Thank you, Professor Göran Ågren, for these interesting comments.

    I agree that, to anyone with a physics background, what I wrote will appear “rather obvious”. Therefore, to a large extent, my targeted audience consists of the non-physicists in the soil science community, and especially among them, the colleagues who have recently started promoting the adoption of machine learning and artificial intelligence as “the” way forward.

    Thank you for pointing out your article with Ernesto Bosatta. I must admit I was not aware of its existence, as I do not frequently scan the pages of American Naturalist. As soon as I manage to get hold of a copy of this article, I will read it in detail, and will mention it in the revised version of my Forum piece.

    Your point about the complexity of models becoming rapidly unmanageable for most soil scientists, as soon as one goes from the relatively simple discrete formulations to the more complicated, continuous ones, is very well taken. Most soil physicists giving seminars to mixed audiences have experienced the rapid glazing-over of the eyes of the non-mathematically-minded attendees as soon as an equation appears on the screen, soil microbiologists being the worst in many ways. This is no doubt a reflection of how the education of soil scientists has been approached in the past, with advanced mathematics being considered unnecessary for most, except soil physicists. One approach to resolving the problem is, as you suggest, for soil physicists to participate in soil science studies, but from my experience, interdisciplinary research works best when participants know sufficiently about what the others are equipped to do to understand what is going on overall in the research. Soil physicists and chemists need to know about the intricacies of genome sequencing, and soil microbiologists need to be comfortable with partial differential equations. It would not necessarily help if at the point of describing things quantitatively, participants just turned to soil physicists and told them “OK, now you do your magic, and it’s a wrap…” Theory and model development will have to be a collective effort, which means we need to rethink the education of the next generation of soil scientists, so that everyone is quantitatively literate. Nothing new there; Some of us have been writing it consistently for the last 30 years.

I am very grateful to Referee #2 for his/her positive comments and for "agreeing strongly" with the message of my Forum piece.

With respect to the second paragraph of Referee #2’s comment, I am not sure I agree with the statement that “the subject in soil science is often vague or to some extent too immense to summarize”. I do not think that the subject in itself is vague or too immense. I believe, instead, that soil processes have often been approached from a perspective that researchers in other disciplines, and especially in physics, would consider non-scientific. To a large extent, the fact that a “data amassing” approach has been adopted for a very long time in soil science has allowed myths to proliferate, which would have been avoided, I think almost entirely, if a more rigorous, mechanistic path had been systematically followed. For example, some researchers have advocated that the incorporation of biochars in soils improves soil structure. This claim has been backed by an accumulation of correlation data showing that in soils amended with biochars, soil structure (i.e., really, aggregate stability) is better. Any researcher with a mechanistic bend would not be satisfied with such evidence, and would try to come up with a detailed explanation of the effect, i.e., would try to find the exact mechanism(s) by which biochars, which are fundamentally inert materials, could improve soil structure. In looking for this mechanism, one may find out that biochars themselves do absolutely nothing, but the various chemical compounds that biochars contain initially as a result of their pyrolysis contribute significantly to stimulate microbial activity, and thereby improve soil structure in the short-run. If that is the case, one would expect the effect to disappear after a few years. A related myth is that biochars increase crop yields. Again, a mechanistically-based approach, trying to uncover causes rather than correlations, might have revealed years ago that biochars do not have much of an effect in the long run on yields. Because this approach was not adopted, the myth has been allowed to go on, unchecked (see in this respect the recent critical article by Chaplot et al., 2025).

In that context, I agree with the referee that a list of essential soil science myths would be a good addition to the text, to provide an idea of what some of the key ingredients of models of soils should be. The problem I foresee in creating such a list is that there are many such myths in soil science, related, e.g., to topics as varied as the importance of the elusive “aggregates” in soils (e.g., Vogel et al., 2022; Baveye et al., 2022), the fuzzily-defined notion of “soil health” (e.g., Harris et al., 2022), or the promise of metagenomics to help us quantitatively describe microbially-mediated processes in soils, that establishing an exhaustive list would be a daunting endeavour. Nevertheless, I agree that mentioning a few examples, in a number of subdisciplines of soil science, to illustrate further the crucial need for a mechanistic theory, would be very worthwhile, and I will try to do that in the revised version of the manuscript.

References

Baveye, P. C., Balseiro-Romero, M., Bottinelli, N., Briones, M., Capowiez, Y., Garnier, P., ... & Vogel, H. J. (2022). Lessons from a landmark 1991 article on soil structure: distinct precedence of non-destructive assessment and benefits of fresh perspectives in soil research. Soil Research, 60(4), 321-336.

Chaplot, V., Baveye, P., Guenon, R., Le Guyader, E., Minasny, B., & Srivastava, A. K. (2025). Biochars improve agricultural production: The evidence base is limited. Pedosphere, 35(1), 295-298.

Harris, J. A., Evans, D. L., & Mooney, S. J. (2022). A new theory for soil health. European Journal of Soil Science, 73(4), e13292.

Vogel, H. J., Balseiro‐Romero, M., Kravchenko, A., Otten, W., Pot, V., Schlüter, S., ... & Baveye, P. C. (2022). A holistic perspective on soil architecture is needed as a key to soil functions. European Journal of Soil Science, 73(1), e13152.