From waste to resource: Assessing the feasibility of municipal sludge as a fertilizer from a soil and microbial perspective

Abstract

Municipal sludge is rich in nutrients and microbial populations, making it a potential soil amendment to enhance fertility. This study aimed to investigate the impact of municipal sludge application on microbial populations and assess its suitability as a fertilizer. The results indicated a significant increase in organic matter content in sandy soil after municipal sludge application (from 9.57 to 23.62 mg·kg⁻¹). Available potassium and phosphorus levels improved from poor to intermediate, and available nitrogen reached an excellent level. Plant parameters such as wet weight, diameter, root length, and aboveground height also showed improvement with municipal sludge addition. High-throughput sequencing revealed Shannon and Simpson indices exceeding 5.26 and 0.98, respectively, across all substrates except B1, indicating enhanced microbial community structure and diversity in sandy soil. Redundancy analysis highlighted the pivotal role of total phosphorus, available phosphorus, organic matter, available nitrogen, total nitrogen, and available potassium in enriching microbial abundance and diversity. In conclusion, using municipal sludge as fertilizer is feasible and beneficial for soil safety, fertility, and microbial populations enhancement.