hadis66
عضو جدید
Soil Formation:
Weathering of rocks: Physical
Weathering of rocks: Physical
- freezing/thawing,
- temp variation,
- salt deposition,
- wind/water abrasion
- root penetration
Chemical
Soil Organic Matter
Surface Charges in soils
Permanent Charge
In clays and other minerals different charged ions in crystal structure are substituted during the formation of the mineral.
(Al +3 for Si +4 ; Mg +2 for Al +3, Fe +2 for Al +3)
pH Dependent Charge
At low pH, soil charge becomes more positive.
At high pH, negative charge increases.
Overall charge is usually negative.
Soil Organic Matter usually has a negative charge due to presence of carboxyl, phenolic groups:
Charge on soil particles affects:
¨ mobility of inorganics in soil
¨ mobility of organics in soil
¨ soil buffering of pH changes
Range of composition of humic material:
45-55% Carbon
30-45% Oxygen
3-6% Hydrogen
1-5% Nitrogen
Significant amount of humus exists as colloidal particles
Generally carries a negative charge and has very high surface area.
Soil Organic Matter
Surface Charges in soils
Permanent Charge
In clays and other minerals different charged ions in crystal structure are substituted during the formation of the mineral.
(Al +3 for Si +4 ; Mg +2 for Al +3, Fe +2 for Al +3)
pH Dependent Charge
At low pH, soil charge becomes more positive.
At high pH, negative charge increases.
Overall charge is usually negative.
Soil Organic Matter usually has a negative charge due to presence of carboxyl, phenolic groups:
Charge on soil particles affects:
¨ mobility of inorganics in soil
¨ mobility of organics in soil
¨ soil buffering of pH changes
Range of composition of humic material:
45-55% Carbon
30-45% Oxygen
3-6% Hydrogen
1-5% Nitrogen
Significant amount of humus exists as colloidal particles
Generally carries a negative charge and has very high surface area.
