Desenvolvimento inicial de leguminosa em solo degradado tratado com resíduos orgânicos e biocarvão

Abstract

In recent decades, public policies aimed at mitigating environmental degradation and promoting recycling/reuse have been introduced to reduce the amount of waste generated and to promote the recovery of degraded soils. Domestic sewage sludge is a promising option as a soil conditioner for the reforestation of degraded areas, as it contains nutrients beneficial to plants. However, it may also contain potentially toxic elements. The co-pyrolysis of sludge with other biomass, resulting in biochar, can concentrate nutrients and reduce the presence of these toxic elements. However, there are still uncertainties about the ideal type and quantity of waste to be used in this process. This study aimed to evaluate the growth of Mimosa caesalpiniaefolia cultivated in degraded soil in response to doses of biochar and the precursor residues of the biochar. The experiment was conducted in a greenhouse, in a completely randomized design, with a 3 x 4 factorial scheme, plus a control treatment and 4 replications, totaling 52 experimental units. The first treatment factor consisted of sewage sludge + pruning residue (LP), sewage sludge (LE), and biochar from LE + pruning residue (B-LP). The second treatment factor was doses of 5, 10, 20, and 40 Mg ha⁻¹ of biochar, 10.4; 20.8; 41.5, and 83.1 Mg ha⁻¹ for sewage sludge, and 17.5; 35.1; 70.2, and 140.3 Mg ha⁻¹ for the mixture. The control was the zero dose. Degraded soil was incubated with the treatments before sowing M. caesalpiniaefolia. The following were evaluated: number of leaves, plant height, and stem diameter. At 76 days after sowing, the plants were harvested for analysis of total dry mass. The Dickson Quality Index was calculated to assess seedling quality. ANOVA, Tukey test, regression analysis, and Dunnet test were performed using the R software. B-LP had no significant impact on the initial development of M. caesalpiniaefolia for most parameters, except for total dry matter at dose 4 (40 Mg ha⁻¹). Increasing doses of sewage sludge showed mixed results: while high doses impaired seedling development, doses up to 70.2 Mg ha⁻¹ were beneficial. The mixture of sewage sludge with pruning residue, in turn, showed an increase of up to 352% compared to the control at dose 4 (140.03 Mg ha⁻¹) for the number of leaves, suggesting that this combination can significantly improve seedling growth when used at adequate doses.