APES Unit 4 Flashcards
(101 cards)
what is soil?
a mix of geological and organic components
soil components
⇨ sand, silt, clay
⇨ humus - main organic part of soil
⇨ nutrients - ammonia, nitrate, phosphates, etc.
⇨ water and air
⇨ living organisms - bacteria, worms, fungi
why is soil important?
⇨ medium for plant growth
⇨ carbon storage
⇨ filters water
⇨ habitat for organisms
⇨ breaks down organic material and recycled nutrients.
weathering
How?
breaking down of rocks into smaller pieces
- physical (wind, rain)
- biological (roots of trees)
- chemical (acid rain, moss, lichen)
erosion
transport of weathered rock fragments by wind, rain carried to new location and deposited.
soil formation from below
weathering of parent material produces smaller fragments that make up geological part of soil (sand, silt clay, minerals)
soil formation from above
⇨ breakdown of organic matter
⇨ erosion deposits soil particles from other areas.
effects on soil formation
parent material
topography
climate
organisms
effects on soil formation parent material
soil pH, nutrient content
effects on soil formation topography
steep slope = too much erosion
more level ground = deposition
effects on soil formation climate
warmer = faster breakdown of organic matter
more precipitation = more weathering, erosion and deposition
effects on soil formation organisms
soil organisms like bacteria, fungi, worms break down organic matter and mix up the soil
soil horizons O layer
Organic layer is layer of organic matter on top of soil provided nutrients and limits H2O loss
soil horizons A layer
top soil is a layer of humus and minerals with the most biological activity
soil horizons b layer
sub soil is lighter layer below topsoil, mostly sand, silt and clay some nutrients
soil horizons c layer
substratum is least weathered soil, composed of rock fragments no organic material
Soil degradation
the loss of the ability to support plant growth
loss of topsoil
tilling (turning soil) & loss of vegetation disturb soil and make it more easily eroded
loss of topsoil dries out soil, removes nutrients and soil organisms that recycle nutrients
compaction
compression of soil by machines (tractors) grazing, lifestock (cows), and humus reduces ability to hold moisture
- dry soil erodes more easily
- dry soil supports less plant growth, less root structure, leading to more erosion
nutrient depletion
repeadingly growing the same crops on the same soil removes key nutrients (N, P, K, Na, Mg) over time
- reduces ability to grow future crops
soil particles
geological portion of soil biggest to smalles
sand>silt>clay
soil texture
the % of sand silt and clay in soil
always adds up to 100% EX 40-40-20 = 40 sand 40 silt 40 clay
less compact soil vs compact soil
sand is bigger it has bigger pores (less compact) this allows water and air to eneter soil easily
clay has smallest pores wo its harder for air and water to enter heavy clay soils
porosity
the pore space within a soil