Effects of Rice Husk Biochar on Carbon Release and Nutrient Availability in Three Cultivation Age of Greenhouse Soils

Round 1

Reviewer 1 Report

This paper has analyzed the effects of biochar co-applied with compost on the improvement of greenhouse soil against the problems of the long-term greenhouse cultivation. The authors have conducted a good work with well-designed experiments and analysis. However, the paper in the current form is more like a scientific report than an article. The authors should make more efforts to combine their results and the problem of greenhouse soils more tightly. It is also suggested that the structure of Results and Discussion part should be re-organized to be clearer. Some more suggestions are listed as follows and a major revision should be required before the acceptance.

1. Lines 19-20 in Page 1, the sentence is not written correctly in grammar.
2. Lines 21-24 in Page 1, please change the phrases into several simple sentences.
3. In the abstract, the authors have mentioned the improvement of soil through biochar application, thus in the results they should make it clear which property alterations were deemed as the soil improvement.
4. Lines 8-9 in Page 6, mistakes in the use of parentheses.
5. It is appreciable to provide the details of all the sample analysis, but if it could be properly simplified it would help to highlight the description of the designed experiment, which is the most important part in M&M.
6. Line 5 in Page 25, I just wonder whether 25 g of mixed soil sample could represent the situation for the soil in greenhouse because of the difference between the experiments of the micro- and macro-scales. Therefore, I’d love to hear the idea from the authors.
7. Same suggestion for the section 3.2, there is no need to precisely discus the property variations of biochar especially when the results corresponded with the general situation. In addition, when the authors did not use those results in details to discus biochars’ performance on soil improvement, that part should be simplified in order not to weaken the other parts.
8. Section 3.3 in Page 10, I would like to say it is a little confusing about the ANOVA since the authors divided the variation into two different categories: 1. Treatment and rate; 2. Soil and rate. Thus, the different results of ANOVA for the “rate” factor would be a little bizarre. If I’m right the experiment design could be considered as a split-split-plot with three levels of factors (soil ages, biochar sorts, and biochar rates) with a control treatment (zero rate for any biochar sort), so maybe in that way the ANOVA could be made clearer.
9. For the PCA results, if the authors intended to conduct a discriminant analysis for the soil under different biochar treatments and soil ages, I suggest to use the canonical discriminant analysis in SAS with PROC Candisc.
10. Lines 21-24 in Page 14, could the authors explain why the EC value had different correlation with the other soil properties in the soils with different ages? It should not just offer the results as a report without any discussion.
11. Lines 30-33 in Page 14, I am not sure the reason offered in the text could interpret the higher content of TP in compost treatment in contrast with the biochar treatments which also had the same application rate of compost.
12. Lines 7 in Page 15, I have noticed that the authors use many times the reference 33 to support their study. However, the woody biochar derived from the material with high lignin would be different from the material of rice husks whose compositions are similar to straws. Therefore, it is better to cite more relevant references with biochar derived from similar materials.

Author Response

Dear reviewer:

Thank referee’s valuable comments and the authors will reply following comments one by one. The revised manuscript has combined the result of rice husk biochar amendments and the problem of greenhouse soils more tightly. The structure of Results and Discussion has reorganized and separated for clarity. The content of Materials and Methods has simplified and highlighted the important part in M&M. And, the descriptions of biochar properties have simplified and the Figure of SEM and FTIR has moved as for the supplemental Figure (supplemental Figure S1 for SEM images and S2 for FTIR spectra). We have revised the manuscript carefully and in details based on the valuable comments of reviewers, and have made the presentation and discussion of manuscript more complete.

best regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Major Comments

The paper aims to contribute to the understanding of biochar benefit to greenhouse cropland for sustainable agriculture production. Though not original, the paper explicitly quantified the effect of biochar made from rice husk on greenhouse soils with diferent cultivation years. The study is relevant to the Journal of Agronomy.

The methodology is relatively quantitatively sound, and the results is reasonable. The conclusions are also clearly presented.

However, the result and discussion should be separated for clarity.

Minor Comments

Line 15: you don’t have to put “etc”. List all the ones important.

Line 28: “3, 14, and 24 year cultivation” not “3-, 14-, and 24-year cultivation”

Line 37 -39: This information is presented in the introduction section and it sounds repetitive. Remove the info from one of the sections.

Line 12-13: Put space between values and units. e.g. , “21 and %” should be written as “21 %”. Check through the manuscript to effect relevant changes for values and units.

Author Response

Dear reviewer:

Thank referee’s valuable comments and the authors will reply following comments one by one. The structure of Results and Discussion has reorganized and separated for clarity. The content of Materials and Methods has simplified and highlighted the important part in M&M. And, the descriptions of biochar properties have simplified and the Figure of SEM and FTIR has moved as for the supplemental Figure (supplemental Figure S1 for SEM images and S2 for FTIR spectra). We have revised the manuscript carefully and in details based on the valuable comments of reviewers, and have made the presentation and discussion of manuscript more complete.

best regards

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

1. P5, L22-30, the authors have given the reason why they use the small amount of soil samples for the incubation in their experiment. That could be acceptable, but the paragraph should be modified. One sentence mentioned the soil sample amount while citing the reference could be enough.
2. For the PCA analysis, I still recommended that a discrimination analysis should be conducted. It was because even though the PCA showed the differences, we can not know whether the results were significant or not. Canonical discriminant analysis had the same process as PCA, it could compare the different groups by mathematical distance.
3. P16, L14-20, I just still found the authors did not explain why the EC had different correlation with the same soil characteristics in 3S and 14S soil. Hence, the detail discussion is demanded.

Author Response

Dear Reviewer:

The authors appreciate reviewer’s comment. The canonical discriminant analysis (CDA) was conducted in the revised manuscript. One Figure (Fig. 2) and one supplemental figure (supplemental Figure S3) have added in the revised manuscript. We have revised the manuscript carefully and in details based on the valuable comments of reviewers, and have made the presentation and discussion of manuscript more complete.

bestregards

Author Response File: Author Response.pdf