Crescimento de mudas sesbania virgata (Cav.) Poir., acnistus arborescens (L.) Schltdl. e platypodium elegans Vogel em resposta à adição de composto orgânico ao substrato

Given the technical and economic importance of the substrate in the seedling production process, this study aimed to evaluate the growth of forest seedlings in response to the addition of organic compost to the substrate. The study was developed at the forest nursery of the Instituto Federal de Minas Gerais, Campus São João Evangelista (IFMG-SJE), in a randomized block design (RBD) with 4 replicates, 3 native forest species (Sesbania virgata, Acnistus arborescens and Platypodium elegans), 5 treatments and 4 seedlings per experimental unit. The treatments consisted of different combinations of the substrate produced in the nursery itself with the commercial organic compost Provaso® (0, 25, 50, 75 and 100% of the organic compost), used to fill plastic tubes (180 cm³) where direct sowing of the seeds was carried out. At 180 days after sowing, the following variables were obtained: total height (Ht, cm), stem diameter (Dc, mm), Ht/Dc ratio, dry mass of the aerial part (MSPA, g/plant) and roots (MSR, g/plant), in addition to the surface area (cm2) and root volume (cm3) with the aid of a root scanner. All variables were analyzed statistically by analysis of variance (F test) and mean test (Tukey test), at 5% significance. For the species in which a significant difference was observed between treatments, a quadratic function was adjusted to represent the growth in height in response to the addition of organic compound in the substrate and the height of maximum economic efficiency (90% of the maximum height) and the proportion of the compound to reach it were calculated. The addition of the organic compound Provaso® to the substrate promoted greater growth of the seedlings of Sesbania virgata and Acnistus arborescens, compared to the seedlings produced only with the substrate from the nursery itself. The height of maximum economic efficiency was 54.9 cm for Sesbania virgata and 24.1 cm for Acnistus arborescens, obtained respectively with the addition of 35.7% and 33.5% of the organic compound to the substrate mixture. For the species Platypodium elegans, the incorporation of the organic compound to the substrate did not provide significant gains in the growth of the seedlings.