Transcript Land and Agriculture - East Penn School District

"Land, then, is not merely soil; it is a fountain of
energy flowing through a circuit of soils, plants,
and animals." - Aldo Leopold, A Sand County
Almanac, 1949
Geology and Soils
Chapter 10
December 2008
Earth Structure and Geological
Processes
• Earth’s Structure
– Crust – lithosphere
• Oceanic:
– generally less than 10 kilometers thick, but more dense than the contenential
cruse
– Most of the present day oceanic crust is less than 200 million years
• Contential
– mostly 35 to 40 km versus the average oceanic thickness of around 7-10 km
– 40% of the Earth's surface is now underlain by continental crust.
• Part of lithosphere
– Mantle
• Asthenosphere
– Core
Spreading
center
Oceanic tectonic
plate
Collision between
two continents
Plate movement
Tectonic plate
Oceanic tectonic
plate
Ocean trench
Plate movement
Oceanic
Subduction crust
zone
Oceanic
crust
Continental
crust
Continental
crust
Material cools
as it reaches
the outer
mantle
Mantle
convection
cell
Two plates move
towards each other.
One is subducted
back into the mantle
on falling convection
current.
Cold dense
material falls
back through
mantle
Hot material
rising
through
the mantle
Mantle
Hot outer
core
Inner
core
Figure 10-4
Page 206
Features of the Crust
Fig. 10-3 p. 205
Plate Boundaries
• Divergent
• Convergent
• Transform
Minerals, rocks, rock cycle
• Element or inorganic “pure” compound
– Gold, silver, sulfur
– Salt, mica, quartz
• Rock: most two or more minerals
• Rock Types
– Igneous: lava rock or granitic (under earth’s surface)
– Sedimentary: sandstone, shale, limestone, dolomite
– Metamorphic: Preexisting rock, due to pressure and
temperature, is changed.
Earthquakes
• Abrupt shifting of earths crust
• Epicenter
• Magnitude : Richter Scale
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Insignificant: less than 4
Minor: 4-4.9
Damaging and destructive: 5-6.9
Major and great: above 7
What is Soil
• NOT DIRT - dirt is a four letter word!
• Mineral particles - non-living - 45%
• Organic matter - 5%
– bacteria and other microorganisms
– partially decomposed plants - humus
– macroinvertebrates
• Pore space - 50%
– air spaces
– water filled spaces
Why Soil Science?
• Soil science at Penn State
Functions of Soil
• Store Water
• Provide nutrients for plants
• Decompose materials
– Recycle nutrients
– Return carbon dioxide
Physical Properties and Use
• Plants - agriculture and forestry
• Building-bearing strength and drainage
• Waste disposal - good drainage
Soil Formation – Factors
"Each soil has had its own history. Like a river, a
mountain, a forest, or any natural thing, its present
condition is due to the influences of many things and
events of the past." - Charles Kellogg, The Soils That
Support Us,1956
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Parent material
Climate
Living Organisms
Topography – slope
Time
Soil Formation
• Weathering
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Temperature fluctuation
erosion
plant roots
Chemical reactions: eg limestone
• Organic Material – amount available
• Climate - determines degree of weathering, type
of plants, rate of decomposition(thus, directly
related to organic material)
Parent Material
• Bedrock
– In PA, most is not the bedrock
• Transported materials:
– glaciers
– water (alluvial)
– erosion and gravity (colluvial)
• Affects particle size and chemistry
Soil Color
• Color determined by minerals and oxygen
availability
• Red, yellow, brown hues - good aeration
• Gray or olive - poorly aerated, poor drainage
• Mottling - seasonable wet; poor drainage
Soil Structure
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Aggregates
Result of soil texture classes
Result of organic matter
Provides pores
Decreased/lost by compaction
Granular, platy, blocky, columnar
Soil Texture
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Sand, silt, and clay
Affects infiltration
Affects water holding capacity (drainage)
Indirectly affects fertility - adhesion ions to clay
“Strength” for building
Affects soil structure
Clay
• Less than .002 mm
• Holds water
• Forms aggregates - provides soil structure “sticky”
• Excess clay - poor drainage and compaction
