Atributos físico-químicos de substratos produzidos com resíduos de produtos amazônicos

Abstract

This work aimed to develop suitable substrate recipes to the cultivation of xerophytic plants using waste products found naturally in the Amazon region. The selection of tested materials was based on bibliographic research, local availability and low acquisition cost. Two types of Brazil nut (Bertholletia excelsa Bonpl.) residues were used: the fruit bark and seed coat. Cupuaçu bark (Theobroma grandiflorum (Willd. ex Spreng.) K. Schum.) and a mixture of decomposed tree barks were also selected. The study was carried out in the city of Itacoatiara, Amazonas, in the nursery of the Flora Guedes company. After processing the materials, nine preparations were made: one with each pure material and one of each material with the addition of crushed charcoal and a portion of soil in a 1:1:1 ratio. A final preparation consisted of the three vegetable residues, also in a 1:1:1 ratio. For a sample of each substrate, the pH values in water, the C/N ratio, organic matter, organic carbon, N, Ca, K, P, Mg, S Cu, Fe, Mn, Zn, were determined. Bulk density, particles density and total porosity were mesured. The main results showed that the pH of cupuaçu bark and tree bark mix had a basic character, with values of 8.3 and 7.7, respectively. Chemical analyzes showed higher percentages of N in all pure substrates; higher percentages of P in the substrates with the presence of cupuaçu bark; and, higher percentages of K in the pure substrates of the nut seed coat of Brazil nut and cupuaçu bark. Regarding micronutrients, higher levels of S were found in the substrate mix of tree bark; higher Mn and Zn contents in the nut seed coat substrate and high Fe contents in all substrates. Regarding physical properties, the results varied between 0.08 g/cm³ for cupuaçu bark and 0.57 g/cm³ for the substrate composed of a mixture of tree bark + charcoal + terra preta. The total porosity ranged between 77.53% for the substrate composed of the three plant materials and 87.84% for the seed coat. Among the pure substrates, the use of cupuaçu bark and a mixture of tree bark is not suggested due to the alkaline pH. The other materials and compositions have desirable physicochemical characteristics for use as substrate and can be subjected to experiments with xerophytic plant species.