Effect of growing media and chemical fertilization on growth and chemical composition of khaya senegalensis,desr.,African mahogany,

This investigation was carried out at the Ornamental Horticulture Department, Faculty of Agriculture, Cairo University, Egypt during two successive seasons; 2007 and 2008, aiming to study the effect of different growing media (clay, sand, and clay + sand 1:1 by volume) and NPK (4:4:1) fertilization at different rates (0, 2, 4 and 6 g/pot) on the growth and chemical composition of Khaya senegalensis seedlings. The results showed that growing the plants in clay medium gave the highest values of plant height, stem diameter, number of leaflets/plant, chlorophyll (a and b) contents and total carbohydrates in the root, in both seasons. Whereas sand medium gave the highest value of carotenoids in the first season, but in the second season clay medium gave the highest value of carotenoids. While the clay + sand medium gave the highest values of total carbohydrates in the leaves and the stems. NPK at 6 g/plant increased plant height, stem diameter, number of leaflets/plant and chlorophyll (a and b) contents. Whereas NPK at 4 g/plant increased total carbohydrates content in the leaves and the application of NPK at 2 g/plant increased total carbohydrates content in the stems and the roots in both seasons. All NPK fertilization treatments gradually decreased carotenoids content as compared with the control plants in the first season, but all NPK fertilization treatments significantly increased carotenoids contents compared with the control plants in the second season. Using clay combined with NPK at 6 g/plant gave the highest values of most characters. The highest value of carotenoids content was obtained from 2 g NPK/plant combined with sand soil in the first season, but in the second season the highest value of carotenoids content. While using clay + sand or clay medium fertilized with NPK at 4 g/plant gave the highest values of total carbohydrates in the leaves. Plants grown in clay + sand medium and treated with 2 g NPK/plant gave the highest values of total carbohydrates in the stems, in both seasons. Whereas using clay soil treated with NPK at 2 g/plant gave the highest values of total carbohydrates in the roots in the first and second seasons.