This document discusses soil properties and index properties of soil. It defines key terms related to soil texture, structure, drainage and composition. Soil texture refers to the relative percentages of sand, silt and clay in a soil. Structure describes how soil particles are grouped. Drainage is influenced by soil color, with greyer soils being poorer drained. The document also examines physical, chemical and biological properties of soil, including the microorganisms and processes involved.

1. SOIL PROPERTIES
INDEX PROPERTIES OF SOIL
INDEX PROPERTIES OF SOIL

2. OBJECTIVES
 Describe soil by physical, chemical, and
biological properties of the soil.
 Distinguish among physical, chemical,
 Distinguish among physical, chemical,
and biological properties of the soil.
 Distinguish between homogenous and
heterogeneous mixtures in soil.

3. Objective 1: TERMS TO KNOW:
 Clay- The smallest soil particle
 Sand - The largest soil particle
 Silt - An intermediate sized soil particle
 Structure - The way individual soil
 Structure - The way individual soil
particles are grouped together
 Texture - A physical property of the soil
referring to the relative percentages of
sand, silt, and clay

4. Objective 1: TERMS TO KNOW: (Cont’d)
 Topsoil - The upper part of the soil profile that is
normally cultivated
 Subsoil - the area in the soil profile below the
topsoil which accumulates clay
 Subsoiling - A method of breaking up the compacted
 Subsoiling - A method of breaking up the compacted
layers of the soil that restrict air and water movement
and root growth using farm machinery
 Tillage pan - areas of compacted soil in the plant root
zone created by repeated plowing of heavy soils
especially when wet; also called a plow pan
 Mottling - Spots of color in the soil that indicates
internal drainage and aeration

5. Texture
 physical property of soil considered rather
permanent
 refers to the relative percentages of the
 refers to the relative percentages of the
three types of soil particles
 Sand
 Silt
 Clay

6. Determining Soil Texture
 Sensing the feel
 It is the varying amount of each soil particle
type that gives soil its texture or feel.
 Mechanical analysis

7. Textural Triangle
 used to obtain a soil
textural name for a
sample after it has
been mechanically
analyzed
analyzed

8. Light Soils vs Heavy Soils
 Light Soils - sandy or coarse texture
 Heavy Soils - clay or fine texture
 Loamy Soils - medium textured
 more desirable characteristics usually
 more desirable characteristics usually
associated with highly productive soils that are
easier to manage

9. Light Soils vs Heavy Soils
When comparing light soils to heavy soils,
the light soil will:
 require less energy to cultivate
 heat and cool faster
 heat and cool faster
 usually lighter in color
 wet and dry faster
 usually subject to greater erosion
 usually lower in fertility

10. Four Main Types of Soil Structure
 Platy - thin horizontal sheets overlapping
each other
 Prismatic - long vertical columns without
rounded tops
rounded tops
 Block-like - irregular shaped cubes
 Spheroidal - rounded and often referred
to as granular or crumb; usually found in
the topsoil

11. Two Types of Structureless Soils
 Single grained soils like sand
 Solid massive condition with no noticeable
peds
peds

12. Internal Soil Drainage
 important for proper plant growth
 Permeability can be determined by the color of
the subsoil.
 Grey with some red or yellow streaks -
poorly drained soils
poorly drained soils
 Yellowish-brown or reddish brown with
some grey mottling - as internal drainage
improves
 Uniform bright color with few or no grey
streaks or mottling – good internal drainage
and aeration

13. Objective 2: TERMS TO KNOW:
 Infiltration - The movement of water
into the soil
 Percolation - The movement of water
through the soil
through the soil
 No-till planting - The planting of a crop
into the previous crop stubble or a
cover crop, disturbing only the
immediate seed zone

14. Objective 2: TERMS TO KNOW: (Cont’d)
 Reduced-tillage - The elimination of one
or more operational procedures from a
conventional system of working the
soil
 Permeability - the characteristics of a
soil which permits variations in the
speed of air and water movement

15. Soil Types Influence Crop Selection
 Light textured soil
 Oats
 peanuts
 beets
 Loamy textured soil
 Loamy textured soil
 majority of Louisiana crops grow best in a loamy
textured soil.
 Heavy textured soil
 Flooded rice
 requires a heavy fine textured soil to prevent loss of
surface water
 Sugarcane

16. Determination of Soil Structure
 determined by the way the particles of
sand, silt, and clay are grouped together
in aggregates
 Peds - naturally formed groups of soil
particles
 Clods - are artificially formed groups of
soil particles

