APBI 200 Lecture Notes - Lecture 5: Filo, Soil Texture, Silt
Document Summary
Sand (0. 05-2mm: visible, angular/rounded, single grain, gritty, non-reactive. Clay (<0. 002 mm: not visible to eye, high specific surface area, hold h2o nutrients, reactive, behave as colloids. Intermediate: not visible, gritty, flour like -> reflect light. Particle size and shape: sand grains: spherical, clay particles: flat. Total porosity in a fine textured soil > total porosity of a coarse textured soil. Primary minerals in sand and silt size fraction (don"t need to know: quartz-> sio2, feldspars, mica, pyroxene, amphiboles, olivine, primary minerals are formed by cooling of magma. Secondary minerals in clay size fraction: phyllo(layered, sheet like)silicates, silicate clay minerals, carbonates (limes): soluble, sulfates: soluble, oxides/hydrous oxides of iron and aluminum: old, environ, amorphous clay minerals (aluminosilicates): no crystal structure, form from weathering of primary minerals. Relationship btw particle size and kinds of minerals. Types of soil colloids (diameter <0. 001 mm: phyllosilicate clay minerals, oxides and hydrous oxides of fe and al (gibbsite, hematite, goethite, amorphous minerals (allophane, imogolite, organic colloids.
