Soil Amendment with Biochar Affects Water Drainage and Nutrient Losses by Leaching: Experimental Evidence under Field-Grown Conditions

Round 1

Reviewer 1 Report

I have reviewed the manuscript ‘Soil amendment with biochar affects water drainage and nutrient losses by leaching: experimental evidence under field-grown conditions’, which is a nice field experiment about the effect of biochar application on the drainage and solute losses. The manuscript contains valuable information and it is relevant because it provides data on the behavior of the soil treated with biochar under conditions of intensive crop cultivation (with irrigation and fertilization). Field trials are necessary to study the behavior of the biochar and its interaction with the soil. In this sense, the work presented here fall within the scope of the Agronomy and might be of interest for its readership. Specific comment and suggestions to the authors are included in order to improve the final version of the manuscript.

Detailed comments:

- Line 102: replace “perculating” by percolating.

- Lines 102-103: “due to precipitations exceeding the soil water holding capacity…” The irrigation should also be included here.

- Lines 105-108: But in the manuscript, the authors do not give details of the number of drainage events in each period or the volume of water per unit area collected in each drainage event. It would also be interesting to study the effect of biochar on the dynamics of drainage and leaching, and the data is available !!!

- Lines 123-124: How many irrigations in each crop cycle? Irrigation frequency in each cycle? How was it measured that soil moisture was less than 50% of available water?

- Lines 131 – 136: An analysis of irrigation water (as an Appendix) would greatly complete the work presented. As the authors point out, the leaching of anions and cations depends on the drainage of water and the concentration of these ions in the water that it percolates. This concentration depends on the inputs to the soil and the transformations that occur in the soil profile. Therefore, it would be convenient to know at least the concentration of nitrate and chloride in the irrigation water.

- Lines 139 – 140: More information on fertilization is necessary: chemical forms used in the nitrogen fertilizer (nitric, ammonium, urea?), number of applications and timing.

- Line 148: Use the similar format for figure caption as in Figure 1.

- Line 151: Although it is commented in the Appendix A3, it would be convenient to include the biochar doses in Mg ha^-1.

- Lines 158-161: Do the Italian technical specifications do not contemplate salinity as a quality criterion?

- Lines 170 – 172: The results of these soil samples are not provided by the authors. How does the pH and EC vary during the two growing cycles?

- Line 174: Change 50-ml by 50 mL

- Line 175: +4ºC

- Line 176: examined? Analysed

- Lines 177 – 179: The ammonium ion (NH₄⁺) has not been considered in the soil or in the drainage water, but its presence could be important as a source of nitrate through the nitrification process. Please comment on the non-consideration of the ammonium ion in your work.

- Line 186: (C, kg m^-3) It would be advisable to use another abbreviation, for example, C_sol so that there is no confusion with the temperature or carbon symbol.

- Line 196: Really, the term ɛ would be the concentration…

- Line 204-206: Please specify that drainage and leaching data are accumulated.

- Line 218: Figure 3 shows the observed main weather conditions (temperature, rainfalls and reference evapotranspiration… Please complete the sentence, i.e., during the experimental period…

- Lines 221-243: Figure 3A. Correct the temperature units.

What is the duration of GS1 and GS2? Lettuce and radicchio are harvested on February 13, but in the figure 3A the GS1 It lasts until April… Clarify.

Figure 3B. Crop evapotranspiration (ETc) could be added.

- Line 247: figure caption: “detected” registered, measured,…

- Line 251: Change GS1and by GS1 and

- Line 261: Similar standard errors (56 and 52 m³ ha^-1) for very different drainages. Any comment?

- Line 265: “Without considering the biochar effect…” Do you mean that the values in table 1 correspond to B0? I think it is the average value of the three treatments, but the statement is confusing...

- Lines 266-268: The high nitrate leaching value in the GS1 is mainly due to the high initial nitrate value in the soil at the beginning of the experiment. According to the value in table A2, 10.78 mg NO₃^- -N in soil profile (0-70 cm), and considering the soil bulk density (1310 kg m^-3), the nitrate content is 434 kg/ha. This nitrate is likely to be leached as soon as drainage occurs!!

It would be convenient to point out the importance of the initial values of the ions in the soil, if comparisons are to be made between different periods.

