Soils and agricultureSoils and agriculture

SoilsSoilsOriginsOrigins

ImportanceImportance

Maturity and HorizonsMaturity and Horizons

Variations with Climate and Variations with Climate and BiomesBiomes

Variations in Texture and PorosityVariations in Texture and Porosity

OriginsOrigins

ImportanceImportance

Maturity and HorizonsMaturity and Horizons

Variations with Climate and Variations with Climate and BiomesBiomes

Variations in Texture and PorosityVariations in Texture and Porosity

Soil isn’t dirt!Soil isn’t dirt!

• Soil is a complex mixture covering most of Soil is a complex mixture covering most of Earth’s land surfacesEarth’s land surfaces– Eroded rockEroded rock– Mineral nutrientsMineral nutrients– Decaying organic matterDecaying organic matter– WaterWater– AirAir– Community of organismsCommunity of organisms

• Is the basis for life and foodIs the basis for life and food

Soils have layersSoils have layers• Soils have horizontal layers called HorizonsSoils have horizontal layers called Horizons• Top 2 layers teem with plant roots and Top 2 layers teem with plant roots and

complex food webscomplex food webs– O HorizonO Horizon

• Surface litter layerSurface litter layer• Freshly fallen partly decomposed leaves etcFreshly fallen partly decomposed leaves etc

– A HorizonA Horizon• Topsoil: Most important layer for agricultural purposesTopsoil: Most important layer for agricultural purposes

– Humus: partially decomposed organic matterHumus: partially decomposed organic matter– Holds water and nutrients taken up by plantsHolds water and nutrients taken up by plants– Inorganic particlesInorganic particles– Decomposers (bacteria, fungi) breakdown organinic Decomposers (bacteria, fungi) breakdown organinic

matter releasing nutrients usable by plantsmatter releasing nutrients usable by plants– Color: Dark = Nutrient rich, Light = Nutrient poorColor: Dark = Nutrient rich, Light = Nutrient poor

Soils have layersSoils have layers

• Lower horizons contain most of a soil’s Lower horizons contain most of a soil’s inorganic material (broken down rock)inorganic material (broken down rock)– B horizonB horizon

•SubsoilSubsoil

•Varied mixture of sand, silt clay and gravelVaried mixture of sand, silt clay and gravel

– C HorizonC Horizon•Parent materialParent material

•Lies on top of bedrockLies on top of bedrock

Soil and hydrologySoil and hydrology

• Pore spaces in soil trap water and air Pore spaces in soil trap water and air needed by plant rootsneeded by plant roots– Infiltration: downward movement of Infiltration: downward movement of

water into spaces within the soilwater into spaces within the soil– Leaching: Dissolution of organic matter Leaching: Dissolution of organic matter

and nutrients in upper layers which and nutrients in upper layers which carries these materials down to the carries these materials down to the lower layerslower layers

Soil texture and porositySoil texture and porosity

• Soil textureSoil texture– Determined by relative amounts of clay, silt, Determined by relative amounts of clay, silt,

sand and gravel in the soil mixturesand and gravel in the soil mixture

• Texture determines soil porosity and Texture determines soil porosity and permeabilitypermeability– Porosity:Porosity: The volume of pore space in a soil The volume of pore space in a soil

• Larger particles = more pore spaceLarger particles = more pore space

• Smaller particles = less pore spaceSmaller particles = less pore space

– Permeabilty:Permeabilty: Rate at which water and air move Rate at which water and air move from the top layers to the lower layers of soilfrom the top layers to the lower layers of soil

Soil Profiles in Different Soil Profiles in Different BiomesBiomes

Fig. 4-27, p. 75

Why do we use grasslands for agricultural purposes?

