Soil Triangle

A soil triangle, also known as a texture triangle or soil texture triangle, is a tool used by soil scientists to determine and describe the texture classification of soil based on its proportions of sand, silt, and clay. The soil triangle is a graphical representation that helps in identifying the textural class of a soil sample by plotting the percentage of these three components.

Structure of the Soil Triangle:

1. Axes:
   • Base (Horizontal Axis): Represents the percentage of sand in the soil sample.
   • Left Side (Vertical Axis): Represents the percentage of clay.
   • Right Side (Diagonal Axis): Represents the percentage of silt.
2. Triangles and Lines:
   • The triangle is divided into regions, each representing a different soil textural class such as clay, silty clay, sandy clay, clay loam, silty clay loam, sandy clay loam, loam, silt loam, silt, sandy loam, loamy sand, and sand.
   • Lines within the triangle guide you to the correct region based on the proportions of sand, silt, and clay.

Using the Soil Triangle:

1. Determine Percentages:
   • Measure or estimate the percentages of sand, silt, and clay in your soil sample. The total should add up to 100%.
2. Plotting:
   • Locate the percentage of sand on the base (horizontal) axis.
   • Locate the percentage of clay on the left (vertical) axis.
   • The percentage of silt can be inferred since the sum of sand, silt, and clay is 100%.
3. Find the Intersection:
   • Move horizontally from the sand percentage, vertically from the clay percentage, and diagonally for silt to find where they intersect within the triangle.
4. Identify the Texture Class:
   • The region where the three lines intersect represents the soil texture class (e.g., loam, clay, silt, etc.).

Example:

• Suppose you have a soil sample with 40% sand, 30% silt, and 30% clay.
  • Start with the 40% mark on the sand (horizontal) axis.
  • Move from the 30% mark on the clay (vertical) axis.
  • The intersection typically falls into the “Clay loam” region of the triangle.

Important Note:

• Accurate estimation of sand, silt, and clay percentages may require specific laboratory tests such as the hydrometer method or sieve analysis.

Using the soil triangle is essential for agronomists, geologists, and environmental scientists as it helps determine soil properties crucial for agricultural practices, construction, and ecological studies.