Short-Term Effect of In Situ Biochar Briquettes on Nitrogen Loss in Hybrid Rice Grown in an Agroforestry System for Three Years
Christopher Nzediegwu
Round 1
Reviewer 1 Report
Introduction:
- Line 68-70: “biochar has a large…reduce soil porosity”, you sure it reduces instead of increasing? Also, please be specific when talking about the effects of biochar since every biochar is different (conditions, raw materials, etc.). For instance, not every biochar has high CEC.
- Line 75: what’s the meaning of H2O next to pH?
- Why it’s necessary to conduct this study? It seems like there’s a big jump or gap from previous paragraph to the objective paragraph. Add a couple sentence to make it transaction smoother is encouraged.
M&M:
- How much rain was detected during the experiment? It would be nice to include the rain data in the paper.
- The soil pH is around 8 (alkaline), why did you decide to use another alkaline biochar (pH 8.15) in this study? What is the rational here?
- You measured the microbial activities in this study, it would be nice to include biochar effects on microbial activities in the introduction and discussion sections.
Results:
- 5 determining the optimum… (delete of)
Author Response
Dear Reviewer,
I extend my gratitude and appreciation to the reviewer who had improved our manuscripts so that our manuscripts become better quality. I had fixed all the revisions. All the improvements we have marked in the manuscript (Please see the attachment). For information, our manuscript has been checked by professional english editing, namely from internal MDPI and ENAGO. Once again, we would thank you very much. Good luck, always.
Best Regards
Authors
Response to Reviewer 1 Comments
Point 1: Introduction: Line 68-70: “biochar has a large…reduce soil porosity”, you sure it reduces instead of increasing? Also, please be specific when talking about the effects of biochar since every biochar is different (conditions, raw materials, etc.). For instance, not every biochar has high CEC.
Response 1: We have corrected this statement so that it is relevant to the condition of the soil texture at the research site, namely clay texture. We meant earlier that biochar could reduce porosity when applied to soils with a sandy texture, and we have also added new, more relevant references. (Lines 69-72).
Point 2: Introduction: Line 75: what’s the meaning of H2O next to pH?
Response 2: H2O figure refers to the acidity of the soil solution.
Point 3: Introduction: Why it’s necessary to conduct this study? It seems like there’s a big jump or gap from previous paragraph to the objective paragraph. Add a couple sentence to make it transaction smoother is encouraged.
Response 3: We have already explained the problem of kayu putih waste and the problem of low N content due to low efficiency on alkaline soil in kayu putih forests, which inhibits rice growth. Furthermore, this solution can be overcome by processing kayu putih waste into biochar to increase N loss in kayu putih forests. (Lines 50-82)
Point 4: Materials and Methods: How much rain was detected during the experiment? It would be nice to include the rain data in the paper.
Response 4: We have included an explanation of the rainfall in lines 103-104. The average rainfall at the time of the study was 1810.13 mm year−1. (Line 105).
Point 5: Materials and Methods: The soil pH is around 8 (alkaline), why did you decide to use another alkaline biochar (pH 8.15) in this study? What is the rational here?.
Response 5: The biochar used in this study was kayu putih waste with a pH of 8.05. We use biochar from kayu putih waste to overcome the problem of kayu putih waste at the research site. This can reduce costs incurred by farmers and is by the principle of recycling residues. In addition, bringing in sources of organic materials from other areas, of course, requires a considerable cost so that farmers' profits will be reduced. The research results that we had presented in the introduction on lines 77-81 state that there is no significant difference between kayu putih biochar and rice husk biochar. This is what we made the basis for using biochar from kayu putih waste.
Point 6: Materials and Methods: You measured the microbial activities in this study, it would be nice to include biochar effects on microbial activities in the introduction and discussion sections.
Response 6: We have added references regarding the effect of biochar on increasing microbial activity in the introduction and the references. (Line 72).
