Fertilizante ogranomineral de lodo de esgoto na produção de Urochloa Brizhantha cv BRS Paiaguás

Abstract

This study evaluated the agricultural potential of organomineral fertilizers formulated from sewage sludge, combining composting with sawdust residues and biochar production. The effects of these inputs on dry matter yield, nutrient accumulation, and heavy metal dynamics in Urochloa brizantha cv. BRS Paiaguás were analyzed. Initially, the sewage sludge was composted with different proportions of sawdust, and the biochar was produced by pyrolysis of sludge and sawdust mixtures, later incorporated into the organomineral formulations. The addition of sawdust residue resulted in a decrease in pH and in the contents of N, P, Na, Ba, and Cr. Changes in organic matter were characterized using mid-infrared (FTIR-MIR) and near-infrared (FTIR-NIR) spectroscopy, revealing an increase in total organic carbon content, degradation of aliphatic compounds, and greater presence of aromatic structures, indicating changes in the humification process. The formulated fertilizers were applied in a greenhouse experiment conducted over 120 days, in a randomized block design with four replications, comprising six treatments: mineral fertilization (NPK), organomineral fertilizer with granulated biochar, organomineral fertilizer with powdered biochar, organomineral fertilizer with granulated composted sludge, organomineral fertilizer with powdered composted sludge, and a control treatment without fertilization (Test). The organomineral fertilizers, especially the granulated biochar, promoted the highest total accumulations of N, P, Mg, Ca, and S, as well as dry matter production, showing performance comparable to mineral fertilization. The application of granulated biochar also led to an increase in cation exchange capacity and a reduction in potential soil acidity, enhancing nutrient availability. The analysis of heavy metal contents in the soil and plants indicated that all treatments with organomineral fertilizers maintained metal concentrations within the limits established by current environmental legislation, without significant increases in plant uptake. Granulated biochar stood out by reducing lead levels in the soil, contributing to its safe retention and mitigating environmental risks. These results highlight the effectiveness of sewage sludge-based organomineral fertilizers as a sustainable alternative to mineral fertilization, promoting agronomic gains, improved soil fertility, and the safe reuse of urban waste.