Download Soil Conservation

Soil Conservation
Why is soil conservation
important?
"A nation that destroys its soil
destroys itself." - President
Franklin D. Roosevelt, 1937
The Value of Soil
• Soil is one of Earth’s most valuable
natural resources, Why?
– Natural resource=anything in the
environment that humans use.
• Plants depend on soil to live and grow.
• Humans and animals depend on plants-or
on other animals that depend on plantsfor food.
• Fertile soil is in limited supply = not
much land for farming.
• Takes a long time for soil to form.
Soil Damage and Loss
• Human activities and changes in the
environment can affect the soil.
• The value of soil is reduced when soil loses
its fertility and when topsoil is lost due to
erosion.
Loss of Topsoil
• Whenever soil is exposed, water and wind can
quickly erode it.
• Plant cover can protect soil from erosion.
• Plants break the force of falling rain, and plant
roots hold the soil together.
• Wind is another cause of soil loss.
• Wind erosion can occur in areas with dry
conditions.
Sheet erosion is the removal of
the thin layer of topsoil by
raindrop splash or water run-off.
Wind erosion is the detachment
and movement of soil by wind.
Gully erosion occurs when small streams unite
and create a stronger flow, cutting a channel
down which water flows during or just after rain
The Dust Bowl
• Great Plains = farmers settled there
because of available fertile soil.
• Region has 8-year drought 1931-1939.
• Plowing removed the grass from the Great Plains
and exposed the soil.
• In times of drought, the topsoil dried out and
turned to dust and blew away.
The Dust Bowl
• By 1930, almost all of the Great Plains had been
turned into farms or ranches.
• Long drought turned the soil to dust.
• The wind blew the soil east in great, black clouds
• Dust Bowl ruined farmland in parts of the Great
Plains.
• Dust Bowl helped people realize the value of soil.
• Farmers adopted new methods to help save soil.
• Dust Bowl occurred during the Great Depression
Worldwide, an estimated 26
billion tons of topsoil are washed
or blown off cropland each year.
Every year 6 million hectares of
productive dryland become
desert.
Improve soil management
Practice:
* contour plowing
* reduced tillage or no
tillage,
* using windbreaks to
reduce wind speeds at the
land surface,
* allowing soils to rest
* promote humus
production
Soil Conservation
• Since the Dust Bowl, farmers have adopted
modern methods of soil conservation
• Soil conservation = management of soil to
prevent its destruction.
• Soil can be conserved by:
– Contour plowing
– Conservation plowing
– Crop rotation
Legumes
A plant that has pods as fruits and roots that bear nodules containing
nitrogen-fixing bacteria
Crop Rotation
Intercropping
Nitrogen Fixation with Legumes
•
Biological nitrogen fixation can be represented by the following equation, in which two moles of
ammonia are produced from one mole of nitrogen gas, at the expense of 16 moles of ATP and a supply of
electrons and protons (hydrogen ions):
N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi
Video
Contour Plowing
• Contour plowing=farmers plow their fields
along the curves of a slope.
• This helps slow the runoff of excess rainfall
and prevents it from washing the soil away.
Conservation Tillage
• In conservation tilage, farmers
disturb the soil and its plant
cover as little as possible.
• Dead weeds and stalks of the
previous year’s crop are left in
the ground to help return soil
nutrients, retain moisture, and
hold soil in place.
• Also called: low-till or no-till
plowing, reduced- tillage.
Crop Rotation
• Crop rotation-a farmer plants
different crops in a field each
year.
• Different types of plants
absorb different amounts of
nutrients from the soil.
• Corn and cotton-absorb large
amounts of nutrients.
• Year after planting these
crops, farmer plants crops that
use fewer nutrients, such as
oats, barley, or rye.
• The year after that the farmer
sows legumes such as alfalfa
or beans to restore the nutrient
supply.
Cover Crops
• A cover crop is a crop planted primarily to manage soil erosion, soil
fertility, soil quality, water, weeds, pests, diseases, biodiversity and
wildlife in an agroecosystem, an ecological system managed and
largely shaped by humans across a range of intensities to produce food,
feed, or fiber.
Clips
• http://www.brainpop.com/
– Soil
– Erosion
– Natural resources