The response of three Leucadendron cultivars (Proteaceae) to phosphorus levels

Abstract The objective of this study was to compare the growth of three Leucadendrons (Proteaceae) cultivars (`Safari Sunset',`Orot' and`Meir') fertigated with three levels of P. The plants were grown in tuff (pyroclastic material, characterized by high porosity) in 10 l pots and fertigated daily. The experiment included control treatment (plants irrigated with tap water) and three levels of P (0, 10 and 20 mg l À1 ), while N and K in the P-treatments were kept at a constant rate of 50 mg l À1 . Under P de®ciency, the development of`Orot' plants was signi®cantly superior to that of`Safari Sunset' and`Meir' cultivars, but as P application increased to 20 mg l À1 ,`Safari Sunset' growth was quite similar to that of`Orot'. The very low growth rate of`Meir', probably eliminates this cultivar as a potential rootstock for commercial purpose. The low sensitivity of`Orot' to nutrient application is a promising characteristic to avoid micro-nutrients de®ciency and a signi®cant advantage, especially under ®eld conditions. No symptoms of P toxicity were observed even at the highest P level (20 mg l À1 ), at any of the cultivars tested.