Soils NR 200

Unit 1The Soils

Around Us

What is soil?

Dictionary – The unconsolidated material that occupies the earth’s surface and supports plant life.

Or perhaps: The link between the living and non-living. (The non-living supporting the living)

I. Functions of Soil in our Human World

A. Medium for plant growth

B. Important component of the hydrological system

C. Mother nature’s way of recycling organisms

D. A sphere for living organisms ie macro and micro organisms

E. Supporting foundations of our human made structures

II. Four major components of soil.

Water

Air

Mineral

O.M.20-30%

20-30%

45%

5%

Minerals: 45%

1) Rocks that are broken down into particles that we call soil

2) Source of 13 of the 16 nutrients needed for plant growth.

Air 20-30%

1) the roots need O2 for respiration

2) organisms need O2 as well

Soil Solution: water with dissolved

minerals held in the soil particles.

20-30%

Organic matter

1) From once living organisms

2) Decaying and making their minerals available again

3) Improves water holding capacity

4) Humus is the longer lasting material that is responsible for this water holding ability, colloidal.

III. Plant Requirements for Soil or

What the soil needs to provide the plant to allow it to grow successfully

A. Anchorage

1)     Needed to allow the plant to have as many leaves positioned to accept sunlight

2)     Keep plant in place to receive water and minerals

B. Oxygen

1) Needed to allow for respiration

2) Needed for microorganisms to flourish

C. Water

1) Almost all the water the plants need

comes from the soil

2) Also important for the microbial

action in the soil

3) Important for nutrient absorption

4) pH: the degree of alkalinity or acidity of the soil solution or soil

pH range - 1 – 7 – 14 a logarithmic relationship

Water continued:

Soil pH is simply the measurement of the H+ ion

D. Temperature moderation

1) The ability of the soil to insulate itself from the extreme hot and cold of the air above it.

2) Allows the roots to grow and an environment favorable to microorganisms

E. Nutrients: 16 essential for

plant growth

1) Only C,H and O are taken in by the plant from the atmosphere the other 13 are from the soil.N,P,K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Mo, and Cl?

A few to watch Ni, Co, Na and Si?

2) Root hairs are the plant structure responsible for bring in the nutrients and water.

3) The elements must be brought into the plant via ionic solution that is, ions dissolved in solution. These ions go into solution from the colloids in the soil. Pg 25

3) The plant obtains these minerals by:

a) Root interception - that is the root

grows into a new area and captures

the ionic solution.

c) Diffusion – ions move from areas of higher concentrations to areas of lower concentrations ie around roots.

b) Mass flow – soil water with ions moves into contact with the root.

F. Free From Harmful Organisms

IV. Soil Profile: Cross

Section of the Soil

Observed Vertically

O- Organic layer

i - undecomposed organic material

a – organic material highly decomposed

A- Topsoil:The Most Productive Soil

1) Best for nutrient holding, water capacity, micro-organisms

2) The most important soil profile for plant life

3) p – plowed or other cultivated disturbance (man made)

E – An area where the greatest eluvation (removal of clay, iron and

OM) occurs, resistant materials such as quartz, sand and silts remain usually light in color.

B – Sub Soil or Zone of Accumulation, Illuviation - Usual Location of Hardpan

m - cemented zone usually silicates or calcium

g - strong gleying

C – Parent material but broken down but not subject to the soil forming properties as the above solum (A&B) and not massive in

structure as R

R- Rock

Soil Profile

V. Soil texture is the amount of sand, silt and clay in the soil.

Sand: 2 - .05 mm Silt: .05 - .002 mm Clays: less than .002 mm

VI. Soil structure is ……….the way these smaller aggregates

form larger particles.

Soil is the interaction of the lithosphere (rock), Atmosphere, Hydrosphere and the Biosphere (living organisms)

With proper management and care our soils can produce a healthy bountiful harvest

Uses of Soil

1) Agriculture

2) Non-Agriculture

a) Recreation

b) Foundations

c) Waste disposal

d) building materials

3) Land use of the future????