Sustainable Agriculture Practices: Utilizing Composted Sludge Fertilizer for Improved Crop Yield and Soil Health

It is desirable to recycle sewage sludge as fertilizer for agricultural fields. The application of sludge to agricultural soils is a measure that replaces chemical fertilizers and plays an important role in improving soil's physicochemical and biological properties. However, there are concerns that the pollutants in sewage sludge will cause negative impacts on soil health. To closely monitor the soil-sludge interactions, a field study was conducted over a 20-year period in the North China Plain. In this study, the long-term effects of sewage sludge on the soil properties and soil microbial diversity were investigated. We examined the effects of various fertilization methods (control, chemical fertilizer, uncomposted sludge fertilizer, composted sludge fertilizer) on wheat production and several soil health indicators, such as the soil's enzymatic activities, microbial biomass, microbial diversity, and crop yield. This long-term experiment supports that the composted sludge fertilizer increased crop production by 124.2% compared to the control treatment. The soil's biological quality (e.g., the concentration of soil microbial biomass carbon) was also improved under the composted sludge fertilizer treatment. The concentrations of soil microbial biomass carbon under the uncomposted sludge fertilizer and composted sludge fertilizer treatments were 560.07 mg/kg and 551.07 mg/kg, respectively. The effect of the composted sludge fertilizer was greater than that of the uncomposted sludge fertilizer. The content of heavy metals did not exceed the national standard. The highest soil health index was 0.79 with the composted sludge fertilizer. Therefore, these results suggest that the application of composted sludge fertilizer has the potential to enhance long-term soil health and promote sustainable agricultural practices.