clay and humus particles;
carry slight negative charge;
quantity of colloids in soil determined by soil texture/OM;
interact closely with chemicals that have positive charge
soil reaction (pH) is an indication of the acidity/basicity of the soil;
at pH 7, Hydrogen ion concentration equals the hydroxyl ion concentration
The Basic Rule
good drainage - outlet to send sodium when it is displace;
source of calcium/exchange process - gypsum (CaCO4 x 2H2O);
source of water to flush sodium from system
What are two things you need to know when managing sodic soils?
the basic rule;
may need to grow salt-tolerant crop until process in complete
What element is essential for Nitrogen-Fixation by Legumes?
Cobalt - only N-fixation
What are three other important soil Elements?
Sodium - high levels cause soil crusting;
Aluminum - becomes toxic to plants in acidic soils;
Silicon - Abundant in soils, no benefit or harm
How is salinity measured?
estimated by measuring the Electrical Conductivity (EC);
mmhos/cm
Form of nitrogen fertilizer application?
ammonium/ammonium phosphate
In what ways is salinity stress similar to draught?
salts have pulling force on water;
soil salinity = root salinity water less likely to enter roots;
soil salinity is to high - water is pulled back into soil and plant wilts and dies;
(most plants respond to salinity in same way as water deficiency)