Point 7: Results: 5 determining the optimum… (delete of)
Response 7: We have omitted the word 'of' in accordance with the suggestions of the reviewers. (Line 391).
Author Response File: 
Author Response.docx
Reviewer 2 Report
Authors studied the “Short-Term Effect of In Situ Biochar Briquettes on Nitrogen Loss in Hybrid Rice Grown in an Agroforestry System for Three Years”
The study is well-designed and the questions addressed are important; however, the authors should clarify the novelty in the introduction section. The results should be synthesized and written in a precise manner and the discussion should be supported by evidence and not mere speculations
Abstract
L18: The abbreviated N is redundant and should be deleted
L28-29: Does the precision of your instrument support a-two decimal places for percent reduction in the usage of fertilizer? Correct this throughout the manuscript
Introduction
L38: What is the meaning of the superscript (-1) attached to the word “year”?
L64-67: The definition of biochar as “the by-product of pyrolysis” should be updated because three products are produced during pyrolysis. See https://doi.org/10.1016/j.scitotenv.2021.151120 for a full definition. It is too general to just write “through physics, chemistry, biology”
L69: What is the essence of using the term “respectively” in this sentence? The term “collect” is used out of context. Biochars “adsorb” and not “collect” nutrients
L89-94: Describe how this study is different from the work of Faridah et al. mentioned in L81
L93: What is the essence of the term “instead” in this statement?
L117: Why the different units for N and P?
L124-128: Clarify if the biochar was added to the soil one time (first year) or multiple times (every year). What is the rationale for selecting the biochar application rate?
L131: Provide more details about the traditional kiln (was it possible to measure the average pyrolysis temperature and the biomass residence time?).
L133: What type of adhesive?
L141: What do authors mean by “strategically placed”?
L145: How was the biochar applied? Manually or with a special kind of machine?
L169-171: Why define those parameters for the second time?
L176: How did you test and ensure that each parameter was normally distributed?
L177-178: What do you mean by “the interaction …utilized an analysis of variance?” Rephrase the statement because it is difficult to understand. In fact, it is illogical.
L184: Equation (3) is missing in the manuscript
L189: How can x1 and x2 be defined as both the linear and squared terms?
Results
The results should be synthesized and written in a precise manner. Quoting p-values almost on every parameter makes the writing untidy and difficult to read. The use of physics, chemistry and biology to represent physical, chemical and biological properties, respectively, should be avoided.
Discussion
Biochar properties (Table 1) should be used to support some of the results in the discussion section. Else, what is the essence of those properties in Table 1?
Page 15
Paragraph 1: What evidence showed that “the surface-area-to-volume ratio is smaller?”
Paragraph 2: What evidence showed there was accumulation of biochar briquette residue in the soil? Or is this a mere speculation? Were the climatic conditions for the different years monitored? Were they similar across the years?
Page 16
Paragraph 2: What do V3, R1 and R3 mean?
Tables
Table 1: Change the Table caption because pH and CHNS-O contents are not the nutrient contents of biochar. Properly calculate the molar element ratios (H/C, O/C, etc). For example, O/C is not just O divided by C. You have to consider their atomic weights in the calculation: See https://labsense.fi/uploads/7/1/9/5/71957143/011269a_01_app_ea_molar_element_ratios.pdf for details.
Tables 1, 2 and 3: Define the abbreviations used in the Table in the Table’s footnote as you did for Table 4
Author Response
Dear Reviewer,
I extend my gratitude and appreciation to the reviewer who had improved our manuscripts so that our manuscripts become better quality. I had fixed all the revisions. All the improvements we have marked in the manuscript (Please see the attachment). For information, our manuscript has been checked by professional english editing, namely from internal MDPI and ENAGO. Once again, we would thank you very much. Good luck, always.
Best Regards
Authors
Response to Reviewer 2 Comments
Point 1: Abstract: L18: The abbreviated N is redundant and should be deleted.
Response 1: We had removed the abbreviation N in the abstract according to the reviewer's suggestion. (Line 18).
