Soil Components

Solid support

Organic - chemicals with carbon
Inorganic - chemicals without carbon

Air including oxygen
Water
Organisms!! 1 acre-foot = 3 tons of organisms!

Inorganic particles

Rock Gravel	ignore these for now but important in New England
	Size	Drainage	Water Retention	Air	Nutrient Capacity
Sand	1-0.1 mm	+++	0	+++	0
Silt	0.1-0.001	+	++	++	++
Clay	< 0.001	0	+++	0	+++

Need a mixture of these for optimum soil texture = LOAM

How to determine soil texture/type:

1. mix soil thoroughly with Calgon in water

   Calgon = Surfactant = surface active agent
   = sodium hexametaphosphate
   breaks up clumps......separates particles

2. let stand
3. soil particles settle in glass cylinder

   sand first
   then silt
   then clay

4. measure height of layers
5. calculate % of total for each layer
6. lookup % combination on soil triangle (see below)

Here is an example:

Layer Height	Total Height	% of Total	Soil Type	What it means
Clay 3.0 cm Silt 2.0 cm Sand 5.0 cm	10 cm	30% Clay 20% Silt 50% Sand	Sandy Clay Loam	= drainage + air = nutrients = good for plants

SOIL TRIANGLE

Organic Particles

rotting material = humus

• improves drainage
• improves nutrient holding capacity
• improves water holding capacity

sources

• leaves
• grass clippings
• compost
• green manure
• manure - esp. Horse

Nutrients Needed

Macronutrients:	CHO air water	PK(i)N limited in soil	S     Ca Fe     Mg -------common in soil--------

Ca Mg found in lime

Micronutrients: Mo Cu Zn Co Mn Si B Al Cl etc.

trace amount needed usually found in soil

Fertilizer: Nitrogen - Phosphorus - Potassium (NPK analysis)

balance important:

20-20-20 a common general purpose fertilizer

10-20-10 common flower or fruit garden ("vegetables")
        (phosphate needed for reproduction)

unbalanced fertilizers:

40-0-0 urea or ammonium nitrate for
      lawn and true vegetables
        (only nitrogen needed for reasonable growth)
        (economical)

0-40-0 super phosphate

0-0-30 potash

make your own mixture for exact needs BASED ON SOIL TEST!

Avoid pollution caused by over-use of fertilizer (eutrophication)

Nutrients available only through WATER in the soil:

Water Dissociates:

H₂O ------> OH^- + H⁺ 10^-7 M = distilled water

pH = - log [H⁺] = 7 for distilled water

10⁰                 10^-7                        10^-14 M H⁺ Conc
0-----------------------7-------------------------------14 pH

acid sour vinegar cranberries	neutral	base = alkalai bitter soap beans & asparagus

	raises pH
lime = Ca(OH)2	----------->
	<-------------	Al2(SO4)3 aluminum sulfate
	lowers pH

Clay Particle has negative charge

Opposites attract, so metal ions with positive charge stick:

Look like this in most soil!

Acid rain = H⁺ This smaller ion replaces large metal ions
      (cation exchange)

Released Cations available for uptake into roots or leach out!

Roots secrete acid, retrieve ions, retrieve acid ions.

Soil Horizons:

black	A	leaching zone organics here - most roots	these layers lost by erosion, esp tropical soils
"red"	B	accumulation zone nutrients collect here
rocky	C	weathered bedrock
solid	D	bedrock

Erosion Prevention:

• Proper Cultivation
• Mulching
• Perennial Planting!