SoilSci

• Pedological approach


  The soil is considered as a natural body with major emphasis on properties related to its genesis and classification as it occurs in its environment. The information gathered by the pedologist would be of interest to road and building contractors or highway engineers.
• Edaphological approach


  Study of soil in relation to higher plants. Considers the physical, chemical and biological properties of the soil as they relate to crop production. The information gathered by the edaphologist would be of interest to farmers, agriculturists and foresters.
• 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 physics
  • Soil fertility
  • Soil microbiology
  • Soil conservation and management
  • Soil chemistry
  • Soil survey and classification
  • Soil genesis
  • Soil mineralogy
• Soil physics


  Deals with the study of the physical properties of soils in relation to plant growth, their measurement and analyses. Characteristics, processes, or reactions of a soil caused by physical forces.
• Soil fertility


  Deals on the study of the inherent capacity of the soil to supply nutrient elements and their availability, evaluation of soil fertility status, use of fertilizer and other soil amendments. Quality of a soil to provide optimum level of nutrients for plant growth.
• Soil microbiology


  Deals on the study of major groups of soil microorganisms, their ecology and microbial activities in relation to soil fertility. Soil biochemical reaction carried out primarily by microorganisms.
• Soil conservation and management


  Deals with the study of soil deterioration and its control, maintenance and improvement of soil fertility and productivity.
• Soil chemistry


  Deals with the study of the nature and composition of soils, physico-chemical properties and reactions, chemical processes and ionic equilibria and study of submerged soils. Interactions of solid, liquid, and gaseous phases or components of soil.
• Soil survey and classification


  Deals with the study of soil formation, horizon differentiation, natural and comprehensive system of classification, mapping and soil survey reports. Referred to as pedology when combined with soil classification.
• Soil genesis


  Covers factors and processes of soil formation. Bridges chemistry, physics, geology, biology, climatology, geography, anthropology, and agriculture.
• Soil mineralogy


  Deals with structural chemistry of the solid components of soil.
• Components of soil


  • Air
  • Water
  • Mineral matter
  • Organic matter
• Mineral materials


  Constitute 45% of the total soil volume. Composed of small rock fragments and minerals of various kinds. Extremely variable in size (sand, silt and clay).
• Sand


  0.02-2.0 mm; feel gritty when rubbed between the fingers; not sticky.
• Silt


  0.002-0.02 mm; feels smooth but not sticky even when wet.
• Clay


  < 0.002 mm; adhere together to form sticky mass when wet and hard clods when dry; others are colloidal particles which can be seen with the aid of electron microscope.
• Rock fragments


  Remnants of massive rocks from which the soil have been formed by weathering. Variable in sizes from large to smaller rock fragments.
• Soil organic matter


  Constitutes about 5%. Consists of a wide range of organic (carbonaceous) substances including living organisms (the soil biomass). Carbonaceous remains of organisms which once occupied the soil, and, organic compounds produced by current and past metabolism in the soil.
• Groups of organic matter

  • Original tissue and its partially decomposed equivalent which constitute undecomposed tops and roots of higher plants
  • Humus which is the most resistant products of decomposition derived from those synthesized by microorganisms and those modified from the original plant tissue. It is usually black or brown in color and is colloidal in nature.
• Importance of organic matter

  • Promotes granulation of mineral particles largely responsible for the loose, easily managed conditions of productive soils
  • Influences soil properties, and consequently on plant growth
  • Increases the amount of water a soil can hold and the proportion of water available for plant growth
  • Major soil source of the plant nutrients and the primary source of nitrogen for most plants
  • The main food that supplies carbon and energy to soil organisms
  • Increases nutrient holding capacity of the soil
• Soil Water


  Sometimes called soil solution because it contains hundreds of dissolved organic and inorganic substances. An important function of the soil solution is to serve as a constantly replenished dilute nutrient solution bringing dissolved nutrient elements (e.g. Ca. K. N. and P) to plant roots. Soil water acts as universal solvent, nutrient carrier, and nutrient in itself. It also stabilizes soil temperature.
• Soil Air


  The amount and composition of air in a soil is determined to a large degree by the water content of the soil. The air occupies those soil pores not filled with water. Soil air differs from atmospheric air in several aspects.
• Crystalline aluminosilicates


  One of the clay fractions.
• Non-crystalline Aluminosilicates


  One of the clay fractions, also called amorphous clays.
• Hydrous Oxides of Fe and Al


  One of the clay fractions.
• Only about half the soil volume consists of solid material (mineral and organic); the other half consists of pore spaces filled with air or water.</b>
• Of the solid material, 45% is mineral matter derived from rocks of the earth's crust; only about 5% is consists of organic matter.</b>
• The mineral particles present in soils are extremely variable in size ranging from 2 mm (sand particles) to smaller than .0002 mm in diameter (clay particles). The smaller particles (<0.001 mm) of clay (and similar-sized organic particles) have colloidal properties and can be seen only with the aid of an electron microscope.</b>
• Soil fertility


  Refers to the quality of a soil that enables it to provide essential chemical elements in quantities and proportions adequate for the growth of specified plants.
• Soil productivity


  Refers to the capacity of a soil for producing a specified plant or sequence of plants under a specified system of management. Productivity emphasizes the capacity of a soil to produce crops and should be expressed in terms of yields.
• Productive soils should be fertile but not all fertile soils are productive.
• Minerals


  Inorganic (nonliving) substances that are homogenous, have a definite composition, and have characteristic physical properties such as shape, color, melting temperature, and hardness. Naturally occurring chemical element or compound formed as a product of inorganic processes.
• Rocks


  Aggregates of one or more minerals; most commonly, two or more minerals.
• Classes of rocks


  • Igneous-cooled molten rock: originate from magma, a hot fluid mass or rock melt
  • Sedimentary-sediments deposited in water and consolidated (made into a hardened mass of rock); consolidated fragments of igneous and/or metamorphic rocks
  • Metamorphic-igneous or sedimentary rocks changed by heat or pressure (hardened or changed minerals orientations) or chemical solution; chemically and/or physically transformed (metamorphism) igneous or sedimentary rock by means of heat and/or pressure.
• Intrusive igneous rocks


  Magma near the surface, but not expelled, cools more slowly and forms plutonic or intrusive igneous rocks comprised of large crystals. Intrusive rocks is the result of crystallization from a magma that did not reach the earth's surface.
• Extrusive igneous rocks


  Volcanic or extrusive igneous rocks include those igneous rocks that reached the earth's surface in a molten or partly molten state. Lava flows that pour from a vent or fracture in the earths's crust tend to cool and crystallize rapidly resulting in finer grain size; if cooling is rapid, resulting rock may be a glass.
• Igneous rocks based on grain size


  • Coarse-grained (phaneritic) - results in slow cooling of magma at great depths (ex. Granite, diorite, gabbro)
  • Fine-grained (aphanitic)- results in rapid cooling of molten materials (ex. Rhyolite, andesite, basalt)
• Igneous rocks based on mineral composition

  • Felsic/silicic (acidic)- increasing silica content (-75% SIO2), light colored (ex granite and rhyolite)
  • Intermediate- considered neutral; total silica content of 50-65% (ex. Diorite and andesite, quarte, feldpar)
  • Mafic (basic)- decreasing silica content; dark-colored (45% SiO2) (ex. Gabbro and basalt)
• Soils developed from acid igneous rocks are normally sandy or contain fairly large amounts of free quartz and are lower in nutrient contents than soils developed from basic igneous rocks.