Notes Soil upload

What’ s the

dirt on dirt?

Definition



_{Soil – relatively thin surface}

layer of the Earth’ s crust

consisting of mineral and

organic matter that is affected

by agents such as weather,

Composition – 4 Distinct Parts



_{Mineral particles}

(45% “ typical” soil)



_{Organic matter (about 5%)}



_{Water (about 25%)}

Importance



_{Organisms, mainly microorganisms, inhabit the}

soil & depend on it for shelter, food & water



_{Plants anchor themselves into the soil}



_{Get their nutrients and water from soil}



_{Terrestrial plants couldn’ t survive without soil;}

therefore, humans…



_{Could not exist without soil either}

Renewability



_{Slowly renewed resource}



_{Begins when bedrock is broken down by}

physical, chemical and biological processes

called

weathering



_{Mature soils}

_{are arranged in a series of}

horizontal layers called

soil horizons



_{Forming 2.5 cm (1 in.) = 200-1000 years}



_{Decomposition can produce new soil but what}

about the nutrients?



_{In tropical rain forests, vital nutrients are caught in}

trees; deforestation removes these nutrients from

the ecosystem

Physical Weathering



_{The break down of rock by physical}

means



_{Movement of this}

broken material is

erosion

Chemical Weathering



_{A plant’ s roots or animal cells}

undergo cell respiration and the CO

produced diffuses into soil, reacts with

H

O & forms carbonic acid (H

CO

);



_{>2mm in diameter = gravel/stones}

 _{Not actually considered soil because it doesn’ t have direct}

value to plants



_{0.05 to 2mm = sand}

 _{Largest soil particles}

 Can be easily seen with the eye



_{0.002 to 0.05mm = silt}

 _{About the size of flour}  _{Barely visible}



_{<.002mm = clay}

 _{Has the greatest surface value}

 _{Only seen under an electronic microscope}



_{Gritty—has a lot of sand}



_{Sticky—high clay content}



_{Should be able to roll it into a clump}



_{Silt—smooth, like flour}



_{How soil particles are organized and}

clumped together



_{EX: Stuck together due to moisture in}

soil pores and air pockets

SOIL PROPERTIES: How it feels



_{How easily the soil can be crumbled}



_{Relates to how easily the land can be cultivated}



_{A measure of the volume of soil and the}

average distances between the spaces



_{Relates to water and nutrient holding capacity}



_{The rate at which water and air}

moves from upper to lower layers



_{Depends on porosity}



_{All about water and nutrients flowing}

SOIL PROPERTIES: Friability

SOIL PROPERTIES: Porosity

SOIL PROPERTIES:

Permeability

0.05–2 mm diameter

High permeability Low permeability Water Water

Clay

less than 0.002 mm Diameter

Silt

0.002–0.05 mm diameter Sand



_{Some soils, like clays, swell when H}

_O

gets in them; then, they dry and

crack



_{Most soils range from 4.0 - 8.0}

 _{Soil of the Pygmy Forest in California is}

extremely acidic (2.8-3.9)

 _{Soil in Death Valley, California, is very}

basic (10.5)



_{Plants are affected by pH because of}

the solubility of nutrient minerals

 _{pH changes stability of nutrients and}

ability of organisms to survive

 _{pH changes the composition a nutrient}

takes

 _{EX: Higher the pH the more}

ammonia instead of ammonium

SOIL PROPERTIES: Shrink-Swell

Potential



_{Steep slopes often have little or no soil on}

them because of…



_Gravity



_{Water Runoff}



_{Moderate slopes and valleys may}

encourage the formation of deep soils



_{Dark soil is rich with lots of organic matter}



_{Light soil (like sand) is not so rich}

SOIL PROPERTIES: Affected by

Slope

SOIL HORIZONS



_Infiltration



_{Downward movement}

of water through soil



_Leaching



_{Dissolving of minerals}

and organic matter in

upper layers carrying

them to lower layers



_{What would determine}

the degree of

infiltration and

leaching?

Organic Layer (O-horizon)



_{The uppermost layer}



_{Rich in organic material}



_{Plant and animal waste}

accumulates & decays



_{In desert soils, the}

O-horizon is completely

absent



_{In certain organically rich}

soils, it may be the

dominant layer

Topsoil (A-horizon)



_{Composed of partially}

decomposed organic matter

(

humus

)



_{Dark brown = fertile}



_{Grey, yellow or reddish = not}

as fertile



_{Contains lots of life (bugs,}

worms, bacteria, fungi, etc.)



