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