• Derived from shales
• Good adsorption of ions
Silt
• .002 to .05 mm
• Optimal amount of soil water retention and soil
air circulation
Sand
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.05 to 2 mm
1000 times larger than clay
Rapid infiltration/low water holding capacity
Good strength for building
Organic Content
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1 to 20%
Determines structure - aggregates of soil particles
Water holding capacity
Rate of infiltration – affect porosity
• aggregates
• Color - darker, more organic
• Fertility (chemistry) and pH - high ion exchange
Soil Texture Classes
• Proportion of sand, silt, clay
• 12 texture classes
• Soil texture triangle (229)
Soil Density
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Largely due to soil texture and organic content
Degree of aggregation important
Affected by human use
Dense soils - high strength, low porosity, low
permeability, poor for plant growth
Lab - Soil Chemistry
• Fertility - Ion exchange important
– nitrogen (nitrates)
– phosphorus
– potassium
• pH: 6.5 to 7.0 is best
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ion (nutrient) uptake
many add lime (“sweetens” soil)
effect of rainfall
PA slightly acid soil
Soil Profile
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Soil Horizons - Stratified horizontal layers
Used to classify the soil
O: partially decomposed organic material
A: topsoil
E: zone of leaching
B: subsoil
C: Parent material
Acidic
lightcolored
humus
Acid litter
and humus
Humus-mineral
mixture
Light-colored
and acidic
Light, grayishbrown, silt loam
Iron and
aluminum
compounds
mixed with
clay
Tropical Rain Forest Soil
(humid, tropical climate)
Forest litter
leaf mold
Dark brown
Firm clay
Deciduous Forest Soil
(humid, mild climate)
Figure 10-15 (2)
Page 215
Humus and
iron and
aluminum
compounds
Coniferous Forest Soil
(humid, cold climate)
Soil Profiles
• Class in Tennessee
Classifying and Naming Soils
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Age of soil
Special features (eg. Fragipans)
water related characteristics
texture
horizons - types and depths
County Soil Surveys – Soil Conservation Service of USDA
Land Degradation
• Every Year
– 7.4 M acres ruined by erosion
– 4 M acres turned into deserts
– 8 million converted to other uses
• ESTIMATES:
– 40% world’s land seriously degrades
– 75% of land in Central America
Erosion (217-221)
• Natural process
• Disaster: wrong place, wrong time, in too great
amounts
• Worldwide soil degradation
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1% of world cropland is lost each year
Has reduced food production on 16% cropland
40% of land seriously degraded(75% in Cent. Am.)
Situation worsening in developing countries as more
marginal lands being plowed and farmed
What is happening to our land?
• The “dirty thirties” (219)
– abuse of land- intensive, monoculture farming
– READ: The Dust bowl, page 219
– Soil Erosion Act (1935)
• SCS born– now Natural Resources Conservation Service
• Soil Conservation Districts formed
• Every Year - worldwide
– 7.4 M acres ruined by erosion
– 4 M acres turned into deserts - removal of natural vegetation
– 8 million converted to other uses - development
Causes of soil degradation
• Loss is “slow” but nearly permanent
– 1 mm year = 25 mm in 25 years
– 500 years to replace this
• Water erosion
• Wind erosion
• Salt and toxic chemicals
Erosion
• Movement of soil by wind or water to new location
• Types of erosion (217)- know these
– Sheet erosion
– Rill erosion
– Gull erosion
• Natural process - in natural ecosystems part of soil
formation process, but
– Disaster: wrong place, wrong time, in too great amounts
Figure 10-18
Page 217
Desertification (221)
• Positive feedback system – explain this
• Area 12X Texas in past 50 years
• About 20% land has been severely affected – reduction
of crop yield
• U.S. – 23% of all irrigated cropland is affected
• Causes
– Natural or human caused local climate change
– Erosion or salinization of topsoil due to excess irrigation
(severe on 21% of world’s irrigated land)
– Solutions (pg. 222)
Land Resources-Developed
Countries
• Less cultivated land than 100 years ago
– Why is there much less cultivated land?
