Restrição hídrica e fertilização fosfatada no crescimento de mudas de Tabebuia aurea (Silva Manso) Benth. & Hook.f ex S. Moore sob diferentes regimes de irrigação

Abstract

The availability of water in the soil is one of the most important factors influencing the successful establishment of saplings in field conditions. The scarcity of this resource serves as a constraining element that hampers both productivity and the prosperous cultivation of forest crops. Implementing applications of phosphate fertilizer can play a pivotal role in fostering the development of a more robust root system, thereby potentially mitigating the adverse impacts stemming from inadequate water availability on the cultivation. Investigations dedicated to silviculture pertaining to native forest species remain relatively scarce, primarily due to a concentration of research efforts around commercially more prevalent species. With the aim of evaluating tolerance and growth, as well as morphophysiological alterations in seedlings of Tabebuia aurea (Silva Manso) Benth. & Hook.f ex S. Moore subjected to water deficit and phosphate fertilization; an experiment was conducted at the greenhouse of the Department of Forestry Science at UFRPE – SEDE. Three irrigation cycles: daily (T); every 5 days (S5); and every 10 days (S10), and 4 phosphorus addition treatments (0, 100, 200, and 300 mg dm-³ of P) were tested following a factorial scheme in a completely randomized design, with 5 replicates. The source of P employed was monosodium phosphate (NaH2PO4). Two seeds were placed per 50 cm³ tubes, and thinning was conducted post germination. Following germination and growth, seedlings were standardized based on height and transplanted into 2,8 dm³ pots containing subsoil substrate. Water deficit induction was conducet after transplantation and phosphorus treatments differenciation. Throughout the experiment, seedling measurements were taken every ten days, encompassing parameters such as height (H) and stem diameter (DC). At the conclusion of the trial, the following aspects were determined: shoot dry matter (MSA), root dry matter (MSR), total dry matter (MST), shoot-to-root dry matter ratio (MSA/MSR), and Dickson's Quality Index (IQD) were calculated. Additionally, H, DC, NF, leaf area, primary root length, and chlorophyll content were determined. The application of phosphorus doses did not act as a mitigating factor for the effects of water stress. Seedlings with better quality were obtained in the treatment with daily irrigation, and the dose that yielded the best responses for the production of T. aurea seedlings was 200 mg dm-3.