- Line 278: As commented above, the Sout term is also affected by input to the soil and the transformation and sinks in the soil.

- Line 282: (rains (W_P) and irrigation (W_I) volumes per unit area)

- Table 1. One decimal is enough.

Change NO^3- by NO₃^-

- Table 2. Below the table include:

** P<0,001; n.s. = not significant; R² = coefficient of determination; RMSE = Root Mean Square Error; CV = Coefficient of Variation.

- Figure 4B: Shouldn't water inflow values greater than 6000 m³ ha^-1 appear?

- Line 327: 36.46%).

- Table 3. Change NO^3- by NO₃^-

- Lines 341-347: The leaching coefficient has units of concentration!!

The leaching of a solute depends not only on mobility and solubility, but also on the greater or lesser amount in the soil. The solute transport in the soil can be convective, diffusive and dispersive. When convective water flow predominates, ion solubility is the most important factor. But when the flow is predominantly diffusive the concentration of the ion is important. Another aspect to consider in the case of dispersive flow is the possibility of anionic exclusion phenomena.

- Figure 5: Separate figures 5A and 5B to avoid overlapping the values of the abscissa axis. Same with 5C and 5D.

- Lines 382 – 391: It would be convenient to know the cation exchange capacity of the soil.

- Lines 395 – 399: It would be convenient to know the cation and anion input for irrigation.

- Lines 412 – 418: According to table A2 the EC value is 2.45 dS/m. How do you explain the variation that appears in the text (0.55 to 0.57 to 2.4 dS/m?

- Lines 424 – 426: See previous comment on drainage dynamics.

- Section 4.2. The argument is good, but the discrepant results found in the literature are due in part to the differences in soil properties used in each experiment. In sandy soils with good conductivity under saturation conditions, biochar improves the reduced water retention capacity of these soils, but in clay soils, the effect on conductivity will be more important.

The hydraulic properties could have been analyzed after the field experiment!!

- Line 446: change structure-[28… by structure [28

- Section 4.3: See previous comment about the need to consider the initial values of Nmin.

- Line 497: Change NO_3-

- Line 521: Change adsorbtion by adsorption.

- Lines 533 – 534: This statement should be included in the discussion section, since the study does not show crop production data or extractions by the plant.

- Line 542: Change “The authors… by The authors

APPENDIX

- Line 723: 1000 L

- Line 730: 0.7 m.

- Line 746 and following: Correct numbering of bibliographic references.

[5] is [1], ….

- Line 750: mL

- Table A1: EC in dS m^-1

Carbon C: use the similar units as H, N, S, O

How is the H/Corg and O/Corg ratio calculated? Using the values of the table, Corg is in one case 6.8% and in another 114%

Ca, Mg, Fe,… Why not in g / kg?

Bulk density in kg m^-3

- Line 809: bulk density 1.3 Mg m^-3

- Line 859: FeSO₄

- Line 859: method

- Line 866: main physico…

Table A2: Why don't they show the values of each layer?

Field capacity: gravimetric soil moisture at field capacity (%)

Wilting point: gravimetric soil moisture at wilting point (%)

Author Response

Department of Science of Agriculture,

Food and Environment,

University of Foggia

Via Napoli, 25

71122 Foggia, Italy

08 November 2019

Manuscript ID: agronomy-615828

“Soil amendment with biochar affects water drainage and nutrient losses by leaching: experimental evidence under field-grown conditions”

Authors: Angela Libutti, Anna Rita Bernadette Cammerino, Matteo Francavilla and Massimo Monteleone.

Dear Reviewer 1,

we would like to thank you for the comments and suggestions that have been very useful in order to improve the quality of the work and clarify possible misunderstandings from the potential readers.

We are resubmitting a new version of the manuscript; every change made was clearly outlined in the revised text.

We really hope to have explained all the issues raised from you.

Please find below our considerations, point by point, in reply to your comments.

REVIEWER 1

I have reviewed the manuscript ‘Soil amendment with biochar affects water drainage and nutrient losses by leaching: experimental evidence under field-grown conditions’, which is a nice field experiment about the effect of biochar application on the drainage and solute losses. The manuscript contains valuable information and it is relevant because it provides data on the behavior of the soil treated with biochar under conditions of intensive crop cultivation (with irrigation and fertilization). Field trials are necessary to study the behavior of the biochar and its interaction with the soil. In this sense, the work presented here fall within the scope of the Agronomy and might be of interest for its readership. Specific comment and suggestions to the authors are included in order to improve the final version of the manuscript.

