Soils 1 Flashcards
Which tectonic plate is pushing the US and Europe apart?
The Atlantic Ridge
What is soil?
The upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles (minerals).
In situ
On the spot
What are the horizons?
O (hummus or organic material)
A (topsoil)
E (eluviated horizon)
B (subsoil)
C (parent material)
R (bedrock)
What are alluvial deposits?
Soils deposited by moving water
What is the life cycle of rock?
- Basic rock is formed
- Soil develops from basic rock
- Aggregation from weathering over millennia
- Soil gets layered and compressed
- Rock gets pushed back towards the core
Sedimentary rocks
Formed through gradual accumulation of sediment
Ex. Sand on beach, mud in river, coal, chalk, limestone
Igneous rock
Crystallized from a melt or magma
Ex. Obsidian, basalt, granite
Metamorphic rock
Once existed as sedimentary or igneous rock but have been subject to varying degrees of pressure and heat within the earth’s crust
Ex. Slate, marble
What are the main constructive forces of land formation ?
Crustal deformation- crushing of tectonic plates forming mountains
Volcanic eruptions
Deposition of sediment
Inversion of relief
When deposits move higher
Folding
When two of earth’s plates collide (and form mountains)
Faults
When plates collide, the earths crust can fracture and a fault can form. Along the fault line, the rock is being pushed together. Sooner or later, the pressure has to be released and an earthquake happens
Volcanic eruptions
An opening in the earth’s crust that allows molten rock to escape. This molten rock, or lava, cools after it escapes and becomes indigenous rock.
What is the Ring of Fire
path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes. The majority of Earth’s volcanoes and earthquakes take place along the Ring of Fire.
Lithification
Over time, when sediment turns to sedimentary rock. Layers depend on the speed of deposits such as the speed of a river.
What are the destructive forces?
Weathering
Erosion
Weathering
The breaking down of rocks, soil, minerals as well as wood and artificial materials through contact with the earths atmosphere, water, and biological organisms.
Occurs in situ
Ex. Plants, wind, ice, freezing/unfreezing
Erosion
The movement of rocks and minerals by agents such as water, ice, snow, wind, waves, and gravity and then being transported and deposited in other locations.
Mechanical/Physical Weathering
Breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice and pressure.
Accentuated in very cold and very dry environments
Chemical Weathering
The direct effect of atmospheric chemicals or biologically produced chemicals in the break down of rocks, soils, and minerals
What determines the mineral content of a soil?
The parent material; weathering converts primary minerals to secondary minerals (clays, carbonates) which combine with organic material to form soil.
Glacial and alluvial sediments are more fertile because they contain numerous rock types and this a variety of minerals.
What helps develop soil?
Water
Temperature changes
Effects of the atmosphere
1000s of years
Biological events
Microorganisms
Cultivation
What are the 4 basic textures ?
(Stones and gravel > 2mm)
Coarse sand 2-0.2 mm
Fine sand 0.2-0.02mm
Silt 0.02-0.002mm
Clay <0.002mm
What percentage of CHOs are given to the soil microbes?
20%; also helps in binding of root structures
PED
A particle or component of soil structure
CRUMBS
Aggregates of soil components
TILTH
The capacity of soil to stick together
What is the texture between the thumb and forefinger for sand l/silt and clay?
Sand/silt- gritty
Clay- soapy
What does soil texture influence?
Soil structure
Drainage profile
Movement of water
Water holding capacity
Availability of water to plant
Which texture hold less water and drains more quickly?
Coarse particles (sand)
Which texture holds more water but tightly so it is not as available to the plant?
Fine particles (clay)
Which soil texture is chemically active?
Clay; it holds water through electrostatic and ionic forces as well as through small pore size (capillary action)
Why do plant roots need aeration?
To diffuse waste gas and take up oxygen
Reasons a plant might not be taking up water?
There is no water
There is no oxygen (roots die if deprived of oxygen)
There are no roots (disease)
What can limit oxygen to plant roots?
Crumbly soil structure, overwatered pores
Sands have large pores, drain faster, but…
Have very low water holding capacities that may lead to plant stress, will fall apart in your hand, and CAN be improved by organic matter
Clays have small pores and stick in your hands but…
Have low air and water permeability;
ARE improved by organic matter
AND calcium additions
What is the field capacity of soil?
The water left in the soil 48 hours after being saturated; the water the soil can hold against gravity
Why are lime based soils good for viticulture?
They hold water well and drain well
When a vineyard has slopes, what should be considered in concern to water behavior and irrigation ?
Water drains down slopes, often below the surface
Have to be careful the valley does not get too wet
Is a superior vineyard on a convex or concave slope?
Convex; it tends to shed water rather than collect it
Soils in these zones may be deeper due to erosion from higher ground
Convex patterns restrict water availability to vines
If a soil has poor structure, when it is watered, it will…
Form a crust
Have no gaseous exchange
Prevent decomposition of OM
Create a hard pan
Have a yellow-green layer that becomes anaerobic (common- H2S, methane)
What causes water logging?
Limited drainage
Typically, by clays with massive structure and by pans
Surface water logging can be overcome by:
OM
Gypsum
Drainage
Ripping
Deep-rooted cover crops
When is soil damage most likely to occur?
When soil is wet?
What does compaction result in?
Shearing of strata
Reduction of pore size
Fills up pores
Induces ‘flow’ in low strength soils
(More likely to occur when soil is wet)
