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Soils and Soil Science

Key Concepts:

Terms in this set (98)

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.
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.