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AP EXAM More review and more review

AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

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Page 1: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

AP EXAM

More review and more review

Page 2: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Soil

• The weathered portion of the earth’s crust that can sustain life– Young soils are not leached of their nutrient– Older soils are leached and have little organic material

remaining– The parent material of soil is rock broken down by chemical

and physical weathering• Humus is the dark-colored organic material that remains after

decomposition of leaf litter, droppings, and plant and animal remains• Leaching is when minerals or matter is dissolved in water percolating

downward• Zone of illuviation is the area in the deeper levels of the soil where

the leached matter is deposited• Illuvial material includes iron; humus and clay depending on soil

Page 3: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Soil Organisms

• Include bacteria and fungi (function as decomposers)

• Algae can be present on surface of soil• Round worms (nematodes) and segmented

worms assist with aeration• Insects (ants), roots, snakes, gophers,

groundhogs and moles all tunnel and aerate soil

Page 4: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Chemical Properties of Soil• pH of the soil should range between 6 and 7 for most plants

– At low pH: aluminum, iron, boron and manganese are more soluble and more available to plants (Al can be toxic if too much)

– Add ground sulfur or aluminum sulfate to increase acidity• Alkaline soil: potassium, iron and manganese are less

available– Add lime: to make soil more alkaline

• Plants require nitrogen, potassium, phosphorus, calcium, magnesium, and sulfur

• Limiting Factors: nitrogen and phosphorus• Humus important for nutrients, water holding capacity,

aeration capacity, allowing root growth and increasing porosity of the soil

• Salinity can be a problem, especially in irrigated areas

Page 5: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Physical Properties of Soil• Color– Dark brown or black soil has lots of humus • High organic component

– Red soil may contain iron• Porosity: pore space in between particles of soil– Very porous soils hold more water and air – Porosity influences the permeability– The more porous a soil, the lower the permeability

• Permeability: rate at which water and air move through the soil

Page 6: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Physical Properties of Soil• Texture of the soil determined by the relative

amounts of different-sized inorganic particles• Three particle sizes– Sand 0.05-2 mm

• High permeability b/c low porosity• Particles are so large that the spaces between them are

large as well, resulting in good drainage– Silt 0.002-0.05 mm– Clay <0.002 mm

• Low permeability b/c it has high porosity• Particles are tiny which allows smaller pores around them,

thus holding water and preventing water permeating through the soil

– Loam: equal mixture of each type of soil

Page 7: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Soil Pyramid

Page 8: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Soil Horizons• Stratified layers in soil• A soil profile is taken to see the horizons• O horizon: organic material on the surface of the

soil (decaying plant litter)• A horizon: topsoil (rich w/ accumulated humus)– E horizon (eluviated): heavily leached soil that can

develop between the A and B horizon• B horizon: subsoil- zone of illuviation for the

leached material from A and E– Can be rich in humus, clay or iron

• C horizon: contains weathered rock and sits upon the parent material

Page 9: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Major Soil Orders• Spodosols form under coniferous forests– Layer of acidic pine litter, have a white-ish, ashy,

leached E horizon– Soil is not suited for agriculture due to the acidity and

nutrient leaching• Alfisols are formed under temperate deciduous

forests– Topsoil is usually gray brown, indicative of high levels of

nutrients– High precipitation leaches the A and E horizons, but soil

fertility is maintained by the constantly replaced litter

Page 10: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Major Soil Orders• Mollisols are found in temperate grasslands– Fertile with thick, dark brown topsoil indicating high

levels of humus– Subject to little leaching in dry seasons

• Aridosols form in arid regions– Little leaching b/c of little rain and little organics

• Histosols formed in waterlogged areas and result in incompletely decayed organic material

• Oxisols and Ulitsols form in hot, wet areas– Low in nutrients b/c they are highly leached due to

the large amounts of rainfall and lack of litter

Page 11: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Soil Problems• Less agricultural land is being used now than in

previous generations b/c we have better crop varieties, fertilizers, irrigation, and pesticides

• Land productivity per unit acre has greatly increased over time

• Vast amounts of land are being degraded by poor ag practice, urbanization and pollutants

• Degraded Land: soil lacks fertility – Or is eroded– Or surrounding water is contaminated – Or has more runoff than is typical– Or amount of vegetation declines– Or area has a decreased NPP and less animal biodiversity

Page 12: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Erosion

• Is the movement of soil from one place (desired) to another (less desirable)

• Erosion can be due to water, wind, or ice• Decreasing amount of topsoil limits fertility

and therefore plant growth• Total amount of soil lost from cropland is

thought to be 25 billion metric tons.