Detailed comments:

- Line 102: replace “perculating” by percolating

We made the recommended change (line 101 of the amended manuscript version).

- Lines 102-103: “due to precipitations exceeding the soil water holding capacity…” The irrigation should also be included here.

Deep percolation of water was due mainly to rains since crop irrigation was performed applying the right amount of water, sufficient to restore the soil water holding capacity (according to the “two steps” FAO methodology). Therefore, water losses by drainage were mainly due to unpredicted rains after irrigation or heavy rains exceeding the soil water holding capacity. We have adjusted the sentence according to the suggestion.

- Lines 105-108: But in the manuscript, the authors do not give details of the number of drainage events in each period or the volume of water per unit area collected in each drainage event. It would also be interesting to study the effect of biochar on the dynamics of drainage and leaching, and the data is available !!!

Drainage water was collected at 15-day intervals, eight times during GS1 with volumes of water varying from 18 to 265 m³ ha^-1; five times during GS2 with volumes of water varying from 40 to 162 m³ ha^-1. This information has been added to the results section (lines 272-274 of the amended manuscript version). Anyway, drainage events are reported in Figure 4 in terms of cumulated volumes of water outflows with respect to the cumulated volumes of water inflows. The slope of each regression line informs about the dynamics of drainage (very different in the two subsequent crop-growing periods).

- Lines 123-124: How many irrigations in each crop cycle? Irrigation frequency in each cycle? How was it measured that soil moisture was less than 50% of available water?

During GS1 (intercropped lettuce and radicchio growing season) three irrigations with a frequency of 17.5 days were applied. During GS2 (zucchini growing season) nineteen irrigations with a frequency of 6.5 days were applied. This information has been added to the results section (lines 265-268 of the amended manuscript version).

The gravimetric soil moisture was frequently measured in order to check the soil water balance performed daily. Every time the soil “available water capacity” (i.e. the difference between the gravimetric soil moisture at field capacity and the gravimetric soil moisture at wilting point) was reduced by 50%, then a watering was applied in order to fully restore the water field capacity.

- Lines 131 – 136: An analysis of irrigation water (as an Appendix) would greatly complete the work presented. As the authors point out, the leaching of anions and cations depends on the drainage of water and the concentration of these ions in the water that it percolates. This concentration depends on the inputs to the soil and the transformations that occur in the soil profile. Therefore, it would be convenient to know at least the concentration of nitrate and chloride in the irrigation water.

As requested, Appendix A5 now reports the main chemical parameters measured on the irrigation water, as average values of the entire experimental period.

- Lines 139 – 140: More information on fertilization is necessary: chemical forms used in the nitrogen fertilizer (nitric, ammonium, urea?), number of applications and timing.

Pre-transplanting fertilization was applied in GS1 by distributing nitrogen as nitrate (16 kg ha^-1) and ammonium (24 kg ha^-1) followed by two fertigations throughout the growing season applying nitrogen as nitrate (22.4 kg ha^-1), ammonium (15.6 kg ha^-1) and urea (42 kg ha^-1). Pre-transplanting fertilization was applied in GS2 by distributing nitrogen as ammonium (12 kg ha^-1) followed by four fertigations throughout the growing season applying nitrogen as nitrate (44.8 kg ha^-1), ammonium (31.2 kg ha^-1) and urea (84 kg ha^-1). This information has been added to the results section (lines 144-150 of the amended manuscript version).

- Line 148: Use the similar format for figure caption as in Figure 1.

We made the recommended change.

- Line 151: Although it is commented in the Appendix A3, it would be convenient to include the biochar doses in Mg ha^-1.

We added the following sentence (lines 158-160 of the amended manuscript version).

Biochar application within the 0.20 m soil depth was 26 and 52 Mg ha^-1, respectively for B1 and B2 (considering the soil bulk density equal to 1.3 Mg m^-3).

- Lines 158-161: Do the Italian technical specifications do not contemplate salinity as a quality criterion?

