Scott Werts Winthrop University

Design of Activity  Activity designed as a homework assignment  Work assigned after lecture material and reading on cation exchange processes in soils.  Students are not to work in groups, and each is responsible for choosing their own locations to investigate  Students in this course already have a background in using the NRCS Online Soil Survey

Assignment Basics  Students are to compare the cation exchange capacity of a particular set of soils with the aspects of that soil that influence the CEC. (pH, organic material and clay)  Students may chose any location they wish Most chose their address or an address of their relatives.

Assignment Basics  Students look at this data at two separate depths Each set of data is taken from 0-10 cm and cm. This gives the students an idea of variation within the area laterally with different soil types and vertically within the same soil type.

Familiarity with the Online Soil Survey  Online Soil Survey Online Soil Survey  A clearing house of very basic data regarding soils.

Assessment  Students are to turn in: The map of the Area of Interest they created (AOI) A Table displaying ○ Soil types ○ CEC ○ Percent Clay ○ Percent Carbon ○ pH Explanation of trends….

Assessment  Trends What should be: ○ As CEC goes up pH goes down Organic Content goes up Clay goes up Sometimes there is variation ○ pH will go down as organic content goes up, for example

Variation from the norm:  Have the students assess the magnitude of the differences. For example – a 10% increase in organic matter may be a stronger driver for an increase in CEC than a 0.2 drop in pH.

Variation from the norm:  Not fool-proof At least once, there was a trend even I, the professor, could not explain. Reinforce that the soil survey isn’t perfect and should represent a generalized trend I had the student write what should influence the CEC and state that the data bucked the traditional trend we discussed in class

Questions? Happy students!