Substratos, bactérias fixadoras de nitrogênio e fungos micorrízicos arbusculares na produção de mudas e plantio de Samanea saman (Jacq.) Merr em estresse hídrico

Abstract

Forest seedlings are mainly produced to meet forest restoration projects and timber production demands. Samanea saman is a fast growing species and easily-obtained seeds. For these reasons, it has been widely used for forest restoration plantations. The interaction of forest species with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) has been extensively studied and the substrate is one of the factors that most influence these symbioses. The objective of the work was to select substrates that optimize the symbiotic association with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi in the production of Samanea saman seedlings and in the growth of the seedlings after planting under water stress conditions. The specific objectives of each chapter were: Chapter I: To select substrates that favor the establishment of BFN and AMF symbiosis and the growth in Samanea saman seedlings correlating the results with the physical, chemical and nutritional characteristics of the substrates; Chapter II: To analyze the double inoculation in the formation of Samanea saman seedlings produced in substrates favoring arbuscular mycorrhizal fungi and nitrogen-fixing bacteria symbiosis; Chapter III: To evaluate the tolerance to water stress after planting of Samanea saman seedlings associated with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi that were produced on substrates favoring symbiosis. In Chapter I, it was verified that the substrate Carolina Soil 0.7 (peat based) was the one that most favored the nodulation and the substrates sewage sludge and clayey subsoil with the addition of 10% poultry litter ( V: V) were the ones most favored the root colonization and the spore multiplication by AMF. In chapter II it was shown that substrate sewage sludge is more suitable for the production of S. saman seedlings because it increased all the growth characteristics of the seedlings and in this substrate the inoculation increased shoot and reduced the rooting and the diameter of the colon. In the standard substrate, the symbioses increased the biomass, leaf area and lap diameter of the seedlings, but in this substrate the growth of the seedlings was lower than in the others. In Chapter III, it was verified that the use of NFB + AMF in the Standard substrate, increased the growth in height and biomass after planting. For the substrate Sewage Sludge, higher height and biomass occurred when neither inoculants nor fertilization were used in the seedlings production, and for this substrate the fertilization reduced the root biomass and the microorganisms reduced the root and shoot biomass of the plants. In this chapter it was also concluded that the planting of Samanea saman under conditions of water stress is not indicated when the seedlings were produced with Commercial substrate