Point 2: Abstract: L28-29: Does the precision of your instrument support a-two decimal places for percent reduction in the usage of fertilizer? Correct this throughout the manuscript.
Response 2: Maybe the reviewer means 23.31% and 26.28% in the abstract. We need to explain that the two percentages are different substances. First, 23.31% is a reduction in the use of standard Urea fertilizer, which is 300 kg/ha. The second percentage of 26.28% is the percentage of N loss in the soil based on the calculation of formula 1 (Line 28).
Point 3: Introduction: L38: What is the meaning of the superscript (-1) attached to the word “year”?
Response 3: We had corrected the sentence to be per year. (Line 38)
Point 4: Introduction: L64-67: The definition of biochar as “the by-product of pyrolysis” should be updated because three products are produced during pyrolysis. See https://doi.org/10.1016/j.scitotenv.2021.151120 for a full definition. It is too general to just write “through physics, chemistry, biology”.
Response 4: We had improved the definition of biochar based on the journal suggested by the reviewer and we have added it to the reference. (Lines 64-67)
Point 5: Introduction: L69: What is the essence of using the term “respectively” in this sentence? The term “collect” is used out of context. Biochars “adsorb” and not “collect” nutrients
Response 5: We had improved according to suggestions from reviewers. (Lines 70-72)
Point 6: Introduction: L89-94: Describe how this study is different from the work of Faridah et al. mentioned in L81
Response 6: Research conducted by Faridah et al. (2021) examined the application of biochar given in the form of powder/bulk to inbred rice varieties, while in this study, the application of biochar was given in the form of briquettes to hybrid rice varieties.
Point 7: Introduction: L93: What is the essence of the term “instead” in this statement?
Response 7: We had corrected the sentence by deleted the word “instead”, making the statement confusing. (Lines 93-96).
Point 8: Materials and Methods: L117: Why the different units for N and P?
Response 8: We refer to the use of units from the USDA. In this manuscript, we use the unit % for the N content in the soil, while for P is ppm. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_045218.pdf. (Line 119)
Point 9: Materials and Methods: L124-128: Clarify if the biochar was added to the soil one time (first year) or multiple times (every year). What is the rationale for selecting the biochar application rate?
Response 9: We added to the soil multiple times (every year). The selection of the rate of biochar based on research conducted by Oladele et al. (2019) related to the application of biochar and urea fertilizer to rice in alfisol and ultisol soils. Our research has similarities between commodities, treatments, and soil texture. The rate of biochar used is 0, 3, 6, and 12ton/ha, which is given in bulk/powder form. From the research results conducted by Oladele et al. (2019), it is still possible to increase N efficiency and rice production. Based on this, we innovated to apply biochar in briquettes to make it more slow release so that it can be maximally absorbed by the rice and more efficient use of N fertilizer. If converted to biochar briquettes in our study, it was 0, 5, 10, and 15 tons/ha and not much different from Oladele et al. (2019) (https://doi.org/10.1016/j.geoderma.2018.08.025).
Point 10: Materials and Methods: L131: Provide more details about the traditional kiln (was it possible to measure the average pyrolysis temperature and the biomass residence time?)
Response 10: Manufacturing biochar using a stainless kiln (capacity 40 liter) at temperature ± 250-350 °C with a long burning time of 3.5 hours. (Line 134-135).
Point 11: Materials and Methods: L133: What type of adhesive?
Response 11: The adhesive material was used molasses. We had added it in the manuscript. (Lines 137-138).
Point 12: Materials and Methods: L141: What do authors mean by “strategically placed”?
Response 12: We had removed the word “strategically” because it will confuse readers. (Lines 146-147).
Point 13: Materials and Methods: L145: How was the biochar applied? Manually or with a special kind of machine?
Response 13: The application of biochar briquettes and inorganic fertilizers was made manually. We had added it in the manuscript. (Line 154).
Point 14: Materials and Methods: L169-171: Why define those parameters for the second time?
