Question

what is the percentage of sand, silt, and clay in soil with the texture indicated in the following figure:

Explanation:

Step1: Analyze the soil texture triangle axes

The triangle has three axes: percent sand (bottom axis, 0 - 100 from right to left), percent silt (right axis, 0 - 100 from top to bottom), and percent clay (left axis, 0 - 100 from bottom to top).

Step2: Locate the red square (Clay region)

The red square is in the "Clay" region. To find percentages:
- **Percent sand**: Follow the horizontal line (parallel to silt - clay axis) from the point to the sand axis. The sand axis at the bottom: the point aligns with 10% sand (since from 100 (sand = 0) to 90 (sand = 10), the point is at sand = 10).
- **Percent silt**: Follow the line parallel to sand - clay axis to the silt axis. The silt axis (right) shows 10% silt (from 0 (silt = 100) to 10 (silt = 90), no, wait: the silt axis is labeled "Percent silt" with 0 at the top (near clay vertex) and 100 at the bottom (near sand - silt vertex). Wait, correction: the three vertices are: top vertex (0 sand, 0 silt, 100 clay), bottom - left (100 sand, 0 silt, 0 clay), bottom - right (0 sand, 100 silt, 0 clay). So for a point in the triangle, the sum of sand + silt + clay = 100.
- For the red square (Clay region):
- Sand: From the bottom axis (sand), moving from right (0 sand) to left (100 sand), the point is at sand = 10 (since at the bottom axis, the x - coordinate for sand: the bottom axis has 0 (right) to 100 (left). The red square's horizontal projection (parallel to silt - clay edge) to sand axis: the sand axis at the bottom, between 0 (right) and 100 (left). The point is at sand = 10 (because the distance from the right (sand = 0) is 10 units? Wait, no. Let's use the three - phase diagram rule: in a soil texture triangle, each side is a percentage axis. The "Clay" region is near the top (clay vertex). So:
- Clay: The left axis (percent clay) goes from 0 (bottom) to 100 (top). The red square is at clay = 80 (since from bottom (clay = 0) to top (clay = 100), the point is at 80% clay).
- Sand: The bottom axis (percent sand) goes from 0 (right, at silt - sand vertex) to 100 (left, at sand - clay vertex). The horizontal line (parallel to silt - clay edge) from the point to the sand axis: the sand axis at the bottom, the point's sand percentage is 10% (because the distance from the sand - clay vertex (left bottom) is 10 units? Wait, no. Let's calculate: sand + silt + clay = 100. If clay = 80, and from the diagram, the point is in clay, so sand and silt are low. Looking at the axes:
- Sand: The bottom axis (sand) has labels 0 (right, silt - sand vertex), 10, 20, ..., 100 (left, sand - clay vertex). The red square's projection to sand axis (horizontal line, parallel to silt - clay edge) is at sand = 10 (since it's 10 units from the sand - clay vertex? No, the sand - clay vertex is at sand = 100, clay = 0, silt = 0. Wait, I think I mixed up the axes. Let's re - orient:
- Vertex A: Top (Clay): sand = 0, silt = 0, clay = 100.
- Vertex B: Bottom - left (Sand): sand = 100, silt = 0, clay = 0.
- Vertex C: Bottom - right (Silt): sand = 0, silt = 100, clay = 0.
- For any point (x, y, z) in the triangle, x = sand, y = silt, z = clay, x + y + z = 100.
- The red square is in the Clay region (near Vertex A). To find x (sand), y (silt), z (clay):
- From Vertex A (0,0,100), moving towards Vertex B (100,0,0) is the sand - clay edge (silt = 0). Moving towards Vertex C (0,100,0) is the silt - clay edge (sand = 0).
- The red square: to find sand (x), draw a line parallel to silt - clay edge (which is the edge between Vertex A and Vertex C, direction: constant sand, varying silt and clay? No, parallel to silt - clay edge (sand = 0) would be a horizontal line (in the diagram) towards the sand axis (bottom - left). Wait, the diagram's bottom axis is sand (from 0 (right, near Vertex C) to 100 (left, near Vertex B)). The right axis is silt (from 0 (top, near Vertex A) to 100 (bottom, near Vertex C)). The left axis is clay (from 0 (bottom, near Vertex B) to 100 (top, near Vertex A)).
- So for the red square:
- Clay (z): left axis, from bottom (0) to top (100). The red square is at z = 80 (since it's 80% up the left axis from bottom to top).
- Silt (y): right axis, from top (0) to bottom (100). The red square's projection to right axis (parallel to sand - clay edge) is y = 10 (10% up from top to bottom on right axis).
- Sand (x): since x + y + z = 100, x = 100 - y - z = 100 - 10 - 80 = 10.

So sand = 10%, silt = 10%, clay = 80%.

Answer:

Sand: 10%, Silt: 10%, Clay: 80%