Co-Application of Charcoal and Wood Ash to Improve Potassium Availability in Tropical Mineral Acid Soils

Round 1

Reviewer 1 Report

Review on „Co-application of Charcoal and Wood Ash to Improve Potassium Availability in Tropical Mineral Acid Soils“ by Puvan Paramisparam et al. Submitted to Agronomy.

The paper summarizes the fundamental knowledge about use of biochar and wood ash as soil amendments to regulate the potassium availability in some mineral soils. The topic fits the journal scope and it of interest for wider public. 

Line 41, “This cation exchange causes the release of H+ ions into the soil solution (hydrolyzation)”. – I am not sure if it is meant hydrolysis. Neverthelees, in both cases (hydrolysis, hydrolyzation), I do not think it is a good expression as the hydrolysis refers to the decomposition by reaction with water.

Line 54: “ is because nutrient availability in soils is not solely regulated by pH” this sentence does not fit here, probably need revision.

Line 67: “hydrolysis releases H+” – see above

Line 115: equation 6 and 7. This reaction does not occur frequently, often reacts SO2 with water giving H2SO3

Line 157: did you mean “from which the organic matter originates”?

Line 157: “For example, some plant residues have low bases”. – unclear

Line 163 and also elsewhere: the nitrate formula is not correct: “3” should be subscript, “-“ should be superscript. Please check whole document, e.g. equation 15, line 404

Line 208: “They are relatively less fertile and low in CEC” – it repeats the information from previous sentence.

Line 244 and further: provide information on pH and CEC.

Line 254 and further:  provide information on pH

Line 271: provide information on pH and CEC

Line 293: pH 8 is not “strongly” basic

Line 382: “The exchangeable K fractions are bound electrostatically at different strength on the outer surface (adsorption sites) of clay minerals and humic substances.” Hard to imagine the outer surface of humic acids, please correct

Whole paragraph about humic substances needs improvement as the theory of humification was questioned repeatedly a new concepts were introduced, i.e. DOI: 10.1016/S0065-2113(02)75003-7 or     DOI: 10.1038/nature16069

Line 552: “Hydrated HA has higher CEC compared with dehydrated HA” – please give values

Table 1: there is an error in the formula of phenol, it should be C6H5-OH

Line 633 and further: please check also works describing also the negative effects of biochar, as its use is not always positive, i.e. DOI: 10.1016/j.scitotenv.2021.148756

Author Response

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Reviewer 2 Report

agronomy-1327882

Co-application of Charcoal and Wood Ash to Improve Potassium Availability in Tropical Mineral Acid Soils

This review paper suggested to review the co-application of charcoal and wood ash to improve K availability in tropical mineral acid soil. The current structure of the manuscript did not meet the basic objective. The manuscript presented the basic knowledge of tropical mineral soil and nutrient availability after the addition of not only ash wood or charcoal but also other organic amendments such as animal manures, plant residues, compost and humic acid on nutrient availability in general and a short not on the role of wood ash and charcoal on K availability in specific. Therefore, the current structure did not meet the requirements of the objective of the manuscript which according to the authors is to discuss on dynamics and availability of K in tropical acid soils and (ii) propose possible mechanisms involved when charcoal and wood ash are used to amend potassic fertilizers in tropical mineral acid soils. Besides, I did not see a single study where authors introduced co- (combine) application of charcoal and wood ash to increase the K availability in mineral acidic soil. Therefore, in its current structure I would not recommend this article for publication in the journal.

I propose that authors first introduce the problems of K unavailability in the tropical mineral acid soil. For instance, if it is the acidity then clarify it that these factors and mechanisms in such soil lead to acidification instead of adding a general introduction in section 2. Development of acidity in soils without mentioning how acidity development occurred in tropical mineral acid soils.  

Similarly, instead of general introduction on nutrient availability or K in the soil, the could introduce what are the processes affecting nutrient availability in the tropical mineral acid soils?

Third, which kind of management practices can be used to influence the nutrient or K availability in the tropical mineral acid soils. i.e., organic amendments application, animal manure, crop residues, humic acid etc but the literature example should be quoted from tropical mineral acid soils. Add the table of those studies with amendments, nutrient availability, %increase or decrease of nutrient or K content in the soil by the amendments to support your text.

Finally, you may introduce charcoal and wood ash on K availability, mechanism and again table with facts and figures to support how much alone application of charcoal or wood ash influence (%increase or decrease) the K availability in such soil.

Another table showing how much co-application of charcoal and wood ash influence (%increase or decrease) the K availability in such soil compared their single application.

