Modern Agriculture

1
Modern Agriculture
Background Green Revolution Agricultural
Ecosystems Pesticides Soils
2
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 -chemicals
• WWII -many deaths due to malaria
• -about equal to battle casualties
• -push to eliminate the disease.
• DDT invented 1939 Nobel prize, Paul Müller,
  Swiss chemist
• Dichlordiphenyltrichloroethane

3
Pesticide Benefits

• Save lives
• e.g. malaria in India
• 1950 -100 million cases per year
• massive aerial spraying DDT
• a lot of people
• a lot fewer deaths
• Increase Food Supply
• e.g. Texas cotton 7200 gtgtgtgtgtgtgt 7800 lbs
  cotton/ acre
• increase 130 / acre
• X 1,000 acres 130,000
• lot of cotton
• lot of Allegheny College T-shirts
• e.g. North Dakota Barley weed control
• -46 gtgtgtgtgtgt 50 bushels
• 51 / acre
• Why need to increase food supply?
• population increase

4
Pest Problems

• 1. Natural vs. agricultural ecosystem
• natural
• diversity of species
• natural pests
• small, individual places to live
• -scattered
• agricultural
• monoculture
• large uniform places to live
• shoppers world
• 2. Many species introduced
• no natural enemies
• e.g. gypsy moth Boston, 1869
• silkworm x gypsy moth
• fragile silk x hardy spinner
• spread extensivley
• 1869 Boston
• 1930 Connecticut
• 1980s Alabama, Texas, Wisconsin, PA

Cotton Monoculture
5
Rachel Carson - 1962
Silent Spring 1962 -noted biologist -biologic
al problems associated with pesticides -
decline in population of songbirds, fish-eating
birds -eagles -ospreys -DDT egg shell
production
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DDT
7
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
greater proportion 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 and large 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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Mobility
Carried into nearby ecosystems
move into groundwater - original pesticide -
pesticide degradation products found throughout
Mississippi River Mississippi River used for
drinking into Gulf of Mexico productive
fishing grounds DDT -found in Antarctic
penguins -in your body
10
Persistence
Pesticide residue remains on most fruits and
vegetables
11
Biomagnification
Fat-soluble compounds remain in organism are
not excreted As food moves up the food chain,
the compounds are increasingly concentrated Reach
levels toxic to higher organisms Even if not
toxic to organisms low on food chain
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Pesticides and Food Production
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Pesticide Resistance leads to Pesticide Treadmill

• Increase tolerance, increase in resistance
• What does this mean?
• Need this amount of pesticide
• to Kill 50 x
• to Kill 90 10x
• to Kill 99 100x
• to Kill 99.9 1000x

- hardiest ones live - next generations
very resistant - increase dosage or find new
pesticide -time-consuming -costly
14
Fertilizer Use
N, P important plant nutrients Add
nutrients Increase Plant Growth (why arent
native levels of soil N and P sufficient for high
plant growth?)
15
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

• N, P added to water
• Increase algae growth
• Algae die
• Bacteria consume dead algae
• What happens to oxygen levels in water?
• What happens to fish?

http//www.fws.gov/midwest/EcosystemConservation/h
ypoxia_map.gif
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Increasing international food needs

• Pakistan

18
Soil Erosion
Erosion Problems Loss of valuable soil Impacts
on stream organisms loss of habitat damage to
fish gills
Stream near French Creek
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Soil Degredation

• Soils are source of all food
• Mantra used to be feed the plant
• But, importance of healthy soils to total
  productivity (nutrients, water, support) leads us
  to 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
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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