Given a soil monolith or two-dimensional vertical sketch of a soil, identify the following: soil profile, soil solum, A horizon, B horizon, C horizon, R horizon, parent material, regolith, soil pedon, surface soil, and subsoil. -Parent material (rock) being to weather the primary silicate minerals, then undergo chemcial decomposition.
-This forms secondary silicate minerals that are called secondary silicate clays.
-This gives soluble bases. Soluble amounts of silica or salic acid. Slightly soluble components of iron, aluminum, oxides and hydroxides.
-In the weathering process that goes from rocks into soils, where we get secondary silicate clays, it releases bases and some silica.
-As a result, soils derived from rocks will be lower in bases than the original rock.
-Expect a decrease in the amount of potassium, sodium, calcium, magnesium in the soil as compared to the original rock.
-The aluminum and iron, the oxides and hydroxides are very insoluble, they tend to build up in the soil compared to the original rock.
-Most of the time there will be a slight loss of silica, very young soils may not lose any.
Parent materials - developing from residum (dead rock), dead rock weathers to give residum, residum is the material from which the soils develop
Modes of transportation -
1. Gravity - colluvium
2. Water - 3 types of water transported materials
a. Alluvium materials - From running waters of rivers or streams, well grated, will contain mostly the same particle size type materials because energy from water will just carry the grains of minerals the same time the sediment is deposited of the same particle size.
Materials deposited very close to the stream channels will be coarser textured than those materials that are deposited the same distance from the stream channel, where the energy of the water will be slow and contain primarily clays.
b. Marine parent material - Accumulated material from oceans, will contain sediments that are fine grain because the energy from the ocean will be low as compared to rivers and streams.
c. Lacustrium parent material - From the bottom of the lake, will contain sediments that are fine grain because the energy from the lakes will be low as compared to rivers and streams. (Silt or clay)
3. Ice - glacial materials, as the glaciers melt, they drop material which is referred to as glacial till. Glacial till will become the parent material, hasn't been sorted by any type of action of water or wind. Can be boulder, gravel, to clay sized.
4. Wind - eolian material, sand-sized particles. If they are silt sized they are referred to as loess, they are highly sorted materials. Accumulated plant debris, is organic matter.
Igneous rock - granite (will contain the more acidic types of minerals such as quartz, potassium fledspar and hornblende) and basalt (fine grain, more basic rock, which will contain larger amounts of hornblende, micas, calcium feldspar)
Sedimentary rock - limestone (of marine origin and contain high amounts calcium carbonate or calcium carbonate and calcite and dolamite and some impurities, the calcite and dolamite dissolve to leave behind the impurities, most of those impurities are silicate clays) , sandstone (formed by burial of sandy material, generally high in quartz), shale (composed of silicate clays, where silicate clays are deposited and later decompresed by deeper burial, when shale is uplifted to the surface it will form soils that are finely textured because the large amount of silicate clays)
Metamorphic rock - marble (forms from limestone that has been put under deep pressure and high temperatures, it is also high in calcite and dolamite, forms from the impurities), slate (shale, which is underground heating and deep burial), schist (soils that are high in micas and has undergone metamorphisis)
Define these terms - texture, structure, consistence, aggregate, bulk density, particle density, porosity, soil colloid, primary particle, secondary particle, loam. Combination of factors, 2 things need to happen, clay needs to be floculated, in order to floculate, cations on the clay surfaces need to be Ca, Fe, Al, Mg because they are good at floculating clays.
Clays which have sodium on the exchange sites have a lesser degree of potassium generally stay in a much more dispersed condition and will not form good structure and will not floculate.
Structure almost always requires some clay being present.
Once the clay floculates, physical activity such as freezing and thawing, wetting and drying, things that change the wetness content of the soil add to the formation of structure.
Freezing is a drying mechanism, as well as the extraction of water by roots, both of these cause clay floculates to shrink.
This shrinkng process causes the particles to be bound tightly together.
OM provides the energy of microorganisms, they in turn produce microbial gums and produce organic matter that is absorbed to the soil surfaces and cause the aggregates to stay together.
In some systems, oxides and hydroxides may also act as cementing agents to stabalize the structural units.
