Effects of applying sewage sludge compost on the physicochemical properties of soil and growth of Trifolium repens

A pot-scale test was carried out to investigate the effects of applying sewage sludge compost (SSC) on the physicochemical properties of soil and the growth of white clover (Trifolium repens). The results showed that after SSC application, pH of the soil was more stable, and the organic content increased by 76.69%－204.80%. The content of total P in soil with SSC amendments was slightly higher than SSCfree soil. At the dosages of 5%, 10%, 15% and 20%, the content of inorganic nitrogen in soil was 5.6, 10.0, 5.1 and 4.5 times of control, indicating that SSC can significantly improve the nutrient content of soil. SSC addition also improved the growth of white clover growing in soil illustrated by the increased biomass. The dry weight of white clover aboveground and its root increased by 82.42%－229.95% and 10.21%－58.23% respectively after SSC dosing. The recovery rates of N from SSC were 4.3%, 5.8%, 26% and 3.5%, and for P were 1.27%, 1.64%, 1.21% and 1.60% at the dosages of 5%, 10%, 15% and 20% respectively. The results reveal that SSC application in soil improves its organic content and physicochemical properties, which favors the growth of white clover. The greatest increases in the content of inorganic N and the recovery rates of total N and total P were seen with a dosage of 10%, suggesting that 10% would be suitable.