Influence of Tobacco Plant on Macronutrient Levels in Sandy Soils
Round 1
Reviewer 1 Report
Line 27: reword to “to the tobacco crop”
Line 31-32: Why does nicotine influence nutrient availability in the soil? I think a brief explanation of this logic is needed.
Line 33-34: Reword as follows: “Nitrogen influences the growth and quality of flue-cured tobacco as well as the taste and aroma of the smoke [8-10].”
Line 34: Reword as follows: “The sufficient leaf N concentration has been reported to range from 3.5 – 6.5% [11].
Line 35: content not contents
Line 36: “symptoms to appear”
Line 36-38: Reword as follows: “The recommendations for N application in tobacco ranges from 60 to 90 kg ha-1 depending on topsoil depth, with lower rates required on shallow clay soils and higher rates needed on deep sands.”
Line 40-41: P response in tobacco is largely dependent upon residual soil P content. For example, Vann and Fisher (2017) did not observe a positive response to P application (0-55 kg P2O5/ha) in soils with residual P ranging from 53-232 kg/ha. Under soil conditions where nutrients and pH are properly managed, a P response is unlikely as tobacco doesn’t need more than 20 kg P/ha for maximum yield and quality.
Line 90: “bred to be higher yielding”
Line 92: “enzyme”
Line 95: “involved in the phosphorylation reaction…”
Line 97: “are reported at 0.20-0.85%”
Line 103-104: “have” instead of “has”, “plants” instead of “plant”, and “affect” instead of “affects”. Remove the word “the”. End the sentence after [5,7]. See next comment.
Line 104-105: Reword as follows: “Nor has previous research linked leaf nutrient concentrations to these factors.”
Line 105-108: Reword as follows: “Therefore, the objective of this study was to investigate the effects of fertilizer application on soil macronutrient levels and leaf nutrient concentrations compared to non-fertilized tobacco systems.” You can include the fertilizer sources in the methods and materials.
Line 108-109: Reword as follows: “This study likewise took into account the effects of nicotine exudation into the rhizosphere and its impact macronutrient availability.”
Line 109-110: Reword as follows: “These findings may help tobacco growers make proper decisions when supplementing macronutrients for planting crops planted subsequent to tobacco”
Line 128: I propose defining NPK and CAN at this point in the M&M (using the definition in line 106)
Line 130 & 154: remove ha-1 following N and P. Only reference ha-1 after K.
Line 154-155: How much N and Ca were applied (per ha) in the CAN application. Give estimates in the same manner as the NPK material.
Line 167: a constant weight
Line 169-171: Reword as follows: “Soil properties, leaf nicotine concentration, and harvested leaf yield are presented for each research site as supplementary tables S1-S7.”
Line 174: change “was” to “were”
Line 176-181: This sentence is too long, revise to improve flow.
Line 181-182: Reword to: “Nicotine was determined in these soils by spectrophotometric analysis using a UV visible single beam fixed at 602 nm.”
Line 202-203: Reword to: “Ratings of the studied parameters in these soils is based on the descriptions compiled by Landon [23].”
Line 241: change “dropped” to “reduced” and “drop” to “reduction”
Line 242: a higher pH
Line 248: delete “in soils”
Line 236-248: I think you could do a better job identifying where the H+ came from. For example, was NH4+ applied to the crop with the NPK fertilizer? If so, there’s a source of H+. The H+ might be a byproduct of nitrification?
Line 268: At the Urambo site,
Line 269-270: What about H+ generated by nitrification?
Line 281: delete the word “a bit”
Line 294: in the loamy sand soil
Line 295: while in the sand soil series (Tabora) an increase in soil N was not observed. At this site, N could have been leached below the rooting and sampling zone following rainfall events.
Line 296-299: I think that mineralization and nitrification are taking place at relatively equal rates in each research site; however, as you explain in the preceding sentence, the leaching potential is lessened in the loamy sand. I think that’s the selling point here. Nicotine is also very water soluble, so it could’ve been leached too.
Line 303-304: “increase in soil acidity, which decomposed OC thereby increasing Ca.”
Line 304-305: delete, you basically said this in the previous sentence.
Line 305-306: reword as follows: “Hermiyanto et al. [27] reported that OC has a significant impact in improving biological, physical, and chemical properties in the soil”.
Line 306-307: It’s probably a stretch to claim that nicotine is impacting soil properties. I looked at the Gulser et al paper and didn’t glean that from the publication.
Line 308-309: Reword as follows: “The increase in total N by 50% and exchangeable Ca by 193% was a direct result of NPK and CAN fertilizer application”
Line 309-316: Im not following where the 1157% increase in exchangeable Ca is derived from, explain that a bit more and end this paragraph with the final sentence stating that more work is needed to determine how Ca is being released. I’m not certain that the plant sensing the need for Ca is viable. However, if the literature suggests otherwise, I could change my mind.
