NRES 201 Lecture 12 Outline of Last Lecture I. Interpretive classification of soilsII. Geographic information systemsOutline of Current Lecture III. Review of Previous CoverageIV. Revisiting TextureV. Soil DensityCurrent LectureReview of Previous Coverage - Soil's basic physical properties:- Coloro Described by hue, value, and chroma- Textureo Size distribution of soil particles- Structureo Arrangement of soil particles to form aggregates or peds- Consistenceo Cohesiveness holding soil particles togetherSoil components:- The soil solidso Inorganic minerals Primary minerals present in the original rock Secondary minerals formed by weatheringo Organic matter Living organisms (biomass) Organismal remains (residues) Decay products (humus)- The soil solutiono Consists of water + dissolved ions, molecules, and gaseso Medium for chemical and biological processeso Vital to plant growthThese 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.o Held within soil pores Mobile in large pores, Immobile in small pores- The soil atmosphere o Consists of gases that occupy soil pores not filled with watero Isolated, not continuous o Differs from ambient air by having Less O2 More CO2 More Humidityo Critical to biological processesTexture:- Particle Size Analysis o Sieve soil to < 2 mmo Removes course particles o Based on Stokes' law, v = kd^2 where - v - the settling velocity k - a constant that depends on water temperature and particular density d - the particle density - Surface area and soil processeso Greater surface area enhances: Water retention - In soil pores or as surface films Adsorption - Surface adhesion of gases or dissolved ions or molecules Weathering - Exposure allows chemical or microbial attack Aggregation - Surface cohesion of soil particles Microbial activity - Microbes colonize surfacesSoil Density:- Density - The weight or mass of an object divided by its volume which is expressed as g/cm^3- Particle density -o The mass per unit volume of dry soil solids o Does not include the volume between particleso Unaffected by - pore space, soil structure, tillage, compaction- Bulk density - o The mass per unit volume of dry
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