Next Steps for Conservation Agriculture

Round 1

Reviewer 1 Report

This is an interesting paper dealing with the past and future of CA and fits well to the Special Issue topic: Next Steps for Conservation Agriculture. The authors present a review of the CA history and the final adoption of ZT or zero soil disturbance for CA.  The authors describe the connection of CA to other definitions of sustainability and to the problem of their clear definition.  Although there is a wide use of CA it still is lagging behind in areas like Europe. There is a difficulty changing the conventional farming methods. I think the paper will be improved with a discussion of methods to improve the acceptance of CA by farmers as well as methods to affect consumers behavior towards preferring products sustainably produced This has to close to cycle in order to enhance adoption by farmers.

The authors use a lot of abbreviations. A Table with them would help the readers to follow the text.

L55 Please explain PES OK it is explained in L 263. Please copy it to L 55

L197 What do the numbers in parentheses mean?

Author Response

Dear Sir or Madam,

We are most grateful for the time you have taken to make this critique of our work, which will benefit greatly from your comments,

First, we would like to explain that we asked for a seven-day extension for submission, which was denied. Therefore, to meet the deadline, the submitted text was admittedly unpolished.

We have improved the redaction to facilitate the reader’s understanding and ordered the text to improve its concatenation for a more logical flow. A list of alterations to the text to include your suggestions in the attached letter.

We believe we have done a good job in executing your comments and wish to reiterate our thanks for your kind review,

Yours sincerely, on behalf of all co-authors,

Dr. John N. Landers, O.B.E.

First Author

Author Response File: Author Response.pdf

Reviewer 2 Report

The concept paper submitted for review addresses an interesting and timely topic and should be of interest to readers of the journal. I appreciate the authors’ attempt to discuss the issues surrounding conservation agriculture and present ways to move it forward. However, I was left confused while reading the manuscript and believe the text needs considerable revision before being considered for publication.

My main difficulty while reading the text was probably a lack of clear objectives at the beginning. The authors seem to try to delineate the objectives of the paper in the first paragraph of the Introduction, but just vaguely. I was never very clear what the true purpose of the manuscript was. Was it to unify the different terminologies related to environmentally friendly agriculture (e.g., CA, RA, OA)? Was it to offer solutions to improve each of them? Or was it simply to clarify what each of them mean and to compare their merits and drawbacks? At points, it seems the authors objective is to try and promote CA to the detriment of RA or OA. Why? That was not very clear in my reading. I would suggest the authors make their objectives very clear at the beginning of the text (enumerate them if needed) to then try to answer the questions they are proposing to address.

Another source of confusion for me was the structure of the text. It does not seem to follow a logical flow. I did not get a good sense as to what CA really means from the outset. What are the principles of CA and how do they compare to conventional agriculture? How does it compare to the other types of agriculture discussed in the text (e.g., RA, OA)? I would suggest the authors start with that and introduce all the different types of agriculture discussed in the text, to then develop the argument they are trying to make (which, as per my comments above, is not very clear to me). At some point, nomenclature and definitions are given, but too late in the text. A formal definition of CA is presented towards the end of the manuscript (under Future Perspectives), but that definition would have been helpful earlier, particularly if the authors intention is to offer a new, unified definition of CA (is that their objective?). I got the sense that’s their objective from section 3.3, but I was confused by the previous section on ‘One Solution’, which introduces another agricultural practice, LF. If the objective is to merge CA, RA and OA (according to section 3.3), then why debate the merits of LF as the ‘One Solution’? In addition to beginning the manuscript with definitions, I would also suggest the authors to lay out the current state of affairs from the outset, to then develop the argument as to why the authors think CA needs to change (or its definition?), to finally culminate with their vision of what CA should be (i.e., unified with the other agricultural practices mentioned in the text?). That would be a more logical flow to me. The inclusion of a section on the origins of CA is valid and welcomed, but there may be the need for some background information prior to that to help readers contextualise the need for CA and why it came about in the first place.

In addition, throughout the text the authors seem to discuss issues of global significance to then abruptly switch to regional issues/examples (including in the Abstract, where Europe is singled out for no apparent reason). I missed some linking sentences between the two (from global to regional). They would help make the text clearer.

