Rizobactérias promovem o crescimento, melhoram a eficiência do uso de nutrientes, alteram a arquitetura de raiz reduzem custos de produção de mudas de palma de óleo.

Abstract

Oil palm (Elaeis guineensis Jaq) is one of the most productive palm species in the world. In Brazil, the main commercial plantations of this crop are concentrated mainly in the state of Pará. Achieving the standard requires a long nursery period, high consumption of chemical fertilizers and high operating costs. Due to this problem, plant growth promoting rhizobacteria (PGPR) are free-living microorganisms that inhabit the soil, colonize host plant roots and exert favorable effects on plant growth through various direct and indirect mechanisms. The objective of this study was to evaluate the growth promotion, hormonal levels, nutritional contents and to analyze the economic efficiency and dynamic of thin roots in oil palm seedlings in response to rhizobacteria inoculation. The first experiment was conducted in a completely randomized design under nursery conditions, with three treatments and 10 replications. Treatments: T1: no inoculation + 50% fertilization (C-); T2: with inoculation + 50% of fertilization (UFRAB01) and T3: without inoculation + 100% of fertilization (C +). Inoculated plants increased hormone levels by 66% indol-3-acetic acid (IAA), 44% abscisic acid (ABA), as well as increased macro and micronutrient content per plant. There was a 24% reduction in 1-aminocyclopropane carboxylic acid (ACC) levels. Inoculation promoted plant growth by increasing by 110% shoot dry matter (MSPA), 123% root dry matter (MSR), 39% plant height (AP) and 19% stem diameter (DC), all in relation to the control plant. Economic efficiency analysis showed that microbial technology reduces nursery time and reduces the cost of seedling production. The use of inoculation reduced by 11% the value of oil palm seedling. The second essay aimed to analyze the dynamics of thin roots in inoculated seedlings. The design was in randomized blocks (DBC), using four treatments with 6 replications. The treatments were: T1: (C-) without inoculation + 50% of fertilization;; T2: plants inoculated with Burlkhoderia pyrrocinia BRM32113 + 50% fertilization; T3: plants inoculated with Bacillus subtilis UFRA92 + 50%; T4: (C +) without inoculation + 100% fertilization. The inoculation positively influenced the root volume with an average increase of 81%, length 24%, total surface area 46%, 35% in the average diameter, 160% number of tips and 63% in the branches when compared to the control. Therefore, microbial technology is 10 presented as a form of management to increase the yield of agricultural production and optimize the use of chemical fertilizers converging to a more sustainable agriculture.