Municipal sewage sludge application on cotton cultivations. Effect on yields soil chemical properties and heavy metal concentrations

Application of municipal sewage sludge (MSS) to agricultural soils is a current practice in EU. European legislation permits its use in agriculture when concentrations of metals in soil do not exceed the maximum permissible limits. In order to study the influence of MSS on cotton yield and soil properties, a filed experiment was conducted in a soil classified as Typic Xerochrepts located in Lamia area, central Greece, for two consecutive years. The experimental design was complete randomized blocks with four treatments: Control (C), inorganic fertilization (IF), application of 6000 dry kg ha(-1) MSS, and 10000 dry SS kg ha(-1), each replicated 4 times. The results showed that MSS application in both rates, increased significantly cotton yield compared to control equally to inorganic fertilization. Soil properties, at the end of the second year of MSS application, were significantly affected by MSS application in a positive way i.e. pH decreased slightly, but organic matter content, available phosphorus, total nitrogen concentrations exchangeable potassium and available zinc and copper increased significantly. The potentially toxic elements lead, chromium, and nickel were not significantly affected by MSS application in both application rates compared to control.