Impacts of Sewage Sludge in Tropical Soil: A Case Study in Brazil

Abstract

A long-term assay was conducted to evaluate the environmental impacts of agriculture use of sewage sludge on a tropical soil. This paper describes and discusses the results obtained by applying a interdisciplinary approach and the valuable insights gained. Experimental site was located in Jaguariúna (SP, Brazil). Multiyear comparison was developed with the application of sewage sludge obtained from wastewater treatment plants at Barueri (domestic and industrial sewage) and Franca (domestic sewage), São Paulo State. The treatments were control, mineral fertilization, and sewage sludge applied based on the N concentration that provides the same amount of N as in the mineral fertilization recommended for corn crop, two, four, and eight times the N recommended dosage. The results obtained indicated that the amount of sewage sludge used in agricultural areas must be calculated based on the N crop needs, and annual application must be avoided to prevent overapplications.