bio 111 food production and agriculture week5

8/2/2019 Bio 111 Food Production and Agriculture Week5

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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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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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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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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

bio 111 food production and agriculture week5

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