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• 6 KEY ROLES OF SOIL TO ECOSYSTEM:

  • SUPPORTS PLANT GROWTH

  • REGULATE WATER SUPPLIES

  • RECYCLE RAW MATERIALS

  • MODIFY THE ATMOSPHERE

  • HABITAT FOR SOIL ORGANISMS

  • ENGINEERING MEDIUM
• The vertical section exposing a set of horizons in the wall of such a pit is termed a SOIL PROFILE.
• COMPONENTS OF SOIL:

  MINERAL MATTER

  ORGANIC MATTER

  WATER

  AIR
• The proportion of particles in these different size ranges is described by soil texture. Terms such as sandy loam, silty clay, and clay loam are used to identify as it.
• Minerals that have persisted with little change in composition since they were extruded in molten lava (e.g., quartz, micas, and feldspars) are known as PRIMARY MINERALS.
• Other minerals, such as silicate clays and iron oxides, were formed by the breakdown and weathering of less resistant minerals as soil formation progressed. These minerals are called SECONDARY MINERALS and tend to dominate the clay and, in some cases, silt fractions.
• SOIL STRUCTURE describes the way these building blocks are associated together in aggregates of various sizes and shape.
• SOIL pH is a logarithmic scale used to express the degree of soil acidity or alkalinity
• SOIL ORDER

  ALFISOLS

  ANDISOLS

  ARIDISOLS

  ENTISOLS

  GELISOLS

  HISTOSOLS

  INCEPTISOLS

  MOLLISOLS

  OXISOLS

  VERTISOLS

  ULTISOLS

  SPODOSOLS
• Minerals that have persisted with little change in composition since they were extruded in molten lava (e.g., quartz, micas, and feldspars) are known as PRIMARY MINERALS.
• MINERALS - are naturally occurring inorganic element

  -inorganic substance that occurs in nature with distinct physical & chemical properties

  -consists of 2 or more elements in chemical combination
• ROCKS - naturally occurring & coherent aggregate of one or more minerals
• Silicate clays and iron oxides, were formed by the breakdown and weathering of less resistant minerals as soil formation progressed. These minerals are called SECONDARY MINERALS
• FACTORS AFFECTING SOIL FORMATION:

  PARENT MATERIAL

  TOPOGRAPHY

  CLIMATE

  TIME

  VEGETATION
• CAUSES OF SOIL DEGRADATION:

  • MISMANAGEMENT OF FORESTS & FARMS BY EROSION

  • ACCUMULATION OF SALTS IN IMPROPERLY IRRIGATED SOILS

  • POLLUTION

  • CONTAMINATION OF SOIL WITH TOXIC SUBSTANCES
• WEATHERING - breaks up rocks and minerals, modifies or destroys their physical and chemical characteristics, and carries away the finer fragments and soluble products.
• DARK-COLORED MINERALS - contains iron and magnesium and therefore are easily weathered
• IGNEOUS ROCKS - formed from molten magma

  -composed of such primary minerals

  -made up of interlocking crystals and are usually very hard to break
• IGNEOUS ROCKS

  • INTRUSIVE/PLUTONIC - igneous rocks formed inside the Earth

  • EXTRUSIVE/ VOLCANIC - formed outside or on Earth's surface
• SEDIMENTARY ROCKS - formed through accumulation and compaction of minerals or organic matter

  -most common type of rock covering 75% of the Earth's surface
• METAMORPHIC - formed when an existing rocks is subjected to very high temperature or very high pressure
• PHYSICAL WEATHERING -breakdown of rocks & minerals into smaller particles without altering it's composition

  -happens near the Earth's surface influenced by wind, air & temperature
• PHYSICAL WEATHERING

  SALT CRYSTALLIZATION

  ABRASION

  FREEZING & THAWING

  EXFOLIATION

  ROOT EXPANSION

  VOLCANIC ERUPTION

  FROST WEDGING
• CHEMICAL WEATHERING

  HYRDROLYSIS

  OXIDATION-REDUCTION REACTION

  HYDRATION

  ACID REACTION
• HYRDROLYSIS - water molecules split into their hydrogen and hydroxyl components, and the hydrogen often replaces a cation from the mineral structure. A simple

  example is the action of water on microcline, a potassium-containing feldspar.
• ACID REACTIONS - weathering is accelerated by the presence of acids, which increase the activity of hydrogen ions in water
• OXIDATION-REDUCTION REACTION - Minerals that contain iron, manganese, or sulfur are especially susceptible to this reactions
• PARENT MATERIAL - The nature of it profoundly influences soil characteristics
• CLIMATE - the most influential of the four factors acting on parent material because it determines the nature and intensity of the weathering that occurs over large geographic areas .
• TOPOGRAPHY - relates to the configuration of the land surface and is described in terms of differences in elevation, slope, and landscape position—in other words, the lay of the land.
• O HORIZON - comprised of organic horizons that generally form above the

  mineral soil or occur in an organic soil profile. They derive from dead plant and animal residues.
• A HORIZON - topmost mineral horizons, generally contain enough partially decomposed organic matter to give the soil a color darker than that of the lower horizon
• E HORIZON - zones of maximum leaching or eluviation to wash out clay, iron, and aluminum oxides, which leaves a concentration of resistant minerals, such as quartz, in the sand and silt sizes.
• B HORIZON - materials have accumulated, typically by washing in from the horizons

  above, a process termed illuviation

  -deposited minerals & metal salts
• C HORIZON - is the unconsolidated material underlying the solum (A and B

  horizons). It may or may not be the same as the parent material from which the solum formed.
• R LAYER - consolidated rock, with little evidence of weathering
• SOIL HORIZON - horizontal layer of soil approximately parallel to land surface
• C horizon material that retains some of the structural features of the parent rock or geologic deposits from which it formed is termed SAPROLITE
• SOIL TAXONOMY - provides a hierarchical grouping of natural soil bodies. The system is based on soil properties that can be objectively observed or measured, rather than on presumed mechanisms of soil formation

  -"taxis" = arrangement; "nomia" =method
• 2 TYPES OF PARENT MATERIAL

  RESIDUAL PARENT MATERIAL

  TRANSPORTED PARENT MATERIAL