soils Flashcards
geologic definition of soil
earth material that has been altered to support rooted plant life
engineering definition of soil
earth material that can be removed without blasting
soil horizons in order from top to bottom
O, A, E, B, C
O horizon?
- most organic materials including decomposing plant material
- dark brown/black
A horizon?
- organic materials and clay
- minerals and organics
- light black/brown
- moves clay and materials to B horizon
E horizon?
- clay and less organics
- light-colored materials from clay leaching
B horizon?
- ions precipitate to form new materials
- rich in clay, iron oxides, silica, carbonate, leached materials
- slightly reddish due to oxidation
C horizon?
- transition to substrates
- partially altered parent material
- usually stained red with iron oxides
why do soils have color?
indicates presence of water and organic materials
- more organic material = darker
- zone of leaching = lighter
- presence of clay and iron oxides = redder
what do changes in color indicate about drainage?
- well-drained and aerated = red
- poorly drained = yellow
how do soils become fertile?
soil fertility: capacity of soils to support nutrients needed for plant growth
hydraulic conductivity?
measure of ability of particular material to allow water to move through it
when did sediment yields peak in the piedmont region and what caused it?
peaked in ~1960-1963 due to construction phase of urbanization which increased runoff and erosion
how does agricultural soil erosion influence the amount and fertility of soil?
- temporarily increase fertility due to artificial fertilizers
- can expose and dry topsoil
- using too many nutrients can lower fertility
methods of combatting agricultural soil erosion
- contour plowing
- no-till agriculture
- terracing slopes
- planting more than one crop
