Soil Science

• SOIL SCIENCE- deals with soil as a NATURAL RESOURCE on the surface of earth including soil formation, classification, mapping; physical, chemical, biological and fertility properties of soils per se; and the relationships of these properties in relation to the use and management of soils.
• SOIL -

  a mixture of organic and inorganic materials which developed on the earth's surface through weathering process of rocks and minerals and whose properties are conditioned in various degrees by the influence of climate, living organisms, the topography acting on the parent material over the period of time.
• • Soil - non renewable resource
  • a natural body with dimensions of thickness and width with indistinct horizontal boundaries enabling it to blend with other soils and vertical boundaries of the air above it and the un-weathered rocks below it.
  • medium for plant growth
• Pedon-

  hexagonal column of soil measuring from 1 to 10 sq.m in top surface.
• Polypedon

  • essential soil individual, comprising an identifiable series of soils in an area.
• Polypedon

  • made up of multiple pedons and has a distinctive characteristics that differentiate it from surrounding polypedons.
• APPROACHES IN THE STUDY OF SOIL

  1. PEDALOGICAL APPROACH
  2. EDAPHOLOGICAL APPROACH
• PEDALOGICAL APPROACH greek: pedon, soil or earth

  study of soils with principal interets on characterization and differentation of their properties and with only minor emphasis on their practical use.

  ex: study of soils for their taxonomic classification soil as a natural body.
• EDAPHOLOGICAL APPROACH

  Greek: edaphos, soil or ground

  study of soils with emphasis on their practical use, particularly the relationship of soil properties to plant growth.

  ex: study of soil fertility, variability of soil productivity; methods of conserving and improving productivity
• FIELD OF STUDY IN SOIL SCIENCE

  • SOIL FERTILITY
  • SOIL PHYSICS
  • SOIL CHEMISTRY
  • SOIL MICROBIOLOGY
  • SOIL CONSERVATION AND MANAGEMENT
  • SOIL SURVEY AND CLASSIFICATION
  • SOIL MINERALOGY
  • LAND USE
• IMPORTANCE OF SOIL

  • Nutrient Reservoir
  • Food and Fiber Producer
  • Valuable Natural Resource
  • Reservoir of Biodiversity
  • Carbon Bank
  • Environmental filter
• SOIL SOLIDS

  • MINERAL MATTER, 45%
  • ORGANIC MATTER, 5%
• MINERAL MATTER, 45%

  • comes from the weathering of rocks and minerals
  • composed of sand, silt and clay particles vary among sizes
  • major source of all nutrient elements, (except N, C and O) needed for plant growth
• ORGANIC MATTER, 5%

  • derived from decaying and decayed remains of plants and animals intimately mixed with the mineral matter
  • the chief natural source of nitrogen; indicative of the nitrogen status of the soil
  • contributes P. S and micronutrients but in smaller amounts compared to mineral sources
  • enables the soil to store cations
  • promotes the formation and stabilization of aggregates,, giving the soil permeability and porosity
  • organic soils contain more than 20% organic matter; most soils contain less than 20% organic matter, thus classified as mineral soils
• PORE SPACES

  1. AIR, 20-30%
  2. WATER, 20-30%
• AIR, 20-30%

  • occupies the pore spaces of the soil
  • composed of elemental N (78%), O (20%), carbon dioxide (0.5%), and traces of other gases
  • provides oxygen for respiration of plant roots
• WATER, 20-30%

  • occupies the pore spaces of the soil
  • contains dissolved gases and salts or compounds as well as dissociated ions of various nutrient elements
  • carries the nutrient to the proximity of roots where they can be absorbed
  • serves as a weathering agent of minerals to constantly renew the nutrient supply in the soil
  • needed by plant in large amounts for their metabolic functions.
• ELEMENTAL COMPOSITION OF THE EARTH'S CRUST

  • The outermost portion of the earth
  • Earth's crust: about 16 km depth
  • Soil chemical composition is derived from the earth's mantle
  • Main source of the material from which inorganic soil is derived
• More than 90% on the crust is composed of silicate minerals.
• Most abundant silicates are feldspars (plagioclase (39%) and alkali feldspar (12%).
•  Other common silicate minerals are quartz (12%) pyroxenes (11%), amphiboles (5%), micas (5%), and clay minerals (5%). The rest of the silicate family comprises 3% of the crust. Only 8% of the crust is composed of non-silicates - carbonates, oxides, sulfides, etc.