Effects of municipal wastewater treatment sludges on some soil properties in field experiment

Introduction: The agricultural use has become the principal disposal method for sewage sludge in Europe, agricultural use accounts for 37% of the total sludge produced and it is expected that stabilized sludge will be used in agriculture in large quantities in the next years in many important EU member states. The reuse of treated municipal sewage sludge (biosolids) in agriculture provides the nutrients and micronutrients (such as N, P, K but also Fe, B, Cu and Ni among others) necessary for plant and crop growth. The use of sludge in agriculture also enhances the organic content of soils, increases the water- holding capacity, the soil aggregation, reduces the soil bulk density, increases the cation exchange capacity, enhances the plant root environment. Therefore, plants are better able to withstand drought conditions, extract water, and utilize nutrients. Material and Methods: This study examines the effect of sewage sludge application on some soil properties. A year-long field experiment was set up in the district of Haymana. Dewatered anaerobically digested sewage sludge were collected from Ankara municipal treatment plants. The sludge doses are adjusted according to the nitrogen requirement of the wheat plant. Within this scope, sewage sludge were individually used in doses of approximately 500, 1000, 2000, and 4000 kg/da with and without chemical fertilizer. Bread wheat (Tosunbey variety) followed its normal pattern and plants were harvested. In the all of experiments, some of properties of soil such as pH, EC, organic matters, total nitrogen, ammonium and nitrat nitrogen, available P2O5, exchangeable K2O, CEC, and CaCO3 were determined. Results: As a result of the field study, increases in total nitrogen, available P2O5, exchangeable K2O, organic matter, CEC and EC values were determined depending on the increasing sludge dose in soil samples. A significant change in the pH values of the soils has not been determined. In all treatments, it was determined that the sludge application affects some chemical properties of soil (OM, CEC, N, P) positively. The lime and pH were unaffected and the salt content of the soil increased. Discussion: Soil salinity is an important problem of Turkey, unconscious use of sewage sludge can affect the salting of the soil. Therefore, this issue should not be taken into consideration when using sewage sludge. The use of the combinations of biosolid and chemical fertilizers may be more effective than alone application of biosolid