15 2 Crops and Soil Traditional Methods Animal

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