37-52 Irrigation, agriculture, and pest control

plowing perpendicular across a hill
- Prevents rills and gullies

Level platforms cut into steep hillsides
This “staircase” contains water

• Crops that live year round

• Harvested multiple times

• Longer and more established roots

• Prevents bare soil after harvest

rows of trees planted along edges of fields
- Slows the wind
- Can be combined with intercropping

reduces the amount of tilling
-Leaves at least 30% of crop residues
in the field

disturbs the soil even less

growing different crops from one year to the next
- Returns nutrients to soil
- Prevents erosion, reduces pests
- Wheat or corn and soybeans
- Pests usually prefer one crop

planting different crops in alternating bands
-Increases ground cover
-Replenishes soil
-Decreases pests and disease

include crop rotation and using green manure and limestone

base will neutralize acids in soil, raises pH so soil is more basic than acidic

regular rotation of livestock between different
pastures in order to avoid overgrazing in a particular area

Leftover plant matter from a cover crop

institutions that preserve seed types as living museums of genetic diversity
Seeds are collected, stored, and periodically planted

stores millions of seeds from around the world

any organism that damages valuable crops

any plant that competes with crops

poisons that target pest organisms

• Insecticides = kill insects

• Herbicides = kill plants

• Fungicides = kill fungi

• Rodenticide = kills rodents

They pass these genes to their offspring

stop being effective

chemists increase chemical toxicity to compete with resistant pests

nontarget organisms (Including predators and parasites of pests, Pest populations become harder to control)

Genetic modification

Bt corn with bacteria that produces Bt crystals toxic to pests

Roundup so weeds are killed and not crop (Monsanto lawsuit)

• Biocontrol

• Chemicals, if necessary

• Population monitoring

• Habitat alteration

• Crop rotation and transgenic crops

• Alternative tillage methods

• Mechanical pest removal

• Intercropping

13% and saved $179 million/yr in phased-out subsidies

uses a pest’s predators to control the pest
- Reduces pest populations without
chemicals
- Reduces chemical use

• Cactus moths control prickly pear

• Ladybugs for aphids

• Parasitic wasps for caterpillars

unpredictable (risky)

“nontarget” effects on the environment and surrounding economies

than halting pesticide use

carefully planned and regulated

• Reduces death and mutation of nontarget species

• Less dangerous health effects on humans

• Less contamination of surface and ground water

pests

• Hummingbirds

• Bats

• Insects (bees, wasps, etc.)

attract pollinators

entire beehives have vanished

is unknown (Insecticides? Parasites? Stress?)

Reducing or eliminating pesticide use and planting
flowering plants

100 crops and contribute $15 billion in services/year