_{Granular texture}



_{Bottom of A-horizon can be}

called the

E-horizon

(

eluviated)



_{Somewhat nutrient-poor due}

to nutrient minerals leaching

to deeper layers

Subsoil (B-horizon)



_{Light-colored subsoil}

beneath the A-horizon



_{Denser than layers above}

due to the fine particles

leaching from above



_{Zone of illuviation where}

nutrient minerals

accumulate



_{Typically rich in iron and}

aluminum compounds

Parent Material (C-horizon)



_{Fairly deep (3+ feet below}

surface)



_{Contains weathered pieces}

of rock



_{Borders the unweathered}

solid parent material



_{Most roots do not go down}

this deep; thus, it is often

saturated with

groundwater.

R-Horizon

Alkaline, dark, and rich in humus Clay, calcium compounds Mosaic of closely packed pebbles, boulders Weak humus-mineral mixture Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts

Desert Soil (hot, dry climate)

Grassland Soil (semiarid climate)

Light-colored and acidic Acid litter and humus Humus and iron and aluminum compounds Acidic light-colored humus Iron and aluminum compounds mixed with clay

Tropical Rain Forest Soil (humid, tropical climate)

Coniferous Forest Soil (humid, cold climate)

Forest litter leaf mold

Humus-mineral mixture

Light, grayish-brown, silt loam Dark brown

firm clay

Deciduous Forest Soil (humid, mild climate)

Erosion



_Definition



_{Erosion is the movement of soil components, especially}

surface litter and topsoil, from one place to another



_{Effects of Soil Erosion}



_{Lowers soil fertility}



_{Can overload nearby bodies of water with sediment}



_{In undisturbed ecosystems, the roots of plants help anchor}

the soil. Humans have aided erosion to deplete 100s –

1000s of years of soil build up in only a few decades by:



_{Farming Logging}



_Construction

_{Overgrazing by livestock}

Seed Blankets

Hydr

aulic

ally

Appl

ied S

oluti

ons

(HAS

)

Global Outlook: Soil

Erosion



_{Soil is eroding faster than it is forming on more than}

Soil Erosion in America



_{1930’ s Dust Bowl}



_{1935 Soil Erosion Act—established the Soil Conservation}

Service now called the Natural Resources Conservation

Service



_{Around 6.5 billion tons of soils are eroded each year}



_{Equal to 320 million dump trucks filled that, if parked}

end-to-end, would extend to the moon and ¾ of the way back



_{This is the amount}

_after

_{we’ ve cut back erosion about}

40% due to the 1985 Food Security Act (Farm Act)



_{Gives farmers a subsidy for taking highly erodible land out of}

production and replanting it with soil saving plants for 10-15

years



_{Some farmers are now backing out to receive subside for}

growing corn to make ethanol

Types of Soil Erosion



_{Splash Erosion}

_{: caused by water hitting the soil surface}



_{Sheet Erosion}

_{: surface water or wind peels off thin layers of soil}



_{Mass Slippage}

_{: occurs when soil is very wet and slips away in}

large chunks (mudslides)



_{Rill Erosion}

_{: fast-flowing little rivulets of surface water making}

microchannels



_{Gully Erosion}

_{: fast-flowing water joins together to cut wider and}

deeper ditches or gullies



_Suspension

_{: airborne soil}



_Saltation

_{: particles come off the ground but near it}



_{Surface Creep}

_{: surface creeping slowly across}

Desertification:

Degrading Drylands



_{About one-third of the world’ s land has lost some of its}

productivity because of drought and human activities that

reduce or degrade topsoil

Salinization

and

Waterlogging



_{Repeated irrigation}

can reduce crop

yields by causing salt

buildup in the soil and

waterlogging of crop

plants

Traditional Agriculture:

Subsistence

&

Intensive

Agriculture



_{Many farmers in developing countries use low-input}

agriculture to grow a variety of crops on each plot of land

(

polyculture

) through:



_{Crop Rotation}

_{: planting different crops on the same plot in}

sequential growing seasons to reduce pests and prevent nutrient

depletion



_{Multiple Cropping}

_:

_{growing two or more crops on the same}

plot of land during a single growing season (

1

green

revolution

)

 _{Double-Cropping: 2}nd crop is planted after the 1st crop is harvested  _{Relay Cropping: 2}nd crop is planted before the 1st crop is harvested  _{Polyvarietal Cultivation: planting several genetic varieties}

 _{Intercropping: planting an additional crop in-between the main crop}  _{EX: 3 sisters (corn, beans, and squash)}

