One of the most exciting times to be involved in science is when a new paper or result comes along that directly challenges the accepted paradigm. The field of soil physics may have recently reached such a juncture. A recent publication in the Soil Science Society of America Journal – titled “What’s wrong with soil physics?” – directly challenges some of the fundamental assumptions of soil physics. First and foremost, the authors object to the concept that soil is formed from a “bundle of capillary tubes”, even though that model has served as the conceptual framework for many of the advances in soil physics over the past century. The authors correctly point out that the bundle of capillary tubes model lacks consistency in how it is interpreted and applied: for example, to predict pore size distribution from water retention measurements the capillary tubes are assumed to be independent and uni-directional, while to explain tortuosity of flow the tubes must be connected and multi-dimensional. Further, the authors worry that the flaws of this conceptual model may cause misconceptions and unsound intuition in many practitioners of soil physics, similar to how many laypeople believe that “groundwater exists in the ground in actual rivers or lakes”. As a way forward, the article suggests use of percolation theory, which has long been used and promoted by the primary author.
Here I must confess that I have not yet taken the time to fully understand percolation theory and its applications, so I cannot state for certain whether I agree with the authors’ claims that percolation theory represents the best framework. From my limited exposure, I think it is safe to say that percolation theory is more mathematically intensive and challenging than derivations based on the capillary bundle concept. For that reason, as we move forward (using percolation theory or any other alternative) we must carefully balance the need for theories that are based on internally-consistent concepts with the need for theories that can be understood and conceptualized by students and practitioners alike.
Overall, this article has made it abundantly clear that the field of soil physics has reached a point where many of the old assumptions must be re-investigated, re-analyzed, and re-worked in a more consistent manner. This represents a tremendous opportunity to all of us who work in the field of soil physics. I for one cannot wait to see how this re-envisioning plays out in the coming years and decades.
Reference:
Hunt, A. G., R. P. Ewing, and R. Horton (2013), What’s Wrong with Soil Physics?, Soil Sci. Soc. Am. J., 77(6), 1877.
Here I must confess that I have not yet taken the time to fully understand percolation theory and its applications, so I cannot state for certain whether I agree with the authors’ claims that percolation theory represents the best framework. From my limited exposure, I think it is safe to say that percolation theory is more mathematically intensive and challenging than derivations based on the capillary bundle concept. For that reason, as we move forward (using percolation theory or any other alternative) we must carefully balance the need for theories that are based on internally-consistent concepts with the need for theories that can be understood and conceptualized by students and practitioners alike.
Overall, this article has made it abundantly clear that the field of soil physics has reached a point where many of the old assumptions must be re-investigated, re-analyzed, and re-worked in a more consistent manner. This represents a tremendous opportunity to all of us who work in the field of soil physics. I for one cannot wait to see how this re-envisioning plays out in the coming years and decades.
Reference:
Hunt, A. G., R. P. Ewing, and R. Horton (2013), What’s Wrong with Soil Physics?, Soil Sci. Soc. Am. J., 77(6), 1877.