In 1988 and again in 1991, when soil moisture was low, lower levels of phosphorus were common in leaf analysis results. Since deficiency symptoms of these elements may also be induced by excesses of phosphorus, visual foliar symptoms of phosphorus toxicity are not reliable. They are characterized by a marginal scorching of the leaves. In stone fruits an upward lateral curling and chlorosis may also become evident with the development of scorching. A heavy fruit crop usually accentuates the appearance of symptoms.
Research suggests there is an inverse relationship between leaf potassium and crop load.
Therefore, the lighter the crop the higher the demand for potassium. As with phosphorus levels in 1988 and 1991 under conditions of low soil moisture, lower levels of potassium were common in leaf analysis results. No known visual symptoms are directly attributable to high levels of potassium. However, magnesium deficiencies tend to appear when there are high levels of potassium. Specific foliar deficiency symptoms of a lack of calcium are rare in orchards.