Soil Science

Understanding the Importance of Soil

Objectives Explain the importance of soil as a life suppor

ting layer;

Explain the importance of soil as a medium for plant growth;

Describe agricultural uses of soil; and Describe non-agricultural uses of soil.

Life-Supporting Layer Soil is a very fragile, limited resource

It develops very slowly All life depends on it

Soil interacts with the atmosphere and Earth’s crust to provide plants and animals with the resources they need

Life-Supporting Layer These resources are usually exchanged

through cycles Can you think of any natural cycles?

Water Carbon Oxygen Temperature

Life-Supporting Layer Oxygen

Needed for adequate root growth

Life-Supporting Layer

Temperature Soil absorbs heat from the sun. It

also loses heat to the atmosphere This cycle provides temperatures

for plant growth and seed germination

Life-Supporting Layer Water

Utilized for growth of plants Water is constantly moving to the next stage of the water

cycle

Life-Supporting Layer Carbon

Utilized in the form of organic matter in the soil

Life-Supporting Layer Nutrients

Chemical fertilizers Organic fertilizers

Plants need soil to grow Plants depend on soil to provide four basic needs.

Anchorage Water Oxygen Nutrients

Anchorage—soil acts to provide a firm support as roots grow throughout the soil.

Water—soil provides nearly all of the water used by plants. Water is absorbed through the plants’ roots.

Plants need soil to grow Oxygen—nearly all living organisms need

oxygen. Plants release oxygen during photosynthesis but

consume oxygen during respiration. Plant parts above the ground have an ample

supply of oxygen; however, those below the ground (roots) have less oxygen available.

This increases the need for good soil aeration, the exchange of soil and atmospheric air in order to maintain adequate oxygen for plant roots.

Plants need soil to grow Nutrients—of the 16 nutrients considered to

be essential for plant growth, 13 are obtained from the soil.

Root hairs absorb the nutrients dissolved in soil water.

Uses for Soil- Agriculture Agriculture depends on soil to grow food,

fiber, and ornamental plants for human societies.

Various uses include the following:

Uses for Soil: Agriculture

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

Most cropland is devoted to annual crops, such as corn, soybeans, cotton, vegetables, etc.

Uses for Soil: Agriculture Grazing land—this is

land used for grazing cattle and sheep.

It is often planted to perennial forage.

Uses for Soil: Agriculture Forest—this is land

used for growing trees which are later harvested for building materials, paper, etc. This use disturbs soil

the least , but conservation is still a major concern

Uses for Soil: Agriculture Water structures—ponds and other reservoirs

are constructed out of soil.

Uses for Soil: Non-Ag. Humans require soil for many other uses

besides growing plants. Such uses include the following:

Uses for Soil: Non-Ag. Recreation—recreational activities include

playgrounds, sports fields, jogging paths, golf courses, parks, campgrounds, and many others.

Uses for Soil: Non-Ag. Foundations—

buildings depend on a solid soil base upon which to be built to remain structurally sound.

Uses for Soil: Non-Ag. Construction

Before building soil must be tested to ensure sound structure in a building or other structure Shrink-swell

Some soils swell when wet and shrink when dry

Load-bearing Capacity Excessive clay or organic matter decreases load-bearing

capacity

Uses for Soil: Non-Ag. Homes and other structures

are occasionally built underground, into hillsides, or even with soil piled over them.

Earth-sheltered buildings help in lowering heating and cooling costs.

Prior to shipping of building materials people used what they had locally Adobe was very common It is made by mixing 3 parts

sandy soil and 1 part clay soil then allowed to bake or dry in the sun.

Uses for Soil: Non-Ag. Waste disposal—soil is

often used for the treatment of human sanitary wastes.

Soil filters some of the material, while microorganisms break down organic portions into less dangerous compounds.

Uses for Soil: Non-Ag. Terms to know

Geotextile Plastic mesh used to hold soils in place Can you think of applications for this?

Shear Usually a problem on athletic fields; the tearing of the

soil surface by sideways pressure from shoes