Soil Composition and Texture

• Soil is composed of mineral particles, organic matter, water, and air
• Texture refers to the proportion of sand, silt, and clay in the soil
• Structure describes the arrangement of soil particles into aggregates
• Color can indicate mineral composition and organic content
• Density affects porosity, water infiltration, and root penetration
• Porosity determines water-holding capacity and aeration
• Water content influences plant growth and soil strength
• Temperature affects biological activity and seed germination
• Soil strength is the ability of soil to resist deformation
• Electrical conductivity indicates the amount of salts in the soil

Soil Texture

• Sand particles are the largest, ranging from 0.05 to 2.0 mm
• Silt particles are medium-sized, ranging from 0.002 to 0.05 mm
• Clay particles are the smallest, less than 0.002 mm
• Loam is a balanced mixture of sand, silt, and clay
• Textural triangle is used to classify soil types based on the percentage of sand, silt, and clay

Soil Structure

• Granular structure consists of small, rounded aggregates
• Blocky structure consists of irregular, cube-like aggregates
• Prismatic structure consists of tall, pillar-like aggregates
• Platy structure consists of thin, horizontal plates
• Single-grained structure consists of individual particles with no aggregation
• Structure affects aeration, water infiltration, and root penetration

Soil Color

• Munsell color chart is used to describe soil color
• Hue indicates the dominant spectral color (e.g., red, yellow)
• Value indicates the lightness or darkness of the color
• Chroma indicates the intensity or purity of the color
• Dark colors often indicate high organic matter content
• Red colors often indicate the presence of iron oxides
• Gray or bluish colors often indicate poor drainage

Soil Density

• Bulk density is the mass of dry soil per unit volume
• Particle density is the mass of solid particles per unit volume
• Porosity is the percentage of soil volume occupied by pores
• High bulk density indicates low porosity
• Compaction increases bulk density and reduces porosity
• Density affects water infiltration, aeration, and root penetration

Soil Water

• Saturation is the state when all soil pores are filled with water
• Field capacity is the amount of water held in the soil after excess water has drained away
• Wilting point is the soil moisture content at which plants can no longer extract water
• Available water is the difference between field capacity and wilting point
• Infiltration is the process by which water enters the soil
• Percolation is the movement of water through the soil

Soil Temperature

• Soil temperature affects seed germination, root growth, and microbial activity
• Mulch can insulate the soil and moderate temperature fluctuations
• Dark-colored soils warm up faster than light-colored soils
• Soil moisture content affects soil temperature
• High soil temperatures can damage plant roots
• Freezing and thawing can affect soil structure

Soil Strength

• Cohesion is the attraction between soil particles
• Adhesion is the attraction between soil and other surfaces
• Soil strength affects root penetration and erosion resistance
• Compaction increases soil strength
• Moisture content affects soil strength
• Dry soils are generally stronger than wet soils

Soil Electrical Conductivity

• Electrical conductivity (EC) measures the amount of salts in the soil
• High EC indicates high salinity
• Salinity can inhibit plant growth
• EC is measured in deciSiemens per meter (dS/m)
• Leaching can reduce soil salinity
• Soil amendments can help to reduce salinity

Explore the components of soil: mineral particles, organic matter, water, and air. Understand soil texture by examining sand, silt, and clay proportions. Learn how to classify soil types using the textural triangle.