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

100 years

Aridisols

10,000 yrs. 100,000 y 1 m.y.

Inceptisols Alfisols

1000 yrs.

Spodosols

Mollisols

Ultisols Oxisols

Soils Defined by Special Constituent Materials

Andisols Volcanic Ash Histosols Vertisols Gelisols Peat, Organic Matter “Self-Mixing” Clay Soils 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 10 15 10 18 J/yr cal/yr = 25 x – Global Energy Use = 474 × 10 18 J/yr

• • • • •

Farming is energy-intensive

Global Food Production = 6 x 10 15 10 18 J/yr cal/yr = 25 x Global Energy Use = 474 × 10 18 J/yr Direct Agricultural Energy Use = 1% of Total or about 5 x 10 18 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