ABSTRACT
Excessive soil acidity must be neutralized in order to attain a desired soil pH and soil environment for better nutrient availability and crop growth. This chapter discusses the chemical and physical properties of acid soils and the consequential effects of liming on soil properties. The use of byproduct gypsum for alleviating subsoil acidity and for ameliorating soil physical and chemical properties will also be covered. Soil acidity is the dominating factor of acid soils, which influences almost every aspect of the soil system. As an intensity factor of soil acidity, soil pH is a master indicator of soil systems and influences many of the chemical and biological processes occurring in soils, though it produces no hint about the total soil acidity. The degree of Al hydrolysis is controlled by soil pH, which further affects total soil acidity and the level of Al toxicity to plants.