Yes, salinity is a biochar quality criterion. It was not reported only by mistake. We have added this information (line 168 of the amended manuscript version).

- Lines 170 – 172: The results of these soil samples are not provided by the authors. How does the pH and EC vary during the two growing cycles?

We considered that a detailed analysis of the soil pH and EC time trend is outside the purpose of the work (to avoid a consequent information overload). We periodically measured the soil pH and EC in order to check that the addition of biochar and the saline water applied with irrigation were below a threshold compatible with suitable crop growth conditions. Further information about soil pH and EC can be retrieved in Section 3.4 (lines 434-440 of the amended manuscript version).

- Line 174: Change 50-ml by 50 mL

We made the recommended change (line 184 of the amended manuscript version).

- Line 175: +4ºC

We made the recommended change (line 186 of the amended manuscript version).

- Line 176: examined? Analysed

We made the recommended change (line 186 of the amended manuscript version).

- Lines 177 – 179: The ammonium ion (NH₄⁺) has not been considered in the soil or in the drainage water, but its presence could be important as a source of nitrate through the nitrification process. Please comment on the non-consideration of the ammonium ion in your work.

Ammonium (NH₄⁺) was considered in drained waters but it was never detected in measurable quantities (at least using our analytical device). The same was observed considering PO₄ ^3-. We have reported this information in the text (line 188 of the amended manuscript version) and modified Table 1 adding a line related to ammonium. Please see also the amendment applied in lines 288-291. Sorry for the mistake.

- Line 186: (C, kg m^-3) It would be advisable to use another abbreviation, for example, C_sol so that there is no confusion with the temperature or carbon symbol.

We eliminated the term “C” in order to avoid confusion with the term “e" (solute concentration into the drainage water, as specified in lines 206-207).

- Line 196: Really, the term ɛ would be the concentration…

Yes indeed, it is a concentration as the unit of measurements (kg m^-3) clearly suggests. Despite this clarification, it anyway expresses the slope coefficient of the regression line S_OUT = e * W_OUT. We have defined this term as “leaching coefficient” considering its mathematical expression e = S_OUT / W_OUT. According to your suggestion, we have specified that the slope coefficient e represents the solute concentration into the drainage water (lines 206-207 of the amended manuscript version).

- Line 204-206: Please specify that drainage and leaching data are accumulated.

Yes, it was done (lines 215-216 of the amended manuscript version).

- Line 218: Figure 3 shows the observed main weather conditions (temperature, rainfalls and reference evapotranspiration… Please complete the sentence, i.e., during the experimental period…

We made the recommended change (line 231 of the amended manuscript version).

- Lines 221-243: Figure 3A. Correct the temperature units.

The temperature unit was corrected.

What is the duration of GS1 and GS2? Lettuce and radicchio are harvested on February 13, but in the figure 3A the GS1 It lasts until April… Clarify.

The duration of GS1 in the Figure 3A has been corrected. Sorry, it was an oversight!

Figure 3B. Crop evapotranspiration (ETc) could be added.

ET₀ is reported in Figure 3B, namely the reference evapotranspiration daily calculated according to the FAO version of the Penman-Monteith equation. ET₀ is only affected by atmospheric conditions while ETc is also affected by crop characteristics, for this reason, ET0 fits better in the Figure side by side with the air temperature and rainfalls (both atmospheric features). We are here defining the environmental conditions of the experimental location.

- Line 247: figure caption: “detected” registered, measured,…

We made the recommended change (line 258 of the amended manuscript version).

- Line 251: Change GS1and by GS1 and

We made the recommended change(line 262 of the amended manuscript version) .

- Line 261: Similar standard errors (56 and 52 m³ ha^-1) for very different drainages. Any comment?

We have no comment about this. You can find below the drainage values as experimentally registered. We think there are no particular remarks to be highlighted.

- Line 265: “Without considering the biochar effect…” Do you mean that the values in table 1 correspond to B0? I think it is the average value of the three treatments, but the statement is confusing...

Yes, you are right; the values reported in Table 1 are the average of the three treatments. We have correct the statement to avoid confusion (line 279 of the amended manuscript version).

