Jiyuan Jin

Crop production is threatened by both water scarcity and poor soil water retention in arid or semi-arid regions. At the same time, the industrial-scale accumulation of municipal sludge creates substantial environmental and resource pressures. The goal of this work was to recycle municipal sludge into a low-cost, environmentally friendly, and multifunctional sludge-based water-retaining material (SBWRM) for enhancing soil water retention capacity and nutritional status. Sludge was used as the primary raw material, and extracellular polymeric substances were extracted using a combined alkaline ultrasonic method. These extracts were then mixed with polyvinyl alcohol to prepare the sludge-based material. The water retention capacity of the material, as well as its effects on seed germination and plant growth in a planting substrate, were systematically evaluated. The results suggested that the SBWRM achieved a maximum water retention capacity of 18.7 times its own weight. The addition of 40% SBWRM effectively promoted ryegrass seed germination and plant height, increased soil moisture and pH value, and enhanced the nutrient contents of nitrogen, phosphorus, and potassium. The findings indicate that SBWRM can effectively enhance water conservation, soil quality, and nutrient supply, thereby providing a practical approach for utilizing sludge resources and supporting ecological restoration in agricultural systems.

Phytoremediation technology has been widely used for the remediation of heavy metals in soil due to its favorable environmental and ecological effects, but establishing a single phytoremediation technology can result in bottlenecks, such as a long cycle, low biomass, and difficulty in root absorption. At present, inoculation with microorganisms that could assist plants in their remediation of contaminated soils is attracting increasing attention. Therefore, in this study we selected ryegrass and Bacillus thuringiensis (SY) and analyzed the effects of SY inoculation on the growth of ryegrass, including the accumulation of Cd in ryegrass, changes in heavy metal forms, and the heavy metal content in rhizosphere soil, using pot experiments. The results indicate that SY inoculation promotes root growth and development of the ryegrass and the accumulation of cadmium in the plants. In addition, SY inoculation increased the levels of soil nutrients and the activities of soil urease, sucrase, and alkaline phosphatase. This study reveals that the use of SY improves the remediation efficiency of ryegrass for cadmium-contaminated soil, and supports the application potential of microorganisms in soil remediation technology.