soils and plant nutrition physical properties. soil properties are characteristics that we see or...
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SOILS and PLANT NUTRITION
PHYSICAL PROPERTIES
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
PHYSICAL PROPERTIES of SOILS
The PROPORTION (%) of SAND, SILT, and CLAY particles
SAND – largest separate, 2 mm - 0.05 mm
SILT – medium separate, 0.002 mm - 0.05 mm
CLAY – smallest separate, < 0.002 mm
SOIL TEXTURE
SAND – largest separate, 2 mm - 0.05 mm
VISIBLE to naked eye
GRITTY FEEL, GRITTY SOUND
DO NOT STICK TOGETHER
SOIL TEXTURE
SILT – medium separate, 0.002 mm - 0.05 mm
INVISIBLE to eye
SILKY or POWDERY FEEL
DO NOT STICK TOGETHER
SOIL TEXTURE
CLAY – smallest separate, < 0.002 mm
TINY SHEET-LIKE CRYSTALS formed out of the SOIL SOLUTION
STICKY, PLASTIC FEEL
STICK TOGETHER
SOIL TEXTURE
PARTICLE SIZE determines many CHARACTERISTICS of soils
SURFACE AREA
As PARTICLE SIZE decreases - TOTAL SURFACE AREA increases
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???
SOIL TEXTURE
DETERMINING SOIL TEXTURE
By SEPARATING out the PARTICLES into SAND SILT and CLAY, to find the % of each
FEEL or RIBBON TEST
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
SOIL TEXTURE
SOIL TEXTURE
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
Soil Classification Triangle
USING the Soil Classification Triangle
SOIL TEXTURE
Can you MODIFY SOIL TEXTURE?
CHANGING SOIL TEXTURE is expensive and largely impractical
Containers Raised beds Golf greens Building 7 & 9
SOIL TEXTURE
SOIL STRUCTURE
STRUCTURE - How particles “CLUMP” together to form SOIL AGGREGATES
PEDS – NATURAL aggregates CLODS – MANMADE aggregates
Some soils are STRUCTURE LESS SOILS
SAND – SINGLE GRAINS
FINE CLAYS - MASSIVE
SOIL STRUCTURE
SOIL STRUCTURE
STRUCTURE is CLASSIFIED by:
TYPE (or shape) and CLASS (or size)
GRANULAR CRUMB
PLATY
BLOCKY
PRISMATIC COLUMNAR
STRUCTURE is also CLASSIFIED by:
GRADE (or how distinct & strong)
WEAK MODERATE STRONG
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)
SOIL STRUCTURE
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
The EASE at which WATER, AIR and ROOTS move through soil
PERMEABILITY CANNOT be MEASURED easily…
INFILTRATION TEST PERCOLATION TEST
http://techalive.mtu.edu/meec/module06/Percolation.html
SOIL PERMEABILITY
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
SOIL CONSISTENCY
SOIL TILTH
How easy a soil is to “WORK”
TILTH is a COMBINATION of PHYSICAL FEATURES
SOIL TEXTURE
SOIL STRUCTURE
PERMEABILITY
CONSISTENCY
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
SOIL PANS
Are COMPACTED LAYERS in the earth
PLOW PANS
CLAY PANS
FRAGIPAN PLINTHITE CALICHE
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
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
SOIL COLOR
SOIL COLOR
MOTTLING
PATCHES of different COLORS - RUST, YELLOW, GREY
SOIL COLOR
DESCRIBING SOIL COLOR
SOIL SURVEYS use the MUNSELL CHART
HUE – red, yellow, green, blue
VALUE – light or darkness 10 - 0 (white to black)
CHROMA – purity of dominant color 10 - 0 (brilliant to muddy)
The STORY of STUFF
http://www.youtube.com/watch?v=9GorqroigqM