Effects of Different Sewage Sludge Concentrations on Soil and Cultivated Raphanus sativus L
G. M. B. Bohm *
Departamento de Gestão Ambiental, Instituto Federal Sul-Rio-Grandense- IFSul, Praça 20 de setembro 455, Pelotas, 96015-360, RS, Brazil.
R. M. Karsburg
Graduado em Saneamento Ambiental, Instituto Federal Sul-Rio-Grandense- IFSul, Praça 20 de setembro 455, Pelotas, 96015-360, RS, Brazil.
C. Heidrich
Graduado em Gestão Ambiental, Instituto Federal Sul-Rio-Grandense- IFSul, Praça 20 de Setembro 455, Pelotas, 96015-360, RS, Brazil.
E. M. Bohm
Graduado em Gestão Ambiental, Instituto Federal Sul-Rio-Grandense- IFSul, Praça 20 de Setembro 455, Pelotas, 96015-360, RS, Brazil.
R. C. O Machado
Departamento de Química, Instituto Federal de Goiás - Campus Luziânia - IFG, Rua São Bartolomeu, s/n, Vila Esperança, Luziânia, 72811-580, GO, Brazil.
*Author to whom correspondence should be addressed.
Abstract
Sewage sludge is a residue rich in organic matter and nutrients important for plant growth and soil fertility, but it may contain in its composition heavy metals that can result in toxicity to the plant, soil and humans when used as fertilizer. The objective was to assess microbial activity and heavy metal residues in soil and radish tubers grown with different concentrations of sewage sludge. Carbon microbial biomass, total organic carbon, soil basal respiration and zinc, copper, chromium and lead levels in soil and radish tubers were analyzed. According to the results, application of 30 Mg ha-1 of sewage sludge promoted higher microbial activity and lower metabolic quotient, and resulted in 490 tili-1 of microbial carbon and 11.12% of soil organic carbon. Heavy metal contents in radish tubers were 266.15, 2.82 and 15.42 mg kg-1 of zinc, chromium and lead, respectively, with the lead content found in the samples were above the maximum extent permitted recommended by the Codex Alimentarius.
Keywords: Radish, microbial carbon, heavy metal, basal respiration