Nitrogen transformation in soil treated with sewage sludge

Abstract

The use of sewage sludge or biosolids in agriculture is a well-known practice worldwide, mainly in Europe and United States. In Brazil, studies on the use of sewage sludge as a source of organic matter and nutrients are still scarce and limited. Therefore, the aim of this study was to evaluate the nitrogen mineralization and soil pH and electrical conductivity changes after application of sewage sludge from Franca and Barueri, ETE-Franca and ETE-Barueri, respectively, in sandy and clay soils. The lowest pH values were observed with the application of sewage sludge from the ETE-Franca in the clay soil amended with the highest dose. The electrical conductivity values in both soils increased after amendment with both sewage sludges, and ranged from 0.18 to 1.85 dS m-1at lower and higher dose, respectively. Higher concentrations of NH4+were observed in the soils that were treated with sewage sludge from ETE-Franca, and reached 513 mg kg-1soil. The N-NO3-concentrations were higher in soils treated with sewage sludge from ETE-Barueri, and reached approximately 800 mg kg-1of soil, regardless of the soil type.