Lecture 16/17
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Why is soil considered an ecosystem
it contains both living and non-living matter
What are the most important areas for agriculture were originally grass lands
• Northern mixed grass prairie (North America) • Tall grass prairie (North America) • Pampas (South America) • Steppes (Europe/ Asia) • Savannah (Africa)
What are the factors that influence soil formation
• organisms • topography • time • climate • parent material
What are the types of weathering processes
• physical (wind, rain, thermal expansion/contraction, water freezing) • chemical (water and gases) • biological (tree roots and lichens)
define humus
dark, spongy, crumbly mass of organic material formed by partial decomposition
What are soil layers described by
• colour, texture, structure, pH
What are the different soil layers
O horizon = surface litter A horizon = topsoil –> contains decaying organic matter (humus) and living soil organisms B horizon = subsoil –> denser than A horizon, higher mineral content, lower fertility C horizon = contains rock in the process of being broken (weathering) to produce new soil R horizon = solid rock that has not been broken down
define ion exchange capacity
• cations (K, Na, Ca, Mg) remain in root zone • anions (NO3, PO4, SO4) leach out of root zone
define agriculture
The practice of growing crops and raising livestock for human use and consumption
define cropland
land used to grow crop plants
define rangeland or pasture
land used for grazing livestock
define subsistence agriculture (traditional agriculture)
families produce only enough food for themselves - supplemented by hunting
define intensive agriculture (traditional agriculture)
produces excess food to sell - uses animals, irrigation, and natural fertilizers - does not use fossil fuels
define monoculture
uniform planting of one single crop - not natural
what are some uses of monoculture
• large-scale mechanization (machinery) • high fossil fuel quantities to boost yields • irrigation (high water needs) • chemicals (pesticides and fertilizers)
define feedlots (factory farms)
CAFO (concentrated animal feeding operations) - Large warehouses or pens designed to deliver energy-rich food to animals living in extremely high density enclosures (pens, cages)
What are some benefits of CAFO’s
• greater production of food • unavoidable in countries with high levels of meat consumption, • reduces demand for land for pasture
What are some drawbacks to CAFO’s
• contributions to water/air pollution • poor waste containment causes outbreaks of disease/infections • high use of antibiotics to control disease – antibiotic resistance
define extensification
bringing more land into production
define intensification
better productivity per unit of land
what is the green revolution dependent on
• synthetic fertilizers • chemical pesticides • irrigation • heavy equipment
what are some positive effects of the green revolution
• prevented some deforestation • preserved biodiversity
what are some negative effects of the green revolution
• pests • pollution (fertilizers) • erosion • salinization • desertification
define pest
any organism that damages valuable crops and/or livestock