text: Finely ground agricultural lime is often applied to acid soils to increase soil pH (liming). The amount of limestone or chalk needed to change pH is determined by the mesh size of the lime (how finely it is ground) and the buffering capacity of the soil. A high mesh size (60 mesh = 0.25 mm; 100 mesh = 0.149 mm) indicates a finely ground lime that will react quickly with soil acidity. The buffering capacity of a soil depends on the clay content of the soil, the type of clay, and the amount of organic matter present, and may be related to the soil cation exchange capacity.  Soils with high clay content will have a higher buffering capacity than soils with little clay, and soils with high organic matter will have a higher buffering capacity than those with low organic matter. Soils with higher buffering capacity require a greater amount of lime to achieve an equivalent change in pH. The buffering of soil pH is often directly related to the quantity of aluminium in soil solution and taking up exchange sites as part of the cation exchange capacity.  This aluminium can be measured in a soil test in which it is extracted from the soil with a salt solution, and then is quantified with a laboratory analysis.  Then, using the initial soil pH and the aluminium content, the amount of lime needed to raise the pH to a desired level can be calculated.
  Amendments other than agricultural lime that can be used to increase the pH of soil include wood ash, industrial calcium oxide (burnt lime), magnesium oxide, basic slag (calcium silicate), and oyster shells.  These products increase the pH of soils through various acid–base reactions. Calcium silicate neutralizes active acidity in the soil by reacting with H ions to form monosilicic acid (HSiO), a neutral solute.