Lab Activity: Determining Soil Texture

Lab Activity: Determining Soil Texture

Background information: For those people who depend upon the soil, the ability of that soil to hold water and resist erosion are concerning factors. Soil texture refers to the ratio of different-sized mineral particles in the soil. Based on size, mineral particles are referred to as clay, silt, or sand.

Clay particles are small and electrically charged, so they attract and hold water molecules. Thus, it is important that soils used to grow crops have some clay content. Clay also helps make soil resistant to erosion.

Like clay, silt particles are also small enough to hold water in the soil. But exposed silt washes away easily, taking nutrients with it.

A soil with too much sand content allows water to pass through very quickly and does not hold enough moisture to support most plants. Exposed sandy soils many be subject to erosion if the angle of the land, the slope, it too severe.

Objective: In this lab you will determine the texture of a soil sample.

Procedure:

1.  Spoon enough loose soil from the bucket to fill your tube half full.

2.  Fill the tube to the top with water.

3.  Cap the tube and shake it until all the soil is wet and well-mixed

4.  Label your tube with your initials and place it upright on the lab table.

5.  Allow the tube to settle over night.

1.  Measure and record the amount of sand, silt and clay in centimeters

2.  Calculate the percent sand, silt and clay.

3.  Determine the soil texture using a soil classification triangle.

Formula

% sand (silt or clay) = [depth of sand (silt/clay) layer in mm] X 100

[total depth of soil in mm]

Data Table 1: Percentages of Sand, silt and clay in a soil sample.

Particle Type / Height (centimeters) / % of total sample size
Total / 100%
Sand
Silt
Clay

Data Interpretation: What is the soil texture?

Data Analysis and Conclusion: Answer the following questions in full sentences in your lab notebook.

1.  Compare your results to other groups. Is the soil texture the same or not? Why or why not?

2.  Make a recommendation of the ability of this soil to hold water and resist erosion. Back up your statements with data your group and others gathered in this lab.

3.  Research what type of soil is primarily in Columbia County and describe its ability to hold water and resist weathering.