Es 110 Agriculture

7/30/2019 Es 110 Agriculture

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Modern Agriculture

Background Green Revolution

Agricultural Ecosystems

Pesticides

Soils


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History of Pesticides 3000 YBP China fields burned to control locusts (no Clean Air Act)

900 AD Arsenic used to kill pests (not just your in-laws)

1182 China citizens required to collect and kill locusts

1900s US -natural derivatives-arsenic

1950s post WWII -chemicalsWWII -many deaths due to malaria

-about equal to battle casualties-push to eliminate the disease.

DDT invented 1939 Nobel prize, Paul Mller, Swiss chemist

Dichlordiphenyltrichloroethane


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Pesticide BenefitsSave lives

e.g. malaria in India1950 -100 million cases per yearmassive aerial spraying DDTa lot of peoplea lot fewer deaths

Increase Food Supplye.g. Texas cotton 7200 >>>>>>> 7800 lbs cotton/ acre

increase = $130 / acreX 1,000 acres = $130,000

lot of cottonlot of Allegheny College T-shirts

e.g. North Dakota Barley weed control-46 >>>>>> 50 bushels+$51 / acre

Why need to increase food supply?

population increaseland fertility in many countries degraded loss of agricultural productivity

Increase profits

Rapid response; ease of application-increase agricultural pressure in producing areas


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Pest Problems1. Natural vs. agricultural ecosystem

natural

diversity of speciesnatural pestssmall, individual places to live

-scatteredagricultural

monoculture

large uniform places to liveshoppers world

2. Many species introducedno natural enemies

e.g. gypsy mothBoston, 1869silkworm x gypsy moth

fragile silk x hardy spinnerspread extensivley

1869 Boston1930 Connecticut1980s Alabama, Texas, Wisconsin, PA

Cotton Monoculture


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Rachel Carson - 1962

Silent Spring 1962

-noted biologist

-biological problems associated with pesticides

- decline in population of songbirds, fish-eating birds

-eagles-ospreys

-DDT egg shell production


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DDT


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Pesticide Use

Pesticide use first peaked in 1982 when cropland used for crops was record-high. This peak can be attributed to increased planted acreage, a greaterproportion of acres treated with pesticides, and higher application rates.Herbicides accounted for most of the increase.

Total pesticides declined between 1982 and 1990 as commodity prices fell andlarge amounts of land were taken out of production by Federal programs.


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Pesticide Problems

Mobility Can leave agricultural fields and enter other

ecosystems

Persistence Can exist for a long time

Biomagnification

Resistance Pests develop resistance to pesticides


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MobilityCarried into nearby ecosystems

move into groundwater- original pesticide- pesticide degradation products

found throughout Mississippi River

Mississippi River used for drinkinginto Gulf of Mexico

productive fishing grounds

DDT -found in Antarctic penguins

-in your body


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Persistence

Pesticide residue remains on most fruits and vegetables


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Biomagnification

Fat-solublecompounds remain inorganism are notexcreted

As food moves up the

food chain, thecompounds areincreasinglyconcentrated

Reach levels toxic tohigher organisms

Even if not toxic toorganisms low on food

chain


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Pesticides and Food Production

US FoodProduction

Pesticides

Million tons % increase Million lbs % increase

1962 320 - 600 -

1970 340 6 1000 67

1980 350 3 1500 50


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Pesticide Resistance leads to Pesticide Treadmill

Increase tolerance, increase in resistanceWhat does this mean?

Need this amount of pesticide

to Kill 50% x

to Kill 90% 10xto Kill 99% 100xto Kill 99.9% 1000x

- hardiest ones live- next generations very resistant- increase dosage or find new pesticide

-time-consuming

-costly


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Fertilizer Use

N, P important plant nutrientsAdd nutrientsIncrease Plant Growth(why arent native levels of soil N and P sufficient for high plant growth?)


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Nitrogen loss

Not all fertilizers is taken up by plants

Not all fertilizer is retained by soil

So, where does it go??

Runoff to aquatic systems


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Gulf Hypoxia Dead Zone

http://www.fws.gov/midwest/EcosystemConservation/hypoxia_map.gif

N, P added to water

Increase algae growth

Algae die

Bacteria consumedead algae

What happens tooxygen levels in

water?

What happens to fish?


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Increasing international food needs

Pakistan


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Soil Erosion

Stream nearFrench Creek

Erosion Problems

Loss of valuable soil

Impacts on stream organisms

loss of habitatdamage to fish gills


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Soil Degredation Soils are source

of all food

Mantra used tobe feed theplant

But, importanceof healthy soils tototal productivity(nutrients, water,

support) leads usto feed the soil


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Time of Soil Formation

Soil = rocks + water + plants/organisms + TIME

Typical soil = 500 years per inch

Current Meadville soils = 13,000 years old


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Natural v Agricultural Ecosystem

Modern Agriculture Natural Everything Alternative Approach

Soil: Approach Till compaction

Problems

Erode

Constant cover

Fluffy soil

Cover crops

No-tillReduced till

Compaction

Nutrients: Approach Fertilize

Problems Add to excess N, P

runoff ($)

groundwater pollution

eutrophication

Recycle Spot additions

Natural fertilizer

Crop rotation

N fixers

Water: Approach Irrigate

Problemscontaminate groundwater

H2O shortage

Siltation

Cover soil Drip irrigation

Below surface irrigation

Cover

Soil our protection

Grass strips

Pests: Approach

Chemical attack

Problems Resistance

biomagnification

pesticides health

loss of good species

Diversity

Natural controls

No monoculture

rotate crops

natural controls

accept some loss

local spray

spray when needed


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Organic Foods

No pesticides

Natural pesticide control

Reduced fertilizer use

Use natural means = N-fixing plants

More costly, but

Compare Price v. Cost

Documents

Es 110 Agriculture