- Lines 266-268: The high nitrate leaching value in the GS1 is mainly due to the high initial nitrate value in the soil at the beginning of the experiment. According to the value in table A2, 10.78 mg NO₃^--N in soil profile (0-70 cm), and considering the soil bulk density (1310 kg m^-3), the nitrate content is 434 kg/ha. This nitrate is likely to be leached as soon as drainage occurs!!

It would be convenient to point out the importance of the initial values of the ions in the soil, if comparisons are to be made between different periods.

Yes, we agree with your observation and we added this consideration in the text (lines 283-285 of the amended manuscript version). Thanks a lot.

- Line 278: As commented above, the Sout term is also affected by input to the soil and the transformation and sinks in the soil.

The sentence reported from line 292 to line 297 is a bridge from section 3.1 and section 3.2. In the former section we presented just the average values of inflows, outflows and leaching, while in the latter the outputs of the two empirical models were reported. The models, indeed, are more effective in the interpretation of the experimental data. Mathematically speaking (as reported in section 2.4), we can write the following:

1) W_OUT = g * W_IN                     and      2) S_OUT = e * W_OUT                   therefore:        3) S_OUT = e * g * W_IN

Just considering the previous equations, S_OUT is directly affected by W_OUT (see equation 2) and, in turn, indirectly affected by W_IN itself (see equation 3). The effect exerted by the high initial solutes concentration (such as nitrate) in the soil at the beginning of the experiment is accounted for by the value of the e coefficient.

Your comment is right and valuable and it was taken in due consideration also elsewhere in the discussion section.

- Line 282: (rains (W_P) and irrigation (W_I) volumes per unit area)

We made the recommended change (line 298 of the amended manuscript version).

- Table 1. One decimal is enough.

We made the recommended change.

Change NO^3- by NO₃^-

The mistake has been corrected.

- Table 2. Below the table include:

** P<0,001; n.s. = not significant; R² = coefficient of determination; RMSE = Root Mean Square Error; CV = Coefficient of Variation.

We made the recommended change (lines 319-320 of the amended manuscript version).

- Figure 4B: Shouldn't water inflow values greater than 6000 m³ ha^-1 appear?

No, the figure is correct. There are no data exceeding the value of 5,000 m³ ha^-1. As can be read in Table 1, the maximum observed cumulated Win value is equal to 1,978.47 m³ ha^-1 in GS1, and 4,341.97 m³ ha^-1 in GS2.

- Line 327: 36.46%).

The mistake has been correct (line 334 of the amended manuscript version).

- Table 3. Change NO^3- by NO₃^-

The mistake has been correct.

- Lines 341-347: The leaching coefficient has units of concentration!!

The leaching of a solute depends not only on mobility and solubility, but also on the greater or lesser amount in the soil. The solute transport in the soil can be convective, diffusive and dispersive. When convective water flow predominates, ion solubility is the most important factor. But when the flow is predominantly diffusive the concentration of the ion is important. Another aspect to consider in the case of dispersive flow is the possibility of anionic exclusion phenomena.

Yes, as already mentioned, the leaching coefficient has the unit of a concentration (kg m^-3). It represents an empirical coefficient whose value is modified by all possible factors affecting the process of solute transport in the soil (irrespective if it is mainly convective, diffusive or dispersive). Considering the comment, we modified the sentence as shown below (lines 352-356 of the amended manuscript version):

“e showed different values for the analysed anions and cations, depending on their concentration in the soil as well as the solubility and mobility within the soil water solution of each considered chemical species. The higher the ion solubility and mobility, the higher its concentration in the soil water solution (i.e. the value of e) and, therefore, the higher the loss of solutes from the rooting zone of the soil due to leaching”.

- Figure 5: Separate figures 5A and 5B to avoid overlapping the values of the abscissa axis. Same with 5C and 5D.

We made the recommended change.

- Lines 382 – 391: It would be convenient to know the cation exchange capacity of the soil.

We are very sorry, but the soil CEC is not available. Unfortunately, our lab is still not able to obtain this data due to the lack of the specific analytical equipment (an Atomic Absorption Spectroscopy device was just ordered but was not available at that time in the lab). We really hope you would understand the situation.

- Lines 395 – 399: It would be convenient to know the cation and anion input for irrigation.

You can find this information in the new Table A3 in Appendix A5.

