Soil Texture Triangle Lesson Plan

Instructor: Josh Corbat

Josh has taught Earth Science and Physical Science at the High School level and holds a Master of Education degree from UNC-Chapel Hill.

Use this lesson plan to introduce students to the soil texture triangle. Students will read a text lesson about the soil texture triangle, practice using the tool with multiple examples, and explore the composition of soil through a hands-on activity.

Learning Objectives

After this lesson, students will be able to:

  • use the soil texture triangle to determine the composition of a type of soil.
  • determine soil types based on multiple variables using the soil texture triangle.


60-90 minutes

Curriculum Standard

  • HS-ESS2-6.

Develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere.


  • Color copies of the text lesson Soil Texture Triangle: Definition & Use. If printing in black and white is a better option, it may be difficult for students to interpret the included soil texture triangles. If you are unable to print the lesson in color, it may be a good idea to highlight important dots and lines with colored pencils or highlighters. This can also be done as a demonstration using the electronic lesson projected on a screen.
  • Optional: extra copies of the soil texture triangle for students to mark up.
  • Small bags of dried black beans, pinto beans, and kidney beans. (For the simulation, any small objects can be used as long as they consist of three distinct types, so marbles or even candy can work if you are unable to find beans.)
  • Small paper cups holding a random number of each type of bean - will be best to divide the beans into the cups ahead of time.


  • To begin the lesson, ask students to think about everything they know about soil. Give them a minute or two to write down their thoughts. Then ask them to share their prior knowledge and write pertinent items on the board.
  • Next, ask students to think about what soil is made of. This may be a bit of a challenge, so ask students to pair up and discuss this question.
  • Distribute the text lesson Soil Texture Triangle: Definition & Use.
  • Ask students to read the Introduction and the first section, 'The Soil Texture Triangle.' Discuss the following as a group:
    • What is the soil texture triangle?
    • What can the soil texture triangle be used for?
    • Why might it be important to identify types of soil?
  • Next, ask students to read the next section, 'Reading It.' When they have finished, give them a type of soil and ask them to individually determine the amount of each component (silt, clay, and sand) the soil type might have. (Note: In this activity, each component will have a range, so it might be useful to have students determine the range of each.) The following are two sample responses for this brief activity:
    • Loam: 28-50% silt, 8-27% clay, 25-52% sand
    • Sandy clay: 0-20% silt, 35-55% clay, 45-65% sand
  • Next, students will explore the soil texture triangle in the inverse direction. Ask students to read the remainder of the lesson. When they are finished, ask a volunteer to talk the class through finding out which type of soil contains the following:
    • 5% sand, 60% silt, 35% clay (answer: silty clay loam)
    • 70% sand, 25% clay, 5% silt (answer: sandy clay loam)

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