To feed the world….To feed the world….• Conservation of matterConservation of matter

– Available resources limit agricultural productionAvailable resources limit agricultural production– Nutrients used by plantsNutrients used by plants

• Nitrates: Protein and DNANitrates: Protein and DNA• Phosphates: DNA, RNA, ATPPhosphates: DNA, RNA, ATP

– Soil degraded as nutrients removed by harvestSoil degraded as nutrients removed by harvest• Conservation of EnergyConservation of Energy

– Trophic level energy lossTrophic level energy loss• Vegetarian vs Carnivorous dietsVegetarian vs Carnivorous diets

• Green revolutionGreen revolution– Increase yield per acreIncrease yield per acre– MonocultureMonoculture– Intensive tillage = soil erosionIntensive tillage = soil erosion– Requires Requires

• Energy: Emissions and oilEnergy: Emissions and oil• Fertilizers and pesticides: Toxic pollution, soil salinizationFertilizers and pesticides: Toxic pollution, soil salinization• Irrigation: Water rights and usageIrrigation: Water rights and usage

2,000

1,500

1,000

500

0

Gra

in p

rod

uct

ion

(mill

ion

s o

f to

ns)

1950 1960 1970 1980 1990 2000 2010

Total World Grain Production

Year

400

350

300

250

150

Per

cap

ita

gra

in p

rod

uct

ion

(kilo

gra

ms

per

per

son

)

1950 1960 1970 1980 1990 2000 2010

World Grain Production per Capita

200

Year

Cal

ori

es p

er d

ay p

er p

erso

n3,700

3,500

3,300

3,100

2,900

2,700

2,500

2,300

2,100

1960

1970

1980

1990

2000

2010

2030

Year

Developed countries

World

Developing countries

Figure 14-3Figure 14-3Page 276Page 276

Croplands

• Help maintain water flow and soil infiltration

• Provide partial erosion protection • Can build soil organic matter

• Store atmospheric carbon

• Provide wildlife habitat for some species

Ecological Services Economic Services

• Food crops

• Fiber crops

• Crop genetic resources

• Jobs

Natural Capital

Croplands

Ecological Services

Economic Services

•Help maintain water flow and soil infiltration

•Provide partial erosion protection

•Can build soil organic matter

•Store atmospheric carbon

•Provide wildlife habitat for some species

•Food crops

•Fiber crops

•Crop genetic resources

•Jobs

Biodiversity Loss

Loss and degradation of habitat fromclearing grasslands and forests anddraining wetland

Fish kills from pesticide runoff

Killing of wild predators to protectlivestock

Loss of genetic diversity fromreplacing thousands of wild cropstrains with a few monoculture strains

Soil

Erosion

Loss of fertility

Salinization

Waterlogging

Desertification

Air Pollution

Greenhouse gas emissions from fossilFuel issue

Other air pollutants from fossil fuel use

Pollution from pesticide sprays

WaterWater waste

Aquifer depletion

Increased runoff andflooding from land clearedto grow crops

Sediment pollution fromerosion

Fish kills from pesticiderunoff

Surface and groundwaterpollution from pesticidesand fertilizers

Overfertilization of lakesand slow-moving riversfrom runoff of nitrates and phosphates fromfertilizers, livestockwastes, and foodprocessing wastes

Human Health

Nitrates in drinking water

Pesticide residues in drinking water,food, and air

Contamination of drinking andswimming water with disease organisms from livestock wastes

Bacterial contamination of meat

4% 2% 6% 5%

17% of totalcommercialenergy use

Crops Livestock Food processing Food distribution and preparation

Food production

Figure 14-10Figure 14-10Page 283Page 283

ConsequencesCauses

Worsening drought

Famine

Economic losses

Lower living standards

Environmentalrefugees

Overgrazing

Deforestation

Erosion

Salinization

Soil compaction

Natural climate change

Figure 14-12Figure 14-12Page 283Page 283

Reduce irrigation

Switch to salt-tolerant crops(such as barley, cotton, sugar beet)

Prevention

Flushing soil(expensive andwastes water)

Not growing crops for 2-5 years

Installing under- ground drainagesystems (expensive)

Cleanup

Solutions

Soil Salinization

Figure 14-13Figure 14-13Page 284Page 284

Reduces erosion

Saves fuel

Cuts costs

Holds more soil water

Reduces soil compaction

Allows several crops per season

Does not reduce crop yields

Reduces CO2

release from soil

Can increase herbicide use for some crops

Leaves stalks that can harbor crop pests and fungal diseases and increase pesticide use

