A popular misconception is that cacti grow in pure sand. They actually require specific physical and nutritional properties in their soil to thrive. This includes a certain amount of organic material to provide the proper nutrients as well as air within the soil. The soil should not be too rich or it will retain water, which will eventually lead to root rot. Cacti need soil that will wet easily and drain well. It is relatively easy to make cactus soil at home with ingredients available from a garden center.
Measure out 20 percent topsoil to 10 percent peat moss to 70 percent pumice or vermiculite into the mixing container. Mix these ingredients thoroughly to form the cactus soil. Moisten the soil so that it is damp but not wet.
Sterilize the soil by placing the mixture in a plastic bag. Insert a cooking thermometer into the soil through the bag. Place the bag on an oven tray and heat the soil, in an oven, until it reaches an internal temperature of 165 degrees F. Allow the mixture to cool completely.
Mix in 1/2 cup of bone meal into the soil for every 12 quarts of soil mixture to ensure a proper pH balance. Mix a good-quality, general-use, time-released fertilizer such as Osmocote into the soil.