A field exercise for introductory soil science
Soils present a marvelous opportunity for science students to see the practical real-world implications and applications of the principles of basic physics, biology and chemistry. Soils play key roles in every type of ecosystem on land, and have major effects on the ecology of aquatic ecosystems, as well. Hands-on experience is an important part of learning about soils. That is why most college level introductory soil science courses include a weekly laboratory. While many analyses can be performed on soil material brought into the lab, to understand soils as natural bodies in the landscape one must go into their natural habitat.
Therefore, the lab portion of introductory soil science courses commonly includes one or more field trips. Examining a catena of soils in the field is an excellent way to help students broaden their knowledge of soil profiles and soil-landscape relationships.
Published in the Journal of Natural Resources and Life Science Education, this paper presents a simple but effective approach for studying a catena in a lab class of 15 to 25 students. The laboratory exercise can be conducted in 1.5 hours, not including travel time to and from the field site. It was designed for an introductory college level class, but could easily be adapted for junior or senior high school science classes. A detailed description of a field exercise allows teachers to help students see and experience the effects of topography on soil morphology using a side-by-side examination of four soil series representing drainage classes from well drained to poorly drained. Attention is drawn to teaching techniques that can maximize the educational benefits of the field exercise.
Catena (from the Latin, meaning “chain”) is a term first coined in East Africa to describe a grouping of different soils that occur together in the landscape, each soil in a catena differing from the others principally because of the effect of topography on horizontal and vertical water movement and proximity to the water table. While topography is the dominant factor influencing the development of soil properties that differentiate among soil in a catena, it should be recognized that this factor can never be completely isolated from other factors of soil formation (parent material, climate, organisms and/or time).
After completing this field exercise, students should be able to recognize a catena of soils in the field, make an auger hole and collect soil from a specified depth using a bucket auger, examine soil during augering to recognize horizon changes, use soil color, texture, landscape position, and horizon changes to associate an auger hole with a soil description in a soil survey report, determine the drainage class of a soil by the depth of redoximorphic features observed while augering, and explain how soil morphological features might be used to rate a soil as well, moderately-, or poorly- suited for use as a septic filter field or as a fruit orchard.
American Society of Agronomy. April 2003.