Structural types -
1. Granular: also called chrome, contains small structure units which will contain more OM, largest amount of pore space (A horizon that have high amounts of OM, occasionally found in upper part of B horizon)
2. Blocky: strong angles between the sides resulting in sharp angles (angular blocky structure) - A horizons and in surface soils, B horizons
3. Subangular blocky structure - can have rounded or subrounded, has less clay (A horizons and in surface soils, B horizons)
4. Plate-like: horizontally arranged on a horizontal plane, more compacted (E horizon)
5. Prismatic: flat top, clay (B horizon), non-rounded tops
6. Columnar:soil structure that has relatively high amounts of sodium on the surfaces of the clays, long axis perpendicular to the soil horizons (B horizon). have rounded tops
Structureless conditions - massive
Single grain - sandy material (no clumping or forming of aggregates because of insufficient amounts of clay to hold the sand together)
Grade: weak, moderate, or strong
Plastico structure (size) - very fine, fine, medium, coarse, or very coarse
Comeplete description: Grade ---> size ---> type
Ex. Weak, coarse, subangular blocky
Subsoils will contain structures that will break apart. Ex. Prismatic structures, which is composed of angular plots or subangular plots, which make even smaller plots of each (compound structures)
Hue: 10 R, 10.5 R, 5 YR, 7.5 YR, 10 YR, 10.5 Y, 5 Y
(Reddest - yellowest - greenest)
--->Hue is the page itself, and is made up of the dominant wavelength that is reflected from the soil
Value: found on each individual page or each individual hue, found in the vertical direction going from darkest to lightest. Quality of light that is reflected. Value of 2 to 8 on a page. 2 is very dark colored soil and 8 is a very light colored soil.
Chroma: is a measure of dullness to brightness (purity of the reflected light). Arranges on a page from 0 to 8, a very dull soil is 0, a bright soil is 8.
Mottle: is a splotch or dash of color different from the background color. Soils have a matrix color which is the background color and then there may be a color that contrasts with the matrix color that is described as the mottle color. This contrast in color between the 2, is a result of oxidation-reduction reactions in the soil. Oxidized colors are reds and yellows. Reduced colors are greens, greys, and blues. Each of these are caused by differences in the oxidation state between Fe and Mg in the soil.
Example: Color description of soil - 10YR 54 ---> with hue of 10 YR, value of 5, and chroma of 4
This is a color that would be described as yellowish-brown, found in color chart. OM makes the soil darker, wet soils are darker than dry soils. The more OM, the lower the value.
Iron an in oxidized state, ferric iron state, may be present as an oxide (Fe2O3, hematite, gives the soil a red color) or hydroxide (goethite, will give a yellow color)
Iron in the +2 state, the ferrous state, it will give off a grey, blue, or green color depending on the degree of reduction. A system where oxygen is highly limited in the +2 state, referred to as reduced condition where O will not be present.
Abundance of quartz grains, calcite, gypsum are soluble salts, causes the soils to be light in color.
Soil aeration: refers to how well air will move from the atmosphere into the soil and also soil air will move from the soil to the atmosphere. The process of which air in the soil is replaced by air from the atmosphere. Therefore, the more carbon dioxide it will contain and the less oxygen the soil air will contain. A well aeriated soil is said to have sufficient amounts of oxygen for the metabolic processes.
Mass flow: refers to the movement of air from one place to another. May account for wind moving from one place to another. Mass flow does not influence the movement of soil air or atmospheric air into the soil.
Diffusion: the rate at which gases move due to differences in partial pressure or differences in concentration. Since soil air is generally depleted, then oxygen enters the soil, diffusion due to the differences in concentration between atmospheric air and soil air. Soil air generally has much higher levels of CO2, so CO2 diffuses from the soil air to atmoshperic air.
Oxygen diffusion rate (ODR): the rate at which oxygen is able to move from the atmosphere to a secure level within the soil. The greater the differences in oxygen to the air, the greater the diffusion rate, unless there is restriction in amount of pores available for the movement. When pores are full of water, there is no good pathway for oxygen to move from the atmosphere into the soil air, diffusion rate would drop rapidly.
Oxidation reduction potential (Eh): refers to the avalability of oxygen in the soil to the environment. The lower the amount of oxygen that is avaliable to oxidize in the soil, then the lower the oxidation reduction potential is within the soil. All the oxygen could be completely depleted, so electrons would need to be accepted by something else, such as, N or S. Low Eh, refer to the soil in a reducing condition.
Define the following words of phrases: adhesion of water, cohesion of water, capillarity, drainage water, available water, field capacity, saturation percentage, satiation percentage, wilting coefficient, percent water by mass, volumetric water content, gravimetric water content, soil water potential, soil moisture tension (SMT) or soil suction, saturated flow, unsaturated flow, and water table.