Utilization of Palm Oil Midrib Biochar as Soil Amendment with a Newly Isolated Bacillus sp. SM11 for Growth Enhancement and Nitrate Reduction in Romaine Lettuce (Lactuca sativa L. var. longifolia)
Round 1
Reviewer 1 Report
In the manuscript titled “Utilization of Palm Oil Midrib Biochar as Soil Amendment with a Newly Isolated Bacillus sp. SM11 for Growth Enhancement and Nitrate Reduction in Romaine Lettuce (Lactuca sativa L. var. longifolia)”, authors conducted a study on the combined application of biochar and biofertilizer to quantify the effects on romaine lettuce growth and nitrate accumulation. This study has important implications for the appropriate use of palm oil plantation waste. However, the authors should improve the writing of the article, supplement the “Introduction” and the “Results and Discussion” sections, and improve some of the tables. The specific suggestions are as follows:
Introduction
L43-44 The introduction did not provide sufficient background. The effects of biochar on plant growth should be described specifically.
L49-51 Studies related to nitrate accumulation should be supplemented in the “Introduction”.
L54 The significance of this study should also be discussed.
Materials and Methods
The location where the experiment was conducted is not clearly stated, including specific climatic characteristics, latitude and longitude, etc.
L117 What is the size of the plastic pots and the number of crops per pot? What is the total number of crops planted?
L118-120 What are the sample sizes and frequency of measurements for all indicators?
L134-136 It is necessary to provide detailed statistical information about asymptotic normality and consistency of variance when using one-way ANOVA. In general, if the number of soil samples for each type of soil is small (e.g. n=3), ANOVA is not appropriate. A nonparametric test, such as Kruskal-Wallis, is recommended.
It is recommended to specify in detail which indicators were analyzed using one-way ANOVA.
Results and Discussion
Tables 3, 4, and 5 In the table, the results of the post hoc test (LSD) are not reflected.
Table 4 It is suggested that this be changed to a graph to better visualize the weekly changes.
L199-120 “treatment 1” should be simply "T1" or maybe “control” and other treatments likewise. Therefore, it is necessary that one consistent term needs to be used throughout the manuscript and tables.
L260-262 It is essential to discuss why leaf spot disease was not observed in T3 and T4. Please enhance this.
Conclusions
L269-271 In the Conclusions section, it would be helpful to add a sentence or two to summarize the specific changes in the growth of romaine lettuce and nitrate reduction.
L274 Future research direction should be shown in the “Conclusions”.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors undertook very interesting and important research on the impact of biochar modified with bacteria on the growth and development of plants. The number of studies on the impact of biochar on soil and plants is very large. However, the synergistic effect of biochar and microorganisms is a relatively new topic, which, similarly to the topic of various types of biochar modifications, introduces new knowledge for agriculture, especially in the context of developing new biofertilizers. Regarding the submitted manuscript I think that the authors need to make some corrections before publication of this manuscript.
Introduction: The introduction is written very generally, it lacks numerical data and other detailed data, for example on the conditions of nitrate accumulation by the plant. I ask the authors to edit the introduction and include more detailed information
29-30: Does this information apply to Thailand or the whole world? If these are data relating only to Thailand, it would be good to also present global data
34-42: this fragment contains repetitive information, for example regarding the impact on microelements and on microorganisms.
43- 44: biomass wasn’t use as biochar. It was used for biochar production
62: Was the process carry out in a nitrogen atmosphere? Add the heating rate.
63: why filtered through 0.2 mm mesh? The particle size of biochar has influence on its effect in soil.
65: provide name of instruments
71: what is the role of Rice husk in this study? For microbial fertilizer preparation? It is unknown in this moment of the manuscript.
105: why did authors mix non-amended soil with rice husk?
113-114: whether the microorganic preparation was mixed with the biochar and then the mixture was added to the soil? or maybe the biochar was added firstly to the soil and then the microorganisms were added?
122 and 128: equation numbering should be added
124: Authors must describe in detail the method for determining nitrates
130: explain Brix
182: I don’t understand sense of “ ..and functions as a soil remediation agent”
205: Table 2 is incorrectly placed in the manuscript
Table 3: Authors have to describe in “methods” the procedures for determination of elements, EC, pH and organic matter in soil.
191-194: It is written incorrectly. Providing literature data in the results and discussion section should take the form of a discussion of the results and refer to the results obtained by the authors. Authors did not measure water retention, long term C sequestration. I think that authors can write that “positive effect observed for lettuce growth was probably caused because biochar was reported in previous studies as ….. “ and in such sentence references can be placed.
211-212: ok, but how can the results of Lu et al. can be compared to the results of the authors?
233-242: ok, there are results and there are literature review. What is the relation of literature to the authors’ results? How results from literature explain the results of authors? This must be linked! Additionally: when we provide any effect of biochar (from literature) the most important parameters of biochars must be provided (pyrolysis temperature and feedstock) because for example biochar produced at 300C will have totally different properties than biochar derived at 600C.
243-244: It should be in methods section
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
All comments have been addressed. I have no new comments.
