| 02 Jul 2026
Fundamental conditions "indicators" should meet to be objective and to guide practice reliably
Abstract. Over the last 2 decades, a significant body of research has been devoted to finding parameters that could serve as “indicators” of a range of soil properties of interest, including soil health and the many functions/services of soils. Even though the topic had been the object of a sustained debate among ecologists between 2001 and 2010, no one seems to have looked so far into conditions soil indicators should satisfy to be objective, nor is it made clear to users and policy makers which ones are objective and which ones are value-laden and therefore subjective. In the present article, we identify the conditions a soil parameter A needs to satisfy in order to be an objective indicator of another property B. We argue that in addition to A and B being measurable and not merely quantifiable approximately, a testable mechanistic theory needs to exist, which causally relates A and B. In most contexts in which soil indicators are currently used, such a theory appears to be entirely lacking, leading us to call for a significant research effort focusing on theory development.
Objectivity is essential in information researchers provide to the public about soil processes
Philippe C. Baveye
Saint Loup Research Institute, 7 rue des chênes, La Grande Romelière, 79600 Saint Loup Lamairé, France.
Dr. Jasper Wubs, the topic editor assigned to handle the review of our manuscript, has expressed a number of “concerns” in his “Justification” of his decision to post our manuscript as a preprint, and to start the discussion about it. This “Justification” has been so far visible only to the authors and reviewers. Given the nature of the concerns expressed, I think that in the interest of open communication and transparency, they should be accessible to everyone and addressed directly, and some kind of a response should be formulated before reviews are turned in. In the interest of time, and since it is the middle of the Summer and my co-authors are off on holiday with their families, I will provide a personal response below.
As a preliminary remark, I would like to emphasize that our manuscript was submitted as a Forum piece, i.e., as a text meant first and foremost to stimulate a debate on a topic that we think is worth discussing more extensively than is the case at the moment. We recognize fully, from the onset, that some of our colleagues in soil science may disagree with what we are writing and proposing. If we were all in agreement, there would be no need for a Forum piece. In that context, the question that should be asked of the reviewers at this stage is not whether they agree with the conclusions we reach, but rather whether we raise a valid question, and whether our manuscript is formulated in such a way that it is likely to stimulate a constructive debate on this question.
Concern 1: “[it’s] not directly apparent what the intellectual step is that is made here, indicators and subjectivity are central elements in measurement theory, epistemology and philosophy of science - what from that discussion is peculiar (and new) to soil? And what is the step you propose?”
Response: One could debate whether the statement that “indicators and subjectivity are central elements in measurement theory, epistemology and philosophy of science” is accurate. That may be true in some fields. However, in the 45 years since I started reading assiduously on these various topics as they potentially related to research in soil science or education, I have developed a viewpoint on them that does not correspond at all with the above statement.
In any event, that is not really the debate. Our Forum piece focuses on the description of processes occurring in soils, and in that context, the question we ask, about the conditions indicators need to meet to be considered “objective”, has, to our knowledge, not been asked explicitly so far. The closest researchers have come to address it is in the ecology literature between 2000 and 2010. But we have not been able to find any echo in the soil literature of the very interesting debate that took place then, before it eventually faded in the background without resulting in any kind of consensus.
The step we propose to move forward is clearly detailed in our text. It is a renewed emphasis on theory development in soil science to establish clear causal relationships between potential indicators and soil properties.
Concern 2: “objectivity seems to be your guide, how do you relate that against the idea that 'all data are value-laden', an important academic notion in much of the social sciences. It applies directly to the field of soil health/quality/functioning where we can't even agree on the definitions of these central concepts, let [alone] agree on their measurement.”
Response: The proposition that “all data are value-laden” is indeed popular in some disciplines, but one could easily argue that, in the context of soils, it is an exaggeration. Some data, like the 43°C surface temperature my (correctly positioned) outdoors thermometer measured yesterday, are not value-laden. One should not confuse “value-laden” with the perspectival character that is associated with the type of instrument that one chooses to use to measure soil properties. However, although very interesting and worth investigating as well, that is an entirely different, philosophical debate than the one we are trying to stimulate in our manuscript.
Objectivity, for us, is not just a “guide”. Our perspective on objectivity departs to some extent from one that at least some researchers seem to espouse. As, e.g., Hundemer et al. (2026) pointed out recently, there is a perception among various constituencies that researchers, in their pursuit of the advancement of knowledge, should “produce objective science”, but at the same time, they should also “use their science and expertise to support the public good” and in that context, the requirement of objectivity should not be as stringent. Hundemer et al. (2026) refer to “tensions” between those two contrasting facets of research endeavours. Again, that may be true in some disciplines, but I am not convincing that with respect to soil science, the need for objectivity is so different among the complementary activities of researchers.