  The minor comments

There is lot English language grammatical, punctuation, syntax, spelling mistakes. Please remove those, few examples can be seen below

Line 67, Al3+ and Fe2+ causes? Line 85, earth’s arable land are? it occur? Line 246, presence of (clay sized) iron oxides and hydrous oxides provide? Line 248, Red and yellow distinguishes? Line 350, non- exchangeable K are? Line 472, Lines 449-450, incomplete sentence

Line 53, Why only charcoal and wood ash is mainly selected for improving K availability and no other organic amendment sources such as compost, animal manures (cow, sheep, buffalo etc.), poultry manure, which are much better source of K than charcoal or wood ash and behave similarly in the soil.

Please correct equation number 13
Introduction about the development of soil acidity is not much important, since this is very basic and known therefore I am not sure whether it add much values and innovative aspect to this review. What is important in this context is the mechanistic understating with schematic diagram how the acidity (pH) influence the K availability in the soil?

Please make it clear why it is necessary to introduce Malaysian soil types in the context of this review? The presented introduction about the soil types is again very basic and did not add much value to the review. I would suggest to add in these subsections how the nutrients availability (especially K) to crop is influenced/hindered by these soil types and what management practices can be adapted to improve the nutrients availability in general and K in specific (detailed mechanism) in such soils.

Fig. 1, How non-exchangeable K directly becomes the part of the soil solution? Please explain.

Line 490, is the enhanced P and K uptake due to increased/improved pH or direct application of P and K by manure?

Line 505-506, replace with “plant residues improve soil structure and increase soil carbon and water holding capacity”

Line 507-508, How increase in soil C and water holding capacity increase water soluble K and K retention in the soil?

Sub section 7.2, please add which kind of plant residue management increase/influence/improve K availability for plant uptake in the soil especially in the context of mineral acid soils.

Lines 524-525, what are the animal-based compost?  Do you mean by slaughter house animal waste based compost?

Line 525, traits is not a proper word used for the characteristics of the compost!! It is mainly used for the characteristics of the organisms.

Please add the current gaps in this field and way forward?

Future considerations?

Please revise the conclusion based on above suggestion

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Manuscript ID: agronomy-1327882

Title: Co-application of Charcoal and Wood Ash to Improve Potassium Availability in Tropical Mineral Acid Soils

I really appreciated the authors’ response to my comments and questions on the previous version of the manuscript. Although authors significantly improve but they still did not address most of the comments on previous version. I again emphasized that the title and objectives of the manuscript is still misleading. I could not find a single reported study in the manuscript where authors reported the co- (combine) application of charcoal and wood ash in improving the potassium availability in acid soils.

The language of the manuscript still need improvements.

Authors claimed in introduction and conclusion sections that study on co-application of charcoal (biochar) and wood ash are scarce in acid soils.  There are studies available in the literature for example Hale et al. 2020, Bieser et al. 2019, Reed et al. 2017, Masto et al. 2013 and many more. These can be added in the manuscript and then make a comparison how much single application of charcoal or wood ash increase/decrease soil K and what would be the impact (positive/negative) of combine application of biochar and wood ash on soil K availability in acid soils. Hence, an extra table can be added to show the percent increase or decrease in K availability or K content by combine application of biochar and woodash in the mineral acid soils.

If you don’t want to change it according to the suggestion then the current title is not appropriate and may mislead the readers. So please then change the title and objectives of the manuscript to more general one like, use of organic amendments improves potassium availability in tropical acid soils.

Please also differentiate between or properly define the wood ash and charcoal in the manuscript. Sometime these are considered the same in literature.

Please make a separate heading of the research gaps in this field and future considerations. This concern is still not addressed or ambiguously addressed.  

Please also add the possible adverse effects of biochar (charcoal or wood ash) on soil nutrients availability especially the K under separate heading or sub heading.  See for example Brtnicky et al. 2021 and many other studies on the negative effect of biochar on soil nutrient availability.

Reference

Bieser, J. M., & Thomas, S. C. (2019). Biochar and high-carbon wood ash effects on soil and vegetation in a boreal clearcut. Canadian Journal of Forest Research, 49(9), 1124-1134.

Brtnicky, M., Datta, R., Holatko, J., Bielska, L., Gusiatin, Z. M., Kucerik, J., ... & Pecina, V. (2021). A critical review of the possible adverse effects of biochar in the soil environment. Science of The Total Environment, 148756.

Hale, S. E., Nurida, N. L., Mulder, J., Sørmo, E., Silvani, L., Abiven, S., ... & Cornelissen, G. (2020). The effect of biochar, lime and ash on maize yield in a long-term field trial in a Ultisol in the humid tropics. Science of the Total Environment, 719, 137455.

Masto, R. E., Ansari, M. A., George, J., Selvi, V. A., & Ram, L. C. (2013). Co-application of biochar and lignite fly ash on soil nutrients and biological parameters at different crop growth stages of Zea mays. Ecological Engineering, 58, 314-322.

Reed, E. Y., Chadwick, D. R., Hill, P. W., & Jones, D. L. (2017). Critical comparison of the impact of biochar and wood ash on soil organic matter cycling and grassland productivity. Soil Biology and Biochemistry, 110, 134-142.

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