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Soil Conservation
"A nation that destroys its soil destroys itself." - President
Franklin D. Roosevelt, 1937
Why is soil conservation important?
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 plants-for 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 managementPractice:
* 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
Crop Rotation Intercropping
A plant that has pods as fruits and roots that bear nodules containing nitrogen-fixing bacteria
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
