5Different compositions of soils: Soil CompositionDifferent compositions of soils:HIGH % Organic MatterLOW % Organic Matter
6Different compositions of soils: Soil CompositionDifferent compositions of soils:HIGH % Air & WaterLOW % Air & Water
7Soil Texture = proportions of different particle sizes U.S. Dept of Agriculture – categories based on amounts of clay, silt and sand.Soil-Texture Diagram (pg 134 Figure 11)Loam has equal parts clay, silt and sand.Loam is best for plant growth.
10Soil Formation Parent Material = source of minerals in soil. Time = how long it took to form the soil.Climate = did it form in dry or wet areas, under hot or cold temperatures, etc.Organisms = what types of organisms are living or dead in the soil.Slope = the angle of the land on which the soil forms.
11Parent Material Who’s the mama? Pg. 135 Figure 12 Residual soil = forms on bedrockformed on top of the parent materialTransported soil = forms unconsolidated soilmoved from parent material to another location.
12Parent Material How did mama affect it? Affects rate of weathering and rate of soil formationUnconsolidated deposits are already weathered some, so they provide more surface area for chemical weathering.Affects the soil’s fertilityMore plant material can grow – more organic matter – better fertility.
13How long did it take to form? TimeHow long did it take to form?The longer it takes to form, the thicker it becomes.As time passes, weathering can reduce the influence of the parent material.
14How did and does “neighborhood” affect soils? ClimateHow did and does “neighborhood” affect soils?Has greatest affect on soil formation.Temperature changes affect rate, depth, and type of weathering.Example: hot, wet climate produces a thick layer of chemically weathered soil.Example: cold, dry climate produces a thin layer of chemical weathered soil.
15How did and does “neighborhood” affect soils? ClimateHow did and does “neighborhood” affect soils?Precipitation influences soil fertility.Climate affects what types and how many animals and plants can live on the soil.Climate can cause similar soils to be produced from different parent materials .
16How does the “family” affect soil? OrganismsHow does the “family” affect soil?Some soils named based on plants living in them.Prairie soil, tundra soil, forest soil, etc.Plants are main source of organic matter.Protozoans decompose organic matter in soil.Burrowing animals stir, pack and move soil.
17SlopeSoils on the edge?Slope varies greatly from location to location.The steeper the slope, the faster the erosion and the less water can soak in.Steep slopes have thin layers of soils or none at all.Flat slopes have thick layers of soils.
18Slope Soils on the edge? The direction a slope faces can affect soils. South-facing slopes receive more sunlight so are warmer and dryer.North-facing slopes receive less sunlight so are colder and wetter.All of these factors work together to affect the formation of soils.
20SOIL PROFILES = shows soil layers and composition of a section of earth. A Horizon“topsoil”loose, partly decayed organic mattermineral matter mixed with organic matterinsects, fungi, worms, microorganisms
21SOIL PROFILES = shows soil layers and composition of a section of earth. B Horizon“subsoil”fine clay washed out of Horizon Asometimes packed into “hardpan” soillower limit of plant roots and burrowing animals.
22SOIL PROFILES = shows soil layers and composition of a section of earth. C Horizonpartially weathered parent materialstill resembles the parent material
23SOIL PROFILES = shows soil layers and composition of a section of earth. Rockparent materialunweathered
24SOIL TYPESThree common types of soil:PEDOCALPEDALFERLATERITE
25SOIL TYPES: Pedalfer Temperate areas receiving > 63 cm/yr Rutherford County, NCB Horizon has lots of iron oxide and aluminum clay.Red or brown color
26SOIL TYPES: Pedocal Areas with grasses and brush vegetation. Western USAB Horizon has lots of iron oxide and aluminum clay.Red or brown color
27SOIL TYPES: Laterite Hot, wet tropical areas. Deeper than other soils. When dry, becomes very hard and almost waterproof.Used in brick-making. Pg 139 Fig 15Red or orange color
28SOIL TYPES: Laterite (cont.) Makes up much of the soil in rainforests.Plants decompose so rapidly in the rainforest there is no organic matter in laterite.Not fertile.
30SOIL EROSION How WATER erodes soil… IMPACT erosion is a physical effect of water on soil.When falling water hits soil it creates a tiny explosion that tosses soil into the air and displaces it.
31SOIL EROSION How WATER erodes soil… This is an erosion bed. It is used to test the affects of running water on different types of soil.Here is the bed BEFORE the water is released.FLOWING water picks up particles of soil and carries them with it.This results in a deposition of soil from its original location to another location downstream.Here is the bed AFTER the water is released.
32SOIL EROSION Rates of erosion… In the past soil erodes more slowly than it does today because more land was covered by plants.
33SOIL EROSION Rates of erosion… Human activities that remove natural vegetation have greatly accelerated erosion.
34SOIL EROSION Rates of erosion… Before humans, rivers carried 9 trillion kg of sediment to the oceans each year.
35SOIL EROSION Rates of erosion… Today rivers carry about 24 trillion kg of sediment to the oceans each year!
36SOIL EROSION Rates of erosion… Excessive erosion causes excessive sediment deposition in rivers.
37SOIL EROSION Rates of erosion… Wind can also carry displace large amounts of soil if the land becomes dry from a severe drought.1930’s Dust Bowl