MADISON, WI, August 2nd, 2010 - Using little more than PVC rings, a trashcan, and a scale, students can literally get a feel for soil water retention and field capacity, concepts that are important and useful in fields from farming to engineering.
The demonstration, developed by Adam Howard, Drs. Josh Heitman and Dan Bowman of North Carolina State University, was designed to illustrate concepts that can be difficult for students to visualize and understand, and the equipment for making measurements of these variables is expensive. They report their method in the 2010 Journal of Natural Resources and Life Sciences Education, published by the American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America.
The demonstration begins by taping short rings of PVC pipe together into a tall column. That column is then filled with soil and placed in a trashcan, and filling the trashcan with water to saturate the soil column. Saturating the column represents a long, soaking rainfall event.
The column is then removed from the trashcan, and allowed to drain for a day or two. When the excess water in the soil is drained away, the water left is the water contained in the soil at field capacity. Then the rings of the column are separated and the soil in each ring is weighed. As the column is sectioned from the top to the bottom, students are able to feel the differences in the soil water content. The soil is then dried and weighed again to determine the water content in each ring.
The concept of field capacity is one that arises often in soil, crop, and horticultural science disciplines. Field capacity is generally defined as the water content of a soil after free water no longer drains from a thoroughly wetted soil.
Field capacity is generally reported as a single number, which would be the average of the water contents in the rings, but few who use this information know wher
|Contact: Sara Uttech|
American Society of Agronomy