Effects of soil mixture, nitrogen and organic matter on performance of Acacia senegal (L.) Willd. under nursery and field conditions

The objective of this study was to investigate the effects of soil mixture, nitrogen and organic matter on the growth of Acacia senegal seedlings under nursery conditions and their establishment and performance in the field. The study was conducted at the Nursery of EIObeid Agricultural Research Station and El Demokeya Reserved Forest (Latitude 13° 10 N;Longitude 30° 12 E) during April 2003 - September 2004. Two soil mixtures in the ratio of 2: 1 sand, clay and 1: 1: 1 sand, clay and organic matter were used as a potting substrate. Five levels of N viz. 0.0, 30, 50, 60 and 80 mg/kg soil were applied at sowing and after one month. Factorial experiments (2x5x2) in randomized complete block design were conducted at the nursery and field. The results showed a significant effect of the soil mixture composed of 2 sand: 1 clay on root length of A. senegal seedlings after two months at the nursery. The soil mixture that contains organic matt er significantly increased the shoot/root ratio of the species after two and three months at the nursery. Similarly, addition of organic matter significantly affected basal diameter, height and number of branches under field conditions. Late application of nitrogen gave significant effects on fresh and dry weight of seedlings after two months at the nursery. Addition of 80 mg N/kg soil significantly increased the dry weight of seedlings and basal diameter in the early stages in the nursery and field, respectively. The interaction of soil mixture and time of nitrogen application gave significant effects on shoot height, fresh and dry weight of two-months-old seedlings. The same interaction gave a ignificant effect on height and root length after three months under field conditions. Addition of 80 mg N/kg soil after one month at the nursery was found to increase the root length of A. senegal after two months in the nursery. In addition, the interaction of nitrogen dose with so i l mixture and with application time significantly affected the basal diameter of the tree. Nodulation was very rare at the nursery and in the field