Resíduos orgânico para enriquecimento do estéril empregado na construção de tecnossolo em mina de bauxita.

Abstract

One of the biggest challenges in bauxite mining is to ensure the reestablishment of vegetation in the post-mining area. The challenge is intensified in cases where topsoil is not available for the construction of the mine soil, being necessary to search for technologies to improve the bauxite mine spoil and thus guarantee the conditions of the plant establishment and, consequently, obtain the coverage of the soil in the initial stages of recovery of the mined area. The objective of this work was to find the most efficient dose and source of organic matter (O.M.) to be incorporated into the substrate to promote the improvement of the spoil's physical and chemical attributes and ensure the development of the indicator plant. Two sources of M.O. namely: wood residues from suppression (WS) and dehydrated food residues (FR) from the company's activities, in three dosages 10, 20 and 40 t/ha-1 and a control (TT), which comprised seven treatments with 5 repetitions, arranged in CBD. Pigeon pea (Cajanus cajan) was used as an indicator plant. The evaluated parameters were the physical attributes: Density (Ds) and Total Porosity (Pt) and; The chemical attributes in layers 0-5, 5-10, 10-20, 20-40 cm. The variables related to the indicator plant were: plant dry biomass and height at 6 and 14 months of the experiment. Data were submitted to ANOVA and means compared by Tukey at 5% in the R-studio program. In both sampling periods, doses of 20 and 40t ha-1 FR and 40 t ha-1 WS provided a significant increase in plant height and dry biomass in relation to TT. From the chemical variables, statistical differences were detected for the organic C (orgC) and for the potential CTC in the 0-5cm layer (p-value < 0.05). For orgC, the treatments 40 t ha-1 WS and 40 t/ha-1 FR were the maximizing doses, thus different from TT. Regarding soil CEC, only the dosage of 40 t ha-1 WS was statistically different from TT only in the superficial layer at 6 months. For the other chemical attributes and at the other analyzed depths, there were no statistical differences in TT. Until the end of the experimental period, Ds and Pt did not respond to doses and sources of M.O. used. The incorporation of organic residues to the spoil at doses of 20 and 40 t ha-1 R and 40 t ha-1 M provided gains in height at the time of the first flowering of pigeon pea. However, 20 and 40 t ha-1 R provided higher values of dry biomass of the indicator plant, presenting the best performance at the end of the experimental cycle; ; The incorporation of 40 t ha-1 WS and 40 t ha-1 FR to the spoil had a positive effect on orgC in both sampling periods and 40 t ha-1 WS positively affected CTC only at 6 months; Therefore, doses of 20 and 40 t ha-1 FR mixed with the bauxite mine spoil are the most promising for increasing the carbon content in the soil and producing plant dry biomass.