Biomass Source of Biochar and Genetic Background of Tomato Influence Plant Growth and Development and Fruit Quality

Round 1

Reviewer 1 Report

Biochar, produced from the pyrolysis of organic feedstock, is considered as a soil amendment that can potentially restore soil quality and improve crop yields. This study evaluated on six biochars on agronomic performance and fruit quality of three tomato cultivars. The result of this study indicated that plant genetic background and biomass source are important variables that should be considered for using biochar as a soil amendment.

My major concerns as followings:

1. The main purpose of adding biochar to soil is to cope with soil degradation caused by excessive production and application of chemical fertilizers. Therefore, it is reasonable to conduct experiments on degraded soil or representative soil . However, in this study, tomato cultivation was carried out on artificial medium, and the growth conditions were strictly controlled in greenhouse, such as suitable temperature, humidity, and irrigation, Therefore, the results of the study are difficult to apply on the field production of tomato.

2. There are only 4 plants in each plot in the experimental design, so the sample size is too small to represent the treatment. However, tomato experimental plots usually require no less than 15 plants, which may be the reason why there is no significant difference in tomato yield and dry matter between treatments in this study. The size of the plot determines the reliability of the experimental results.

3. Biochar mainly improve soil structure, ability to hold nutrients and water, so that the soil should be the most direct research item. Its impact on plant growth should mainly be on root growth, however, it is seem lack of relevant research in this study.

My minor concerns as followings

1. The title of the article seems not to accurately reflect the research content. could you please consider optimize it?

2. Since the nutrient content has already been measured, could you please fill it in the table 2? only simply listed ‘Y’or  blank is somewhat rough.

3. In Figures 2-5: P<0.1 as the significance criterion is not as common criterion, P<0.05 is used as the significance criterion, and P<0.01 used as the extremely significant criterion.

4. The data given in Tables 3 and 4 only have one significant digit, and often the last significant digit is an estimated, so the data is not qualified and does not have significance in explaining the results.

Author Response

Reviewer 1:

1. The primary purpose of adding biochar to soil is to cope with soil degradation caused by excessive production and application of chemical fertilizers. Therefore, it is reasonable to conduct experiments on degraded soil or representative soil. However, in this study, tomato cultivation was carried out on an artificial medium, and the growth conditions were strictly controlled in a greenhouse, such as suitable temperature, humidity, and irrigation. Therefore, the results of the study are difficult to apply to the field production of tomatoes.

Response: The primary purpose of this study was to evaluate whether different biochars derived from diverse biomass sources and the genetic background of the plant interact to influence plant growth and development. Therefore, the study was conducted in controlled conditions. However, the reviewer's point was clearly addressed within the manuscript; see Lines 351-357. This is why the discussion did not focus on the direct application to field tomato production. Indeed, the two variables – source of biochar and plant genetics influence plant parameters. This has implications in the study of biochar as a soil amendment.

2. The experimental design has only 4 plants in each plot, so the sample size is too small to represent the treatment. However, tomato experimental plots usually require no less than 15 plants, which may be why there is no significant difference in tomato yield and dry matter between treatments in this study. The size of the plot determines the reliability of the experimental results.

Response: This has been accounted for within the statistical analysis. ANOVA, for example, considers sample size when calculating significance. While the number of plants per treatment group could improve the discovery of significant responses, Tables 3 and 4 (4 and 5 in the revised manuscript) identify a significant influence on several plant performance parameters at a very stringent significance threshold (p<.001).

3. Biochar mainly improve soil structure, ability to hold nutrients and water, so that the soil should be the most direct research item. Its impact on plant growth should mainly be on root growth, however, it is seem lack of relevant research in this study.

Response: Biochar is usually considered inert, as the reviewer pointed out. However, several recent publications, including ours, have demonstrated that biochar impacts microbial function and physical changes to the soil. While the mechanisms that underlie root interactions with the soil after biochar application are interesting and merit study, this falls outside of the scope of this study. Biochar trials (including most cited in this study) that do not measure root growth are more common than those that do.

