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1. WHAT IS SOIL?
Soil is a collection of natural bodies of earth’s
surface, in places modified or even made by man
or earthy materials, containing living matter and
supporting or capable of supporting plants
outdoors.

2. PHYSICAL PROPERTIES OF
SOILComposition
Soil microbes make a small
portion of the organic make up.
For example worms
Texture
Sand >>>>>>>large>>>>>>rough
Silt>>>>>>>>medium>>>>medium
Clay>>>>>>>small>>>>>>fine/soft
Soil texture is measured by size of soil particles

3. Soil texture determines the amount and size of
spaces between soil particles. This controls
how quickly water moves through the soil
profile and how much water the soil holds.

4. SOIL PARTICLES
Soils vary in the size of the
particles they contain, the
amount of space between
these particles, and how
rapidly water flows through
them.

5. Structure: refers to the arrangement of soil
particles.
Granular
Platy
Wedge
Columnar

6. The best soil structure is high in proportion of
medium sized aggregates and a significant
number of large pores through which water
and air can move.
Structure is important in both A and B
horizons

7. BULK DENSITY
Bulk density is the mass of dry soil per unit
volume, including the air space.
Bulk density has a major effect on the
movement of air and water in soils.
Soils with high bulk densities are often
compacted.

8. No
Compaction
Compaction
(plow pan)
Soil compaction restricts
rooting depth, which reduces
the uptake of water and
nutrients by plants.

9. Compaction also
decreases infiltration,
thereby increasing
runoff and the hazard of
water erosion.

10. Soil Depth: Total depth of topsoil subsoil, and
parent material.
This allows for root growth to occur.
Soil depth will affect the yield of crop
Production

11. Soil Color: helps in recognizing the different soil
types but color is also an indicator of certain
physical and chemical characteristics. Color is due
to two factors
1.Humus content (organic matter)
2.Chemical nature of iron compounds present in
soil.

12.  Larger the pore space the less water the soil
holds.
Smaller the pore space the more water the
soil holds.
WATER HOLDING
CAPACITY

13. SOIL PROFILE
Broken into Horizons
Refers to the arrangement and
properties of the various soil
layers.
Layers are horizontal and
formed during the development
of the soil.

14. Topsoil
Surface or very top layer. This may be a few
inches or a few feet.
Very dark with organic matter
Subsoil
Just under topsoil
Lighter in color and nutrient value
Parent Material
Lower layer.
Layer in which the sub and top soil develop
from.

15. SOIL PROFILES OF THE PRINCIPAL
TERRESTRIAL
SOIL TYPES

16. ORGANIC MATTER
Soil organic matter consists of plant and animal
residues in various stages of decay.
Adequate levels benefit soil in four ways
1. Improves physical condition and structure
2. Increase water infiltration
3. Decreases erosion losses
4. Supplies plant nutrients

17. REACTION (pH)
Reaction is a measure of acidity or alkalinity of a
soil. Acidity or alkalinity is determined by the
amount of hydrogen and hydroxyl ions in the soil.
When hydrogen ions outnumber hydroxyl ions the
soil is acidic. In the reverse condition the soil is
basic. A pH scale is used to measure the level of
acidity or alkalinity.

19. REACTION
In NC, the natural soil pH will range
from 4.0 to 8.0 with most soils tending
to be acidic with pH values of 4.5 to
6.0.
In order to optimize plant growth,
farmers and homeowners commonly
adjust the pH of a soil by adding soil
amendments such as lime. The
amount of lime that needs to be added
should be determined by a soil test.

20. SOIL pH
Importance of Soil pH
Affects solubility of minerals
More soluble in slightly acidic soils
Most crops do best at pH – 6.5
Plants preferring acid soil -----pineapple
Plants preferring basic soils------Barley, sugar
beets
High Ca demand
Alfalfa – neutral/slightly basic pH

21. Also affects soil microbes
Decreased soil microbe activity w/ acidic
soils
Slow/stop decomposition of beneficial
materials
Decreased N availability
SOIL PH

22. CATION-EXCHANGE CAPACITY
Cation-exchange capacity (CEC) is
a measure of the ability of a soil to
hold and exchange cations. It is one
of the most important chemical
properties in soil and is usually
closely related to soil fertility. A few
of the plant nutrient cations that are
part of CEC include calcium,
magnesium, potassium, and
ammonium.