Line 323: change “between” to among
Line 324-332: Reword as follows: “The highest increase of nicotine was observed in the Sikonge soil, with an increase from 0.01 mg kg-1 to 4.66 and 13.13 mg kg-1 for unfertilized and fertilized tobacco soils, respectively”
Line 335-340: I’m not sure that all of this is relevant, as I’m still not understanding why soil nicotine is relevant in this entire paper. Yes, N application and nicotine accumulation are directly correlated and one would expect that there would be more nicotine synthesis in the fertilized plots. However, I think that just stating that there was more nicotine in the soil following the fertilized treatments and that the nicotine could possibly be mineralized and contribute to legacy N is the message. It would be useful to go one step further and quantify the N that might be derived from nicotine in the next crop. I know you don’t have that kind of data, but if you know the nicotine concentration in soil and how much N is in nicotine, you can estimate this.
Line 348: replace “in” with “under”
Line 363: remove “in soils” and “except for soil total N an Mg”
Line 374-386: why is this information presented both here and in the preceding section (lines 345-359)? To me, most of the information in lines 345-359 could be excluded from that section and just reported here.
Line 374: remove the word “total”
Line 375-377: Reword as follows: “Total soil N increased significantly (P<.001) from 0.04 to 0.05 and 0.06% in unfertilized and fertilized tobacco, respectively.”
Line 380: insert “was” before “observed”
Line 381: insert “was” before “reduced”
Line 382: Reword as follows: “Before tobacco cultivation at the Tabora site, soil P was 53.31 mg kg-1 and was reduced to 14.22 mg kg-1 at the end of the season.”
Line 383: insert “the” before Urambo
Line 384: remove “and” and “soils” insert treatments in place of soils
Line 393: insert “was” before “reduced”
Line 463: remove “lower as”
Line 474: insert “was” before “reduced”
Line 483: remove “crop”
Line 510: remove “cultivated soil”
Line 590: change “significant” to “significantly”
Line 595-597: Reword as follows: “The initial P in soils at each site was adequate (>25 mg P kg-1 soil) which is likely the reason why a response in foliar accumulation of P was not observed [32].”
Line 598: remove the word “observed”
Line 609: Change “comparison” to “comparisons” and delete “,”
Line 610-611: delete “upon fertilization of tobacco plants” and insert “when fertilized”
Line 623: insert “and is” before “also”
Line
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
All comments were included in the paper.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
Title:
I would suggest using “Influence of Tobacco Plant on Macronutrient Levels in Sandy Soils” instead of “Influence of Tobacco Plant on Macronutrient Levels in Different Soil Textures”. The title suggests that the authors studied various soil texture classes but this is not true. In the research, the results relate only to two texture classes of sandy soils.
Author Response
Please see the attachment
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.
Round 1
Reviewer 1 Report
Tobacco production is an important source of income for farmers in some regions of the world. Therefore, research into tobacco growing is needed. The research presented in the article concerns not only the crop itself, but also the soil effects that this crop causes, depending on soil conditions and fertilization.
I suggest that the article is publishable in the journal after addressing few comments.
Comments for author File: Comments.docx
Reviewer 2 Report
Comments to authors:
Title:
The title of the article refers to different soil types, while the manuscript has no information about soil types, even in relation to the World Reference Base (WRB). The study shows that the authors related the research results only to soil texture classes.
Abstract:
Line 10: Research applies only to sand and loamy sand not to sandy loam. From the results of the percentage content of clay, silt and sand given in Table 1, it appears that it is a Loamy sand not Sandy Loam in Urambo soil.
Introduction:
Line 64: “Our findings will help tobacco growers on proper decisions in supplementation of limiting macronutrients for planting a subsequent crop after tobacco” In my opinion, the authors did not achieve their goal in their work. The research was really based on two sandy soils, which is definitely not enough to conclude in this way.
Material and Methods:
Table 1.
The table contains an incorrectly defined texture class for sites Urambo. This is not Sandy loam. The percentage of clay, silt, sand shows that it is Loamy sand. It would be better if the authors planned their experiment on more diversified soil material, not only sandy soils.
Conclusions:
Due to the very modest soil material, the authors' conclusions can only refer to sandy soils, sand and loamy sand.
In summary, the manuscript contains very modest research material of rather regional significance. Therefore, in my opinion, it is not suitable for publication in the scientific journal Agronomy.
Reviewer 3 Report
General Comments:
I suggest that you update the Smith 2009 reference to reflect a more up to date version of the NC State Production Guide which has changed substantially since 2009. Most of the application rate ranges you report are not currently recommended.
It is also suggested that you consider merging the Results section and the Discussion section to improve the flow of the paper. The discussion section essentially repeats itself and then attempts to explain treatment differences. Merging the two sections will reduce much of the redundancy.
It may also be suggested to consider analyzing parameters within each environment instead of identifying treatment interactions across environments. Statistically, I think you may be able to identify treatment differences that are hidden in the larger data analysis. Traditionally, when there is a treatment*environment interaction we analyze each environment separately.
