Soils and Sustainable Agriculture
Jeff Walker, Earth Science and Geography, Vassar College
This intermediate-level lecture/lab earth science course explores the relationships between the geological parent and the character of the resulting soils. The lecture portions discuss the theoretical background and are closely tied to lab and field experiences which include mapping and sampling soils, determining physical and chemical characteristics, and evaluating biota such as seeds and invertebrates. Assessment is through lab reports, a final project, and a final exam.
Lecture and lab
Private four-year institution, primarily undergraduate
Prerequisites for the course are one introductory-level lab course in biology, chemistry, earth science, or environmental studies. Because of this, the student body is diverse with about half ENST majors (who may or may not concentrate in sciences) and the rest a combination of ESCI, BIOL, and CHEM majors. Because of facility limitations, the lab work is all done in small groups, and I try to pair students with more background in ESCI with students who have less so some peer to peer learning can occur and everyone can be brought up to speed on the geological background relatively quickly.
This course concentrates on the physical basis of soils - parent material, climate, chemical and physical characteristics, and rates of formation. Sustainability is introduced because soils, while sharing broad similarities, are in other important ways unique to their place of formation so that the essence of sustainability in agriculture is understanding the specific characteristics that make the soil unique and then working within that context.
Students will be able to dig, describe and sample a soil test pit, perform most common laboratory tests on soils (texture, LOI, moisture), and measure and interpret soil chemical data (nutrients, CEC). Students will be able to use the general soil classifications, but will also be able to measure and describe the specific characteristics that make each soil unique.
The final project in the course is an oral presentation and written paper on sustainable production of a food crop of the student's choice. This project emphasizes the importance of soils as the basis of sustainable food systems. Local farmers are invited for the presentations (and a local foods potluck).
This course was developed by combining two previous courses: Principles and Practices of Sustainable Agriculture (ENST introductory lecture course) and Soils and Terrestrial Ecosystems (ESCI intermediate level lab course). It was designed as a way to introduce the growing number of students interested in sustainable agriculture (some of whom tend to avoid science courses) to field and laboratory-based scientific inquiry as a way to help them understand the physical basis (and limitations) of sustainability.
Assessment is done by the traditional methods of lab reports, final project (with oral presentation, and final exam. However, the final is open ended in that it is based on the essay "Odyssey" by Aldo Leopold which describes the movement of nutrients through an ecosystem. I ask them the tell me all they can about the scientific basis for the things the author (a scientist attempting to communicate science to a lay audience in a compelling manner) says in the essay. Finally, assessment is done continually in discussions with the small groups during field or lab work. In this way I can gauge their level of understanding and be aware of concepts that may need to be re-emphasized.
midterm lab report guidelines (Microsoft Word 2007 (.docx) 119kB Jun20 12)
cation exchange capacity lab (Microsoft Word 2007 (.docx) 115kB Jun20 12)
procedures for a seed bank study (Microsoft Word 30kB Jun20 12)
References and Notes:
Brady, N.C. and Weil, R.R. (2010) Elements of the Nature and Properties and Soils, Pearson/Prentice-Hall.