The question we ask in our Forum piece is, at its root, a very pragmatic one. If we are trying to convince a farmer that s/he needs to increase the microbial biodiversity of her/his soil to increase crop yields or to help mitigate climate change, s/he will immediately ask what evidence we have that there is a clear link between biodiversity and these processes, in other what guarantees we can give her/him that increasing the soil microbial diversity will automatically produce the desired outcome. Even before the quintessential question is discussed of how much that would cost, it is important in practice for the farmer to know whether what we are talking about is a reasonably established fact, and how strong the evidence for it is, or whether it is just a personal opinion. In that context, what we are discussing in our Forum piece is the set of conditions that need to be met for a statement we make to be considered a sound, reliable piece of information. That is needed by practitioners, policy makers, and, I would argue, anyone who deals with soils or benefits from their services, in one way or another. With farmers, the guarantee that there is evidence in support of a new practice does not automatically mean that they will adopt it widely. From my experience, some of them, closely monitored by their neighbours, may try it in a corner of one of their fields, and if the results are conclusive after 2 or more seasons, they may adopt it more widely. But in order to get a foot in the door, there definitely has to be more than a subjective opinion at the onset.
The issue of soil health is a good example in that context. There has been a sustained debate on what the concept means and a number of researchers in recent years have commented on the protracted absence of an operational definition of it (e.g., Stewart et al., 2018; Janzen et al., 2021; Baveye, 2021, 2025; Powlson, 2021; Harris et al., 2022; Matson et al., 2024; Fausak et al., 2024). If, when one tries to convince farmers that they should improve the health of their soils, we are honest with them and admit that, in the soil science community, not only do we not know how to define this concept, but we do not know either how to measure it, the response of the farmers, from my experience, is rarely very enthusiastic. If the government agreed to pay for it, farmers around me would be willing to paint their soils pink with big yellow dots, without asking whether that makes any sense, and the same goes with campaigns to increase “soil health”, but overwhelmingly from the farmers’ perspective, in the absence of sizeable subsidies, full adherence would be difficult to obtain to a concept that is neither defined nor measurable or convincingly profitable. Farm advisors, at least in the part of France where I live, as well as apps targeting farmers in my region, have understood that very well, it seems. Omitting to mention the absence of a consensus in the soil science community about what soil health is, they tend to provide an arbitrary definition of soil health that suits the farmers they interact with, without pointing out the entirely subjective nature of the list of parameters their definition involves…
Concern 3: “Even in something seemingly solid and objective like agricultural soil testing for nutrient concentrations there is huge variation in methods (e.g. type of P extraction), and labs don't always agree in the estimated concentrations, and may get sample rank-orders jumbled up. So, even if such chemistry metrics could be objective indicators in theory, how far is that theory away from daily practice and does that then still qualify under your objectivity paradigm?”
Response: I guess the key word in that concern is the word “seemingly”... If agricultural soil testing for nutrient concentrations were really “solid and objective”, there would not be different methods to assess some of the key parameters, like the available phosphorus concentration, and the answer farmers would get about how much phosphorus they need to add to their soil would not depend on which laboratory they send their samples to, or on the person they consult.
It is difficult for me to imagine that this current state of affairs, as described in this Concern, would be deemed satisfactory to anyone in the soil science community, let alone to those who depend on reliable information, independent of whoever they happen to talk to, to manage their soils. On this particular question, and I would argue on quite a few others about soils, we need to get to a point where we are able to provide reasonably consensual answers. That will clearly require some fundamental research and the development of theory. How long that is going to take is difficult to forecast. Perhaps if soil scientists stopped publishing inordinate amounts of articles promoting endlessly the same sales pitches about soil carbon sequestration, soil health, soil security, etc…, and devoted time instead to designing and carrying out careful, targeted experiments, it would be possible in the not too distant future to reduce significantly the amount of subjectivity in the practical advice we give to farmers and the public at large about soil management.
References
Baveye, P. C. (2021). Soil health at a crossroad. Soil Use and Management, 37(2), 215-219.
Baveye, P. C. (2025). Why a mechanistic theory of soils is crucially important: Another line of supportive argument exists, seldom invoked in soil science. Soil, 11(2), 1131-1140.
Fausak, L. K., Bridson, N., Diaz-Osorio, F., Jassal, R. S., & Lavkulich, L. M. (2024). Soil health–a perspective. Frontiers in Soil Science, 4, 1462428.
Harris, J. A., Evans, D. L., & Mooney, S. J. (2022). A new theory for soil health. European Journal of Soil Science, 73(4), e13292.
Hundemer, S., Loizzo, J., Peterson, A. L., Stoutamire, S., & Paxson, S. B. (2026). Scientific objectivity and the pursuit of the public good. Science and Engineering Ethics. In press
Janzen, H. H., Janzen, D. W., & Gregorich, E. G. (2021). The ‘soil health’metaphor: Illuminating or illusory?. Soil Biology and Biochemistry, 159, 108167.
Matson, A., Fantappiè, M., Campbell, G. A., Miranda-Vélez, J. F., Faber, J. H., Gomes, L. C., ... & Chenu, C. (2024). Four approaches to setting soil health targets and thresholds in agricultural soils. Journal of Environmental Management, 371, 123141.
Powlson, D. S. (2021). Is ‘soil health’meaningful as a scientific concept or as terminology. Soil Use and Management, 37(3), 403-405.
Stewart, R. D., Jian, J., Gyawali, A. J., Thomason, W. E., Badgley, B. D., Reiter, M. S., & Strickland, M. S. (2018). What we talk about when we talk about soil health. Agricultural & Environmental Letters, 3(1), 180033.