Evaluation of Composted Sewage Sludge Application to Soil

The physicochemical properties of soil amended by composted sewage sludge and the growth of Tall Fescue in amended soil were investigated by pot-scale experiments. The incubation experimental results showed that organic nitrogen and ammonia in soil can be mineralized and nitrified simultaneously during 60 d, both of which stayed at relatively stable levels afterwards. The concentration of NO3--N in amended soil was significantly higher than that in the soil without CSS. The pH of amended soil kept stable whereas the electric conductivity varied with the evolution of the concentration of organic matters resulted from nutrients mineralization and immobilization. After a slow release of phosphorus in the initial 100 d, there was a sharp decrease in the concentration of total phosphorus in amended soil, which meant a fast mineralization of phosphorus-containing organic compounds. The planting assays of Tall Fescue showed that the highest amount of biomass in 180 d was obtained at a dosage of 15%. However, during the initial 60 d, a dosage of 5% led to a greatest biomass growth. Based on the uptake and recovery of N and P from amended soils, a CSS dosage of 5% in amended soil was suggested for a good growth of Tall Fescue.