A triangle graph is used to show the relationship between three different components. It consists of three axes, divided into 100 intervals representing percentage values, forming an equilateral triangle. Lines are drawn at angles of 60° from each axis. This type of graph is usually used to show soil composition data (Fig. 15.9), but they have other applications including population analysis.
To read triangle graphs: start with the left axis, find the value and then moving in an anticlockwise direction find the values along the other two axes. Figure 15.9, for example, shows the respective compositions of two soil samples, A and B.
CHECK YOUR LEARNING
Study Figure 15.9 and calculate the composition of soils C and D. SOIL A
SOIL B
Component Clay Silt
Sand %
30 15 55
Component Clay Silt
Sand %
75 5
20 SOIL C
Component Clay Silt
Sand % SOIL D
Component Clay Silt
Sand % 40 30 20 A Clay loam D Loam 90 Silt loam Silt 10
