NRES 201 Lecture 3 Outline of Last Lecture I What is soil II Soil Components III Functions of soil IV Soil as an environmental interface Outline of Current Lecture II Introduction to soil physical properties III Soil color IV Soil texture V Soil structure VI Soil consistence Current Lecture I The basic properties a Color described by hue value and chroma b Texture size distribution of soil particles c Structure arrangement of soil particles to form aggregates or peds d Consistence cohesiveness holding soil particles together II Importance of soil physical properties a Direct effects on i Water storage and flow ii Aeration iii Temperature b Indirect effects on i Plant species suitability and growth ii Nutrient availability iii Pollutant transport iv Erosion v Tillage and compaction vi Engineering applications home road construction III Soil Color a Hue Dominant spectral colors which varies by chart b Value Lightness or darkness of the grayscale mask applied to the hue It decreases vertically from pure white 10 to pure black 0 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 IV V VI VII c Chroma Intensity or brightness of the hue which increases toward the right where the hue is brightest d Range in soil color From nearly black to nearly white i Variation with landscape position profile depth and ped aeration Factors affecting soil color a Organic matter content i Dark coatings on mineral surfaces b Water content i Lowers color value c Presence of iron and manganese oxides i Well drained soils are bright red or brown high chroma ii Poorly drained soils are gray or bluish low chroma Soil Texture a Range of particle sizes From boulders to fine clay b Particle size groups i Sand Feels gritty individual particles visible to the naked eye rounded or angular composed mainly of quartz very low in specific surface area does not cohere to form aggregates no stickiness or plasticity low capacity to store water and nutrients ii Silt Feels silky like flour individual particles invisible to the naked eye low in specific surface area highly susceptible to wind and water erosion iii Clay Individual particles invisible to the naked eye sticky and plastic when wet hard and cloddy when dry tiny pores limit water movement and aeration Changes in soil texture a A very slow process during soil formation and weathering b Artificial changes not feasible on a field scale i Would require a massive input of soil with a different texture ii Adding sand to a fine textured soil can produce concrete c Textural management more feasible for a gold green or athletic field Structural grade and size a Grade refers to the distinctness of the peds i Strong moderate or weak b Class refers to their size i Smallest size limits for spheroidal or plate like structure ii Largest size limits for prism like structure
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