Effects of Different Rates of Liquid Sewage Sludge Amendment on Nutrient Content of the Soil in Rabat, Morocco

Abstract

The objective of this study was to evaluate different rates of the liquid sewage sludge fertilizer developed by a treatment plant in Skhirat, Rabat, Morocco on improving soil fertility indicators. The results revealed that the application of liquid sludge on the soil increased soil pH from 7.3 to 7.7, electrical conductivity from 227.1 to 416.21 µS.cm−1, and other nutrients such as soil organic matter from 9.0 to 21.4%, Kjeldahl nitrogen (TKN) from 0.1 to 0.7%, and total organic carbon (TOC) from 2.4 to 16.5%; the phosphorus ranged 79.1 to 127.8 mg.kg−1 in a dose-dependent manner in amended soil compared to untreated controls. However, the results also showed increase in heavy metal content in the following order: Zn > Cu > Pb > Ni > Cd, (Zn = 136.69 mg.kg−1, Cu = 69.05 mg.kg−1, Pb = 17.91 mg.kg−1, Ni = 4.73 mg.kg−1, Cd = 0.03 mg.kg−1); nevertheless, we noticed that their concentrations were lower than the critical values established by the European Union for the agronomic use of the soil.

Keywords

• soil
• sludge
• electrical conductivity
• agriculture