Understanding the Importance of Soil Lesson Plan NRES B2-1

Anticipated Problems What is the importance of soil as a life- supporting layer? What is the importance of soil as a medium for plant growth? What are the agricultural uses of soil? What are the nonagricultural uses of soil?

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

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.

Soil as a Life-Supporting Layer The earth consists of: A solid part: core, mantle, and crust The atmosphere surrounding it

Soil as a Life-Supporting Layer 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.

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

Resources for Living Things 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.

Resources for Living Things 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.

Resources for Living Things 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.

Resources for Living Things 6. Carbon is the element most essential to all life. life.

Resources for Living Things 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

Resources for Living Things 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.

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

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.

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.

Oxygen All living creatures, except for a few microscopic organisms, need oxygen. Plants release oxygen during photosynthesis, but they consume it during respiration.

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.

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.

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).

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.

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.

Agricultural Uses of Soil Different agricultural uses require different soil management practices. Cropland is land on which soil is worked and crops are planted, cared for, and harvested.

Agricultural Uses of Soil 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.

Agricultural Uses of Soil 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 soil

Agricultural Uses of Soil 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)

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

Uses of Soil: Recreation Recreational uses of the soil surface have become important. Playgrounds Ball fields Jogging paths Golf courses Parks and campgrounds

Uses of Soil: Recreation 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.

Uses of Soil: Recreation 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.

Uses of Soil: Recreation 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.

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

Uses of Soil: Recreation 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

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

Uses of Soil: Engineering 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)

Uses of Soil: Engineering 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

Uses of Soil: Engineering 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.

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.

Uses of Soil: Disposal 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.

Uses of Soil: Disposal

Uses of Soil: Disposal 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.

Uses of Soil: Disposal 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.

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.