Caliche is a natural hardened cement, which is composed of calcium carbonate. It is a layer of soil which binds the other soil materials like sand, gravel, silt and clay together.
Caliche is naturally formed in desert soil after rainstorms. During precipitation, the calcium dissolved in rain water is added to the desert soil, which then combines with the dissolved carbon dioxide in the soil water to form insoluble calcium carbonate, known as calcite.
Oasis and underground river supplies also provide important sources of water for farming. Irrigation allows farmers to grow crops in areas that would normally be unsuitable for farming.