• Astounding 400% increase in yield per acre
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Improved crop varieties
Fertilizers
Pesticides
Irrigation
Developing Countries
• Many reaching limits of potential cropland
• Tropical Soils: fertility rapidly depleted
• Loss of tropical forests
Problems of Erosion
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Reduced land fertility and thus productivity
Sedimentation of waterways
Smothering of wetlands and coral reefs
Siltation of reservoirs
Sources of Erosion
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Agriculture (60 % in U.S.)
Construction
Logging
Off-road vehicles use
Amounts in U.S.
• Many areas exceed replacement limit:
– max 1mm/yr
• 50 million boxcars of soil lost per year
– 500,000 trains, 100 cars long
• Agricultural Losses: Account for 60% of
impaired river miles in U.S.
Soil Conservation - Four Basic
Approaches (222 -226)
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Managing Topography
Reduced Tillage Systems
Providing or allowing ground cover to remain
Maintain and increase soil structure and
fertility
– Organic methods help
Providing Ground Cover
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Cover cropping (don’t let the soil bear!)
Mulching
“Green” mulches
Agroforesty (223)
Conservation Tillage: Minimum
Tillage Systems (223)
• Less frequent plowing
• Only plow where planting will occur
• Reduces
– Erosion
– Water loss
– Fertilizer leaching into waterways
• Cons:
– Purchase different equipment
– May delay planting
– May require more herbicides (weed killers)
Managing Topography (pg 224)
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Contour plowing (11.19)
Strip-cropping
Terracing
Perennial species
Don’t farm on steep slopes
Farm Act of 1985: made U.S. first major food
producer to make soil conservation a national
priority (223)
Preserving Farmland
• Accomplished through the purchase of
agricultural conservation easements (also known
as the purchase of development rights) on eligible
Lehigh County farm properties.
• As of June 2005, more than 175 farms totaling
over 15,000 acres have been secured with
perpetual agricultural conservation easements
Why Preserve Farmland
• Pennsylvania's #1 industry, agriculture
• local supplies of fresh food
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protect surface and ground water resources
air quality
wildlife habitat
scenic beauty and open space
Other Causes of Erosion
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Construction - homes, developments, malls
Highway construction
Mining
Logging
• Solution: use BMPs
– some examples
Soil Fertility
• Soil nutrients- chemicals needed by plants from
the soil
• Source in natural ecosystem
– decomposition – thus, recycling of chemicals from
living organisms
– Minerals – eroded and leached from rocks
– nitrogen fixation from air
Soil Chemistry –
• Fertility = soil nutrients Ion exchange
important
– Macronutrients
• nitrogen (nitrates)
• phosphorus
• Potassium
– Micronutrients: calcium, magnesium, sulfur, iron, etc.
• How are the proportions indicated on a bag of fertilizer?
• What do plants do with these nutrients?
– What VERY important elements of life are missing from the above
list?
• How is this different from how animals obtain the
“chemicals of life”?
Primary nutrients - NPK
• Nitrogen -growth of plant leaves (chlorophyll)
and stems
• Potassium - stem development, fruit and flower
formation
• Phosphorus - fruit and flower formation
• Soil testing - includes above and pH
Effect of pH
• pH: 6.5 to 7.0 is best
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ion (nutrient) uptake
many add lime (“sweetens” soil)
effect of rainfall
PA slightly acid soil
• Different types of plants “prefer” different pH
levels
• How do farmers/gardeners/lawn specialists
change the pH of their soil?
Fertilizers: Organic vs.
