SOIL FERTILITY AND FOLIAR ANALYSIS ASSESSMENT OF SEVERAL PROTEA AND LEUCOSPERMUM CULTIVARS IN AZORES ISLANDS

Fertilization of Protea and Leucospermum cultivars in Azorean volcanic soils with high organic matter is often neglected due to naturally high nutrient levels and frequent poor response to fertilization practices. During the growing season of 2008-2009, foliar and soil samples were collected at mid-vegetative, early flowering and mid-flowering developmental stages of four Protea and three Leucospermum cultivars. The soil fertility analysis showed that these plants are mostly grown in stable pH and organic matter (OM) conditions, but at variable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) levels. In the case of P, the upper levels in Azorean volcanic soils are very high, but plants are still commercially grown in such conditions. The foliar analysis showed that Protea cultivars had the tendency to have low levels of K, Mg and zinc (Zn), whereas Leucospermum cultivars frequently had low levels of P, Ca, Mg and Zn. A critical analysis of the data is presented in this study.