NRES 201 1nd Edition Exam 1 Study Guide Lectures 1 13 Introduction What is soil and how is it important Soil is the surface layer of the earth supporting plant life How has soil exploitation led to erosion Soil erosion has been caused by mismanagement When and where did the Dust Bowl occur The Dust Bowl occurred in the 1930 s in the eastern and mid western states and then in the southern plains What were black blizzards They first appeared in 1935 from early March to April 14th Black Sunday and was severe through 1938 Due to it there has been a serious loss of valuable topsoil drastic decline in wheat and cattle output health hazard and abandoned farms and refugees What has been the major type of soil erosion in Illinois The damage has been done by water not wind Soils Soil Properties Where does soil occur and what are the two principal constituents Soil is the upper part of the Earth s crust composed of mineral and organic matter and formed by the interaction of the five soil forming factors What are the fve soil forming factors Climate organisms topography parent material time What is the solum and how does it differ from the regolith Which horizons are included Solum consists of three horizons layers O organic A plow layer B subsoil The C horizon is parent material but not yet soil and is not included in solum Regolith is O A B C How does texture differ from structure Texture is the proportion of particles by size Sand coarse Silt medium Clay fine Structure is the aggregation of soil particles which is important to soil air and water movement as well as root growth How is organic matter content important to soil properties and processes Organic matter content has many important effects on soil physical chemical and biological properties including aggregation of soil particles water storage and availability microbial energy source and nutrient supplying power What is the soil solution and where in the soil does it occur The soil solution is water dissolved ions molecules and gases It is held within the soil pores mobile in large pores but immobile in small pores What is the soil atmosphere and how does it differ from ambient air Soil atmosphere is when gases occupy soil pores that are not filled with water It differs from ambient air by having less O2 more CO2 and more humidity What is a typical composition of a loam surface soil Mineral 45 Air 20 30 Water 20 30 Organic 5 What are the six functions of soil 1 Medium for plant growth 2 Regulator of water supplies 3 Waste recycling systems 4 Habitat for soil organisms 5 Engineering medium 6 Atmospheric modifier Which three nutrient elements are not supplied by soil minerals Carbon Hydrogen Oxygen What is the pedosphere and how is it important The pedosphere is soil and it is the outermost layer of the Earth where soil forms and life begins How are hue value and chroma represented by the Munsell system They all deal with color Hue is the dominant spectral colors which vary by chart Value is the lightness or darkness of the grayscale mask applied to the hue which decreases vertically from pure white 10 to pure black 0 Chroma is the intensity or brightness of the hue What effect does organic matter have on soil color Organic matter content means the soil color will have dark coatings on mineral surfaces What are the size ranges for sand silt and clay Sand 0 05 2mm Silt 0 002 0 5mm Clay 0 002mm What is meant by the term loam A mixture with equal properties of sand silt and clay How do the textural classes differ in sand silt and clay content Sand Feels gritty rounded or angular very low in specific surface area Silt Feels silky like flour Low stickiness and plasticity Clay Sticky and plastic when wet hard and cloddy when dry Tiny pores to limit water movement and aeration What are the different types of soil structure and where do they occur in the profle 1 Structureless Single grained massive loose sand or dust very large clods and difficult to break 2 Spheroidal Granular or crumb prominent in surface soils under grassland key role of organic matter 3 Plate like Horizontal peds or plates found in surface and subsurface horizons 4 Block like Angular sharp edges or sub angular rounded usually found in B horizons good for drainage aeration and root growth 5 Prism like Columnar rounded tops or prismatic flat tops usually found in B horizons most common in arid and semiarid regions What soil properties affect consistence Soil consistence is a qualitative property which is affected by soil moisture content It is completely characterized when evaluated for dry moist and wet soils Soil Formation What is the original source of parent material for soil formation Rocks What are the four soil forming processes Transformations Chemical or physical changes in soil constituents Destruction or synthesis Translocations Movement of materials within or between horizons Water is the transporting agent Additions From external sources Ex Fallen plant leaves sloughed off roots Losses To the external environment Ex Leaching to groundwater erosion What are the major mineral groups that make up rocks Igneous rocks Originate from molten magma below the Earth s crust and forms by the cooling of volcanic lava Sedimentary rocks Formed from igneous rocks Sediments settle under water and recement and is the dominant type of rock Metamorphic rocks They are formed from igneous or sedimentary rocks under extreme temperature and pressure What are the two most abundant elements in the Earth s crust Oxygen and Silicone How does residuum differ from colluvium and alluvium Residuum Derived from rock that weathers in place and has no transporting agent It is often the parent material for older soils Colluvium It is material moved by gravity and deposited at the base of steep slopes They are poorly developed and often lack horizons Alluvium It is material deposited by flowing water Where would you expect to fnd Alluvial fans Formed by sudden descent in stream flow that deposits sediment at the base of a slope They are often highly fertile and prone to flooding Deltas Formed at the mouth of some rivers as sediments deposit from slow moving water It is an extension of the floodplain Lacustrine deposits Freshwater lakes Lacustrine soils are layered fine textured and poorly drained Which parent materials were transported by glaciers Glacial till Which parent materials would qualify as eolian deposits Dune sand loess aerosolic dust volcanic ash Which parent materials are the