Cutting Edge > Hydrogeology > Hydrogeology, Soils, Geochemistry 2013 > Teaching Activities > Soils —Field Characterization, Collection, and Laboratory Analysis

Soils —Field Characterization, Collection, and Laboratory Analysis

Abir Biswas, The Evergreen State College

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This page first made public: Jun 6, 2013

Summary

Field characterization of soil profiles in coniferous and deciduous settings; sample collection of soils from different horizons; laboratory analysis of soil moisture, soil organic carbon (by loss on ignition), and grain size distribution (by sieving)

Context

Audience

Equivalent of 100 or 200 level geology class with soils, weathering, or Earth surface processes focus

Skills and concepts that students must have mastered

Students would benefit from prior reading on soil horizons and soil formations (because students sometimes have a hard time identifying distinctions between soil horizons without a sense of "what to look for"). I used the Chapter 3 of the Chapin textbook, Principles of Terrestrial Ecosystem Ecology.

How the activity is situated in the course

Sequence of field and lab sessions to allow for soil characterization and collection (in the field) and analysis (in the lab, including overnight step for loss on ignition)

Goals

Content/concepts goals for this activity

soil formation and development, investigating role of geology in influencing soil development, influence of different types of vegetation on organic matter input and storage in underlying soils

Higher order thinking skills goals for this activity

Formulation of hypotheses (soil development in coniferous vs. deciduous forests), Analysis of data (comparing coniferous vs. deciduous forests, and surface vs. deeper soil horizons)

Other skills goals for this activity

-introduction to fieldwork, sample collection, and maintaining a field notebook
-developing familiarity with lab setting (balances, oven)
-working in groups

Description and Teaching Materials

This sequence of field and laboratory "lab sessions" work well with groups of 3-4. Students' work and learning are reported in their field/lab notebooks, their calculations, and the depth of interpretations.
Day 1- students dig soil pits (or work in pre-dug soil pits), characterize soils in the field, and collect samples from O and B or C horizons to bring back to lab. Students pre-weigh samples and place samples in ~60-70 deg C oven to dry (and later quantify soil moisture)
Day 2- students post-weigh soils to quantify soil moisture content and take subsamples for analysis of soil organic carbon by loss on ignition. Bake samples ~6 hours to overnight in ~550 deg C oven. Use remainder of dried soil with series of seives to quantify grain size distribution (basically for pebble vs. sand vs. silt/clay).
Day 3- students post-weigh baked soils to quantify soil organic matter content and complete sieving to quantify grain size distribution. Students report their data on board and discuss reasons for differences among groups (to address human error), sites (to address different settings), depths (to address soil formation processes), etc. and complete summarizing their methods, results, and interpretations/conclusions.

Student handout for "Soils —Field Characterization, Collection, and Laboratory Analysis" (Microsoft Word 2007 (.docx) 173kB Jun10 13)



Teaching Notes and Tips

Assessment

I assessed their lab and field notebook for details, calculations, depth of interpretations/conclusions. I later asked about soil profiles and a soil development scenarios in long/answer or essay questions on subsequent exams.

References and Resources

Chapin textbook, Principles of Terrestrial Ecosystem Ecology, Ch.3

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