Soil Texture: When the percentage of sand, silt, and clay is measured, the soil may be assigned a textural class using the USDA textural triangle. Within the textural triangle are various soil textures which depend on the relative proportions of the soil fractions.
![Soil Texture](https://biologyteach.com/wp-content/uploads/2023/05/suvaysgz9lc-1024x683.jpg.webp)
Twelve soil textural classes are recognized, and their compositions are designed on a textural triangle. The class name can be determined by plotting these values on a textural triangle using the following technique:
- Clay; extend the line horizontally from the percent clay (parallel with the triangle’s base, sand).
- Silt; extend the line downward from percent silt at 60° (parallel with the right side of the triangle, clay).
- Sand; extend the line upward from percent sand at 120° (parallel with the left side of the triangle, silt).
For example, if the soil is 50 % sand, 35 % silt, and 25 % clay, the texture is sandy clay loam.
Figure 1. USDA soil textural triangle; indicated example, sandy clay loam: 50 % sand, 35 % silt, and 25 % clay.
How to determine soil texture
- Take about 2 tablespoons of soil in one hand and add water, drop by drop, while working the soil until it reaches a sticky consistency.
- Squeeze the wetted soil between the thumb and forefinger to form a flat ribbon.
- Determine the texture based on the length of the ribbon that can be formed without breaking—see the following table.
Texture | Length of ribbon (mm) | Root growth not restrictedModerately susceptible to mechanical compactionModerate plant available water moderate infiltration rate |
---|---|---|
Sandy | <15 | Root growth is not restricted, but highly susceptible to mechanical compaction and may be hard settingModerate infiltration rateModerate plant available water |
Sandy loam | 15–25 | Slight resistance to root growthHigh infiltration rate low plant available water. |
Loam | 25 | Root growth not restrictedModerately susceptible to mechanical compactionModerate plant available waterLow to the moderate infiltration rate |
Silty loam | 25 | Root growth is frequently restrictedModerately to highly susceptible to mechanical compactionSome restriction on water movement leading to periodic waterloggingModerate to high plant available water |
Clay loam | 40–50 | Root growth not restrictedModerately susceptible to mechanical compactionModerate to high plant available water |
Clay | 50–75 | Root growth moderately to severely restrictedHigh susceptibility to mechanical compactionWater drains very slowly except in self-mulching soils. |
Heavy clay | >75 | Root growth moderately to severely restrictedHigh susceptibility to mechanical compactionWater drains very slowly except in self-mulching soils. |
Read Also:
References and Sources
- https://www.qld.gov.au/environment/land/management/soil/soil-properties/
- https://en.wikipedia.org/wiki/Soil_texture
- https://www.fao.org/fishery/docs/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e06.htm