2 What is arable land? Land that can be used to grow crops Only 10% of land on earth is arable.Urban areas occupy 3% and are currently invading arable land.
3 What is the history of agriculture? Traditional AgriculturePlows pulled by animals to turn & loosen soil.Organic fertilizer (animal manure) used to enrich soil for plant growth.Drainage ditches were dug to bring water to plants for irrigation.Weeds pulled by hand.
4 What is the history of agriculture? Modern AgricultureLarge machines plow land and harvest crops.Synthetic chemical fertilizers used instead of manureOverhead sprinklers & drip systems irrigate cropsSynthetic chemical pesticides are used to kill pestsThe chemical fertilizer & pesticides are often oil based.
5 How does soil form?Rock breaks down into fine particles and mix with decomposing matter to make topsoil.Chemical WeatheringRock is broken down by chemical rxn btwn water & a substance in rock that can be dissolvedEX: Lichen secrete acids that break rock downPhysical WeatheringWaterWindBacteria, fungi, earthworms all break down dead matter & recycle nutrients back to soil.Earthworm burrows allow air to circulate in soil
6 What are the layers of soil? Surface litter/Organic layer- leaf litter, partially decomposed organic matterTopsoil- organic matter, living organisms, fine rock particles; also water & airSubsoil- larger rock particles, some organic matter, mostly inorganic compoundsParent Rock- bedrock that has been weatheredBedrock- solid rock layer
7 What problems are associated with our use of soil? ErosionMovement of rock & soil by wind or water½ of topsoil in US has eroded- affects ability to grow cropsFarming increases rate of erosion through plowing & irrigationDesertificationLand in arid/semi-arid areas becomes more desert-likeDue to overgrazing & planting too many cropsSalinizationSoil too salty to grow plants in.Becomes salty fromOver-irrigationLow rainfallFlooding field with freshwater can remove excess saltWhite salt deposits on cropland
8 What steps are taken to conserve soil? Terracing- cutting levels into steep hillside to slow water erosionContour plowing- plowing across hill on gentle slope to slow water erosionStrip plowing- leaving strips of vegetation in every other row so roots hold soil in place
9 What steps are taken to conserve soil? Drip irrigation- using series of hoses to drip water around plant roots; expensive but very effectiveNo-till harvesting- harvesting crop without turning soil. Roots hold soil to prevent erosionCons- old crop might crowd out new crop and decrease crop yields
10 What steps are taken to conserve soil? Crop Rotation-Rotating crops to replenish nutrients in soil.Corn crops remove nutrients from soil so planting a crop of soybean the next year will replenish those nutrients back to the soil.CompostPartly decomposed organic matter from yard waste, home food waste, or crop wasteAdded with chemical fertilizers to enrich soil.
11 You should be able to…Explain the difference between traditional and modern farming methods.Describe the structure and composition of fertile soil.Explain why the presence of plants helps prevent soil erosion.Explain why soil conservation is an important agricultural practice.