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

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 lÿ1), while N and K in the P-treatments were kept at a constant rate of 50 mg lÿ1. 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 lÿ1, `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 lÿ1), at any of the cultivars tested. # 2000 Elsevier Science B.V. All rights reserved.