Potassium (K+) is important ion in sugar/starch formation and the synthesis of proteins. It is a catalyst for enzymatic reactions and nuetralizes organic acids. K+ also acts as a ionic balance functioning to open stomates (how the plant "breathes").
Deficiencies
Potassium deficiency is easily identified by marginal necrosis (death of tissue along the leaf edges) of the older leaves. This may be preceded by small areas of yellowing (chlorosis) near the margins. As the deficiency progresses younger leaves will become necrotic.Mild deficiencies can occur during fruit maturation. This is expected as it is a normal part of the growth cycle, most of the K is translocated to developing fruit. Fruit that develop during K+ stress conditions can be puffy, soft, low in acidity, irregular shaped and susceptible to ripening diseases. It is important to make sure there is enough K+ as the fruit develop.
Lack of potassium can result in misshapened fruit, ripening problems, soft or mushy fruit texture, low acidity and puffiness.
K+ is easily leached from most soils.
Conditions which favor K+ deficiencies
- light, sandy soils
- leaching rains
- acid soils
- organic soils
- inadequate fertilization
Excess K+
Excessive amounts of K+ can compete for the uptake of other ions such as calcium. Lack of sufficent calcium supply may lead to blossom end rot.