Inorganic
Synthetic - chemical - fertilizers
• Nitrogen - need high input of fossil fuels
• Phosphate - phosphate rock; altereted and
concentrated using fossil fuels
• Potassium - potash - from mines, extracted from
earth
• Negative – Supplies of some depend on use of fossil fuels
– if only synthetic, organic matter in soil decreases, soil looses
structure - then pore space, etc.
• What are the positive aspects of using synthetic chemical
fertilizers?
Organic Fertilizer
• Made from dead organisms or waste products
• Cottonseed meal, blood meal, fish emulsion, manure
and sewage sludge are examples of organic
fertilizers.
• Compost – define this
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kitchen garbage
leaves
grass clippings
manure
Organic Advantages
• Increase water-holding capacity of the soil.
• Improve the physical structure of the soil which
allows more air to get to plant roots.
• Bacterial and fungal activity increases in the soil.
– Mycorrhizal fungi make other nutrients more available to
plants thrive in soil where the organic matter content is
high.
• Organically derived plant nutrients are slow to leach
– less likely to contribute to water pollution than synthetic
fertilizers.
• Does not use fossil fuels - imitates natural cycles, so
unending supply
Disadvantages of Organic
Fertilizers
• In some cases, more expensive
• Requires more knowledge and research
• Harder to obtain in some cases
Chapter 13 - Food Resources
How is food produced?
• Croplands – primarily grains
– Rice, wheat, corn
• Rangelands
• Oceanic fisheries
Types of Agriculture (280-281)
• Industrialized
– High inputs – of energy, water, fertilizers
– Plantation agriculture
• Traditional
– Subsistence
– Traditional intensive
What are the Inputs into
Agriculture
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Water
Fertilizers
Energy
Crop diversity
Water
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Amounts
Salinization
Waterlogging
Pollution by nutrients
Pollution by sediments
Fertilizers
• Inorganic:
– 1950-20 kg/ha
– 1990: 91 kg/ha
• Why do some farmers over fertilize?
• Why is this a problem?
Alternatives to High Input
Fertilization
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Crop residues
Green manure
Compost
Crop rotation
Energy
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Fossil fuels supply most of energy
Machinery
Fertilizers and pesticides
Water pumping
Food processing, storage, distribution
The “Green Revolution”
Chapter 13- page 281
• See 10.8 - Per capita food production
• Two key contributors:
– High yield crop varieties
– Intensive fertilizer use
• “Miracle strains” rice, wheat, etc.
– Require high inputs of resources - fertilizers, water,
pesticides
• Encouraged corporate agriculture
Crop Diversity
• Much of increase in crop production has come from
high-yield varieties
• Can we outpace pests?
• Is preserving genetic diversity important?
• Are there advantageous genetic trait that have been
“lost” ?
Low Input Sustainable
Agriculture
• What are the inputs into agriculture and food
distribution?
• How can these inputs be reduced?
• Is it practical to reduce inputs?
– Advantages and disadvantages?
Sustainable Agriculture
• Maintain and replace soil
• Uses traditional methods
• Uses new, scientific methods
Coffee & Sustainability
• Equal Exchange
http://www.equalexchange.com/
• Ecological sustainability?
• Supply sustainability?
• Economic sustainability?
• Social sustainability?
Fisheries-Potential Protein Source
• 70% of global commercial fish stocks have been
depleted or nearly depleted
• A “Tragedy of the Commons”
• WHY?
– “Better” technology
– Increased population
– Global ocean pollution
• What to do?
– Read 213: Collapse of Canadian Cod Fishery
The “Blue Revolution”
• Fish Farming…Is this the answer to a world protein
shortage?
• Now: $5 billion/year industry
– 15% of world seafood market
• Trout & salmon in U.S.: 3/4 farmed
• Shrimp, crawfish, shellfish
• But….is there a down side to the Blue Revolution?
