Effect of the different substrates on root pruning of Acacia auriculiformis A. Cunn. ex Benth. and Acacia mangium Willd. seedling in the nursery.

Abstract

The effects of different substrates and genotypes on root pruning were estimated in order to recommend a technical plan for the production of Acacia spp. in the nursery. Two randomized tests-- were conducted on Acacia auriculiformis A. Cunn. ex Benth and Acacia mangium Willd., in six types of substrates made of humus soil, crushed coal and fine sawdust in different proportions. After sprouting, young seedlings aged three weeks were transplanted into in SAPPI trays, alveolar cells filled with substrates and observed closely until planting season. A low dose of NPK fertilizer (20 20 20) in granule formulation (30g diluted in 10l of water) was provided weekly to the plants. Seedlings heights and diameters were measured during months 1, 2 and 3 in the acclimation area. When the planting age was reached, roots dry matter mass (RDM) was estimated for both species with the aim to appreciate seedling roots pruning. Results indicate that, at the planting age, seedlings from substrates 6 (75% soil + 25% charcoal) and 4 (50% soil + 50% charcoal) had the best growth performances, followed by plants from substrates 1 (75% sawdust + 25% charcoal) and 5 (50% soil + 25% charcoal + 25% sawdust). Substrate 5, because it does not generate compaction, was selected for plants production. A variance analysis revealed a genotype effect on root pruning (0.31g vs 0.24g respectively for Acacia auriculiformis A. Cunn. ex Benth. and Acacia mangium Willd). At the plantation age, this study results showed strong correlations between diameter and height (r = 0.65, P <0.001), diameter and (RDM) (r = 0.44; P <0.001) on the one hand, and between hei