The manuscript also comes across as thin on evidence at points, and it seems the authors are providing personal opinions rather than arguments based on evidence (e.g., L470-471; L594-596). I would suggest the authors back up their claims with better reference to evidence (citations) throughout the text.

I would also suggest the authors make better use of abbreviations throughout the text. Some abbreviations are introduced without their long names first (which are sometimes introduced later in the text). It comes across as if sections were copied and pasted without revising the use of abbreviations. I had that same impression when reading the portions on soil health. The implications of CA for soil health seem to be scattered throughout the text. Would it be better to have one section where the implications for soils are discussed?

Overall, I believe this could offer some useful insights into different agricultural practices and their future direction, but the quality of the text needs to improve considerably before being considered for publication. The text could also benefit from some English language editing for clarity.

Author Response

Dear Sir or Madam,

We are most grateful for the time you have taken to make this detailed critique of our work, which will benefit enormously from your comments.

First, we would like to explain that we asked for a seven-day extension for submission, which was denied.  Therefore, to meet the deadline, the submitted text was admittedly unpolished, for which we apologize.

We realize that these comments were all valid. on the English language both myself and co-author Eric Kueneman are native speakers (UK and USA) and authors of a number of peer-reviewed papers. We took this observation to mean that the text could be upgraded and clarified to facilitate the reader’s understanding and to order its concatenation for a more logical flow. That we believe we have done.

Had the extension deadline originally requested been authorized, we would have alleviated you of most of the painstaking work you applied in your review. Below, please find atttached a letter with a list of changes made in accordance with your observations. A spell check in American English was also accomplished.

We wish to re-iterate our thanks for a very objectve review that has greatly contributed to the quality of the paper.

Yours sincerely, on behalf of all co-authors,

Dr. John N. Landers, O.B.E.

 First Author

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments by line:

General proposal: the term Conservation Agriculture, if it refers to the farming concept under the FAO definition or the Madrid declaration, should be written in capital letters to show, that it is a technical term.

General comment: the article is written in a newspaper style language, not so much in a scientific language. There are opinions and proposals expressed without scientific founding. These should be sorted out and eventually deleted to reduce redundancy, since some arguments are repeated in different parts of the paper. There is an abundance of acronyms and new term, which should be reduced. Most statements are without references.

Abstract: the sentence “Hidden cost: each ton of carbon immobilizes 187 20 kilograms of nutrients.” Is questionable and not scientific: The immobilization of mineral nutrients in the soil depends very much on the form, in which the carbon is existing in the soil and the surrounding conditions. Such statement is difficult to prove and adds no value to the paper.

Abstract: rephrase: “Sustainable, profitable, and compatible new technologies are emerging, and CA needs to embrace them.” There is no rationale given for this statement. CA is clearly defined as the minimum set of principles to achieve sustainable land management. In the literature it is described as the foundation for sustainable intensification, in which it will achieve not only sustainability, but also productivity and profitability with the combination of all other technologies, and so called good agricultural practices, as long as they do not disturb of disrupt the soil ecosystem. Therefor there is no need to “embrace” other technologies in the definition of CA, but they could be included in the definition of sustainable intensification or be it regenerative agriculture. Yet, this is already published knowledge.

34-39: at this point it would be better to quote the exact definition of CA, as it had first been published by FAO and was then copied in several publications of the originators of the definition. The quote given in this text is not the exact wording of the congress declaration. The congress declaration is also not a useful support for the statement for no- or zero tillage, since it still allows for minimum tillage in its text. The original definition is also quoted in the CA-CoP-L news alerts as footnote: Conservation Agriculture is an ecological approach to regenerative sustainable agriculture and ecosystem management based on the practical application of context-specific and locally adapted three interlinked principles of: (i) Continuous no or minimum mechanical soil disturbance (no-till seeding/planting and weeding, and minimum soil disturbance with all other farm operations including harvesting);  (ii) permanent maintenance of soil mulch cover (crop biomass, stubble and cover crops); and (iii) diversification of cropping system (economically, environmentally and socially adapted rotations and/or sequences and/or associations involving annuals and/or perennials, including legumes and cover crops). These practices are complemented with other good agricultural production and land management practices. Conservation Agriculture systems are present in all continents, involving rainfed and irrigated systems including annual cropland systems, perennial systems, orchards and plantation systems, agroforestry systems, crop-livestock systems, pasture and rangeland systems, organic production systems and rice-based systems. Conservation Agriculture systems operate regeneratively at multiple levels to harness a range of productivity, economic, environmental and social benefits as well as address local and global concerns related to food and water security, climate change, land degradation, biodiversity and smallholder agricultural development. Conservation Tillage, Reduced Tillage, Low tillage and Minimum Tillage are not Conservation Agriculture, and nor is No-Till on its own

40-42: this statement is unnecessary, if the correct definition of CA is used. Pls. delete

48: these are not steps in CA (which is not possible), but in the adoption or promotion of CA based sustainable farming; pls. rephrase.