- Lines 412 – 418: According to table A2 the EC value is 2.45 dS/m. How do you explain the variation that appears in the text (0.55 to 0.57 to 2.4 dS/m?

The EC value reported in Table A2 refers to the measurement we made on the soil at the beginning of the experimental trial, i.e. at the end of the summer season. This value perfectly matches with the GS2 value resulting after the summer irrigation with saline water. Differently in wintertime when the EC values are significantly reduced due to the leaching effect of rainfalls.

- Lines 424 – 426: See previous comment on drainage dynamics.

Please, refer to our previous answer to your comment.

- Section 4.2. The argument is good, but the discrepant results found in the literature are due in part to the differences in soil properties used in each experiment. In sandy soils with good conductivity under saturation conditions, biochar improves the reduced water retention capacity of these soils, but in clay soils, the effect on conductivity will be more important.

The hydraulic properties could have been analysed after the field experiment!!

Your comment is welcome and we agree with you. Different results concerning biochar application can be interpreted by considering the large differences in the soil properties. In our experiment a loam textured soil was used. Actually, we did not plan to detect the soil hydraulic properties (such as water infiltration and conductivity) so we do not have the availability of this very interesting data. We apologize for this. We honestly admit this in lines 498-499 of the amended manuscript version

- Line 446: change structure-[28… by structure [28

We made the recommended change (line 469 of the amended manuscript version).

- Section 4.3: See previous comment about the need to consider the initial values of Nmin.

Yes, thank you. We added your observation in lines 505-506 of the amended manuscript version.

- Line 497: Change NO_3-

We made the change (line 523 of the amended manuscript version).

- Line 521: Change adsorbtion by adsorption.

We made the change (line 547 of the amended manuscript version).

- Lines 533 – 534: This statement should be included in the discussion section, since the study does not show crop production data or extractions by the plant.

We modified the sentence (line 558-559 of the amended manuscript version), according to your suggestion, thank you.

- Line 542: Change “The authors… by The authors

We made the recommended change (line 567 of the amended manuscript version).

APPENDIX

- Line 723: 1000 L

We made the recommended change (line 747 of the amended manuscript version).

- Line 730: 0.7 m.

We made the recommended change (line 754 of the amended manuscript version).

- Line 746 and following: Correct numbering of bibliographic references.

[5] is [1], ….

We made the recommended change (lines 770 and following of the amended manuscript version).

- Line 750: mL

We made the recommended change (line 774 of the amended manuscript version).

- Table A1: EC in dS m^-1

We made the recommended change.

Carbon C: use the similar units as H, N, S, O

We made the recommended change. It was an oversight!

How is the H/Corg and O/Corg ratio calculated? Using the values of the table, Corg is in one case 6.8% and in another 114%

Please, consider that H/Corg and O/Corg are ratios of molar units.

Ca, Mg, Fe,… Why not in g / kg?

We made the recommended change.

Bulk density in kg m^-3

We made the recommended change.

- Line 809: bulk density 1.3 Mg m^-3

We made the recommended change (line 832 of the amended manuscript version).

- Line 859: FeSO₄

We made the recommended change (line 881 of the amended manuscript version).

- Line 859: method

We made the recommended change (line 881 of the amended manuscript version).

- Line 866: main physico…

We made the recommended change (line 888 of the amended manuscript version).

Table A2: Why don't they show the values of each layer?

We performed the analysis of each soil layer (0-20, 20-40, 40-60 cm) but we did not observed significant differences among soil samples from different layers. This is probably due to a certain soil homogeneity along the profile as a consequence of a possible soil mixing when the experimental trenches were excavated and the soil was dug out and then put again in place. For this reason, we decided to provide only the average values considering the entire excavated soil profile, 0-70 cm.

Field capacity: gravimetric soil moisture at field capacity (%)

We made the recommended change.

Wilting point: gravimetric soil moisture at wilting point (%)

We made the recommended change.

Thank you for your kind consideration and and we really hope our explanations have been satisfactory.

Best regards,

The authors

Angela Libutti,

Anna Rita Bernadette Cammerino,

Matteo Francavilla and

Massimo Monteleone

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript presents data on soil amendment with biochar affects water drainage and nutrient losses. The present study was a field experimental research conducted under crop growing environment to assess whether biochar application to soil under conditions of intensive crop cultivation on the losses of soluble elements from the soil profile.

