Soil Science Fundamentals

Soil Texture

• Refers to the proportion of sand, silt, and clay particles in the soil
• Classified into three main categories:
  1. Sandy soil: high sand content (>50%), coarse, well-draining, and often lacks nutrients
  2. Silty soil: high silt content (20-50%), moderate drainage, and holds more nutrients than sandy soil
  3. Clay soil: high clay content (>50%), fine, poor drainage, and often retains more nutrients
• Texture affects soil's water-holding capacity, aeration, and nutrient availability

Soil Structure

• Refers to the arrangement of soil particles into aggregates or clusters
• Classified into four main categories:
  1. Granular structure: well-aggregated, porous, and allows for good water infiltration
  2. Blocky structure: moderately aggregated, moderate porosity, and moderate water infiltration
  3. Prismatic structure: poorly aggregated, low porosity, and poor water infiltration
  4. Platy structure: very poorly aggregated, very low porosity, and very poor water infiltration
• Structure affects soil's water-holding capacity, aeration, and root growth

Subsoil

• The layer of soil below the topsoil, typically 10-20 cm deep
• Often has a different texture and structure than the topsoil
• May have a higher concentration of minerals and nutrients
• Plays a crucial role in water filtration and storage

Topsoil

• The uppermost layer of soil, typically 5-10 cm deep
• Rich in organic matter, nutrients, and microorganisms
• Supports plant growth and is essential for agricultural productivity
• Often has a higher pH and water-holding capacity than the subsoil

Soil pH

• A measure of the soil's acidity or alkalinity
• Ranges from 0 (very acidic) to 14 (very alkaline), with 7 being neutral
• Most plants grow best in a slightly acidic to neutral soil pH (6.0-7.0)
• pH affects nutrient availability, microbial activity, and plant growth

Bedrock

• The solid, unbroken rock that underlies the soil
• Can be composed of various types of rock, such as granite, basalt, or limestone
• Affects soil formation, drainage, and fertility
• Can influence soil pH, nutrient availability, and plant growth