54-55: There is no need for this in the light of the CA definition. Pls. rephrase

56: delete this point; this is included in the definition

59-63: there is no “one size fits all”; the farmer needs universally applicable concepts, such as CA, and locally appropriate and adapted technologies. Those can be bundled in protocols, for example for certification, with names, for example regenerative agriculture.

64-66: it would be good, to use, where available, existing definitions instead of changing them; however, with exception of Conservation Agriculture and Conservation Tillage there are very few consistent definitions; if at all, the definitions of RA or Sustainable Agriculture describe the goals, but not the means or protocols. See also lines 115-119, where this is mentioned.

69: there is no justification to create another “world congress” as the proposal does not show, why such a congress would be more successful than, for example, the existing WCCA with its several declarations.

72: this is redundant: CA is already a combination which includes ZT

76-77: clarify: what is meant with “technoloy”? “…the next steps for CA promotion must en-76 compass…”: the word promotion should be added, otherwise the sentence is meaningless.

78: this is already happening, as in the beginning of the paper is stated: the CA area worldwise is increasing. The topic of climate is addressed with “climate smart agriculture”, which is also based on CA as sustainable land management. Pls. reconsider this phrase.

97-98: see above: the Madrid declaration did not display the original CA definition but included minimum tillage. This reference should be changed.

128: unnecessary acronym. Qed can be used in a speech or opinion piece, but in this given context it is redundant.

133: check the date; was the straw burning ban in the 1970? In those years straw burning was allowed in most European countries and according to Wikipedia it only was banned in the UK in the 1990s?

135-137: something is missing in the sentence: Herbert Bartz was not called plantio direto, but the practice he applied was called plantio direto in Brazil. Pls. correct. Suggestion: The first successful farmer to adopt no-till farming in South America was Herbert Bartz in the State of Paraná, Brazil, in 1972, who then called the practice “Plantio Direto” (Direct Planting) [20].

143: delete the . behind No-Till; consistency: no-till should be spelled in the same way throughout the text, either with capital letters or not. Pls. check.

161: there is no FAO-based CA; FAO created a clear definition for the system described above and used the term CA for its universality; the term direct seeding or direct planting has different meanings in different parts of the world and is not universally applicable; yet CA as defined by FAO reflects the system described by Bartz as plantio direto. Pls. correct and rephrase. (see 179-184; the coining of the term CA was already in 1997 and the definition appeared before the 1^st WCCA).

162: if the farmers do not adhere to the CA definition, they should not be called CA farmers. Pls. change the wording.

227: consider rewording: ZT is the technology underlying one of the three principles of CA, it is not the only “bedrock”; as stated in several papers on carbon sequestration (for example Powlson, D.S., et al. 2014. Limited potential of no-till agriculture for climate change mitigation), no-till or ZT alone does not guarantee increase of soil organic matter, if not combined with the other three principles. But CA is the bedrock of RA or any other sustainable farming concept.

266: in China and India there are more 4-wheel tractors in CA, than two-wheel tractors; latter predominate in Bangladesh. Pls. correct to both, 4 and 2-wheel tractors.

270: reconsider term “bedrock” into principle of CA.

277: change “evolving” to “complemented”

307-308: missing rationale for this proposal: if CA is supposed to be the foundation of sustainable agriculture, why is a new congress necessary, having the WCCA as triennial congresses. The proposal could be for a topic of the next WCCA, however, this topic has already been covered.

317-325: add: reduced use of inputs (fertilizer, agrochemicals) and machinery resulting in reduced emissions for the production of those inputs.

330: this point is repeated; in addition, it is questionable: Brazil and Paraguay, despite high and successful adoption levels in CA, have very high land clearing rates.

