occur. Phosphorus is also an important macro-nutrient
in stimulating early root growth and promoting early
plant vigor (Longstreth and Nobel, 1980; Verberic et
al., 2002). Potassium plays an essential role in the metabolic
processes of plants and is required in several enzymatic
reactions, particularly in those involving the
adenosine phosphates (ATP and ADP), which are the
energy carriers in the metabolic processes of plants
and animals. Potassium is also essential in the metabolism
of carbohydrates, a process by which energy is obtained
from sugar. There is also evidence that potassium
plays a role in photosynthesis and protein synthesis
(Navarro, 2000; Verberic et al., 2002).