Soil

Importance of Soil

Why is soil important?

one of the earth’s most fragile resources.

very thin and fragile layer of life-supporting material

All life depends on it in one way or another.

What are the earth’s components?

CoreMantleCrust

Most covered by water

Atmosphere Soil forms a very thin interface between the continental crust, which is about 50 miles thick, and the atmosphere, which is about 170 miles deep.

Cross Section of the Earth

What resources do living things need?

The atmosphere, crust, and soil interact to provide these nutrients.

Proper oxygen

Proper temperature

Water

Carbon

Other various nutrients

How do living things generate these resources?

The resources are exchanged in the soil, usually in cycles that allow elements to be recycled rather than lost.

Breakdown of Cycling and Exchange

Plant roots need oxygen to grow.

Plants grow best in certain temperature ranges.

Breakdown of Cycling and Exchange

Water seldom stays in one place long.

Breakdown ofCycling and Exchange

The Carbon CycleCarbon is the element most essential to all life.

Two types of nutrient cycles.

Plant nutrients = chemicals a plant needs to grow

Two Types:Nitrogen cycle

Other Mineral cycles

Nitrogen Cycle

Nitrogen comes entirely from the atmosphere, where it occurs as a gas that plants cannot use.

Soil organisms change gaseous nitrogen to forms that plants can use.

Other Mineral Cycles

Other nutrients come from rocks in the earth’s crust.

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

Folder Reflection

How is soil a part of your life?

Why is soil important to you?

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

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

Plants depend on soil to supply four needs.

All living creatures need oxygen.

Of the 16 essential nutrients for normal plant growth, 13 are obtained from the soil.

Soil supplies four needs….

Anchorage

Water

Oxygen

Nutrients

Anchorage

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

Plants that are grown hydroponically often require a wire framework for plant support

Newly planted trees may need to be staked until the tree is firmly rooted.

WaterRoots 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

Plants release oxygen during photosynthesis, but they consume it during respiration.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 CO2.

Oxygen

Soil air has less oxygen and more CO2 that the atmosphere.

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

Nutrients

Of the 16 nutrients considered to be essential for normal plant growth, 13 are obtained from the soil.

Carbon, Oxygen, and hydrogen come from the air and water, the rest are stored in the soil (P, K, Na, 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.

What are the 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.

Soil Management Practices

Different agricultural uses require different soil management practices.

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

Soil Management Practices

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

Annual crops 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.

Soil Management Practices

Perennial forages are in the ground for a few years.

Some may be harvested for hay or used for grazing.These crops cover the soil completely and keep the soil from washing away.Since the soil is not tilled each year, fertilization is different and the soils tend to build themselves up and improve the soil.

Grazing

Much of the land in the U.S. 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, which has a drier climate, most grazing is on rangeland, that consists of native gasses and shrubs.

Forests

Forests disturb the soil the least, but soil management is still a major concern.

The harvesting of trees requires special considerations.

If the trees are harvested after many years of growth, the logging equipment may tear-up the vegetative cover and compact the soil.

Forests

Other considerations for forestry might include choosing the best trees for each soil type, and ensuring good conditions for new plant seedlings.

What are the nonagricultural uses of soil?

Human activities, other than growing plants, require soil.

Non-farming soil uses include:Recreation

Engineering projects

Disposing of waste

Recreational uses of soil.

Playgrounds

Ball fields

Jogging paths

Golf courses

Parks

Campgrounds

Sports playing fields

Recreational uses of soil.

Sports playing fieldsThe best playing fields are engineered mixes of loam, specific sizes of sand and other ingredients.

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.

Recreational uses of soil.Sports playing fields

Soil managers dealing with playing fields are concerned with the sideways pressure from shoes tearing the soil surface, an action called shear.Playing fields are designed to have good shear resistance and hardness. They must provide a proper playing surface that helps to reduce injuries.They must dry quickly after a rain, yet hold enough water to grow good turf.

Engineering considerations for soil.

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

The structural soundness of the structure depends not only on the skill of the builder, but also o the soil under it.

Foundations will crack if the soil settles under the structure.

Engineering considerations for soil.

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 braking buried pipes.

Engineering considerations for soil.

Soils high in clay or organic matter have low load-bearing capacity

Structures built on such soils may shift and crack.

Engineering considerations for soil.

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.

Modern applications of soils are being developed in the search for energy-efficient housing.

Engineering considerations for soil.

Buildings can be built underground, into hillsides, or even with soil piled over them.

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

Soil used for waste disposal.

Society has generated large amounts of waste and handling them in a safe manner becomes difficult and sometimes hazardous.

Soil used for waste 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.

Soil used for waste 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, as long as possibly harmful materials in the sludge are taken into account.

Soil used for waste 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 / Summary

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?