SOILS and PLANT NUTRITION PHYSICAL PROPERTIES SOILS and PLANT NUTRITION

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

SOIL TEXTURE 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 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

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

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

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

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

SOIL PERMEABILITY 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 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

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

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

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