Requires investment in expensive equipment

DisadvantagesAdvantages

Trade-Offs

Conservation Tillage

FigurFigure e 14-14-14a14aPage Page 285285

(a) Terracing

FigurFigure e 14-14-14b14bPage Page 285285

(b) Contour planting and strip cropping

FigurFigure e 14-14-14c14cPage Page 285285

(c) Alley cropping

FigurFigure e 14-14-14d14dPage Page 285285

(d) Windbreaks

Trade-Offs

Inorganic Commercial Fertilizers

Advantages Disadvantages

Do not add humus to soil

Reduce organic matter in soil

Reduce ability of soil to hold water

Lower oxygen content of soil

Require large amounts ofenergy to produce,transport, and apply

Release the greenhouse gas nitrous oxide (N2O)

Runoff can overfertilizenearby lakes and kill fish

Easy to transport

Easy to store

Easy to apply

Inexpensive to produce

Help feed one of every three people in theworld

Without commercialinorganic fertilizers,world food output coulddrop by 40% FigurFigur

e e 14-14-1515Page Page 286286

DO

NO

T P

OS

T T

O I

NT

ER

NE

T

Table 23-1Table 23-1Page 520Page 520

Table 23-1 Major Types of Pesticides

Type

Insecticides

Chlorinatedhydrocarbons

Organophosphates

Carbamates

Botanicals

Microbotanicals

Examples

DDT, aldrin, dieldrin, toxaphene, lindane, chlordane, methoxychlor, mirex

Malathion, parathion, diazinon, TEPP, DDVP,mevinphos

Aldicarb, carbaryl (Sevin), propoxur,maneb, zineb

Rotenone, pyrethrum, and camphorextracted from plants, synthetic pyrethroids (variations of pyrethrum), rotenoids (variations of rotenone), and neonicotinoids(variations of nicotine)

Various bacteria, fungi, protozoa

Persistence

High (2–15 years)

Low to moderate (1–2 weeks), but some can last several years

Low (days to weeks)

Low (days to weeks)

Low (days to weeks)

Biologically Magnified?

Yes

No

No

No

No

Table 23-1Table 23-1Page 520Page 520

Table 23-1 Major Types of Pesticides

Type

Herbicides

Contact chemicals

Systemic chemicals

Soil sterilants

Fungicides

Various chemicals

Fumigants

Various chemicals

Examples

Atrazine, simazine, paraquat

2,4-D, 2,4,5-T, Silvex, diuron,daminozide (Alar), alachlor (Lasso),glyphosate (Roundup)

Tribulan, diphenamid, dalapon, butylate

Captan, pentachlorophenol, zeneb, methyl bromide, carbon bisulfide

Carbon tetrachloride, ethylene dibromide, methyl bromide

Persistence

Low (days to weeks)

Mostly low(days to weeks)

Low (days)

Most low (days)

Mostly high

Biologically Magnified?

No

No

No

No

Yes (for most)

FigurFigure e 23-423-4Page Page 523523

600

500

400

300

200

100

1950 1950 1950 1950 1950 1950

Nu

mb

er o

f g

enet

ical

ly r

esis

tan

t in

sect

sp

ecie

s

Year

Neonicotinoids(1995)

Pyrethroids (1978)

Carbamates (1972)

Organophosphates (1965)

DDT/cyclodienes (1946)

Figure 23-7Figure 23-7Page 528Page 528

MH

MH

JH

MH

JH

JH

MH

Pupa

Eggs

Larva

Black

Producing and eating meatProducing and eating meat

• Land use issuesLand use issues– More land neededMore land needed

•More land needed for grazing than grain More land needed for grazing than grain productionproduction

•Acre of grain for human consumption feeds Acre of grain for human consumption feeds more than an acre used for grazingmore than an acre used for grazing

•Land needed to grow forage AND raise Land needed to grow forage AND raise animals: Housing, food storage and waste animals: Housing, food storage and waste disposaldisposal

Producing and eating meatProducing and eating meat• Energy issuesEnergy issues

– Eating at a lower trophic levelEating at a lower trophic level• More solar energy available to humans, less lost More solar energy available to humans, less lost

through trophic transferthrough trophic transfer

– Storage of grain less energetically expensive Storage of grain less energetically expensive than processing and storing meatthan processing and storing meat• Transport, slaughter and refrigerationTransport, slaughter and refrigeration

– Energy costs associated with meat productionEnergy costs associated with meat production• Producing grain for livestockProducing grain for livestock

– Fertilizers, irrigation, pesticides, farm machineryFertilizers, irrigation, pesticides, farm machinery

