Caliche forms because evaporation exceeds precipitation and plants continually remove water from the soil. The process of evaporation and transpiration leaves calcium behind. Such deposits may be tens or hundreds of thousands of years old. The deposits are formed in the rooting zone of plants. Deep deposits such as we see here were probably formed during the Pleistocene and were subsequently buried.
Soils vary throughout our area.
The Soil Conservation Service provides soil maps that are used for many purposes. Soil texture is one of the most fundamental properties of soil. Texture affects the ability of water to enter the soil and affects the amount of water that is of use to plants. Generally, sandy soils hold less water than soils with a lot of clay. Conversely, heavy clay soils lack air spaces which are important for allowing oxygen to reach plant roots.