The great depth and high fertility of the soils of arid and semiarid regions have made possible the profitable production of agricultural plants under a rainfall very much lower than that of humid regions. To make the principles of this system fully understood, it is necessary to review briefly our knowledge of the root systems of plants growing under arid conditions. Functions of roots The roots serve at least three distinct uses or purposes: First, they give the plant a foothold in the earth; secondly, they enable the plant to secure from the soil the large amount of water needed in.
