GGY 130 1st Edition Lecture 22Soils Part Two-Soil Forming Factors• Geological Factor-Parent material is the main source of rock fragments that make-up the soil-Physical and chemical characteristics influence soil properties-Young soil reflect the rocks or sediments from which they originated; this influence diminishes with time• Climatic Factor-Temperature and moisture significant to soil formation-Chemical and biological processes accelerated by high temperatures and moisture (deepin humid regions and shallow in dry regions)• Topographic Factor-Lowering of top (due to erosion) and bottom (due to rock weathering and plant root extension) of soil-Soil is mostly deep in flat areas and shallow on steep slopes• Time Factor-Soil processes are very slow-From human perception of time, it is a nonrenewable resource-Soil erosions can occur in only a few years-Length of time needed depends on parent material and environmental characteristics• Biological Factor-Plant and animal contributions to soil development-Vegetative roots-Bioturbation -Earthworms are most important• Numerous tunnels• Crumbly surface • Drag leaf litter downward, which fertilizes subsoil-Microorganisms help decompose organic materials in humus-Pedogenic Regimes• Laterization-Brick red-coloured soil-Requires high temperature and annual moisture surplus-Rapid weathering of parent material, dissolution of minerals and speedy decomposition of organic matter -Little humus but adequate nutrients-Latosol: general term for a soil formed by laterization-Soils can be up to tell of feet deep, not good for agriculture• Podzolization-Grey soil (ashy soil)-Found in humid cold mid-latitude climates and coniferous-Boreal forests; limited nutrient requirements-Podizolization soils show strong development of the E horizon• Gleization-Muddy soil-Poor drainage-Slow decomposition rate-Highly organic soil-Too acidic and oxygen poor-Gley soils: general term for soil formed by gleization• Calcification-Where the precipitation is less than evapotranspiration -Calcium carbonate; Hardpan in B horizon-Natural Vegetation here consists of grasses and shrubs• Salinization-In arid/semi-arid-Intense evaporation leaves behind salts; white colour-Salts are toxic to most plants and soil