Chapter 11: Soil Resources
Chapter 11: Soil Resources GEOL 1005
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This 4 page Class Notes was uploaded by Kerrigan Unter on Monday October 19, 2015. The Class Notes belongs to GEOL 1005 at George Washington University taught by Brown, C in Summer 2015. Since its upload, it has received 16 views. For similar materials see Environmental Geology in Geology at George Washington University.
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Date Created: 10/19/15
GEOL 1005 Chapter 11 Soil Resources 11 What Soil Resources Are Soil is an essential resource for life Dirt that plant grow in Medium for growing plants the loose surface material developed by weathering and a foundation materials for structures Mixture of mineral particles of varying size and organic matter of varying composition Soil play many roles in the environment Supporting the plants that provide us with food and fiber Cleaning and storing water Recycling waste Providing habitat for diverse forms of life Transferring matter among Earth systems Soil both cleans and stores water Sewage sludge from community treatment facilities can be used as a fertilizer Biosolids treated sewage sludge Soil has a high biodiversity Contains bacteria fungi protozoa arthropods and worms Soil is a membrane that connects Earth systems Photosynthesis by plants is the main process that provides carbon to soils 112 How Soils Form Soils are dynamic natural materials Soil life aids weathering Humus organic matter that accumulates in shallow parts of soil giving it a dark color Horizons stratified layer with a soil Climate topography and the nature of underlying parent materials can strongly in uence the rates and end results of soil development Soil profile layered sequence of horizons Climate directly in uences the physical and chemical weathering processes that form soils Aspect orientation of a slope with respect to the rays of the Sun Slope soil materials are susceptible to erosion Soil orders categories of soil variations Spodosols cool moist coniferous regions acidic and have a surface accumulation of humus that is combined with aluminum and iron oxides or hydroxides Aridisols arid regions low concentration of organic matter Adhesion attraction of water to mineral grain surfaces Capillary action wicking process Biological soil crust composed of cyanobacteria mosses and lichen Mollisols in grasslands thick and darkcolored from the accumulation of organic material from plant roots very fertile Oxisols laterites in warm wet tropical forests deeply weathered soils that have been leached of much of their original mineral content 113 Soil Properties Texture density structure shear strength and compressibility Texture is determined by grain size Granular soils break into small pieces Block soils break into large pieces Platy soils break into small platy pieces Prismatic soils break unto elongate blocks Density the mass of soil per unit volume Density depends on the type of solid material and on the proportion of voids porosity in the soil Shear strength measure of how well the soil resists forces before fracturing internally Compressibility measures how a soil compacts under applied forces Compositional properties of soil Air and water in its pores pH amount of nutrients available to plants Moisture content amount of water in a soil pH measure of acidity 7 is natural less than 7 is acidic greater that 7 is basic nutrient content amount of nutrients in soil Protozoa mobile organisms in soil Fungi stationary organisms that absorb food from their surroundings Worms help recycle nutrients I soil Arthropods churn soil helping improve soil structure and making nutrients more available to plants Soil quality capacity to sustain plant growth and animal productivity maintain or enhance water or air quality and support human health and habitation Highquality soils have a diverse biology control water ow and water character facilitate interactions among Earth systems and store matter involved in Earth system cycles 114 Soil Degradation and Loss Erosion causes soil loss People contaminate soils deplete its biodiversity and nutrients and cover it up or otherwise change it by their land uses Topsoil organic and nutrientrich soil Soil is susceptible to erosion where vegetation cover is removed Wind erosion is more likely in arid regions Erosion also occurs under wet conditions when soil is exposed to rain and surface runoff water Rills small streamlets Sheet ow thin nonchannelized overland ow Rills and sheet ow are mostly responsible for soil erosion on cropland Deforestation Salination contamination of soil by salt Irrigation can lead to salination Fertilizers cab ne a source of both pathogens and toxic elements in soil 0 Pesticides contain many manufactured chemicals 0 Biomagnification process Where chemicals become more concentrated in individual organisms as they are passed up the food chain 115 Sustaining Soil Resources 0 Sustainable farming practices Contour farming Terracing Tilling fields When storms are not likely Machinery that aerates plants and weeds field Without greatly churning the soil Cultivation crops is parallel strips Planting barriers that protect fields from Wind Rotation different crops Reducing tillage and adding organic waste 0 Bioremediation technology that uses natural or enhanced microbial action in the soil 0 degrade contaminants o Phytoremediation use of plants to remove contaminants from soil