Coal-bearing kaolinite-based plant growth-promoting fertilizer with integrated slow-release and water-retention properties

The development of ecological fertilizers has become crucial in modern agriculture due to the increasing global population and diminishing arable land resources. Herein, a plant growth-promoting fertilizer (UKS) with dual functions of slow-release and water-retention was prepared by combining liquid-phase intercalation method and crosslinking gel method. The physicochemical properties of UKS were analyzed and its dissolution, slow-release, and water-retention properties were systematically evaluated. The intercalation ratio was able to reach 53.3 % after intercalation for 5 days, exhibiting the slow-release potential of nitrogen fertilizer. The incorporation of sodium alginate improved the mechanical strength of the frame structure and effectively enhanced the water retention and slow-release properties of the fertilizer. Moreover, the cultivation experiments had shown that UKS can promote the growth of crops' leaves and roots, as evidenced by the fact that the length of them reached 9.8 cm and 5.4 cm, representing a respective growth of 16.8 % and 16.9 %, respectively. This strategy delivers a new approach for the development of eco-friendly agricultural fertilizers, and also provides a potential way to use coal-based solid waste for ecological restoration nearby.