Double Advantages of Nutrients and Biostimulants Derived from Sewage Sludge by Alkaline Thermal Hydrolysis Process for Agricultural Use: Quality Promotion of Soil and Crop.

Low-carbon alkaline thermal hydrolysis of sewage sludge for the production of high-quality plant-growth-promoting nutrients and biostimulants is a growing concern for sludge resource utilization in agriculture. Thus, this study aims to investigate functional characteristics and soil biochemical effects of sewage sludge-derived nutrients and biostimulants (SS-NB). The content of heavy metals in SS-NB decreased by 47.39-100%, and an increase in soil protease, invertase, and soil nutrient utilization rates are observed in SS-NB groups. SS-NB substituted for chemical fertilizer increased the diversity and evenness of microbial community and reduced the abundance of the soil-borne bacterial genus Arthrobacter. The dominant community of SS-NB100 group is mainly enriched in Microvirga, Ensifer, Novosphingobium, Bosea and Ellin6055, which are principally beneficial symbiotic bacteria of plants and participated in C and N cycles. Moreover, SS-NB reduced the accumulation of Ktedonobacteria and Nitrosospira, which are involved in the production of CO 2 and N 2 O, and also enhanced the coordination of soil microorganisms with enzyme activities and nutrient utilization rate. In conclusion, the results suggest that SS-NB exerts a positive effect on reducing greenhouse gas emissions and preventing soil-borne diseases, and can further enhance collaboration with soil enzyme activity and soil nutrient utilization by stimulating soil microorganisms.