3. Exchangeable Sodium hydrolysis nAt Colloid 2+ 4Na Collo1d2Nat Cat+ 2+ Colloid XNa+yH20+CO2 ColloR y) Nat nAoh ( Affect the factors of soil alklization 1. Climatic factor 2. Biological factor 3. Parent factor3、 Exchangeable Sodium hydrolysis Ca2+ 2Na+ Mg2+ + 4Na+ 2Na+ + Ca2+ + Mg Colloid Colloid 2+ xNa + yH2O +CO2 （x-y）Na+ + yNaOH yH+ Colloid Colloid （二） Affect the factors of soil alklization： 1．Climatic factor 2．Biological factor 3．Parent factor