Lecture 18 Development of Agriculture

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19 Apr 2012
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Lecture 18 BIO220 Development of Agriculture: Some Basic Ecology of Food
Production
Introducing Staple Foods
Primitive diet: opportunistic, unreliable
Humans do not adapt to folivary
What makes fruits good? Selection attractiveness = > dispersal
Seeds, tubers: energy storage organs
Artificial selection on native plants
Grasses: wheat, rice, maize, barley
Key innovations
oNon shattering seed heads (plant evolution)
oAmylase evolution (human evolution)
Legumes
Fruits
Ancient technical innovations
Fishing by net (mass technology)
Irrigation channels
Domestication of agricultural animals and lactose tolerance evolution
Plow replaced digging sticks
Limitations of primitive cropping systems
Intrinsic growth performance of crops
oLimited areas suitable for growth
oEdaphic factors: soil moisture, fertility
oSoil exhaustion, buildup of insects, disease
Leaching of soils
When rainwater, snowmelt percolate downward through soil,
dissolving ions carry down to water tables, out of reach to plant
roots.
Ions dissolved depend on temperature, pH
Ancient soils heavily leeched
Prairie plants ~ perennials with immense root systems: enrich soil with organic matter
Legumes enrich soil with N
Form root nodules: bacteria capture inert N2 soluble, reactive form
American Midwest best agricultural soil
High in nutrients (especially N)
High organic content, High H2O, nutrient retention, indicated by black color
European farmers bias American agriculture: cleared forests rather than use prairie soil
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