23-36 Agriculture and Irrigation

Growing one species

Wheat, corn, and soy

• Highly efficient

• Little/no biodiversity

• More prone to pests

mixing and breaking up soil to make it easier to plant

• More erosion since soil is loosened

• Less organic matter and nutrients

• More particulate matter in the air and sediment in nearby water

cutting down vegetation and burning it to clear land for agriculture

Returns nutrients in plants to soil

• Loss of biodiversity, forest ecosystem services, loss
  of habitat

• Air and water warmer – no shade from trees

• More sediment in water and particulate matter in air

• Do not return organic matter to the
  soil

• Do not help soil to hold more water

• Do not add soil decomposers

• Leaching

• Groundwater contamination
  and eutrophication of surface waters

Aquifers

Water can flow easily in and out

Surrounded by impermeable rock and clay, slows down water flow

The uppermost level the groundwater fully saturates the rock or soil

How precipitation moves (percolates) through soil and goes into groundwater

confined aquifer

Water naturally flows to the surface

hole is drilled into a confined aquifer and the pressure is used to move the water to the surface

Overused by agricultural irrigation

Overused for irrigation

when water is quickly withdrawn from a well
and there is no groundwater around it

artificially providing water to support agriculture

Irrigation

overirrigated soils

Too much water in soil which raises the water table and inhibits plants’ ability to absorb oxygen through their roots

the buildup of salts in surface soil layers

• Worse in arid areas

• Can make soil toxic to plants

20% of irrigated cropland, costing over $11 billion/year

1. Furrow

2. Flood

3. Spray

4. Drip

a trench along crop rows that is flooded with water
inexpensive but about 1/3 of water is lost to evaporation and runoff (tree orchards)

the entire field is flooded with water & about 20% of water is lost to evaporation and runoff, and can also lead to waterlogging

an apparatus sprays water across a field, more efficient, only ¼ of water is lost to evaporation or runoff – more expensive and requires energy to run

a slow dripping hose is laid on or buried beneath the soil, most efficient, only 5% of water is lost to evaporation or runoff, expensive so often not used

• allowed people to settle in one place

• Populations increased

• Leading to more intensive agriculture

• biologically powered

• Uses human and animal muscle power

• Hand tools, simple machines

• Subsistence agriculture

• Polyculture

families produce only enough food for themselves

different crops are planted in one field

• Uses large-scale mechanization and fossil fuels to boost yields

• Uses pesticides, irrigation, and fertilizers

• Monoculture

• More efficient, increases output

• Devastates biodiversity

• Susceptible to disease and pests

Uniform planting of a single crop

does not deplete soil, pollute water, or decrease genetic diversity

uses smaller amounts of pesticide, fertilizers, growth hormones, water, and fossil fuels than industrial agriculture

• Uses no synthetic fertilizers, insecticides, fungicides, or herbicides

• Relies on biological approaches (e.g., composting and biocontrol)

• To prevent any potentially harmful cancer-causing food ingredients

• There are naturally occurring compounds that can cause and prevent cancer