Module 5: Principles of Soil Quality 2 Flashcards
soil at saturation
Soil pores are filled with water
Water drains from pores with gravity
soil at field capacity
Soil pores are approximately half filled with water and half filled with air
Water does not drain with gravity - accessible to plant roots
soil at permanent wilting point
Soil pores primarily contain air
Water is unavailable to plants
does soil water holding capacity increase or decrease with increasing sand content?
decreases
macropores
low surface area
micropores
high surface area
holds onto more water and drains slowly
what explains soil behavior and reactivity?
Pore size
and surface area
what happens when a soil is at saturation?
water drains freely from the large pores. And this water drains with gravity. Once the
gravitational water moves out of the larger soil pores, the soil has reached field capacity
what does soil texture determine?
the soil’s capacity to hold water
how do you determine plant available water?
Once we subtract the amount of water
remaining at permanent wilting point from the water stored at field capacity, we get an estimate
of plant available water. As a result, the water holding capacity of the soil is greater than the
water available for plants.
what factors influence plant available water?
pore size
What factors/soil properties determine water holding capacity?
pore space
Which soil textural class has the highest water holding capacity?
clay
Which soil textural class has the highest plant available water?
loam
CEC is a function of what?
minerology and surface area
highly organic soils, more than 20% organic matter content
Histosols
recently formed alluvial soils, no B horizons, least oil profile development
entisols
must have spodic horizon within 2 m of soil surface, accumulation of sesquioxides
spodosols
high base saturation of more 50%, soft grassland dark soils
mollisols
also known as red clay soils, low nutrient status, common in subtropical regions
ultisols
has a large amount of roots and decaying organic matter
horizon A
has lost fine particles due to leaching and eluviation
horizon E
accumulates the fine particles such as organic matter/clay that move down the soil profile
horizon B