Page 13: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Erosion• Three types of water erosion– Sheet erosion is when water moves down a slope and

erodes topsoil evenly– Rill erosion cuts shallow channels in soil– Gully erosion cuts deep channels

• Is the most severe• Occurs on steep slopes

• Streambank erosion is loss of sides of stream as the water flows along the soil– Arises from cattle grazing in riparian areas or removal

of vegetation from riverbanks

Page 14: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Wind Erosion

• Occurs most severely in areas with dry seasons and flat terrain– African dust can be detected in St. Petersburg, Florida,

due to summer dust storms in the Sahara desert– Soil erosion also leads to increased sediment flowing

into surface water, which decreases water quality by increasing turbidity

– If the soil is contaminated with fertilizer or pesticides the erosion may pollute the water and induce eutrophication or animal death from the pesticide

Page 15: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Nutrient Depletion

• When crops are harvested nutrients are removed

• Farmers replenish these nutrients with fertilizers

• Fertilizers are high in phosphates and nitrates, which may induce eutrophication

• Nitrates in groundwater have also been shown to be a problem (blue baby syndrome)

Page 16: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Salinization and Waterlogging• Salinization occurs when land is irrigated over a

long period, especially from wells– Salt collects in topsoil when the water evaporates and

stunts plant growth, which reduces crop yields– The excess salt could be flushed by precipitation– To decrease salinization, irrigation can be via drip

irrigation or underground pipes– One option is to plant salt tolerant crops

• Water logging arises when soil is saturated– Plant roots die due to the lack of oxygen required for

cellular respiration

Page 17: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Desertification

• Is the conversion of marginal lands to desert due to climate and human behavior

• Rangeland and pastures are the most likely to become desertified as they are too arid for crop cultivation

• Desertification is increased by overgrazing and deforestation

Page 18: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Soil conservation• Avoid conventional tillage– Conservation tillage leaves the root residues from prior

crops• No Tillage: seeds are planted in a furrow• Pests and weeds may persist in the area

• Crop rotation• Plant cover crops• Fields can lie fallow• Mulch can be placed over soil• Increase water and mineral absorption by adding

spores of basidiomycota fungi (mushrooms and puffballs) which form mycorrhizal relationships with plants

Page 19: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Pesticides and Pests• Pesticides are chemical substances that kill organism– Include herbicides (plants), rodenticides (rodents),

fungicides (fungus), nematocides (nematodes), and insecticides (insects)

– Biocides kill many species– US uses about 5.3 billion pounds of pesticides per year– US uses 20 percent to the world’s consumption of

conventional pesticides– Nearly half of that amount is the chlorine and

hypochorites used to treat water to prevent waterborne illness• Other half is conventional pesticides

• Golf courses frequently have higher pesticide application rates than farms

Page 20: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

History Lesson• Ancient Romans burned infested locust fields to prevent

their spread• Sumarians used sulfur as an insecticide• In China, Mercury and arsenic were used on ectoparasites

and added ants to orchards to kill caterpillars• Spices were valued b/c they decreased pests in foods• Modern era began with DDT

(dichlorodiphenyltrichlorethane)– Inexpensive to manufacture, stable, easy to apply and lethal to

insects– Mass production began in WWII– Helped eradicate malaria in the US by destroying the Anophles

mosquito Anopheles mosquito– Birds were bioaccumulation DDT that was biomagnified in the

top of the food chain birds

Page 21: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Chemical Group of Pesticides

• Inorganic pesticides include simple compounds of sulfur, arsenic, copper, lead and mercury– These chemicals are toxic and persistent

• Natural organic pesticides are usually extracted from plants– Tobacco produces nicotine sulfate, toxic to insects and

mammals– Pyrethrum is extracted from chrysanthemums– Rotenone is used to kill fish is from derris root

