bio 111 food production and agriculture week5
TRANSCRIPT
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Food Production and
Sustainable Agriculture
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Soil formation is slow and complex
soil is formed from eroded rock, lava, volcanic
ash weathering - processes that break down rocks
to form soil
physical - wind, rain, freezing and thawing chemical - reactions with water, acids, or other
materials
biological - organisms (such as lichens) break
down the rocks this takes a long time
(Note: see the article on soil in this week's assignmentmodule)
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Soil degradation has many causes
soil degradation
results fromdeforestation,agriculture andovergrazing
over the past 50years, soildegradation hasreduced global
grain productionby 13%
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Effects of overgrazing
strips land and causes erosion
animals trample and compact the soil
decreases fertility non-native invasive species may move into
the area
new vegetation less palatable to livestock new species may out-compete and replace
native vegetation
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Streamside ecosystem before and aftercattle grazing - this is the same location!
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Soil erosion is a global problem desertification - loss of
more than 10%productivity
humans are primarycause of desertification
and erosion
is occurring atunnaturally high rates
in Africa, erosion overthe next 40 yearscould reduce cropyields by half
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Dust Bowl occurred in 1930s - poor
farming practices causedserious erosion problems
drought made conditionsworse
thousands of farmers lefttheir land and had to rely ongovernmental help
dry soil, stripped of its
vegetation, blew on windtraveling all the way acrossthe country (people in NewYork City had houses filled
with eroded dust)
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Winds carry eroded soilNote: I took this photo recently!
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Erosion of sediments into the Gulf ofMexico (Landsat photo)
light
color is the
eroded soil in
the water
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Protecting the soil
shelterbelts(windbreaks)- rows oftrees or other
tall, perennialplants that areplanted alongthe edges of
fields to slowthe wind
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Protecting the soil
plant cover
reduces erosion roots of trees
and other plantstrap and holdsoil particles
whenvegetation isstripped froman area, wind
can blow thesoil away andrain can washsoil into riversand streams
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Sustainable agriculture contour farming -
plowing furrowsacross a hillside,perpendicular to the
slope
terraces - levelplatforms cut into
steep hillsides
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Monocultures increase production, butcause other problems
monoculture - largeexpanse of a single crop
but:
devastates biodiversity
more susceptible todisease and pests
narrows human diet
places world food securityat risk - 90% of our foodcomes from only a fewcrop and animal species
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Sustainable agriculture
crop rotation alternating the
crops grown fieldfrom one season
or year to thenext
cover crops
protect the soilwhen the maincrops arentplanted
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Sustainable agriculture
intercropping -planting differenttypes of crops inalternating bands or
other spatially mixedarrangements
reduces pestpopulations andprevents erosion
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Result of irrigation in the U.S.
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Sustainable agriculture
it's easier and cheaper
to prevent salinizationthan to fix it
don't plant water-
intensive crops inareas without enoughrainfall
irrigate efficiently -
supply only the waterthe crop requires
drip irrigation targetswater directly to
plants
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Fertilizers
inorganic fertilizer use
has skyrocketed
over-applying fertilizercan ruin the soil and
cause water pollution nutrient runoffcauseseutrophication of
aquatic ecosystems nitrates leach
through soil andcontaminate
groundwater
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Fertilizers boost crop yields butcause problems
fertilizer - contains essential nutrients (nitrates,phosphates, and other minerals)
inorganic fertilizers - mined or synthetically
manufactured organic fertilizers - the remains or wastes of
organisms
manure, crop residues, fresh vegetation compost = produced when decomposers break
down organic matter
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Pesticides cause health andenvironmental problems
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Problems with pesticides
pesticides areexpensive andnot usuallyavailable to
subsistencefarmers
pest populationsdevelop
resistance(review: naturalselection)
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Logic of Natural Selection
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Evolution of Pesticide Resistance
pesticide kills most
insects, but strainswith geneticresistance survive
resistant insectspass their genes tonext generation
percent of resistant
insects increases most of population
becomes resistantto pesticide
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Other problems with pesticides
also kills valuable,non-pest species(such as bees andother pollinators)
pesticide residues
are passed upthrough foodchains, poisoningupper trophiclevels
(bioaccumulation)
l f d
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Bioaccumulation of pesticides
d ( )
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Integrated Pest Management (IPM)
IPM uses multiple techniques to suppress pests
and minimize use of pesticides using pesticides that are specific for particular insect
pests (and not harmful to predator insects)
using pesticides only when absolutely necessary
economically beneficial for farmers and helps theenvironment as well
encourages sustainable practices
decreasing dependence on chemical fertilizers
switching to sustainable measures such as croprotation, encouraging pest-destroying predators,planting soil enriching crops (such as legumes),breeding new pest-resistant crop species, etc.
d d
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IPM case study: Indonesia
within 4 years of using IPM in Indonesia, rice
yields rose 13%, and $179 million saved byphasing out subsidies
what did they do to accomplish this?
used several sustainable IPM methods planted new strains of insect resistant rice
since many of their serious insect pests haddeveloped resistance to pesticides, pesticide use
was dramatically reduced those pesticides still used killed pests without
harming helpful natural predators (such asspiders)
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Indonesia continued
other sustainable IPM methods were used natural predators were introduced to the fields
harmful insects were also removed by hand
crop rotation helped reduce pest numbers byremoving their food source
success of this program depended on extensive
farmer education and implementation ofmethods that were suited to the environmentaland social conditions of the country
Ri fi ld
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Rice fields(Note: the people working in the fields will give you an
idea of the size of the fields)
A i id d d i I d i
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As pesticide use decreased in Indonesia,what happened to rice production?
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Sustainable agriculture
organic farming uses no synthetic fertilizers or pesticides
healthier for you and the environment
support local farmers locally grown foods don't travel as far so you
get them when they're fresher
uses less fossil fuel for transportation(reduces food costs and helps with globalwarming too!)
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Preserving crop diversity
modern agriculture uses only a few,selectively bred varieties of crops
food security - preservation of crop
diversity ensures against the loss of anentire crop due to diseases or pests
"heirloom" crops have many valuablequalities (resistance to pests and diseases,
valuable nutrients, etc.) example: quinoa
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Quinoa (pronounced keen-wa) a grain that comes from
the Andes Mountains ofSouth America
origins are truly ancient was one of the three
staple foods, along with
corn and potatoes, of theInca civilization contains more protein than
any other grain - anaverage of 16 %
compared with 7.5 % forrice and 14 % for wheat
some varieties of quinoaare more than 20 percentprotein
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Quinoa grain
tastes great - email me for a recipe