23-36 Agriculture and Irrigation

APES 2024

Monocropping

Monocropping

Growing one species

What crops are typically used for monocropping

Wheat, corn, and soy

Effects of Monocropping

• Highly efficient

• Little/no biodiversity

• More prone to pests

Tilling

mixing and breaking up soil to make it easier to plant

Effects of tilling

• More erosion since soil is loosened

• Less organic matter and nutrients

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

Slash and burn agriculture

cutting down vegetation and burning it to clear land for agriculture

Effects of slash and burn agriculture

Returns nutrients in plants to soil

Deforestation

• 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

Synthetic (inorganic) fertilizers

• 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

Groundwater is stored in pore spaces of permeable rocks and sediment called

Aquifers

Unconfined aquifer

Water can flow easily in and out

Confined aquifer

Surrounded by impermeable rock and clay, slows down water flow

Water table

The uppermost level the groundwater fully saturates the rock or soil

Groundwater recharge

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

Water cannot go into a

confined aquifer

A spring is where

Water naturally flows to the surface

An artesian well is when a

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

Aquifer can be depleted if

Overused by agricultural irrigation

The Ogallala Aquifer in the central US has been

Overused for irrigation

Cone of depression

when water is quickly withdrawn from a well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

Irrigation

artificially providing water to support agriculture

What uses the most freshwater at 70%

Irrigation

Waterlogging

overirrigated soils

What does waterlogging cause

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

Salinization

the buildup of salts in surface soil layers

What does salinization cause

• Worse in arid areas

• Can make soil toxic to plants

Salinization inhibits production of

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

What are the four types of irrigation

1. Furrow

2. Flood

3. Spray

4. Drip

Furrow

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)

Flood

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

Spray

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

Drip

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

Agriculture

• allowed people to settle in one place

• Populations increased

• Leading to more intensive agriculture

Traditional agriculture

• biologically powered

• Uses human and animal muscle power

• Hand tools, simple machines

• Subsistence agriculture

• Polyculture

Subsistence agriculture

families produce only enough food for themselves

Polyculture

different crops are planted in one field

Industrialized agriculture

• 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

Monoculture

Uniform planting of a single crop

Sustainable agriculture

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

Low-input agriculture

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

Organic agriculture

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

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

Delaney Clause of the Food, Drug and Cosmetic Act (1958)

• To prevent any potentially harmful cancer-causing food ingredients

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