• Fumigants: Carbon tetrachloride, ethylene dichloride and methyl bromide volatilize and penetrate materials – sterilize soils and stored grain

Page 22: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Organochlorines

• Chlorinated hydrocarbons are toxic and nearly all are banned or restricted in the US– DDT, aldrin, kepone, dieldrine, chlordane, and

toxaphene– Nerve toxins that acutely cause nausea, vomiting,

concusions, and death by respiratory failure by interfering in nerve impulses

– Linked to all fertility disorders– Probable human carcinogens– Highly persistent and fat soluble and biomagnify

Page 23: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Organophosphates

• Malathion, parathion, and tetraethylpyrophosphate– WWII nerve agents– Inhibit enzyme that breaks down the

neurotransmitter acetylcholine– Break down relatively quickly and not likely to

bioaccumulate– More expensive to produce – and more toxic in lower amounts b/c they are

rapidly absorbed

Page 24: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Organophosphates

• Subacute doses induce headache, slow heart beat, confusion, vomiting, and difficulty breathing

• Acute doses may lead to paralysis, tremors, coma and death

• Roundup (glyphosate): does not affect the nervous system

Page 25: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Carbamates• Are used as insecticides, herbicides and

fungicides• Have the same mode of action, toxicity and lack

of persitence and bioaccumulation as organophosphates– Sevin (carbaryl) and Temik (aldicarb)– Toxic to bees!!!!

• Many pesticides have chronic health effects that include cancers, birth defects, immunological problems, neurological problems, and endometriosis

Page 26: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Pesticide Benefits

• Eradicated many insect vectors, including mosquitoes (malaria, dengue and yellow fever), rat fleas (bubonic plague), typhus (lice and fleas), and tsetse flies (African Sleeping sickness)

• Many countries feel the health risks are small compared to the benefits of saving lives from illness.

• Increased food supply and decreased cost of producing food

Page 27: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Pesticide Problems• Pesticides often kill nontarget species– Ecological pest controls are killed (spiders)

• Kill honeybees and other insect pollinators– resulting in decreased fruit production

• Pest resurgence: insects that survive spraying b/c of resistance– Positive feedback loop as farmer increases application– Secondary pest outbreaks can occur– Grasshopper Effect: chemicals migrate from the site

to condense and precipitate in colder regions where bioaccumulation occurs in top carnivores

Page 28: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Relevant Pesticide Legislation• Three federal agencies regulate

– EPA– Food and Drug Administration (FDA)– US Department of Agriculture (USDA)

• 1938 Food, Drug, and cosmetic act allows the EPA to set tolerance levels for pesticide residues in food

• 1958 Delaney Clause- no chemicals would be added in food if they cause cancer

• 1947 FIFRA (Federal insecticide..) allows EPA to regulate sale and use of pesticides

• EPA licenses pesticides if they will not pose significant risk• FDA and USDA enforce levels set b the EPA• 1996 Food Quality Protection Act: accounts for aggregate exposure

– Banned Dursban b/c of risk to children– CCA, chromate copper arsenate, treated lumber, banned in homes

Page 29: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Relevant Pesticide Legislation

• 2001, 127 countries banned persistent organic pollutants (POPs) – Aldrin, chlordane, deledrin, DDT, mirex,

toxaphene, PCBs, diocins, and furans– Production of chemicals in US continues– Sent back to US on imported crops• Cycle of Poison!!!

Page 30: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Bhopal

• December 1984– Local Union Carbide plant producing SEVIN – Released many gases used to generate the

pesticide, including methyl isocyanate– Plant next to shanty town• 15,000 instant deaths• 800,00 people exposed

– Union Carbide paid India $470 million in compensation• Monies not paid to victims

Page 31: AP EXAM More review and more review. Soil The weathered portion of the earth’s crust that can sustain life – Young soils are not leached of their nutrient

Integrated Pest Management

• IPM uses low doses of nonpersistent, nonbiomagnified pesticide to reduce pest numbers for specific pests

• Increase crop diversity– Strip cropping or polyculture– Crop rotation prevents population buildup– Shelterbelts for insect eating birds and predators– Plant around insect hatching– Create trap crops around desired crop

• Marigolds planted around garlic