INFLUENCE OF CLAY SOIL ON TWO PROTEA CULTIVARS PLANTED DIRECTLY OR GRAFTED ON CLAY-SOIL RESISTANT ROOTSTOCK. STUDY OF SOIL FERTILITY, FOLIAR NUTRITION, AND NUTRIENT CONTENT OF CUT FLOWERS

Leucospermum is a genus of the Proteaceae family that has achieved an increasing importance in the market of cut flowers worldwide. Some Leucospemum plants do not grow properly in clay soils, but grafting on a clay-soil resistant rootstock could provide better performances. The nutrient composition of two cultivars of Leucospermum (‘High Gold’ and ‘Succession II’) cultivated in clay soil was evaluated planting them directly or grafting on Leucospermum patersonii rootstock. The assay consisted of four treatments, T1 = ‘High Gold’ planted directly, T2 = grafted ‘High Gold’, T3 = ‘Succession II’ planted directly, and T4 = grafted ‘Succession II’. The experiment was carried out over three years, following a randomized block design with four replications per treatment. Foliar calcium (Ca) decreased in grafted plants of both cultivars. Nitrogen, phosphorus, potassium, Ca, and magnesium contents of the cut-flowers of ‘High Gold’ treatments were higher than those of ‘Succession II’, though in the third year no co...