Investigating Soil Texture
Earth ecoSTEM Kit Materials Used: Trowels
ENGAGE - Students Observe This Phenomenon
EXPLORE a Kit-Supported Learning Experience
Students will observe and sketch one soil horizon pit (+ 12 inches deep) and then use their trowels to dig 4” deep samples from various locations. They will use Earth Learning Ideas’ Soil Donuts protocol to feel soil samples in their hands, estimate the texture, and classify it as sand, silt or clay. The Soil Texture by Feel video from University of California Davis is a variation.
Formative assessment: Students should be able make a model which shows that soil is composed of mineral content (broken bits of rocks or ‘parent material’) as well as water, air, and organic material (living roots or dead and decomposing plants and animals). Differences in texture can be modeled using a jar which student fills with three sized balls (largest = sand; smallest = clay) to represent particle sizes, with spaces between to represent porosity.
Students can conduct a Jar or Shake Test to calculate soil texture by following this protocol from the Clemson Cooperative Extension. Then they can use their data to identify the proportion of silt, clay and sand in their soil sample, using a Soil Triangle such as this one from Soils4Teachers, where more lessons can be found by grade.
This video from NRCS explains Water Movement in Soils . Students can calculate the porosity (% of space between soil particles) and permeability (the rate at which water flows down into soil through spaces between particles) by doing the How Full is Full? activities from Teach Engineering. This video from Bozeman Science explains Soil Dynamics.
Students may propose solutions to compacted or lifeless mineral soils and implement a project to improve soil health.