The relationships that exist between soil and plant are very complicated and have aroused man's curiosity for centuries. Many studies have been done in order to understand and clarify this relation. Among these is the hypothesis that plant roots exhibit cation exchange capacity (CEC) and that this is in some way responsible for differential cation uptake . The CEC of the roots was defined by Helmy (l958a) as the total cations which can be exchanged or replaced from the root surface under a given set of conditions and is usually expressed as milli-equivalents per 100 grams (me/100 g) of dry roots. The CEC hypothesis of cation uptake proposes that the uptake of cations from soil by plants is in some extent controlled by the CEC of the plant roots and the valence of the cations. The CEC may therefore account for the differences between species in taking up different amounts of nutrients from the same soil.