15-2 Crops and Soil

• Traditional Methods– Animal or human power– Organic fertilizers and

mulch– Flowing water through

ditches– Weeds removed by hand

or machine

• Modern Methods– Machine power with

fossil fuels– Synthetic chemical

fertilizers– Synthetic pesticides and

herbicides used to kill pests

– Variety of irrigation methods

Erosion

• Two main causes – wind or water

• When vegetation is removed by plowing or cutting the roots that anchor the soil can no longer do so.

Desertification

• Land in arid or semi-arid regions converting from grassland to desert

• Worldwide – grasslands are farmed most.

• When they are overgrazed or crops are not rotated a type conversion results

Sahel - Africa

Salinization

• Accumulation of salts – problem in arid environments

• Can eventually result in unusable land

• Ex: Westlands water district

Westlands salinization

Conserving and enriching the Soil

• Management techniques include– Contour plowing– Row crops– Drip irrigation– No-till farming

• Compost and inorganic fertilizers

SECTION 15-2 PART II

Pests, Pesticides and Pest Control

• Any organism that occurs where it is not wanted or that occurs in large enough numbers to cause economic damage

• Plants, fungi, microorganisms, insects etc.. Gypsy moth – Eastern Forests

• Wild plants often have natural resistance to pest species

• One reason crops are susceptible is that they are not genetically diverse and are grown in monocultures

Pesticides• Used to kill insects,

weeds and other pests• Some are synthetic

others are derived from natural chemicals (nicotine)

Pesticide resistance

• Over 500 species of insects have evolved resistance to pesticides since 1940

• Many plants are now resistant to herbicides

Human Health Concerns

• Cancer risk • Biomagnification (DDT)• Hormone mimics

(chlordane)

Biological Pest Control

• Using living organisms to control pests– BT used to control

caterpillars (bacteria that eats them from the inside)

– VNT – uses natural barriers and chemical defenses

– Biodegradable toxins from plants

Chrysanthemum

Integrated Pest Management

• Includes a mix of sustainable approaches

Sustainable Agriculture

• Keeps land productive indefinitely

• Minimizes use of energy, pesticides, water and fertilizer

• Make use of natural controls and crop rotation