Soil Formation and Topography: Interactions and Impact on Soil Properties, Study notes of Agricultural engineering

Download Soil Formation and Topography: Interactions and Impact on Soil Properties and more Study notes Agricultural engineering in PDF only on Docsity! The five factors of soil formation • Climate • Organisms • Topography/relief • Parent Material • Time Soil = f (cl,o,r,p,t) Topography as an Influence on Soil Formation – terms to know • Relief • Aspect • Elevation (steep vs. flat) (slope faces N,S,E,W) (link to climate, organisms) Effect of Topography on Soils Position Summit Shoulder Backslope Footslope Toeslope % OC in A horizon Thickness of A (cm) Texture of A 4.0 1.5 lowest 3.0 4.5 5.5 highest 15 6 lowest 10 18 25 highest si l l si l si c lMost clay si c l Most clay data from an E. Colorado grassland pH 7.0 7.2 Landscapes and Soil Properties • Theoretical landscape models may be used to evaluate soil spatial variation • Landscapes and landscape components display systematic differences in soil properties as soil forming processes are modified by relief The five component hillslope model of Ruhe and Walker (1968) characterizes landscapes according to discordance in slope and slope shape. Components of Hillslopes • Backslope - linear slopes, surface and subsurface transport of soil and water • Footslope - concave slopes, additions of moisture through surface and subsurface flow • Toeslope - concave to linear slopes, deposition of soil and organic material, high water table Water Movement on Landscapes • The distribution of water on slopes has a fundamental control on the nature of soils. • Water movement integrates soils existing on different parts of the landscape and is governed by a complex set of interrelated landscape properties. Water movement across landscapes is governed by • external variables - rainfall duration and intensity • intrinsic properties - soil texture, vegetation type, slope form and angle shoulder Topographic Gradient Summit Shoulder Backslope Footslope O C (g c m -2 m -1 ) 0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 0.0 1.0 2.0 nd sis nd ss nd shale chey wells goodland oberlin hockley Parent Material Gradient Topographic Gradient 0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 1.0 2.0 nd sis nd ss nd shale Moisture Gradient Summit Shoulder Backslope Footslope O C (g c m -2 m -1 ) 0.2 0.4 0.6 0.8 1.2 1.4 1.6 0.0 1.0 chey wells goodland oberlin