understanding the importance of soil lesson plan nres b2-1 1

Understandingthe Importance of Soil

Lesson Plan NRES B2-11

Anticipated Problems

1. What is the importance of soil as a life-supporting layer?

2. What is the importance of soil as a medium for plant growth?

3. What are the agricultural uses of soil?

4. What are the nonagricultural uses of soil?

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Terms

• Adobe• Cropland• Geotextile• Load-bearing capacity• Shear• Shrink-swell capacity

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Soil as a Life-Supporting Layer

• Soil is important because it is one of the earth’s most fragile resources.

• A very thin and fragile layer of life-supporting material.

• All life depends on it in one way or another.

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• The earth consists of:

• A solid part: core, mantle, and crust

• The atmosphere surrounding it

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• The earth:

• Most of the crust is covered with sea

• Where the continents are, the crust is thicker

• The continental crust, made of rock is about 50 miles thick

• The atmosphere is about 170 miles deep.

• Soil forms a very thin interface between the crust and atmosphere. 7

Resources for Living Things

• The atmosphere, crust, and soil interact to provide plants and animals with the resources they need. Living things need:

• Proper oxygen

• Temperature

• Water

• Carbon and all other nutrients

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1. These factors are exchanged in the soil,

usually in cycles that allow elements to be recycled rather than lost.

2. Plant roots need oxygen to grow.

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3. Plants grow best in certain temperature ranges. Soil temperature, and to some degree the air above the soil, is controlled by a heat-exchange mechanism.

4. Water seldom stays in one place long, always on its way to the next stage of the water cycle.

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5. Water evaporates from the land, lakes, and ocean and forms clouds in the atmosphere.

• Rain falls from the clouds, moistens the soil and fills streams and lakes.

• Evaporation starts the cycle again.

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6. Carbon is the element most essential to all life. life.

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7. Plant nutrients, chemicals a plant needs to grow, cycle through the soil. Two types of nutrient cycles are:

• The nitrogen cycle

• Other mineral cycles

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8. Other nutrients come from rocks in the earth’s crust. These chemicals are

released when rock is broke down by weather, plants, and other factors.

9. In the interchanges between the crust, soil and atmosphere, soil temporarily stores resources for plant use.

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Importance of Soil as a Medium for Plant Growth

• Soil has an important function in recycling resources needed for plant growth.

• An individual plant depends on soil to supply four needs: • Anchorage• Water• Oxygen• Nutrients for roots

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Anchorage

• In deep soils where roots grow freely, plants are firmly supported or anchored, so they can grow to reach sunlight.

• Plants grown hydroponicly often require a wire framework for plant support.

• Newly planted trees may need to be staked or “guyed” until the tree is firmly rooted.

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Water

• Roots are a plant’s best water absorbing body. The soil supplies nearly all the water a plant uses.

• For each pound of dry matter produced by growth, different plants obtain between 200 and 1,000 pounds of water from the soil for photosynthesis, sap flow, and other uses.• Water-holding capacity of a soil is

important in its agricultural uses. 17

Oxygen

• All living creatures, except for a few microscopic organisms, need oxygen.

• Plants release oxygen during photosynthesis, but they consume it during respiration.

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Oxygen

• The parts of the plant above ground, suspended in an atmosphere that is 21% oxygen, have all the oxygen they need.

• Plant roots and organisms that live underground in the soil use up the oxygen and give off carbon dioxide.

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Oxygen

• Soil air has less oxygen and more carbon dioxide than the atmosphere.

• Soil aeration exchanges soil and atmospheric air to maintain adequate oxygen for plant roots.

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Nutrients

• Of the sixteen nutrients considered to be essential for normal plant growth, thirteen are obtained from the soil.

• Carbon, oxygen, and hydrogen come from the air and water

• The rest are stored in the soil (P, K, NS, Ca, Fe, Mg, B, Mn, Cu, Zn, Mo, Cl).

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Nutrients

• Plant leaves are able to absorb some of the nutrients, but the roots are specialized for this purpose.

• Root hairs absorb plant nutrients dissolved in the soil solution by an active process that moves nutrients into root cells.

