Changes in fertility parameters and contents of heavy metals of soddy-podzolic soils upon the long-term application of sewage sludge

Abstract

The effect of the long-term sewage sludge (SS) application on the chemical, agrophysical, and biological properties of a soddy-podzolic soil (Umbric Albeluvisols Abruptic) was studied. Regular SS application in the course of five crop rotations (1976–2013) ensured the improvement of the soil fertility parameters, i.e., a rise in the contents of humus, available phosphorus, and exchangeable potassium; a better state of the soil adsorption complex, bulk density, and aggregation; and higher cellulolytic, nitrification, and urease activities. The efficiencies of SS and the traditional organic fertilizer (cattle manure) were compared. The effect of the long-term application of SS on the accumulation of heavy metals in the soils was also studied. It was found that the application of SS caused a rise in the bulk content of heavy metals and in the contents of their acid-extractable and mobile forms by 1.1–6.0 times. However, the maximum permissible concentrations of heavy metals in the soils were not exceeded. In the soil subjected to the application of SS for more than 25 years, the cadmium concentration somewhat exceeded the maximum permissible concentration.