detect overall differences, as it cannot detect pairwise differences. However, there are instances where no overall difference exists, but a difference is present between two specific groups. Therefore, we selected the Duncan test for further analysis.

7. In Table 6 and 7, the authors put the maximum value in bold font, which is helpful to the reader. This should be stated in the figure captions or footnotes. It would also be helpful to do this in Table 8.

Response: The bold values in Tables 6, 7, and 8 represent the maximum values for each indicator. We have noted this at the bottom of each table. Please check lines 314-315, 318-319 and 393-394.

8. 8. The word “Tukey” is missing the “y” in caption for Table 9.1

Response: We have changed "Tuke" to "Tukey." Please check line 395.

9. Add labels and units to the Y axes (or headings) to the three graphs shown in Figure 11.

Response: Thank you for your careful review. We have updated Figure 11 and added a title to the Y-axis. Please check lines 493-494.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The current work was undertaken to evaluate the influence of different treatments  on various parameters including water content of lettuce shoots, NPK concentration and uptake, biomass, plant height and crown diameter, yield, quality, water use efficiency, and NPK use efficiency in lettuce; (2) investigate the mechanisms through which lettuce 104 yield and water-fertilizer use efficiency respond to the interactions among water, fertilizer regulation, and ozone interactions; and (3) determine optimal irrigation and fertilization management practices to improve the quality and efficiency of lettuce in soilless cultivation systems. This study is also important when improving the crop yield, quality, and resource use efficiency. There are minor aspects that require authors’ attention for the improvement of the document, especially on the figures and references.  Figures 6,7 and 9 demonstrated the yield response based on treatments applied. The authors need to add a statement saying “Means followed by the same letters do not differ significantly”. This also applies to Figure 8. Scientific names mentioned in the listed references should written according to the rule (see lines 606, 624, 630, 648, 671, 673 and 675). There are lots on inconsistencies in writing the publication names in the references. For example, some publication names are abbreviated. Refer to lines 617, 633, 640, 643, 680 and 697. Some are written in capital letters. See lines 612, 622 and 632.

Comments for author File: Comments.pdf

Author Response

Dear editor and reviewers,

Thank you for your valuable comments and patient feedback on our manuscript. According to your valuable comments, we have revised our previous manuscript. The manuscript with highlighted changes/additions with red word are given in revised version. The detailed corrections in the manuscript and response to your comments are as follows:

Reviewer #3: Comments on manuscript agronomy-3049708:

1. The current work was undertaken to evaluate the influence of different treatments  on various parameters including water content of lettuce shoots, NPK concentration and uptake, biomass, plant height and crown diameter, yield, quality, water use efficiency, and NPK use efficiency in lettuce; (2) investigate the mechanisms through which lettuce 104 yield and water-fertilizer use efficiency respond to the interactions among water, fertilizer regulation, and ozone interactions; and (3) determine optimal irrigation and fertilization management practices to improve the quality and efficiency of lettuce in soilless cultivation systems. This study is also important when improving the crop yield, quality, and resource use efficiency. There are minor aspects that require authors’ attention for the improvement of the document, especially on the figures and references.  Figures 6,7 and 9 demonstrated the yield response based on treatments applied. The authors need to add a statement saying “Means followed by the same letters do not differ significantly”. This also applies to Figure 8. Scientific names mentioned in the listed references should written according to the rule (see lines 606, 624, 630, 648, 671, 673 and 675). There are lots on inconsistencies in writing the publication names in the references. For example, some publication names are abbreviated. Refer to lines 617, 633, 640, 643, 680 and 697. Some are written in capital letters. See lines 612, 622 and 632.

Response: Firstly, thank you for your careful review. We have added significant difference annotations to parts such as Figure 8. Please check lines 353-354, 357-358 and 419-420. Additionally, as per journal requirements, we have thoroughly reviewed and revised all references, including the publication names and overall formatting. Please check lines 642-785.

Thank you again for reviewing and annotating the manuscript in PDF format, which made it very clear to me. I have made the modifications as per your request and highlighted them in red in the manuscript. Please check.

Author Response File: Author Response.pdf