Agriculture and the Environment

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Agriculture and the Environment
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Introduction

• There is no such thing as a free lunch.
• No major efforts to date to increase the global
  food supply have been free of environmental
  costs.

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Possible Environmental Effects
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How Agriculture Affects the Environment

• Agriculture is the worlds largest industry, it
  is the most dependent on land, and has a wide
  variety of impacts on the environment.

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How Agriculture Affects the Environment

• Agricultural effects can be classified as
• Primary Direct or on-site
• Secondary indirect or off-site.
• These effects can be identified as
• Local
• Regional
• Global

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How Agriculture Affects the Environment

• Local effects
• Those which occur in close proximity to the farm
  area.
• These include
• Soil erosion
• Soil nutrient depletion
• Waterway sedimentation.

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How Agriculture Affects the Environment

• Regional effects
• The result of farming activities impacting large
  areas.
• These include
• Desertification
• Major changes in large waterways
• Large-scale soil fertility changes.

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How Agriculture Affects the Environment

• Global effects
• Climatic changes
• Disruption of major chemical cycles.

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Soil Components

• Inorganic
• Minerals Responsible for soil texture
• Gravel/rock gt2.0 mm
• Sand 2.0 0.02 mm
• Silt 0.02 0.002 mm
• Clay lt0.002 mm
• Organics
• Living organisms
• Detritis dead organic matter
• Humus residue left by decaying organic matter
  highly reactive.

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Soil Organisms
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Soil Profile
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Soil Characteristics

• Aeration
• Air located in spaces between soil particles.
• Allows oxygen and carbon dioxide exchange with
  roots.
• Sandy best, clay worst.
• Water
• Balance between infiltration, retention and
  evaporation.
• Sandy soils good for infiltration, poor for
  retention.
• Clay soils the opposite

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Balance of Water in Soil
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Soil Characteristics

• Water-holding capacity is directly related to
  nutrient-holding capacity because most nutrients
  are dissolved in the water
• A good water-holding soil is also a good
  nutrient-holding soil
• Sandy soil poor at water and nutrient holding
• Clay soil good at water and nutrient holding
• Workability
• ease in cultivating the soil
• Sand best clay worst

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Overall Soil Quality

• Results from a mix of the abiotic and biotic
  components

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A productive soil type Loam, a mixture of clay,
sand, and silt has soil particles of different
sizes combines the best properties of the
different pure soils.Even betterhumus-rich
loamcontains the organic matter from decaying
plant and animal remains (mostly leaf litter)
Soil Productivity
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Maintenance of productive soil depends on
replenishing organic matter as it is used
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Affects on Soils

• Extensive and in some cases irreversible damage
  has occurred to the Earths productive soil base
  as a result of past farming, grazing and forestry
  practices.
• Disturbed soils are highly susceptible to
  erosion, structural damage, and nutrient
  depletion.

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Soil Degradation

• Erosion loss of organic matter and fine
  particles due to wind and water

Mineralization
Desertification
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Impacts to Soil

• Plowing activities
• Disturbs the soil in ways unlike any natural
  force or process severe, long-term stress on
  soil.
• The primary detrimental effects on soil from
  plowing
• Erosion
• Loss of soil organic content

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Impacts to Soil

• Sediment damage
• Deposition of eroded materials into waterways or
  reservoirs.
• Damage fisheries.
• Damage ocean ecosystems (e.g. coral reefs).
• Reduce water quality through the addition of
  excess nutrients and chemicals.

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Other Causes of Erosion

• Deforestation loss of forest cover due to
• Need for agricultural land (often due to
  increasing population size and switch to
  rangeland to satisfy increasing demand for meat
  by developed countries)
• Timber harvest for wood products again, often
  demanded by developed countries (teak, mahogany)
• Firewood for cooking and heating (especially
  common in developing countries)

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Secondary Causes of Erosion

• Increased suspended solids in aquatic systems.
• Sedimentation in aquatic systems.
• Eutrophication of aquatic systems.

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Soil Degradation Additional Causes

• Long-term effects of irrigation
• Salinity increase
• Water logging
• Salt-rise
• A problem in areas with saline soils
• Nutrient loss
• Reliance on fertilizers
• Secondary impacts on aquatic systems

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Irrigation

• Types
• Flood
• Center-pivot

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Consequences of Soil Degradation

• Crop failure/food shortage
• Immigration from area
• Additional deforestation.

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Soil Degradation
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Making Soils Sustainable

• Ideally, good farming practices would maintain a
  balance between soil formation and soil loss.
• Contour plowing follows the land contour and
  plowing perpendicular rather than parallel to
  slopes. Traditionally the single most effective
  method for minimizing erosion.

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Making Soils Sustainable

• Other techniques
• Strip cropping Alternate strips of crop with
  good soil-binding vegetation to minimize soil
  erosion by water and wind.
• Shelterbelts Plant trees/shrubs at edges of
  field to minimize wind erosion.
• Terracing Grade sloping farmland into a series
  of flat steps plant crops on only level ground
  to decrease water erosion.

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Making Soils Sustainable

• Other techniques
• Crop rotation Alternate cash crops every third
  year or so with non-cash crops.
• Allowing a portion of the land to lie fallow for
  a year, but this is not often feasible.

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Making Soils Sustainable

• Other techniques
• No-till agriculture
• Reduce weeds through herbicide use
• Leave plant stubble from previous crop and allow
  to decay
• Accomplish several steps in one pass of the land
  (create planting furrows, drop seed, fertilize,
  and cover seeds simultaneously).
• Minimizes soil exposure and erosion.