• Animal waste managementAnimal waste management– Pumping, treatment, transport, disposalPumping, treatment, transport, disposal

• Animal care and round up of free range livestockAnimal care and round up of free range livestock

Problems and consequencesProblems and consequences

• ProblemProblem– OvergrazingOvergrazing

– Water PollutionWater Pollution• SlaughterSlaughter• WastesWastes• Riparian grazingRiparian grazing

– Land useLand use• Fencing, deforestationFencing, deforestation

– Uses more waterUses more water

• ConsequenceConsequence– Desertification, erosion Desertification, erosion

nutrient lossnutrient loss

– Groundwater Groundwater contamination, ^BOD, contamination, ^BOD, Eutrophication, etcEutrophication, etc

– Habitat loss & Habitat loss & fragmentation, decreased fragmentation, decreased biodiversitybiodiversity

– Water shortages / depletionWater shortages / depletion

Eating less meat: Pro and Eating less meat: Pro and ConCon• AdvantagesAdvantages

– Reduced risk of diseaseReduced risk of disease• CholesterolCholesterol

– Clogged arteriesClogged arteries– HypertensionHypertension– Heart diseaseHeart disease

– Reduced chemical Reduced chemical exposureexposure

• HormonesHormones• SteroidsSteroids• AntibioticsAntibiotics• Pesticides (Biomag!)Pesticides (Biomag!)

– Reduced exposure to Reduced exposure to diseasedisease

• Mad CowMad Cow• Salmonella/ E. coliSalmonella/ E. coli• ParasitesParasites

• DisadvantagesDisadvantages– Meat an excellent source Meat an excellent source

of proteinof protein• Essential amino acidsEssential amino acids

– Rice and Beans!Rice and Beans!• Difficult to get enough Difficult to get enough

protein without meatprotein without meat– Nutritional deficienciesNutritional deficiencies

• Kwashikor: ProteinKwashikor: Protein• Blindness: Vit. ABlindness: Vit. A• Pollegra: Vit. BPollegra: Vit. B• Anemia: IronAnemia: Iron• Inadequate essential fats Inadequate essential fats

balancebalance

Spotter airplane

Fish farmingin cage

Trawlerfishing

Purse-seinefishing

sonartrawl flap

trawllines

trawl bag

Long line fishing

lines withhooks

Drift-net fishing

fish caughtby gills

float buoy

fish school

100

80

60

40

20

01950 19701960 200019901980

Cat

ch(m

illio

ns

of

met

ric

ton

s)

Year

Total World Fish Catch

25

20

15

10

5

01950 19701960 200019901980

Per

cap

ita

catc

h(k

ilog

ram

s p

er p

erso

n)

Year

World Fish Catch Per Person

800

600

400

200

01960 1970 1980 1990 2000

Year

80

70

60

50

40

30

20

Har

vest

(th

ou

san

ds

of

met

ric

ton

s)

Ab

un

dan

ce(k

ilog

ram

s/to

w)

Abundance

Harvest

10

Highly efficient

High yield in smallvolume of water

Increased yieldsthrough cross-breeding and genetic engineering

Can reduce over-harvesting of conventional fisheries

Little use of fuel

Profit not tied to price of oil

High profits

Advantages

Large inputs of land, feed, And water needed

Produces large and concentrated outputs of waste

Destroys mangrove forests

Increased grain productionneeded to feed some species

Fish can be killed by pesticide runoff from nearby cropland

Dense populations vulnerable to disease

Tanks too contaminated touse after about 5 years

Disadvantages

Trade-Offs

Aquaculture

What are GMOs and how What are GMOs and how are they producedare they produced

Online activitiesOnline activities

ProjectedDisadvantages

Need less fertilizer

Need less water

More resistant to insects,plant disease, frost, anddrought

Faster growth

Can grow in slightly saltysoils

Less spoilage

Better flavor

Less use of conventionalpesticides

Tolerate higher levels ofpesticide use

Higher yields

ProjectedAdvantages

Trade-OffsGenetically Modified Food and Crops

Irreversible andunpredictable genetic and ecological effects

Harmful toxins in foodFrom possible plant cellMutations

New allergens in food

Lower nutrition

Increased evolution ofPesticide-resistantInsects and plant disease

Creation of herbicide-Resistant weeds

Harm beneficial insects

Lower genetic diversity