Understanding Soil Texture Classification Quiz

Soil Classification

• Soils can be classified into 12 textural classes or grades, including sand (85% sand or more), loamy sand (75-85% sand), coarse-textured soils, sandy loam (43-52% sand), loam (less than 52% sand, 7-27% clay, 28-50% silt), silt loam (less than 50% silt), medium-textured soils, clay loam soils, sandy clay loam, silty clay loam, sandy clay, and fine-textured soils.

Soil Texture Determination

• Soil texture can be determined in three ways: by feel method, roll method, and by mechanical analysis.
• The feel method involves rubbing moist soil between the fingers to estimate the characteristic "feel" of the dominant soil separate.
• The roll method involves kneading a moist soil sample into a rod to approximate the soil texture.
• Mechanical analysis is a more accurate method that involves separating soil particles into different size fractions.

Soil Properties

• Soil properties can be classified into three categories: physical, chemical, and biological.
• Physical properties of soils include soil texture, color, consistency, temperature, structure, densities and porosity, and water/soil moisture and aeration.

Soil Separates

• Soil particles can be grouped into three soil separates: sand, silt, and clay.
• Each separate has a specific range of particle sizes, and they are often referred to as fractions (e.g., sand fraction, silt fraction, or clay fraction).
• The characteristics of each separate affect the overall properties and behavior of the soil.

Characteristics of Soil Separates

• Sand: low water-holding capacity, good aeration, high drainage rate, low compactibility, and low surface area.
• Silt: medium to high water-holding capacity, moderate aeration, slow to medium drainage rate, medium compactibility, and medium surface area.
• Clay: high water-holding capacity, poor aeration, very slow drainage rate, high compactibility, and high surface area.