EFFECT OF SUMMER APPLICATION OF NITROGEN AND POTASSIUM ON MINERAL COMPOSITION OF OLIVE LEAVES
Nitrogen applications (0.5kg N as NH4N03 per tree in early July or 2% urea spray repeated four times during July and August) led to rapid increase in the content of N in the leaves. This increase remained significant throughout the sampling period (eight months after application). Each of the NH4NO3, KNO3 and urea applications were, in most samplings, equally effective in raising leaf N %, but urea plus KNO3 application was consistently the most effective treatment in raising the content of N in the leaves. Urea sprays tended to increase the contents of K and B, but decreased Mg and Ca.
Potassium fertilizer, sprayed (4% KNO3 applied four times during July and August) or applied to the soil (1kg K2O per tree as potassium sulphate in early July), increased the potassium content of the leaves and slightly decreased the content of magnesium. This decrease occurred primarily in N-treated trees. N and P contents of the leaves were increased by potassium spray applications.
The applications of urea, shortly before KNO3 sprays, significantly enhanced the uptake of K in the leaves, whereas the content of K in the leaves of trees sprayed with KNO3 alone, or treated by soil application of potassium fertilizer, did not differ substantially.