Efeitos do lodo de curtume compostado nos atributos químicos e biológicos do solo e na cultura do milho

Abstract

Population growth has driven the generation of wastes from urban and industrial activities, causing serious environmental problems such as soil contamination and groundwater. These organic wastes with high concentrations of chemicals, such as hydroxides, sulfides and sulfates, as well as the presence of heavy metals, have a high potential for environmental pollution. This study aimed to evaluate the effects of the application of composted tannery sludge (CTS) on the chemical and microbiological properties of the soil and the development of corn. To evaluate these implications were applied five sludge concentrations of CTS in the soil, 0.0; 2.0; 5.0; 10.0; 20.0 and 40.0 Mg.ha-1. The results for the heavy metals, chemical and biological attribute of the soil, as well as biometric were submitted regression analysis and multivariate analysis. The addition of CTS contributes to the increase of the metals in the soil, with values ranging between 8.0 and 16.3 mg.kg-1 for Cu, 4.6 and 25.9 mg.kg-1 for Cr, 18. 8 and 21.3 mg.kg-1 for Zn and 10.3 and 13.9 mg.kg-1 to Pb. The metals Cr, Cu and Ni have a high affinity with the organic fraction. The evaluated metals showed values within the limits allowed for the use of waste in agriculture according to the “Conselho Nacional do Meio Ambiente” (CONAMA). The metals Cr, Cu and Ni have a high affinity with the organic fraction, while Mn, Fe and Zn were found in higher concentrations linked to oxidic fraction. On the other hand, Pb showed affinity for the organic fractions, oxidic and exchangeable. The CTS promoted an increase of the soil pH ranging between 5.7 and 6.5, contributes to the increase of microbial biomass carbon (MBC) and the basal soil respiration (BSR). The addition of CTS up to 20 Mg ha-1 favored the development of corn with plant height ranging from 102 to 132.4 cm. Thus, we conclude that the addition of CTS contributes to the increase of heavy metals in soil. However, the concentrations were within the range values allowed in agriculture; The metals Cr, Cu and Ni have lower bioavailability for soil solution, remaining connected to the organic fraction. The Mn, Fe and Zn have less influence of soil pH, because they are linked to oxidic fraction; But the Pb is highly mobile in soil, due to its affinity for the organic fraction, oxidic and the exchangeable fraction, being the last fraction highly influenced by soil pH change; CTS application contributes to improvement of the chemical and biological soil attributes and growth development of corn, favoring the production of shoots and roots. Cr, Cu, Pb, Zn, Ni, Zn and Fe, generally have low correlations with the chemical and biological soil attributes.