It would also consolidate the paper to merge the soil and tissue data. For example, it was interesting to see negative impacts to P in soil and no effect to foliar uptake. This is useful data when presented in totality.
Was yield not collected? That was not clear.
Page 1
Line 23: Reword to “The tobacco (Nicotiana tabacum) plant requires large quantities of primary (N, P, and K) and secondary (Ca, Mg, and S) macronutrients in order to attain high cured leaf yield and good quality.”
Line 24-25: This sentence does not make sense. Reword to “Soil depletion of macronutrients is plausible because of the large input requirements”. I think this is what you are trying to say.
Line 25-27: Delete sentence, incorporated into first sentence.
Line 27-31: Combine sentences to read as follows: “Recently, investigators have reported an increase in total soil-N levels after tobacco cultivation (4,5), while others have reported a decline in soil macronutrients such as K, P, and S (5-7). The release of nicotine into the rhizosphere was considered to have a major impact on the increase or decrease of these nutrients.”
Line 32-33: Insert this sentence after line 28-29 and reword as follows: “The residual levels of other macronutrients, such as Ca and Mg, have not been studied following tobacco cultivation.”
Line 33: Ca and Mg are considered to be secondary nutrients, not micronutrients – in fact, you stated that they were secondary macronutrients earlier. Do not label them as micronutrients. I would delete this sentence.,
Line 35: Begin paragraph two with this sentence.
Line 37-38: Reword sentence: “Recommendations for N application to tobacco range from 50 to 200 kg ha-1.” Where did the 200 kg recommendation come from? I’ve not read where NC State or Virginia Tech recommend that much N/ha.
Line 38-39: Insert the word “as well as” after the comma but before the word “improvement”. Delete the comma.
Line 39-40: Reword to: “The sufficient concentration of P in tobacco leaves ranges from 0.1 to 1.0%.”
Line 40-41: Reword to: “Studies have revealed that for optimum tobacco production, P must be supplied at an application rate range of 15-70 kg ha-1”
Line 41-42: Reword to reflect that K may do those things. Vann et al 2012 and 2013 doesn’t really agree with that thought process. Perhaps in K deficient soils…
Vann, MC, LR Fisher, DL Jordan, WD Smith, DH Hardy, and AM Stewart. 2013. Potassium Rate and Application Effect on Flue-Cured Tobacco. Agronomy Journal. 105:304-310. doi:10.2134/agronj2012.0259
Vann, MC, LR Fisher, DL Jordan, WD Smith, DH Hardy, and AM Stewart. 2012. The Effect of Potassium Rate on the Yield and Quality of Flue-Cured Tobacco (Nicotiana tabacum L.). Tobacco Science. 49:14-20.
http://dx.doi.org/10.3381/12-019R.1
Line 43-44: Reword: “The adequate foliar K range is 1.6 to 4.1% for tobacco (11), which typically requires a minimum of 100 kg K2O ha-1 to obtain maximum yield and quality (13,14).
Page 2
Line 45: insert the word “the” before “tobacco”
Line 46: insert the word “the” before “cell”
Line 47-48: This sentence is hard to follow, consider rewording as follows: Calcium may also have a positive influence on N uptake and the activation of enzymes associated with N assimilation.
Line 48-49: Sufficient foliar Ca concentrations range from 1.5 to 3.5% (11).
Line 75: Experimental soil should read as experimental area
Line 80-81: Reword to read “…of 1.5 m x 2.0 m and fertilized with 5 kg of N10P18K24 fertilizer.
Line 81: Remove “in the nursery”
Page 3
Line 92: general comment, it could be useful to include the total quantity of nutrients applied in NPK and CAN. While the percentages are useful, they could be easier to interpret if they were in kg/ha just as you presented the NPK kg/ha in the NPK blend.
Line 95: Border, not boarder
Page 6
Line 157: why might pH decline in the fertilized treatment?
Line 169: Why might OC decline?
Line 169: Why would OC decline at one location and not another?
Page 7
Line 185: What is the practicality of nicotine presence in the soil? Is it the contribution to the total N pool? This part is not clear to me, as I’ve not seen this in the literature previously.
How did fertilizer programs impact nicotine concentration in leaves?
Page 8
Line 189: Tobacco, not tobacco
Line 191: significantly what?
Line 194: remove “,” after the word significant
Page 9
Line 220: remove “,” after the word that
Page 10
Line 252: Why would Ca increase in the unfertilized soil? Was there mineralization from parent material?
Page 11: Why would nicotine reduce the presence of certain nutrients in the soil? Further explanation would be useful.
Page 14: Table 5 – It would be useful to compare some of these results to the Byson publication to demonstrate where nutrients were sufficient and deficient. Also define when samples were collected in the table.
Page 15
Line 294: why was P not different across field sites? This is interesting given the variation in soil P concentration across the sites and the extreme nature of your treatments.
Page 16
Line 348: Remove the word “to”
Page 17
Figure 8: check the legend, “unfertilized” is misspelled.
Line 323: Influenced, not influence