Erosion Control

 _{Shelterbelt or Windbreak}

 _{Long rows of trees are planted to partially block the wind}

 _{Helps retain soil moisture, supply some wood for fuel, and provide}

habitats for birds  _{Strip Cropping}

 _{Alternate your crop in strips with another crop that has}

a large root system to hold soil in place

 _{Also can help prevent the spread of pests and plant diseases}

 _{Contour Farming}

 _{Plowing or planting perpendicular to the sloped contour of the land}

 _{Catches and reduces water runoff}

 _{Terracing (often what you use for contour farming)}

 _{Broad, nearly level terraces that run across the land contour}

 _{Helps to retain water for crops at each level and reduce}

soil erosion by controlling runoff  _{Cover Cropping}

 _{Planting crops to cover soil after main crops are harvested}

 _{Reduces water loss by evaporation}

 _{Alley Cropping}

 Crops are in-between trees and shrubs that can provide shade  _{Helps to retain and slowly release soil moisture}

Erosion Control Cont…



_{Minimum Tillage}

_{– to disturb the soil as little as}

possible while planting crops

 _{Special tillers break up and loosen the subsurface soil}

without turning over the topsoil, previous crop residues, and any cover vegetation

 _{Allows humus to accumulate}  _{Conservation-tillage farming:}

 _{Increases nutrients in the soil}

 _{Increases crop yield}

 _{Increases habitat}

 _{Raises soil carbon content}

 _{Improves water holding capacity}

 _{Lowers water use}

Soil Nutrients



_{Macronutrients}



_{Need lots of (vital for every function}

performed)



_{EX: Nitrogen, Phosphorus & Potassium}



_{Micronutrients}



_{Needed in small amounts}



_{EX: Copper, Zinc, and Iron}

Soil Nutrients

Fertilizers

 _{Fertilizers can help restore soil nutrients}

 _{Organic Fertilizers: from plant and animal materials}  EXAMPLES:

 Animal manure

 _{Crop residues}  _{Bone meal}  _Compost

 _{Inorganic Fertilizers: man-made from chemical compounds (contain}

N, P, K, and other trace nutrients)

 BENEFITS:

 Exact compositions are known

 Soluble and thus immediately available to the plant  COSTS:

 Quickly leaches away thus polluting water

Can we grow things without

soil?

Hydroculture



_Hydroponics

_—

_{growing plants in fertilized water}



_{EX: Cranberries are grown this way}



_COSTS:



_{Labor-intensive}



_Expensive



_BENEFITS:



_{You can control the environment & grow}

The Green Revolution



_{Since 1950, high-input agriculture has produced more crops}

per unit of land due to:

 _{Selective breeding Fertilizers Irrigation}

methods

 _{Pesticides Multicropping}



_{In 1967, fast growing dwarf varieties of rice and wheat were}

developed for tropics and subtropics.

 _{Since 1978, the amount of irrigated land per person has declined}



_{Expansion of the revolution has been hindered by:}

 _{Lack of water (especially depletion of aquifers)}  _{High costs for small farmers}

 _{Inefficient irrigation}

 _{Physical limits to increasing crop yields}

 _{Salt build-up}



_{Loss of a variety of genetically different crop and livestock}

strains might limit raw material needed for future green and

gene revolutions

 _{In the U.S., 97% of the food plant varieties available in the 1940 no}

The Gene

Revolution

CASE STUDY: Industrialized Food

Production in the United States



_{Industrialized agriculture uses about 17% of all}

commercial energy in the U.S. and food travels an

average 2,400 kilometers or 1491 miles from farm to

plate

Producing More Meat

 About half of the world’ s meat is produced by livestock grazing on grass

 The other half is produced under factory-like conditions (feedlots)

 Concentrated Animal Feeding

Operation

 Densely packed livestock are fed grain or fish meal

 Eating more chicken and farm-raised fish and less beef and pork reduces harmful environmental impacts of meat production

Trade-Offs Animal Feedlots Advantages Increased meat production Need large inputs of grain, fish meal, water, and fossil fuels Higher profits

Concentrate animal wastes that can pollute water

Less land use Reduced overgrazing Reduced soil erosion Antibiotics can increase genetic resistance to microbes in humans Help protect biodiversity Disadvantages

Producing More Meat More Efficiently

Solutions: Moving Toward a

More Sustainable Future



_{We can increase food security by:}



_{Slowing populations growth}



_{Sharply reducing poverty}



_{Slowing environmental degradation of the world’ s}

Fern Mature soil Honey fungus Root system Oak tree Bacteria Lords and ladies Fungus Actinomycetes Nematode Pseudoscorpion Mite Regolith Young soil Immature soil Bedrock Rock fragments Moss and lichen Organic debris builds up

Grasses and small shrubs Mole Dog violet Wood sorrel Earthworm _Millipede __ horizon __ horizon __ horizon __ horizon Springtail Red Earth Mite