17. Structured Soil
more desirable because it:
 is easier to cultivate
 allows more water intake
 does not restrict root growth
does not restrict root growth
 encourages better drainage within pore
spaces
 allows entry of oxygen into the pore
spaces after the water has drained
 facilitates organic matter decomposition
and the release of plant nutrients

18. Destruction of Soil Structure
Soil structure can be destroyed by:
 working the soil when it is wet
 repeated movement of equipment or livestock
 repeated use of equipment at the same depth in
the soil
 continual flooding of the soil

19. Improving Soil Structure
 Leaving it alone, in time it will repair itself
 Planting a green manure crop
 Incorporating plant residue into the soil

20. Infiltration and Percolation Rates
 Rapid - spheroidal structure and single
grained structure less soils
 Moderate - blocky and prismatic
 Moderate - blocky and prismatic
structure
 Slow - platy structure or massive
structure less soil

21. Tillage Pans and Traffic Pans
 Tillage pans - areas of compacted soil in
the plant root zone caused by repeated
plowing at the same depth.
 Tillage and traffic pans are serious
Tillage and traffic pans are serious
problems in many parts of the country
because the area of root restriction is
generally in the topsoil.
 reduces the movement of air, water, and roots
and therefore limits crop yields.

22. Fragipans
 Fragipans (silt pans) and clay pans can
occur naturally in or near the subsoil. A
fragipan is the result of too much silt in or
near the B horizon, and is not the result of
mans actions.
mans actions.

23. Alleviating Traffic or Tillage Pans
 Subsoiling breaks up or shatters
compacted layers using deep plowing
equipment.
 Reduced or minimum tillage means less
movement over the soil which results in
movement over the soil which results in
less compaction of the soil. Deep
Subsoiling should precede reduced or
minimum till operations.
 No till reduces the formation of traffic
pans because planting is done directly in
the stubble of the previous crop.

24. Biological Properties of Soil
 refers to the living organisms found in
the soil
 includes both the micro and macro plants
and animals.
Plants
 Micro
 Bacteria
 Fungi
 Actinomycetes
 Macro – roots of higher plants

25. Biological Properties of Soil
Animals
 Micro
 Nematodes
 Protozoa
 Macro
 Macro
 Earthworms
 Rodents (prairie dogs, moles, gophers, etc.)
 Arthropods (mites, insects, spiders, etc.)
 Gastropods (slugs, snails, etc.)

26. Biological Properties of Soil – Food Web

27. Chemical Properties of Soil
The ability of soil to provide the essential
elements needed for plant growth
includes:
 the availability of these elements
the availability of these elements
 other chemical properties
 clay minerals present
 humus content
 cation exchange
 soil reaction (pH).

28. Objective 3: TERMS TO KNOW:
 Homogenous mixtures – soil mixtures that
contain the same type of soil particles
 Heterogeneous mixtures – soil mixtures that
contain different types of soil particles
 Aerobic – occurring only in the presence of free
 Aerobic – occurring only in the presence of free
oxygen
 Algae – soil plant microorganisms capable of
photosynthesis
 Anaerobic – growing or occurring in the
absence of free oxygen

29. Objective 3: TERMS TO KNOW: (cont’d)
 Bacteria – single-celled soil plant
microorganisms, some of which are responsible
for organic matter decomposition, while others
are responsible for nitrogen fixation
 Fungi – soil plant microorganisms responsible for
organic matter decomposition, especially the
cellulose, lignin and gum
organic matter decomposition, especially the
cellulose, lignin and gum
 Microorganisms – life forms too small to be
seen with the unaided eye or barely visible
 Nematodes - soil animal microorganisms that
are responsible for the decomposition of organic
mater, consumption of other animal
microorganisms and parasitism on the roots of
certain higher plants

30. Objective 3: TERMS TO KNOW: (cont’d)
 Nitrogen cycle – the biochemical changes undergone by
this atmospheric gas from its use by living organisms to
decomposition and conversion back to the atmosphere
 Organic matter – soil materials including plant and animal
residues at various stages of decomposition
 Rodents – small gnawing animals such as rats and mice
 Acid soil – one having a pH below 7.0 on a scale from 0 to
14
 Alkaline soil – one having a pH below 7.0 on a scale from
0 to 14
 Ion – charged atoms or groups of charged atoms
 pH – a numerical measure of the degree of acidity or
alkalinity of the soil solution

31. Homogenous Soil Mixtures
 Sand
 Silt
 Clay

32. Heterogeneous Soil Mixtures
 Any combination and proportion of
sand, silt, or clay