Chapter 10: Farming: Conventionaland 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 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)

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 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

Mollisols Feed The World

Aridisol, Kuwait

Ultisols:Alabama

Tennessee

Soils of the U.S.

Oxisol, California (a Paleosol)

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

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

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

• 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

• 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