what is soil. what is soil???? the relatively thin surface layer of the earth’s crust consisting...
TRANSCRIPT
What is Soil
What is SOIL????The relatively thin surface layer of the Earth’s crust consisting of mineral and organic matter.
Soil is not DIRT!
Q: What’s the difference between soil and dirt?
A.Location, location, location!
Dr. Greg Pillar, Queens College
The 5 Soil-Forming Factors
• climate (water, wind, temperature)
• biology (macro- and microorganisms, plants)
• relief (topography)
• parent material (rocks/minerals)
• time
Which is the MOST important??CLIMATE!!!
Formed from parent material (bedrock) that’s slowly broken down through
weathering processes.
What is Soil?How would you describe soil?
Color• Texture
Dr. Greg Pillar, Queens College
Texture
Soil Composition
Water (~25%)
Air (~25%)
Mineral(~45%)
Humus (~5%)
Mineral matter comes from parent material
Air & Water percents are interchangeable
Humus is organic matter!
Soil Composition continued…
Mineral Matter– Provides nutrient
minerals for plants– Provides pore space
for water & air
Older soils are:– More weathered– Lower in certain
essential nutrient minerals
Humus: black/dark brown organic material remaining after
decomposition– Leaf litter, animal dung, & decaying organisms– Increases the soil’s water-holding capacity by
acting like a sponge
Soil Composition continued…
As water infiltrates the soil, it can carry dissolved materials with it.
Leaching: Removal of dissolved materials from the soil by water percolating downward
Illuviation: Deposition of leached material in lower layers– Some substances completely leach out
of the soil because they’re so soluble that they migrate right down to the groundwater.
Observe this Observe this SOIL PROFILESOIL PROFILE through soil through soil
Soil layers are Soil layers are horizonshorizons and and assigned lettersassigned letters
O: Organic materialO: Organic material (may be absent)(may be absent)
A: A: TopsoilTopsoil - Organic - Organic material & mineral material & mineral grainsgrains
E: Leached zoneE: Leached zone (may be absent)(may be absent)
B: B: SubsoilSubsoil – rich in – rich in clay, iron, aluminumclay, iron, aluminum
C: Weathered bedrockC: Weathered bedrock
R: Bedrock R: Bedrock (parent material)(parent material)
Soil Color – Variation by Geography
Red soils: Southeast US
Dr. Greg Pillar, Queens College
Soil Color – Variation by Geography
Brown/black soils: Midwest
Dr. Greg Pillar, Queens College
http://www.scienceclarified.com
Soil Color – Variation by Geography
White (gypsum) sands: New Mexico
Dr. Greg Pillar, Queens College
Soil OrganismsEx: bacteria, fungi, algae, microscopic worms, protozoa, plant roots, insects, earthworms, moles, snakes, groundhogs, etc.
Soil organisms provide several Ecosystem Services (important environmental functions).– maintaining soil fertility– preventing soil erosion– breaking down toxic materials– cleansing water– affecting atmospheric composition
Earthworms & Ants: – Cycle minerals– Aerate the soil– Decomposing corpses
contribute organic matter– Assist plants in
reproduction by burying seeds
Mycorrhizae– Symbiotic relationship
between fungi and the roots of vascular plants
– Fungus absorbs nutrients from the soil, and provides it for the plant.
– Plant produces food (photosynthesis), and provides it for the fungus.
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Physical Soil
PropertiesPHYSICAL properties:Texture (%sand, silt, clay)
Porosity & PermeabilityIonic Charge
Texture is determined by its % sand, silt, and clay.
Texture determines the type of soil, and the soil’s properties.
Physical Property: Texture
Loam: ideal for
agricultural soil
Fine Texture - Clay
https://www.soils.org/lessonsDr. Greg Pillar, Queens College
Course Texture - Sand
https://www.soils.org/lessonsDr. Greg Pillar, Queens College
Soil TextureThe relative portions of sand, silt, and clay-sized particles
Sand: 2.0 – 0.05 mm
Silt: 0.05 – 0.002 mm
Clay: < 0.002 mm
Dr. Greg Pillar, Queens College
B
Soil Texture Diagram PracticeWhat type of soil has:1. 20% clay, 40% silt, 40% sand2. 40% clay, 10% silt, 50% sand3. 30% clay, 60% silt, 10% sand
Find the % of each particle at:
1. A2. B3. C
A
C
60%clay, 20%silt, 20%sand
30%clay, 40%silt, 30%sand
10%clay, 30%silt, 60%sand
(1) Loam(2) Sandy clay(3) Silty clay
loam
Property Sand Silt Clay
Water holding Low Med-high High
Aeration Good Med Poor
Nutrient supplying Poor Med-high High
Pollutant Filtering Low Med High
Why is Soil Texture Important?
Physical Characteristics (review)
Why would 100% sand be undesirable for plants?Why would 100% clay be undesirable for plants?
Answer SAND / SILT / CLAY for the following:– A soil with a lot of _____ would have good drainage,
but poor nutrient-holding characteristics.– A soil with a lot of _____ would have poor drainage,
but good nutrient-holding characteristics.– A soil with a lot of _____ would have low porosity.– A soil with a lot of _____ would have high
permeability.
Two soil cores
Bottom of corecontains filter
paper and cheese cloth
Demonstration
Two unknownliquids
Pollutant #1
Pollutant #2
Demonstration
Liquids passedthrough soil
cores
Leachate collected below
What will you observe?
Demonstration
What happened to the original liquids?
What does a change or no change
in color mean?
To what extent did the soil contribute to
this change?
Soil Soil
Adsorption of Organic Dyes
S+
N
NN
Cl-
O
SO
O
HO
OH
Cl
Cl
Chlorophenol red
Methylene blue
CR-
MB+
Soil
CR-
CR-
CR-
CR-
MB+
MB+
MB+MB+
MB+
MB+
MB+
MB+MB+
MB+
Chemical Property: Acidity
Most soil pH is 4-8. Plants are happiest at 6-7. Plants are affected by soil pH.(1) The solubility of certain nutrient minerals varies
with differences in pH• Low pH = Al & Mn are more soluble, and can be
absorbed in toxic amounts.• High pH = some salts are less soluble, and are less
available to the plants.(2) Soil pH affects the leaching of nutrient minerals.
• Acidic soil = positively charged ions are less soluble and are unavailable for plants.
Soil stores important nutrients
http://www.lesco.com/
Phosphorus (P)Nitrogen (N)
Potassium (K)Calcium (Ca)
Magnesium (Mg)
Dr. Greg Pillar, Queens College
Soil Conditioners (Lime)CaCO3 or MgCO3
Soil amendment / conditioner… not a fertilizer!Important functions:
1. Corrects soil acidity2. Adds important plant nutrients— Ca & Mg3. Reduces solubility & toxicity of certain elements
in the soil Al, Mn, FeThis toxicity could reduce plant growth under acid conditions.
4. Promotes availability of major plant nutrients. Zn, Cu, P
5. Increases bacterial activity & mutualistic relationships.
http://www.wvu.edu/~Agexten/hortcult/turf/liming.htm
Soil Conditioners (Compost)
Decayed organic matterReplaces some nutrientsImproves soil structure
– The soil becomes more porous, increasing air circulation and the ability of the soil to absorb and hold moisture.
– Makes the soil more spongy!
http://www.wvu.edu/~Agexten/hortcult/turf/liming.htm