The story telling the current study is interesting and falls into the scope of Agronomy.

After carefully checking the manuscript, I found the manuscript was generally well designed in experimental trials and well written throughout the entire section, however, there are some flaws in introduction and methodology sections. Also, the manuscript needs some revision in written English throughout the manuscript. I would recommend the manuscript as minor revision.

Detailed comments;

The manuscript needs some revision in written English.

The main physio-chemical properties of soil used should be included in the methodology section not in the appendix.

Introduction: I suggest the introduction section should be described more concised format to enhance logical connection on the background of the current study.

Methodology: general soil physio-chemical characteristics should be included in the relevant position not as the appendix to better understand the audiences.

Results:

- for figure 3. Unit for temperature should be double-checked. What is ET0 ?

- I think if the content related to the table 1 was described in the text, the table 1 itself is not necessary to present in the results section.

Discussion:

- need more logical description between the drainage model and the leaching model.

Author Response

Department of Science of Agriculture,

Food and Environment,

University of Foggia

Via Napoli, 25

71122 Foggia, Italy

08 November 2019

Manuscript ID: agronomy-615828

“Soil amendment with biochar affects water drainage and nutrient losses by leaching: experimental evidence under field-grown conditions”

Authors: Angela Libutti, Anna Rita Bernadette Cammerino, Matteo Francavilla and Massimo Monteleone.

Dear Reviewer 2,

we would like to thank you for the comments and suggestions that have been very useful in order to improve the quality of the work and clarify possible misunderstandings from the potential readers.

We are resubmitting a new version of the manuscript; every change made was clearly outlined in the revised text.

We really hope to have explained all the issues raised from you.

Please find below our considerations, point by point, in reply to your comments.

REVIEWER 2

The manuscript presents data on soil amendment with biochar affects water drainage and nutrient losses.

The present study was a field experimental research conducted under crop growing environment to assess whether biochar application to soil under conditions of intensive crop cultivation on the losses of soluble elements from the soil profile.

The story telling the current study is interesting and falls into the scope of Agronomy.

After carefully checking the manuscript, I found the manuscript was generally well designed in experimental trials and well written throughout the entire section, however, there are some flaws in introduction and methodology sections. Also, the manuscript needs some revision in written English throughout the manuscript. I would recommend the manuscript as minor revision.

Detailed comments;

The manuscript needs some revision in written English.

We tried to do our best to overcome the detected flaws in the introduction and methodology sections. We significantly improved (in our opinion) the written English and the manuscript was finally checked by an English native language colleague.

The main physio-chemical properties of soil used should be included in the methodology section not in the appendix.

We really prefer to avoid additional information load to the manuscript and facilitating an easier reading. For someone who is interested in this information, the Appendix is readily available. We really hope you will understand our opinion.

Introduction: I suggest the introduction section should be described more concised format to enhance logical connection on the background of the current study.

We managed to improve the introduction section to facilitate a better understanding from the readers. Thank a lot for your suggestion.

Methodology: general soil physio-chemical characteristics should be included in the relevant position not as the appendix to better understand the audiences.

Sincerely, we really prefer to avoid additional information load to the manuscript and facilitating an easier reading. For someone who is interested in this information, the Appendix is readily available. We really hope you will understand our opinion.

Results:

- for figure 3. Unit for temperature should be double-checked.

We made the recommended change.

What is ET0 ?

ET₀ is the “reference evapotranspiration” calculated daily by applying the Penman-Montheit. We added this acronym in line 127 were first it was presented.

- I think if the content related to the table 1 was described in the text, the table 1 itself is not necessary to present in the results section.

Table 1, in our opinion, is a valuable and very understandable way to present the experimental data and give a useful overall view of the experimental results. We really hope you will understand our opinion.

Discussion:

- need more logical description between the drainage model and the leaching model.

Thank you very much for your comment. We have added what requested to the discussion (see line 443, 450, 502, 519) thus improving the logical understanding of the two empirical models and their linkage.

Thank you for your kind consideration and and we really hope our explanations have been satisfactory.

Best regards,

The authors

Angela Libutti,

Anna Rita Bernadette Cammerino,

Matteo Francavilla and

Massimo Monteleone

Author Response File: Author Response.docx