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