Response 14: We observed NUE more than once, and we did it during the research (2019-2021). We want to know the percentage efficiency of nitrogen use during this research.
Point 15: Materials and Methods: L176: How did you test and ensure that each parameter was normally distributed?
Response 15: Before analysing variance, we performed a normality test and a homogeneity test. Normally distributed with Q-Q plot and homogeneous variance with residual vs value graph. The results of checking with the Q-Q plot graph showed that model had normally distributed data. We had added it in the manuscript. (Lines 213-214).
Point 16: Materials and Methods: L177-178: What do you mean by “the interaction …utilized an analysis of variance?” Rephrase the statement because it is difficult to understand. In fact, it is illogical.
Response 16: We had corrected the sentences in the manuscript to avoid confusion. (Lines 184-186).
Point 17: Materials and Methods: L184: Equation (3) is missing in the manuscript
Response 17: We had fixed the error. (Lines 174 and 191).
Point 18: Materials and Methods: How can x1 and x2 be defined as both the linear and squared terms?
Response 18: Sorry, there was an error in the manuscript. X1 should be X1 and X2 should be X2. We have fixed in the manuscript. (Lines 196-197)
Point 19: Results: The results should be synthesized and written in a precise manner. Quoting p-values almost on every parameter makes the writing untidy and difficult to read.
Response 19: We had deleted the p-value in each parameter according to the reviewer's suggestion.
Point 20: Results: The use of physics, chemistry and biology to represent physical, chemical and biological properties, respectively, should be avoided.
Response 20: We had fixed it according to the reviewer's suggestions.
Point 21: Discussion: Biochar properties (Table 1) should be used to support some of the results in the discussion section. Else, what is the essence of those properties in Table 1?
Response 21: We had added information from Table 1 to reinforce the statement that biochar made from kayu putih waste can improve soil properties in this research. (Lines 431-439).
Point 22: Discussion (Paragraph 1): What evidence showed that “the surface-area-to-volume ratio is smaller?”
Response 22: The sentence is the assumption of the authors. We could not prove this because there were no related observations of the structure of the biochar briquettes, so we decided to delete the statement so as not to be ambiguous. (Lines 431-439).
Point 23: Discussion (Paragraph 2): What evidence showed there was accumulation of biochar briquette residue in the soil? Or is this a mere speculation? Were the climatic conditions for the different years monitored? Were they similar across the years?
Response 23: Applying biochar during the study (2019-2021) will increase the residue in the soil. This follows the statements of many papers that say that biochar residue will persist in the soil for hundreds of years or even thousands of years. Based on this, it can be seen in Table 4 that the application of biochar increases soil properties every year. We also include information related to the average climate data for the three years of the study (rainfall, air temperature, relative humidity, and wind speed) on the materials and methods. The dynamics of the macro and microclimates during the study (2019-2021) were relatively the same because our research was carried out in the wet tropics with a ustic moisture regime. So, in our opinion, the macro and micro climates do not affect the research. (Lines 431-439).
Point 24: Discussion (Page 16): Paragraph 2: What do V3, R1 and R3 mean?
Response 24: We had described the V3, R1, and R3 phases of groundnuts in the manuscript. (Lines 460-461).
Point 25: Table 1: Change the Table caption because pH and CHNS-O contents are not the nutrient contents of biochar. Properly calculate the molar element ratios (H/C, O/C, etc). For example, O/C is not just O divided by C. You have to consider their atomic weights in the calculation: See https://labsense.fi/uploads/7/1/9/5/71957143/011269a_01_app_ea_molar_element_ratios.pdf for details.
Response 25: We had used references from reviewers to calculate the molar ratio. (Lines 142-143)
Point 26: Tables 1, 2 and 3: Define the abbreviations used in the Table in the Table’s footnote as you did for Table 4
Response 26: We had added abbreviations as suggested by reviewers. (Lines 143, 222-226, 237-241).
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