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Carrying Capacity of Grazing Land

• Overgrazing lands whose carrying capacity for
  livestock is surpassed.
• The effects of overgrazing include
• Loss of species diversity
• Soil erosion
• Wetland/waterway degradation.
• Carrying capacity for livestock varies greatly
  from region to region.

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Grazing Land

• The classification of rangeland condition
  reflects a comparison between actual condition
  and estimated potential condition.
• Modern livestock industries employ such practices
  as feedlot production that has a severe impact on
  resources, such as energy and water quality.

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Grazing Land

• Traditional herding practices have effects on the
  soil ranging from beneficial to seriously
  detrimental, depending on the size of the herd
  and the resiliency of the ecosystem.

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Desertification A Regional Effect

• Deserts are the natural result of climatic
  conditions that do not provide enough steady
  moisture for plant growth and soil enrichment.
• Desertification Human activities that produce
  the formation of deserts. (More than under normal
  conditions.)

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Desertification

• Causes of desertification
• Poor farming and forestry practices
• Overgrazing
• Conversion of rangelands to farm lands
• Pollution
• Excessive irrigation of poorly-drained soils in
  arid regions and an increase in salt build-up in
  those soils destroys a soils productivity and
  create a desert.

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Preventing Desertification

• The major symptoms of desertification are
• Water table lowering
• Increased soil erosion
• Soil salinization
• Reduction of surface water
• Loss of natural vegetation.

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Preventing Desertification

• Desertification prevention depends on monitoring
  the aquifers and soils to check for onset of the
  previously mentioned indicators.
• Soil conservation programs and reforestation are
  important in preventing the spread of deserts.

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Global Effects of Agriculture

• Agriculture can have global environmental effects
  including
• Change in albedo (reflectivity of the land) due
  to vegetation removal
• Change in water evaporation rates
• Change in land surface texture
• Change in global chemical cycling.

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Global Effects of Agriculture

• Modern agriculture can upset the global carbon
  cycle through fossil-fuel usage (CO2 emissions)
  and by hastening soil organic carbon loss.
• The use of fire to clear lands for agriculture
  can affect the climate by increasing atmospheric
  particulate load.
• Agriculture can lead to loss of biodiversity and
  potentially to species extinction.

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Pest Control

• Ecological pests defined as
• Those organisms that outcompete, parasitize, or
  prey upon desirable species.
• Loss to pests is enormous.
• In the U.S., 33 of potential harvest and 10 of
  factual harvest is lost to pests.

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Chemical Pesticides
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Pest Control

• Major agricultural pests
• Insects
• Nematodes
• Bacteria
• Viruses
• Plants
• Certain vertebrates.

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Chemical Pesticides

• Most common approach used.
• Insecticides
• Inorganics lead, arsenic, cyanide
• Second Generation Chlorinated hydrocarbons
  DDT
• Third Generation Organophosphates, Carbamates,
  Pyrethroids
• Herbicides
• Rodenticides
• Fungicides

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Weeds

• Agricultural practices create ideal conditions
  for the spread and establishment of weeds, most
  of which are hardy pioneer species.
• Weeds are highly competitive and can dramatically
  reduce crop yields.
• The most pesticides sold in the U.S. are
  herbicides.

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Development of Pesticides

• Narrow spectrum.
• Broad spectrum (earliest pesticides).
• Some natural-based pesticides are comparatively
  safe, but are not a successful as synthetic
  pesticides.

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Development of Pesticides

• DDT chlorinated pesticide and originally thought
  to pose no hazard.
• Has been found to be
• Biologically mobile
• Bioaccumulate
• Bioconcentrate
• Pose a threat to non-pest species, even humans.

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Development of Pesticides

• DDTs most harmful effects showed up in birds
  that occupy the highest trophic level.
• Banned in 1971 in the U.S.
• Still widely used world-wide, especially in areas
  prone to malaria and yellow fever, but insects
  are developing genetic resistance.

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Development of Pesticides

• Organophosphates have replaced chlorinated
  pesticides as the preferred choice in most
  developed nations.
• O.P.s have shown more specificity and less
  persistence in soils and tissues, but are more
  acutely toxic in humans.

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Major Challenges Associated with Pesticide Use

• Effects on non-target organisms
• Wildlife and humans
• Causes
• Over-spray
• Run-off
• Spills
• Improper application/use

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Contamination Associated with Over-Spray
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Biomagnification
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Development of Pesticides

• Extended use of pesticides can lead to
• Secondary pest outbreaks by creating a
  competitive advantage for some infrequent or
  naturally-controlled pests.
• Pesticide carousel.

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Pesticide Carousel
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Integrated Pest Management

• IPM is a modern approach to pest control that
  emphasizes management over eradication.
• IPM utilizes a variety of approaches.
• An effective IPM system will recognize species
  interactions in ecosystems and use them as an
  advantage for pest control.

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Integrated Pest Management

• IPM uses
• Natural predators
• Increasing crop diversity
• Adopting minimum tillage agriculture
• Highly specific pesticides.

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Integrated Pest Management

• IPM governed by four principles
• Control not eradication
• Maximum use of natural control agents
• Ecosystem management
• Awareness or and preparedness for unexpected or
  unwanted effects.

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Integrated Pest Management

• IPM is applied through
• Chemical use
• Advanced plant breeding
• Biological control
• Effective land culture.

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Integrated Pest Management

• Biological Control
• Uses natural ecological interactions (predation,
  parasitism, and competition).
• Uses insect predators, parasitic bacteria and
  insects and habitat manipulation.
• A new group of synthetic chemicals imitate sex
  pheromones to disrupt the life cycles and mating
  patterns of insect pests.

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Natural Enemies

• Ladybird beetles eat scale insects.
• Parasitic wasps control caterpillars.
• Grass carp to control aquatic weeds.

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Biological Control
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Integrated Pest Management