Bioinsumos na produção de mudas de oliveira: efeitos no enraizamento de estacas e no desenvolvimento em viveiro

Abstract

The olive tree (Olea europaea L.) is predominantly propagated by cuttings, conventionally using indole-3-butyric acid (IBA) to induce rooting and sand as a substrate. The application of bioinputs based on plant growth-promoting microorganisms represents a potential alternative for improving rooting efficiency. This study was conducted to evaluate, in two experiments, the rooting capacity of olive cultivars using microbial biostimulants and the effect of different biostimulants on seedling development during the nursery phase. The first experiment, focused on cutting rooting, was carried out in October using four olive cultivars: Arbequina, Maria da Fé, Ascolano 315, and Koroneiki. Cuttings were prepared and placed in masonry beds containing sand as substrate under controlled humidity and temperature conditions. The experimental design was completely randomized in a 6 × 4 factorial scheme (six biostimulants × four cultivars), with four replications and 25 cuttings per replication, totaling 100 cuttings per treatment. In addition to the control treatment (T1, IBA only), treatments consisted of biostimulants associated with IBA, including three Bacillus species: Bacillus amyloliquefaciens (T2), Bacillus licheniformis (T3), Bacillus subtilis (T4), Trichoderma harzianum (T5), and the commercial rooting product Bioraiz® (T6), all applied in liquid form to the substrate. Solutions were prepared according to the manufacturers’ recommendations, with a final volume of 3000 mL per treatment. Evaluations included rooting percentage, callus formation, and root system characteristics. The results indicated that the application of biostimulants enhanced rooting, with responses varying among cultivars. Increased rooting percentages were observed in the cultivars Maria da Fé, Ascolano 315, and Arbequina when treated with Trichoderma harzianum and Bacillus spp. Callus formation, particularly in Arbequina, was greater in the presence of Trichoderma harzianum, suggesting that this microorganism induces physiological processes related to rhizogenesis and improves root emission. The second experiment was conducted using olive seedlings approximately one year old, derived from the rooting phase and maintained under 70% shading. The experimental design was completely randomized in a 4 × 4 factorial scheme (cultivars × biostimulants), with three replications per treatment and two plants per replication. Plant height, stem diameter, and SPAD index were measured monthly over four months. Destructive analyses were performed to determine fresh and dry biomass of shoots and roots. The results demonstrated that seedling responses to biostimulants depended on genotype and the type of product applied, indicating interaction between cultivar and treatment. The use of seaweed extract proved promising for cultivars such as Ascolano 315, promoting greater initial growth and root system expansion. The use of microbial bioinputs can contribute to improved rooting of cuttings and enhanced growth of olive seedlings under nursery conditions.