Soil Ratios and Types

Using the formula below, calculate the percentage of each soil type: sand, silt, or clay present in the soil column of half-pint bottle. Record results on Table 2   Results of   Lab Report .

% sand =     Depth of sand layer in mm.      x  100 %
Total depth of soil in mm.

Determining Soil Type-Texture:   Use Figure 1 to determine the soil type for the sample as follows:
  • Find each percentage on the proper axis of the soil triangle.
  • Follow the dotted lines from each percentage to the point where they intersect inside the soil triangle.
  • Identify soil sample type by identifying the region of the soil triangle that contains the point of intersection.
  • If the dotted lines intersect on the boundary between two regions, assign the soil type of the graph region of greater area.


As each lab group determines the soil type of their samples, students place a mark inside the corresponding region of the soil triangle. Answer the following questions:

  1. Do the marks fall in one area of the triangle?
  2. Which type of soil particle is most common in your region?
  3. Do some samples on the triangle fall outside the main cluster of samples?
  4. Look at the features of the collection site. What factors at the collection site are associated with those types of soil?
  5. Which two soil samples in class could be mixed to obtain the best soil?
  6. Which soil sample will hold the most water?
  7. Which soil sample will be most subject to erosion?