NRES 201 Lecture 10 Outline of Last Lecture I The benefit of taxonomy II Soil orders III Lower level taxonomic categories Outline of Current Lecture IV Soil spatial variability in the field V Techniques and tools for mapping soils VI Making a soil survey VII Using soil surveys Current Lecture Soil Variability Geographic context o Soils are inherently heterogeneous in a multitude of properties and even at a micro scale o Vertical variability profile characteristics v Horizontal variability land management Small scale soil variability o Linked to topography thickness of parent material layers vegetation differences o Within a farm field or across a residential lot Landscape scale soil variability o Topography is a key factor o Drainage differences form a catena Sequence of soil types down a slop Moderate drainage on top Best drainage on slope Poorest drainage at bottom o Never linked to land use for cropping or construction o A drainage catena defines a soil association group of individual soils that comprise a recurring landscape pattern Regional scale soil variability o Primary controlling factors climate vegetation o Secondary controlling factors parent material Techniques and Tools for mapping soils These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 The soil pit a Still the heart of soil mapping b Excavation by hand or with a blackhoe 2 Soil auguring a Standard practice in soil mapping b Making borings in strategic locations i By transect sampling relative to topography and vegetation c Hydraulic probes can also be used 3 GPS a Global Positioning System b At least four satellites accessible from any point c Precise determines position by timing satellite signals 4 Ground Penetrating Radar a Detects contrasting subsurface soil layers i By measuring reflectance of downward directed electromagnetic waves b Eliminated the need for manual borings and their expense c Unsuitable for some soils due to interaction of moisture salt and clay 5 Air Photos a Used as base maps for soil surveys i Soil boundaries drawn directly on black and white ortho photographs that reveal buildings roads and streams 1 Corrected for optical distortion 2 Digital photos used for new surveys b Source of supplemental soil information i Dark tones indicate moist high organic matter surface soil ii Vegetation may be linked to soil type iii Drainage patterns usually reflect soil type and parent material 6 Satellite Imagery a Generated by computer processing of digital data from multispectral scanners b Spectral scanning of different bands can identify Vegetation types surface soil properties landform features water
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