L1 /
3
CH3041
SODIC SOILS
• Sodic soils
have primarily exchangeable Na+ available - not
free Na+ (saline soils).
Exchangeable
Sodium Percentage (ESP) is
used to assess sodicity. (< 4 mS/cm Sodic)
ESP / (100 - ESP) = 0.015 SAR (> 15%
Sodic)
SodiumAdsorptionRatio
SAR = [Na+] /Ö{ ([Ca2+] + [Mg2+]) / 2}
SAR = [Na+] /Ö{ ([Ca2+] + [Mg2+]) / 2}
• The pH of a sodic
soil can rise to 10 as the
hydrolysis of the Na+-CE sites releases
OH-. =|Na+ + H2O D =|H+ + OH- + Na+
hydrolysis of the Na+-CE sites releases
OH-. =|Na+ + H2O D =|H+ + OH- + Na+
