1. SOILS and PLANT NUTRITION
PHYSICAL PROPERTIES
SOILS and PLANT NUTRITION

2. PHYSICAL PROPERTIES of SOILS
SOIL PROPERTIES are CHARACTERISTICS that we SEE or FEEL in soils
KNOWING PHYSICAL PROPERTIES helps us to understand:
How WATER, AIR & ROOTS move through soils
WATER & NUTRIENT HOLDING CAPACITY of soils
& how these are IMPORTANT for PLANT GROWTH

3. SOIL TEXTURE The PROPORTION (%) of SAND, SILT, and CLAY particles
SAND – largest separate,
2 mm mm
SILT – medium separate,
0.002 mm mm
CLAY – smallest separate,
< mm

4. SOIL TEXTURE SAND – largest separate, 2 mm - 0.05 mm
VISIBLE to naked eye
GRITTY FEEL, GRITTY SOUND
DO NOT STICK TOGETHER

5. SOIL TEXTURE SILT – medium separate, 0.002 mm - 0.05 mm
INVISIBLE to eye
SILKY or POWDERY FEEL
DO NOT STICK TOGETHER

6. SOIL TEXTURE CLAY – smallest separate, < 0.002 mm
TINY SHEET-LIKE CRYSTALS formed out of the SOIL SOLUTION
STICKY, PLASTIC FEEL
STICK TOGETHER

7. SOIL TEXTURE PARTICLE SIZE determines many CHARACTERISTICS of soils
SURFACE AREA
As PARTICLE SIZE decreases - TOTAL SURFACE AREA increases

8. SOIL TEXTURE PARTICLE SIZE determines many CHARACTERISTICS of soils
PORE SIZE - SPACE BETWEEN soil particles
LARGE PARTICLES like SAND have larger pores called MACROPORES
SMALLER PARTICLES like CLAY have smaller pores called MICROPORES 
BUT… Which has the most TOTAL PORE SPACE called POROSITY???

9. SOIL TEXTURE DETERMINING SOIL TEXTURE
By SEPARATING out the PARTICLES into SAND SILT and CLAY, to find the % of each
FEEL or RIBBON TEST

10. SOIL TEXTURE DETERMINING SOIL TEXTURE MECHANICAL ANALYSIS
SIEVE TUBES (Keck tube)
SEDIMENTATION TEST
Or …“The BIGGER they are the FASTER they FALL”
Can CONFIRM the “FEEL” TEST done in the field, but far MORE ACCURATE

11. SOIL TEXTURE Soil Classification Triangle SOIL TEXTURAL CLASSES
12 CLASSIFICATIONS are determined by % of SAND, SILT, and CLAY
Soils in the SAME CLASS have SIMILAR properties
LOAM is soil in which SAND, SILT and CLAY contribute EQUALLY to the soil’s PROPERTIES
CLAY has the most DOMINANT effect on SOILS

12. SOIL TEXTURE
USING the Soil Classification Triangle

13. SOIL TEXTURE Can you MODIFY SOIL TEXTURE?
CHANGING SOIL TEXTURE is expensive and largely impractical
Containers
Raised beds
Golf greens
Building 7 & 9

14. SOIL STRUCTURE
STRUCTURE - How particles “CLUMP” together to form SOIL AGGREGATES
PEDS – NATURAL aggregates
CLODS – MANMADE aggregates  

15. SOIL STRUCTURE Some soils are STRUCTURE LESS SOILS
SAND – SINGLE GRAINS
FINE CLAYS - MASSIVE

16. SOIL STRUCTURE STRUCTURE is CLASSIFIED by:
TYPE (or shape) and CLASS (or size)
GRANULAR
CRUMB
PLATY
BLOCKY
PRISMATIC
COLUMNAR

17. SOIL STRUCTURE STRUCTURE is also CLASSIFIED by:
GRADE (or how distinct & strong)
WEAK
MODERATE
STRONG

18. SOIL STRUCTURE FORMATION of AGGREGATES takes 2 steps:
LOOSE aggregates are formed by COMPRESSION
Plant roots, freezing and thawing, wetting and drying (basically SHRINK - SWELL, vertical fractures first, horizontal second)
STRONGER aggregates are CEMENTED together:
MICROBES – secrete GUMS as they break down OM (A horizon)
CLAY and IRON OXIDES – CHEMICALLY cement together (B horizon)

19. SOIL PERMEABILITY
The EASE at which WATER, AIR and ROOTS move through soil
Depends on SIZE and CONTINUITY of soil pores
SOIL TEXTURE
SOIL STRUCTURE  

20. SOIL PERMEABILITY
The EASE at which WATER, AIR and ROOTS move through soil
PERMEABILITY CANNOT be MEASURED easily…
INFILTRATION TEST
PERCOLATION TEST

21. SOIL CONSISTENCY The BEHAVIOR of soil when PRESSURE is applied
CONSISTENCY depends on how MOIST a soil is and the CLAY CONTENT
WET – sticky to plastic
MOIST – friable, loose or firm
DRY – hardness, softness, looseness

22. SOIL TILTH How easy a soil is to “WORK”
TILTH is a COMBINATION of PHYSICAL FEATURES
SOIL TEXTURE
SOIL STRUCTURE
PERMEABILITY
CONSISTENCY

23. SOIL TILTH
Any PRACTICE that DESTROYS SOIL STRUCTURE or DECREASES PERMEABILITY will destroy TILTH!
IMPROVING TILTH
Improve SOIL STRUCTURE
Add OM
LOW or NO TILL
Don’t WORK soils when WET
Improve PERMEABILITY
AVOID COMPACTION

24. SOIL PANS Are COMPACTED LAYERS in the earth PLOW PANS CLAY PANS
FRAGIPAN
PLINTHITE
CALICHE

25. SOIL TEMPERATURE
Critical for SEED GERMINATION, ROOT GROWTH and CROP development
DARK or DRY MINERAL soils absorb HEAT and WARM up faster
DARK ORGANIC soils are COOLER – MORE WATER in soil to buffer temperature

26. SOIL COLOR Can be an INDICATOR of soil CONDITION WHITE / LT GREY
BROWN / BLACK
YELLOW / RED
BLUISH / GREY / GREENISH
called GLEYING
MOTTLING
PATCHES of different COLORS - RUST, YELLOW, GREY

27. SOIL COLOR
MOTTLING
PATCHES of different COLORS - RUST, YELLOW, GREY

28. SOIL COLOR DESCRIBING SOIL COLOR SOIL SURVEYS use the MUNSELL CHART
HUE – red, yellow, green, blue
VALUE – light or darkness
(white to black)
CHROMA – purity of dominant color
(brilliant to muddy)

29. The STORY of STUFF