Universal Soil Classification System Can It Really Be Done?

Universal Soil Classification System—Can it Really be Done? Curtis Monger New Mexico State University, USA

Can a universal soil classification be built? Yes, of course. But when? What will it take? It seems to me that for our working group to achieve the task there are at least seven fundamental questions that must be answered:

1. Who is the audience—pedologists, soil scientists, other scientists, policy makers, the public?

2. What words should we use—Greek and Latin root words or common words like desert, forest, urban?

3. What should we group—soil properties essential for utilitarian functions or soils as natural phenomena regardless of their usefulness to humans?

4. Should we organize soils into phenetical hierarchies or phylogenetical hierarchies?

5. From the start, should the classification system be built to accommodate future information from anticipated technologies?

6. As a working group, should we start with the topics on which we agree (e.g., Histosols) and save the controversial topics (e.g., soil climate) until last?

7. What is the deadline?

In answer to question 4, one possibility is to combine a phylogenetic system with a phenetic system (Fig. 1). If, on the other hand, a purely utilitarian system designed solely for industrial agricultural is decided to be pursued (question 3), another possibility is to simply combine the most important soil physical properties for crop production with the most important chemical properties (Fig. 2).

One last question that might help this working group is the following: “What advantage do we have today; that is, what prevented soil taxonomists from building a universal soil classification system in the past?” Of course we have more data on soils today. But perhaps it’s our global connectedness— environmental, political, economic, and technological—that is most different. Maybe we need a USC system more today than it was needed before. Time, as well as the success of our working group, will tell. Figure 1. Hypothetical soil classification system based on evolutionary relationships of soils (phylogenetic) with groupings based on similarities among soils (phenetic).

Figure 2. Simplified utilitarian soil classification designed solely for industrial agriculture. It plots soil available water capacity and slope steepness versus soil pH and fertility.