4. The title of the article seems not to accurately reflect the research content. could you please consider optimize it?

Response: Considering the data within Table 3, the source of biochar and the genetic background of the plant influenced various plant parameters and fruit quality. As suggested by the reviewer, we have changed the title. See Line 2 of the revised manuscript.

5. Since the nutrient content has already been measured, could you please fill it in the table 2? only simply listed ‘Y’ or blank is somewhat rough.

Response: To clarify that these elements have been tested for and have not been detected, this table has been modified to include a dash instead of being left blank in these boxes. The use of the letter “N” has been avoided to avoid the misconception that these elements are not present, as they were simply below the detection threshold. See Line 238 of the revised manuscript.

6. In Figures 2-5: P<0.1 as the significance criterion is not a common criterion, P<0.05 is used as the significance criterion, and P<0.01 is used as the extremely significant criterion.

Response: In studies involving trials with plants, a threshold of p<0.1 is reasonably standard because of the immense amount of inherent variability in such experiments. Even Ronald Fisher – who developed the concept, cautioned against declaring p-values as significant or non-significant based on an arbitrary cut-off (e.g., 0.05 or 5%).  [1] “The threshold value, P < 0.05 is arbitrary. As has been said earlier, it was the practice of Fisher to assign P the value of 0.05 as a measure of evidence against the null effect. One can make the “significant test” more stringent by moving to 0.01 (1%) or less stringent moving the borderline to 0.10 (10%). Dichotomizing P values into “significant” and “nonsignificant” one loses information the same way as demarcating laboratory finding into normal” and “abnormal”, one may ask what is the difference between fasting blood glucose of 25mmol/L and 15mmol/L?”

6. The data given in Tables 3 and 4 only have one significant digit, and often the last significant digit is an estimated, so the data is not qualified and does not have significance in explaining the results.

Response: The data within these tables are p values rounded for readability and brevity. They are neither estimated nor insignificant.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4111019/#:~:text=As%20has%20been%20said%20earlier,of%20evidence%20against%20null%20effect.

Author Response File: Author Response.pdf

Reviewer 2 Report

Brief summary.

Interesting article that studies the interaction between the application of two concentrations of biochar from six different raw materials and the behavior of growth, development and fruit quality of three tomato cultivars.

General concept comments

The manuscript relevant to the field and presented in a well-structured way Introduction and material and methods are clear and put forward coherent hypotheses. Results and discussion are appropriate to the experimental approach. However, the conclusions section is excessive and includes more recommendations or perspectives than conclusions. It should be specified in the heading or appropriately separated.

Specific comments

Line 130- 134. The information in Table 1 (A and B) should be presented in the defined format of Horticulturae and unified into a single table. Otherwise, the data should be presented in two different tables with their respective headings. The same applies to Table 2 (Lines 225-228)

Author Response

Reviewer 2:

The manuscript relevant to the field and presented in a well-structured way Introduction and material and methods are clear and put forward coherent hypotheses. Results and discussion are appropriate to the experimental approach. However, the conclusions section is excessive and includes more recommendations or perspectives than conclusions. It should be specified in the heading or appropriately separated.

Response: We appreciate the reviewer's opinion. While separating out a “Perspectives” section could improve the manuscript’s structure, Horticulturae’s formatting instructions do not provide for such a section. The formatting guide indicates a Conclusion “can be added to the manuscript if the discussion is unusually long or complex,” which, as you noted, is the case here.

Line 130- 134. The information in Table 1 (A and B) should be presented in the defined format of Horticulturae and unified into a single table. Otherwise, the data should be presented in two different tables with their respective headings. The same applies to Table 2 (Lines 225-228)

Response: Figures 1 A and B have been split into two tables (now Tables 1 and 2) to conform to Horticulturae’s format guidelines. See Lines 132-138 of the revised manuscript.

Author Response File: Author Response.pdf