Effects of Active Learning Interventions On Student Learning Outcomes in a 250-Student Introductory Soils Course.

In Fall 2012, a number of active learning interventions were tested in a pseudoexperimental design as part of a large-format introductory soils course at Montana State University.  Here we report on the results from three of these interventions: (i) four successive fieldtrips to educational soil pits, (ii) a multi-part “Favorite soil report” writing assignment, and (iii) two in-laboratory team competitions relating to soil infiltration rates and substrate-induced soil respiration rates.  The class has been taught for more than 30 years, and with recent enrollments of ~250 students, students are split between two biweekly lecture sections and six to ten laboratory sections.  In Fall 2012, one-third of students were sophomores and one-third were juniors, with students bracketing >20 majors.  More than 200 end-of-semester responses were obtained to an electronic survey.  Student learning outcomes showed improvement in terms of knowledge (32% of respondents described their knowledge of soils as "Excellent, excellent/good, or good" before the course vs. 81% at the time of the survey), skills ("field description techniques, laboratory measurements, fluency with Soils Taxonomy"; 35% before vs. 82%), and attitudes ("including curiosity"; 59% before vs. 75%).

The course traditionally has kicked off with four successive fieldtrips to local destinations (three local farms and the nearby Gallatin National Forest).  The focus of the first fieldtrip is to introduce students to soil morphological properties, which we acronymize as DRoCTS: depths, rocks, colors, textures, structures.  Students build on this knowledge through subsequent fieldtrips to a Typic Haplustoll (Amsterdam series), a conglomerate terrace pit and floodplain pit, and finally to a lithosequence with adjacent soils overlying quartzite and shale.  Although the logistics of mobilizing students to remote fieldsites is challenging, student responses to these fieldtrips was overwhelmingly positive, with 74% strongly agreeing or agreeing the fieldtrips were helpful.

The multipart “Favorite soil report” was originally conceived as a vehicle for focusing individual student interests on the abundance of data available through tools such as Web Soil Survey or SoilWeb.  In Fall 2012, we modified the requirements to focus the first two written reports on physical and then chemical properties, with a final team presentation during laboratory.  Student responses to these exercises were less positive, with only 37% considering them helpful.  Some findings and planned iterations will be discussed.

Finally, we incentivized ~60 4-student teams to first decide whether they would compete for either the fastest or slowest rates, for two laboratory exercises: only the top- and bottom-ranked teams for each pair of laboratories obtained a giftcard to a local food establishment.  For the first lab, student teams had to configure ~1 liter of loam and ~1 liter of sand in such a way as to maximize or minimize infiltration rates through Plexiglas “root boxes.”  In general, the fastest infiltration rates were obtained in configurations that enabled the sand to be isolated from the loam; the slowest infiltration rates were associated with repeated thin layers of the loam and sand.  For the second lab, student teams had to configure a pair of septum-sealed 50-ml centrifuge tubes in such a way that they obtained either a maximum or minimum soil respiration rate upon the addition of various substrates.  The winning respiration rate was obtained after one team added Mountain Dew to their soil; the slowest respiration rates were associated with the addition of handsoap, hydrochloric acid, or polyurethane.  Student responses to these team-based competitions were quite positive (60% agreed they were helpful).

Together, these interventions suggest that active learning exercises, whether in field or laboratory settings, can contribute to improved learning outcomes in a large format introductory soils course.