Soil Field Descriptions and Soil Forming Processes

Jeff Clark
Lawrence University
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This assignment covers the basic techniques of soil descriptions in the field using a modified version of the NRCS Field Book for Describing and Sampling Soils (2002). Students investigate soil profiles at locations that differ in their vegetative cover and topographic position. They then make comparisons between these pits to infer the influence of topography and vegetation on soil formation processes.

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This activity is for an undergraduate course in geomorphology.

Skills and concepts that students must have mastered

Prior to this field lab students will have done readings and attended lectures on chemical weathering, soil formation, soil nomenclature and soil characteristics/descriptions.

How the activity is situated in the course

It is a stand alone lab during the second week of the course.


Content/concepts goals for this activity

Preforming field descriptions of soils.
Conducting laboratory analysis of soil moisture and organic matter content.
Assessing the relative importance of soil forming factors.

Higher order thinking skills goals for this activity

Students will compare and contrast the differences in soil horizons between 5+ pits in a relatively small area. They will need to reason what soil forming processes are probably the same for the pits and which are different. They can then infer the effects of topography and vegetative cover on soil profile development.

Other skills goals for this activity

The students work in groups of 2-3. The must give a brief description of their soils while in field to the rest of the class. Back at campus they must also share their data with the rest of the class in using electronic notebooks and annotated photographs.

Description of the activity/assignment

In this field activity students break into small groups and dig soil pits. The pits are distributed among different vegetative covers and topographic positions allowing comparisons of soil profiles under different soil forming processes. Each group prepares a field description of their soil using a shortened version of the NRCS Field Book for Describing and Sampling Soils (2002). Before leaving the field the class takes a tour of the pits and each group gives a brief oral presentation of their profile. Samples from each horizon are later analyzed in the lab to determine the % soil moisture and organic matter. Data from each group is compiled on a share drive which is then utilized by the rest of the class for comparison.
Designed for a geomorphology course

Determining whether students have met the goals

All pits are located in the same type of soil so the main differences are in the thickness of the O and A horizon, soil moisture, organic matter content, and the presence or absence of mottling. pH would also likely vary though we do not measure that. I conduct formative assessment of their techniques in the field and summative assessment of the lab report.

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