381-390: while some nutrients are tied up in the build-up of organic matter, others are retained by the organic matter in a form available to plants and are therefore not lost by leaching or erosion; therefore, overall farmers observe generally a decreased fertilizer bill, which compensates the mentioned fixing. Pls. reconsider.

450-453: delete repeated sentence; in addition, the argument appears to suggest, that tillage is a valid weed control practice. This has been questioned by several papers, being one of the “myths” of tillage.

468-469: the same sentence repeated again; delete

470-479: why is this in italics? This paragraph is repeating contents and does not add new ideas. Delete.

490: spelling: Regenerative without –

518: the CA definition is proven and scientifically confirmed on all the aspired outputs; however, it was never meant as “umbrella”, but as the definition of the foundations for sustainability. This is still valid and hence the need to update or change is is not given. Pls. rephrase, also to be in line with the above declaration to simplify and clarify instead of adding new terms and definitions.

522: delete “.” after question mark

523: correct: … the former promotes has a just completed … (missing noun with two verbs)

524: the WCCAs are triennial, not every 4 years.

531-532: contradiction to the above statement that we do not need new terms; the term RA only needs a meaningful definition, no new term.

549: block chain technologies would offset many of the saved emissions due to their high energy demand.

580: repeated phrase, delete

584: as CA is not an umbrella but a foundation, additional technologies cannot be incorporated under this term, but could be promoted as complementary measures. Rephrase.

586: this is a claim, which is unattainable and unrelated to sustainable farming; delete

596: reorient or delete this section: there is no point to modify or update the CA definition, but there might be a point to rectify wrong definitions, as they even appear on the FAO website. However, such proposal should be directed to FAO and not subject to a scientific paper. The paper could call to citing the correct version of the definition and not repeating wrong versions in scientific papers, which then perpetuates the wrong versions in literature.

601-604: delete; see above, those statements are included in the original FAO definition of CA.

605-612: delete; minimum soil disturbance is the term used in the CA definition. The calculations on the width of the disturbed strips is pointless, since it ignores the 25% limit to soil surface disturbance; the 15 cm is the maximum permitted for strips of wide spaced rowcrops, since the 25% limit could allow for even wider strips. As soon as the row distance is reduced, the 15 cm in not the measure, but the 25%.

613: delete; this is also an academic, but pointless discussion. The CA definition calls for permanent soil cover, which means ideally more than 100% (not only 100% of the surface covered, but with a certain thickness). The three categories were included for statistical purposes. The lower limit of 30% is definitively not sustainable in the long term, but the definition needs to have a minimum level, which is attainable under all conditions, not meaning, that this is the ideal. It reflects the lowest possible soil cover during the cropping cycle (usually just after planting) to still qualify as CA. The value is taken from the USDA definition of conservation tillage, which represents the refraction point from where on the danger of erosion increases sharply.

624: delete; this is hair splitting, since the term rotation, alternation, sequence as used excludes repetition of the same crop in monocropping. In addition, some crops like wheat, rice and maize have a certain tolerance to repeated cropping and are therefor not treated as strictly as legume crops, in particular soya. Again, 3 crops is the bare minimum, the definition mentions “diversity” as the goal of this pillar which includes different plant families to the extent possible (even trees and animals).

633: change this sentence: the entire paper states, that CA is the base of sustainability for RA and OA; hence the three are no valid alternatives for sustainable farming.

660-666: change or delete this paragraph: the development of CA with a definition as a concept for sustainable land management has been an important step ahead of the so far used terms of sustainable or best practices. There is no single practice, which in isolation can be called sustainable. Sustainability can only be achieved in the synergetic combination of principles, for which CA is defining the bare minimum to achieve safely and universally sustainability. Other practices will complement this to achieve better productivity. Also, the time frame of 5 years to define such concepts is unrealistic: time is running and we have to accelerate the adoption of CA, not finding new definitions to only then promote those systems.

685: this statement should be extended to the declarations of the following 7 WCCAs.

Author Response

Dear Reviewer,

You received our text already reviewed by two reviewers in which we have already considered their comments.

Here follow our responses to your incisive comments. Where applicable, we will incorporate these comments in a final version when we receive feedbacck on the revised version from the first two reviewers. We have some differences of opinion, where I quote our British philosopher Bertrand Russel “Ïn intelligent dissent there lies a more fundamental understanding than in superficial accord”.