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Agricultural Uses of Soil

• Human societies depend on soil to grow food, fiber, timber, and ornamental plants.

• If the soil is to be designated agricultural use, the main use is to grow plants.

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• Different agricultural uses require different soil management practices.

• Cropland is land on which soil is worked and crops are planted, cared for, and harvested.

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• Annual crops account for the greatest acreage of cropland planted and harvested within one growing season.

• Allow for yearly soil preparation to control weeds and to work fertilizer and organic matter into the soil.

• If the soil surface is bare or moderately bare, erosion concerns must be considered.

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• Perennial forages are in the ground for a few years. • May be harvested for hay or used for

grazing

• Cover the soil completely

• Keeps the soil from washing away.

• Soil is not tilled each year

• Fertilization is different

• Soils tend to build themselves up

• Improves the soil28


• Much of the land in the United States is used to graze animals.

• In the eastern half of the country• Pasture is planted to perennial forages.

• In the western half of the country• Most grazing is on rangeland, that consists

of native grasses and shrubs (drier climate)

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Nonagricultural Uses of Soil

• Non-farming soil uses include:• Recreation• Engineering projects such as structures• Disposing of waste

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Uses of Soil: Recreation

• Recreational uses of the soil surface have become important. • Playgrounds

• Ball fields

• Jogging paths

• Golf courses

• Parks and campgrounds

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• The design of such recreational areas is a specialized skill that requires knowledge of soil properties.

• Sports playing fields require the most demanding of all soil uses.

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• To grow turf against the punishment of the human foot can challenge the best of managers.

• Rather than native soil, the best playing fields are engineered mixes of loam, specific sizes of sand and other ingredients.

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• Geotextile, a plastic mesh, may be used to hold the soils in place.

• The fields generally have several soil layers that are carefully graded, drained and well maintained.

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• Soil managers dealing with playing fields are concerned with the sideways pressure from shoes tearing the soil surface, an action called shear.

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• Playing fields are designed to have good shear resistance and hardness.

• Provide a proper playing surface that helps to reduce injuries

• Dry quickly after a rain, yet hold enough water to grow good turf

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Uses of Soil: Engineering

• Before the construction of a building, highway, railroad or bridge, the soil is tested to a depth of several feet.

• Part of the structural soundness depends on the soil under it

• Foundations will crack if the soil settles under the structure

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• Important engineering properties of shrink-swell and load-bearing capacity must be considered prior to construction.

• Many soils swell when wet and shrink as they dry, cracking walls, destroying foundations, and breaking buried pipes.

• Soils high in clay or organic matter have low load-bearing capacity. (structures can shift/crack) 39


• Before long-distance shipping of building material became practical, most often people built their homes on locally available materials.• Adobe, a sun-baked mixture of three parts

sandy soil to one part clay soil, has been used as a building material for thousands of years.

Brick made from adobe mud & straw

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• Modern applications of soils are being developed in the search for energy-efficient housing. Buildings can be built:

• Underground, into hillsides, with soil piled over them

• Earth-sheltered buildings are warm in the winter and cool in the summer, lowering the heating and cooling costs.

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Uses of Soil: Disposal

• Soil has long been used for waste disposal.

• Society has generated large amounts of waste

• Handling them in a safe manner becomes difficult and sometimes hazardous.

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• Treatment of human sanitary waste often relies on soil because it filters out some of the material, while microorganisms break down organic portions into less dangerous compounds.

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• One way sewage treatment plants handle the end products is to spread them on soil.

• Sewage sludge can be useful as a source of nutrients and/organic matter

• Harmful materials in the sludge must be taken into account.

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• Sanitary, especially hazardous chemical or radioactive waste landfills, require soils that will not allow hazardous materials to leach into the water table or runoff into neighboring streams or lakes.

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Review

• Explain the reasons why soil is important.

• What are the four needs that an individual plant depends on soil to supply?

• What is land on which soil is worked and crops are planted, cared for, and harvested?

• Name three main nonagricultural uses of soil.

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understanding the importance of soil lesson plan nres b2-1 1

Documents

soil temperature

nonagricultural uses

plant roots

plant nutrients

fragile resources

plant needs

recycling resources

plant growthsoil