Where There’s Up….There’s Down
• Loss of coastal wetlands - conversion to shrimp and
fish pools
• Waste concentration
• Interbreeding with native fish - loss of natural
adaptations
• Competition of escapees with native fish
• Economic competition with native fisheries
Pest ControlChapter 20
BUGS….can’t live without ‘em, but
tough to live with ‘em
Pests
• What is a pest?
• A matter of perspective - not so easy to define
• Why not a problem in a balanced ecosystem or
balanced, polyculture agricultural system?
Pests
• What is a pest?
– Why not a problem in a balanced natural ecosystems?
• Examples
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weeds
grasshopper - $400 million each year in U.S.
Boll weevil and cotton borer
Many fungi on fruit trees
Trees
• Hemlock wooly adelgid
• Gypsy moth
• Fungi-chestnut blight, Dutch elm disease
– Transmit diseases - malaria, yellow fever, West Nile virus,
heartworm in dogs
What is a pesticide
• What is a pesticide?
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Rodenticides
Herbicides
Insecticides
Fungicides
Where are Pesticides Used - U.S.
• Agriculture: 3/4
• Herbicides: 59% (Figure 12.5, 252)
• Household application:
– 12% of pesticides
– 23% of insecticides
Second Generation of Pesticides
• First generation mostly natural substances
– pyrethrum, rotenone, nicotine sulfate
• Paul Muller - DDT - 1939
• Since 1950, more than 50X increase in pesticides
– $44 billion annually
The DDT Story
• Dichloro-diphenyl-trichloroethane
– Degradation product DDE
• What were the benefits?
– Use against mosquitoes and malaria reduction
• The decline of predatory birds- What
happened??
• Banned in early 1970’s in developed countries
Pesticide Use in the U.S.
• Trend in use:
30
25
20
15
Billion $
10
5
0
1950
1970
1996
Where are Pesticides Used - U.S.
• Agriculture: 3/4
• Herbicides: 59% (Figure 12.5, 252)
• Household application:
– 12% of pesticides
– 23% of insecticides
Categories of Pesticides
• Inorganics
• Natural organics or “botanicals”
• Chlorinated hydrocarbons-DDT,dieldrin,
paradichlorobenzene - moth balls
– very persistent and biologically magnified
• Organophosphates - malathion
• Carbanates-Sevin and Mirex (product names)
• Microbial agents/biological controls: bacteria, viruses
Chemical Pesticides Variables(514)
• Variables:
– Persistence (stability) in environment
• High: chlorinated hydrocarbons
– Biomagnification: Chlorinated hydrocarbons
– Effects on other organisms
• Broad vs. narrow spectrum Pesticides
• Toxicity to non-target organisms
Pesticides - Their Good Side
• Disease Control
– Malaria: 50 million humans saved
– Other diseases for which insects vectors
• Bubonic plague and Yellow fever
• Often very and quickly effective - thus, increase
profits for farmers & lower food costs
• Have increased food supplies for growing
population
• Risk vs. benefit
– If used properly relatively safe and newer pesticides
safer
The Case Against Pesticides (516)
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Effects on non-target species
Resistance and resurgence
Creating a new pest
Pesticides in the environment
Effects on human health
Effects on Nontarget Species
• Up to 90% of pesticides never reach target
• Effects on other insects - eg, honeybees
• Kill more than 67 million birds and 6-14 million
fish each year (517)
• Killing beneficial predators (both insect and
non-insect) (see next slide)
Creating “New” Pests
• Broad spectrum pesticides - eliminated natural
predators and parasites that previously kept pest
insects in check
• Examples of beneficials: ladybugs, parasitic
wasps, and praying mantis
Resistance & Resurgance:
Creating “superbugs”
• Percentage crops lost to insects increasing!
