Chapter10: Agriculture

Report
Chapter 10: Farming: Conventional
and Sustainable Practices
10.1 Resources For Agriculture
• Soils are complex ecosystems
• Healthy soil fauna can determine soil fertility
• Your food comes mostly from the A horizon
Soil Formation
Young Soils
• Strongest Influence Is Parent Material
Mature Soils
• Strongest Influences: Climate, Vegetation,
Drainage
Never Safe From Weathering
Soil Formation Processes
Leaching from Surface
• K, Mg, Na
• Ca
• Si
• Al, Fe
Accumulation beneath Surface
• Al, Fe in Humid Climates
• Ca in Arid Climates
• Clay (Mechanical Movement)
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
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
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
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
"The 7th Approximation"
• U.S. Soil Conservation Service
• 12 Soil Orders
"The 7th Approximation"
Degree of Weathering and B Horizon Development
Little
Slight
Moderate Large
Extreme
Entisols
Aridisols 10,000 yrs. 100,000 y 1 m.y.
Inceptisols Alfisols
Spodosols Ultisols
100 years 1000 yrs. Mollisols
Oxisols
Soils Defined by Special Constituent Materials
Andisols
Volcanic Ash
Histosols
Peat, Organic Matter
Vertisols
“Self-Mixing” Clay Soils
Gelisols
Soils on Permafrost
Mollisols Feed The World
Aridisol, Kuwait
Ultisols:
Alabama
Tennessee
Soils of the U.S.
Oxisol, California (a Paleosol)
Soils and Organisms
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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
10.2 Ways We Use And Abuse Soils
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Arable land is unevenly distributed
Soil losses reduce farm production
Wind and water move most soil
Deserts are spreading around the world
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
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
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
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
People have always used pest controls
People have always used pest controls
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)
10.6 Organic And Sustainable
Agriculture
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What does “organic” mean?
Careful management can reduce pests
Useful organisms can help us control pests
Integrated Pest Management uses a
combination of techniques
10.7 Soil Conservation
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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
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
Soil Depletion
• Wind
• Water
• Remedies
– Windbreaks
– Contour plowing
– Strip Cropping
– No-till Agriculture
Contour Plowing
Strip Cropping

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