Chapter 10: Farming: Conventional and Sustainable Practices
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Transcript of Chapter 10: Farming: Conventional and Sustainable Practices
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Chapter 10: Farming: Conventionaland Sustainable Practices
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10.1 Resources For Agriculture
• Soils are complex ecosystems • Healthy soil fauna can determine soil fertility • Your food comes mostly from the A horizon
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Soil Formation
Young Soils• Strongest Influence Is Parent Material Mature Soils• Strongest Influences: Climate, Vegetation,
Drainage
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Never Safe From Weathering
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Soil Formation ProcessesLeaching from Surface• K, Mg, Na • Ca • Si • Al, Fe Accumulation beneath Surface• Al, Fe in Humid Climates • Ca in Arid Climates • Clay (Mechanical Movement)
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Soil Horizons and Profiles• Soil Horizons– Layers in Soil– Not Deposited, but Zones of Chemical Action
• Soil Profile– Suite of Layers at a Given Locality
• Some CSI myths– You can’t generally identify a soil from surface
material– You can’t generally pinpoint a location from a soil
sample
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Principal Soil Horizons
• O: Organic (Humus)– Often Absent
• A: Leaching– K, Mg, Na, Clay
Removed• B: Accumulation– Absent in Young Soils– Distinct in Old Soils– Al, Fe, Clay (Moist)– Si, Ca (Arid)
• C: Parent Material
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Limits of Soil Formation• Balance Between: – Downward Lowering of Surface – Downward Migration of Horizons
• If erosion rapid or soil evolution slow, soils may never mature beyond a certain point. – Soils on Steep Slopes– Soils in Arid or Cold Climates
• Extremely ancient soils may have lost everything movable
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Soil Classification• May be the most difficult classification problem in
science • Varied Bases for Classification– Age– Parent Material– Climate and Drainage
• Multiple Objectives– Scientific– Agricultural– Engineering
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"The 7th Approximation"
• U.S. Soil Conservation Service• 12 Soil Orders
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"The 7th Approximation"
Degree of Weathering and B Horizon DevelopmentLittle Slight Moderate Large ExtremeEntisols Aridisols 10,000 yrs. 100,000 y 1 m.y.
Inceptisols AlfisolsSpodosols Ultisols
100 years 1000 yrs. Mollisols OxisolsSoils Defined by Special Constituent Materials
Andisols Volcanic AshHistosols Peat, Organic MatterVertisols “Self-Mixing” Clay SoilsGelisols Soils on Permafrost
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Mollisols Feed The World
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Aridisol, Kuwait
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Ultisols:Alabama
Tennessee
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Soils of the U.S.
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Oxisol, California (a Paleosol)
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Soils and Organisms• Bacteria• Fungi• Nematodes• Springtails• Earthworms (not always good?)– Aerate and Mix Soil, but….– In northern U.S. and Canada, most are exotic– Consume Organic Matter
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10.2 Ways We Use And Abuse Soils
• Arable land is unevenly distributed • Soil losses reduce farm production • Wind and water move most soil • Deserts are spreading around the world
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The Counterfeit Paradise
• Year-round growing season – but ---• Tropical Soils are nutrient poor• Tropical ecosystems ruthlessly recycle
nutrients• Agriculture rapidly depletes nutrients– Slash and burn agriculture– Need for Fertilizer for intensive agriculture– Hardpan development
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10.3 Water And Nutrients
• All plants need water to grow• Plants need nutrients, but not too much– "Brawndo's got what plants crave. It's
got electrolytes"• Farming is energy-intensive– Global Food Production = 6 x 1015 cal/yr = 25 x 1018
J/yr– Global Energy Use = 474 × 1018 J/yr
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Farming is energy-intensive• Global Food Production = 6 x 1015 cal/yr = 25 x
1018 J/yr• Global Energy Use = 474 × 1018 J/yr• Direct Agricultural Energy Use = 1% of Total or
about 5 x 1018 J/yr• By Some Estimates We Use More Energy Than
We Get Out• We Cannot Grow Enough Crops to replace
Fossil Fuels
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10.4 Pests And Pesticides• People have always used pest controls• Modern pesticides provide benefits, but also
create problems– Kill beneficial organisms– Toxic to humans– Resistance
• There are many types of pesticides
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People have always used pest controls
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People have always used pest controls
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10.5 Environmental Effects Of Pest Controls
• Pesticides accumulate in remote places • Many pesticides cause human health
problems• Hormone Disruptors• “Organic” Pest Control Can Backfire– Mongooses in Hawaii to Control Rats– Cane Toads in Australia to Control Beetles– Mosquito Fish (Worldwide)
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10.6 Organic And Sustainable Agriculture
• What does “organic” mean? • Careful management can reduce pests • Useful organisms can help us control pests • Integrated Pest Management uses a
combination of techniques
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10.7 Soil Conservation
• Contours reduce runoff • Ground cover protects soil • Reduced tillage leaves crop residue • Low-input agriculture can be good for farmers
and their land• Consumers’ choices play an important role
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Natural and Human Processes
• Most human processes are “natural”• What’s unnatural:– Rate of human processes– Scale of human processes– We Now Move More Material Than Natural
Erosion
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Soil Depletion
• Wind• Water• Remedies– Windbreaks– Contour plowing– Strip Cropping– No-till Agriculture
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Contour Plowing
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Strip Cropping