– 1940s: 31% US crops lost to pests
– today: 37% lost, yet 33X increase in synthetic
pesticides
• Genetic diversity results in pest resurgence
• Pesticide treadmill
Persistence and Mobility
• Vary with pesticides
• Found in air, surface water, groundwater, animal
and human tissues
• 100% of people in U.S have detectable amounts
of DDT or DDE
• Some human mother’s milk: could not be sold
due to high levels of some pesticides
• Bioaccumulation - especially fatty tissues
Effects on Human Health (Pg.519)
• Acute (short term)
– High doses
– Accidental spills (Bhopal, India-1984)
• Chronic
– Low doses
– Long time periods
– Synergism
– How to effectively assess health risks?
– Potential hormone disrupters - rat experiments
Extrapolation to humans??
• Circle of Poison (pg. 518)
How are Humans Exposed - Acute?
• Acute:
– Occupational - U.S. farmworkers - 300,000 suffer
pesticide related illnesses
• worldwide over 3 million; est. 18,000 deaths
• Home use and misuse - no license, training for home users lawns and interior
– Think about your pets!!
– Accidents:Accidental spills (Bhopal, India-1984)
How are Humans Exposed Chronic?
• How get exposed
– food (264)
• children may get larger exposure & more susceptible
• endocrine disrupters
• Nat Academy of Sciences: 4-20,000 cancer per year in
U.S.
– water
• Agent Orange in Vietnam- 2,4 D (contamination
with dioxin)
Can you reduce your risks?
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Follow directions
Minimize use
Buy organic
Grow organic
Wash all foods
Dispose of properly
Don’t demand perfection - see The Perfect
Apple (266)
BUT, what about malaria?
• Soon after the program collapsed, mosquito control lost access to its crucial
tool, DDT. The problem was overuse—not by malaria fighters but by
farmers, especially cotton growers, trying to protect their crops. The spray
was so cheap that many times the necessary doses were sometimes applied.
The insecticide accumulated in the soil and tainted watercourses. Though
nontoxic to humans, DDT harmed peregrine falcons, sea lions, and salmon.
In 1962 Rachel Carson published Silent Spring, documenting this abuse and
painting so damning a picture that the chemical was eventually outlawed by
most of the world for agricultural use. Exceptions were made for malaria
control, but DDT became nearly impossible to procure. "The ban on DDT,"
says Gwadz of the National Institutes of Health, "may have killed 20 million
children."
National Geog Magazine online
• Use of DDT to control mosquitoes- photo images
What is Sustainability
Sustainability rests on the principle that we must
meet the needs of the present without
compromising the ability of future generations
to meet their own needs.
“Sustainable” Agricultural
• Organic Farming
• IPM
Alternatives to Current Pesticides
In many cases…50 to 90% reduction in pesticide use w/o
reducing production
Read:” How Effective…Crop Losses?”
 (pg. 517)
Integrated Pest Management (IPM)
Biological Controls
Behavioral Changes
Organic farming and Gardening
Alternatives to Current
Pesticides
• Resistant plant varieties
• Don’t use monoculture
• Biological Controls
– Beneficial insects - (276-280)
• parasitic wasps, lady beetles (parasites)
– Bacteria that infect specific insects (B.t.)
– High technology:Computer programs and careful
monitoring - spray at exact time
– Birth control: Sterilized males released (so sorry
ladies)
– Phermones- devastate the bugs sex life
Integrated Pest Management
(IPM)
Replacing the Sledgehammer with the Scalpel
Penn State IPM
• High Technology/Education are Keys
• Precision of application of pesticides
• Mechanical cultivation and bug vacuums
• Success Stories
– MA apples
-Brazil soybeans
– Indonesian Rice (Fig. 12.21)
IPM - The Tenants
– Economic thresholds : economic losses greater
than costs of pesticides
• Information IPM relies upon close monitoring of pest
populations
• Scouting -method of monitoring pest populations
• Monitoring is employed in tracking populations of
beneficials as well as pests.
– Positive environmental effects - reduction of
excessive and
Organic Farming and Gardening
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No pesticides
No inorganic (chemical) fertilizers
Build up humus in soil
Focus on soil “health”
Focus on consumers health
Focus on farm workers health
Rodale Organic Research Farm