We have inserted our replies to your comments in red and alterations to the manuscript text have green shading.

On behalf of the co-authors and myself, I thank you for your diligent appraisal of our manuscript that will greatly contribute to its impact. We are including our reviewers in the Acknowledgments.

Yours faithfully,

Dr. John N. Landers O.B.E

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Most changes are accepted, with exception of one on line 684: the word continuous is nessesary to exclude periodic tillage, as this is still recomended by some experts. Therefore it is an essential part of defining CA not only as a no-till or zero-till but a never till system. The part requesting removal of continuous needs to be deleted.

I will not enter into arguments about the responses, since it will end up in hairsplitting. However, some points need clarification, as this paper is meant to have global validity and not only validity for Brazilian conditions:

The term zero tillage or no tillage is not equivalent to minimum soil disturbance. There are plenty of zero tillage or no tillage planters with high soil disturbance reaching up to 100% of the soil surface. Tillage is the purposeful alteration of soil structure, soil disturbance is any alteration of soil structure; therefor zerotillage only excludes the soil disturbance with the objective to alter the soil structure, not the disturbance which might occur when placing the seed. In this sense I agree, that the term strip till is not ideal, since we really mean strip seeding to allow for example for chisel type furrow openers as used with many animal traction no-till planters, or the rotary strip-till seeders which would seed two rows of small grains into 8 cm slots providing for about 25% of surface soil disturbance.

The second point is the 30% soil cover as the absolute minimum at any time of the year to still qualify for CA. Experience has shown, that in some extreme climatic conditions, such as arid lands, it is difficult to guarantee higher soil surface covers throughout the year. Yet, with this lower limit and under those conditions the benefits of CA can still be achieved, although the increase of soil organic matter, if any, is definitively very slow. I agree, an improved wording of the definintion is possible in the sense, that whenever possible higher soil cover rates must be achieved.

Author Response

Dear Reviewer,

On behalf of the co-authors and myself, I thank you for your comments and your suggestion.

Here follows our response to your comments:

Most changes are accepted, with exception of one on line 684: the word continuous is necessary to exclude periodic tillage, as this is still recommended by some experts. Therefore it is an essential part of defining CA not only as a no-till or zero-till but a never till system. The part requesting removal of continuous needs to be deleted  > Accept the suggestion to delete the statement in the line 684 626: “and continuous must not be used as an adjective to minimum soil disturbance” (attached file).

I will not enter into arguments about the responses, since it will end up in hairsplitting. However, some points need clarification, as this paper is meant to have global validity and not only validity for Brazilian conditions:  The term zero tillage or no tillage is not equivalent to minimum soil disturbance. There are plenty of zero tillage or no tillage planters with high soil disturbance reaching up to 100% of the soil surface. Tillage is the purposeful alteration of soil structure, soil disturbance is any alteration of soil structure; therefor zerotillage only excludes the soil disturbance with the objective to alter the soil structure, not the disturbance which might occur when placing the seed. In this sense I agree, that the term strip till is not ideal, since we really mean strip seeding to allow for example for chisel type furrow openers as used with many animal traction no-till planters, or the rotary strip-till seeders which would seed two rows of small grains into 8 cm slots providing for about 25% of surface soil disturbance. > agreed

The second point is the 30% soil cover as the absolute minimum at any time of the year to still qualify for CA. Experience has shown, that in some extreme climatic conditions, such as arid lands, it is difficult to guarantee higher soil surface covers throughout the year. Yet, with this lower limit and under those conditions the benefits of CA can still be achieved, although the increase of soil organic matter, if any, is definitively very slow. I agree, an improved wording of the definintion is possible in the sense, that whenever possible higher soil cover rates must be achieved.  >  agreed.  In extreme climatic conditions such as in the Brazilian semi-arid region and in Morocco, it is a challenge to achieve sufficient soil surface coverage.  However, in these conditions, the integration of crop and livestock, with or without forest component) are reported (Research Groups of Dr. Rachid Mrabet - INRA-Tangier, Morocco, and of Embrapa Caprine and Sheep, Sobral CE).

Yours faithfully,

Dr. John N. Landers O.B.E

Author Response File: Author Response.pdf