Transcript Crops and Soil

Crops and Soil
Arable Land
• Land that can be used to grow crops
– As the human population increases, the
amount of arable land decreases
Basic Processes of Farming
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Plowing
Fertilization
Irrigation
Pest control
Traditional Agriculture
• Plows pushed by farmers or pulled by
livestock
• Organic (manure and plant waste)
fertilizers used
• Fields irrigated by flowing water in ditches
• Weeds removed by hand or machine
Modern Agriculture
• Machines powered by fossil fuels for
plowing and harvesting crops
• Synthetic chemical fertilizers used
• Overhead sprinklers and drip irrigation
used
• Synthetic chemicals used to kill pests
Soil
• Fertile Soil: soil that can support the
growth of healthy plants
• Soil forms when rock is broken down into
smaller fragments by wind, water, and
chemical weathering
– Can take hundreds or thousands of years to
form just a few centimeters of soil
Soil
• Rock particles add mineral nutrients
• Decomposed dead plant matter add more
nutrients
• Earthworms, insects, and small animals
break up soil and allow air and water into it
– Helps plants grow
Soil Erosion
• Erosion- the wearing away of rock or soil
by wind and water
– About half of the original topsoil in the U.S.
has been lost to erosion in the past 200 years
– Almost all farming methods increase the rate
of soil erosion
Land Degradation
• Occurs when human activity or natural
processes damage the land so that it can
no longer support the local ecosystem
Desertification
• Process by which land in arid or semiarid
areas becomes more desertlike because
of human activities or climate change
– Causing some arable land to disappear
– Often from too many crops planted too
frequently and overgrazing
Soil Conservation
• Protects and manages topsoil and reduces
erosion
• Soil usually erodes downhill
– Many soil conservation methods designed to
prevent downhill erosion
Soil Conservation Methods
• Soil retaining terraces built across a
hillside
• Contour plowing
• Windrows
– Catch soil and water
• No till farming
• Areas may be better suited for forests or
grazing land
Enriching the Soil
• Traditionally organic
• Inorganic fertilizers used to double world
food production
• Often pollute water through runoff
Modern Soil Enhancement
• Use both organic and inorganic fertilizers
by adding compost and chemical fertilizers
to the soil
– Compost: partly decomposed organic material
Salinization
• The accumulation of salts in the soil
– Major problem in areas with low rainfall and
naturally salty soil
– Irrigation water comes from rivers or
groundwater which is saltier than rainwater
– When the water evaporates, the salts are left
behind
– The soil may become too salty to support
plants
– May be slowed if irrigation canals are lined to
prevent water from seeping in to the soil or
water the soil heavily to wash out the salts
Salinization
How can you protect our soil?