Acid and Allkali

After planting for a period of time, the soil becomes acidic.

The farmer adds lime (calcium oxide) to the soil, in order to neutralize the excess acid in the soil as the lime is basic. The excess lime then reacts with atmospheric carbon dioxide to becomes calcium carbonate, which is insoluble in water and thus does not affect the pH of the soil. As a result, the pH of the soil is adjust to a pH suitable for planting.

The soil may become acidic and the lime is used to neutral the pH of the soil