Often, when mapping soils we note soil consistence, along with soil water content as being useful pieces of information about the soil. Soil Consistence refers to the strength and adhesion of soil particles or how the particles stick together. The strength of a soil varies according to the soil water content.
Soil Consistence is measured as the force required to just break or deform a small soil aggregate, about 20mm in diameter, between the thumb and forefinger.
Soil Science is a very tactile process and this is another example of this.
Footprints appear in the soil, like in the photo, because of the consistence or strength of the soil.
There are a standard set of consistence ratings applied to soils in most soil mapping systems. These Strength Classes and their descriptions are as follows:
- Loose - No force required. Separate particles such as loose sands
- Very Weak - very small force, almost none required.
- Weak - Small but significant force required
- Firm - Moderate or firm force required
- Very Firm - Strong force, but within the power of the thumb and forefinger.
Further categories for Soil Consistence are:
- Strong - Beyond the power of the thumb and forefinger but crushes underfoot on a hard flat surface with small force.
- Very Strong - Crushes underfoot on a hard, flat surface with full body weight applied slowly
- Rigid - Cannot be crushed underfoot by full body weight applied slowly.
The soil’s ability to hold a footprint relates to the soil’s moisture content and consistence.
