Chapt 1

• Soil


  A mixture of organic and inorganic materials formed from the weathering of rocks and minerals and whose properties are conditioned in various degrees by the influence of climate, living organisms, and relief acting on parent material over a period of time
• Soil


  • Natural and dynamic body formed on the land surface
  • Made up of porous mixture of inorganic and organic materials
  • Composition and properties influence the growth of plants

  
• Factors influencing soil properties

  • Climate
  • Living organisms
  • Relief
  • Parent material
  • Time
• Importance of soil


  • Supports the growth of plants
  • Controls the fate of water in the hydrologic system
  • Functions as nature's recycling system
  • Provides a habitat for soil organisms
  • Engineering medium for infrastructure
  • Source of food, clothing, shelter, and medicines

  
• Soil science


  Deals with the study of soil as a natural resource on the surface of the earth which includes soil formation, classification and mapping, physical, chemical, biological and fertility properties in relation to the management for crop production
• Fields of specialization in soil science

  • Soil chemistry
  • Soil mineralogy
  • Soil microbiology
  • Soil physics
  • Soil fertility
  • Soil genesis
• Edaphological approach


  Study of soil in relation to higher plants, soil properties vs plant growth, variability of soil productivity, methods of conserving and improving productivity

  
• Pedological approach


  Origin and classification of soils, soil as a natural body
• Soil components


  • Mineral matter (45%)
  • Organic matter (5%)
  • Soil air (20-30%)
  • Soil water (20-30%)

  
• Mineral matter


  Extremely variable in size (sand, silt and clay)
• Organic matter


  Consists of a wide range of organic (carbonaceous) substances including living organisms, carbonaceous remains of organisms, and organic compounds produced by current and past metabolism in the soil
• Soil air


  The amount and composition of air in a soil, occupies those soil pore spaces not filled with water, generally has higher moisture content and higher CO2 content than the atmosphere
• Soil water


  Also called soil solution, contains hundreds of dissolved organic and inorganic substances, serves as constantly replenished dilute nutrient solution, acts as a universal solvent, nutrient carrier, and nutrient in itself, stabilizes soil temperature
• Approximate composition of soil: 50% solid (45% inorganic, 5% organic), 25% liquid, 25% gas
• Composition of the Earth's crust: Oxygen (46.6%), Silicon (27.7%), Aluminum (8.1%), Iron (5.0%), Calcium (3.6%), Magnesium (2.1%), Sodium (2.8%), Potassium (2.6%)
• Essential mineral elements and their available forms

  • Macronutrients: Nitrogen (NO3-, NH4+), Phosphorus (H2PO4-, HPO4=), Potassium (K+), Calcium (Ca++), Magnesium (Mg++), Sulfur (SO4=)
  • Micronutrients: Manganese (Mn++), Iron (Fe++), Boron (BO3-3), Zinc (Zn++), Copper (Cu++), Molybdenum (MoO4=), Chloride (Cl-)
• Essential nutrient criteria: Plants cannot complete their life cycle in the absence or deficiency of any one of the nutrient elements, the nutrient is an integral component of a plant structure and/or participates in one or more metabolic processes in the plant, no other element can substitute for that element if it is absent or lacking in supply