Fabrication of stalk fiber/geopolymers-based slow-release fertilizer with agricultural waste and loess for promoting plant growth

The reutilization of agricultural waste is an important strategy to ensure the sustainable development of modern society. In this work, corn stalk fiber (CoS), a typical discarded biomass from agricultural production, was composited with loess-based geopolymer (LoGP), along with loading urea and in-situ grafting polymer of acrylic acid, which afforded a novel slow-release fertilizer of corn stalk fiber/geopolymer (N @ CoSP/LoGP). Its composition, microstructure and morphology were characterized by SEM, FT-IR, XRD, TG and BET. Its water absorption, water retention capacity, swelling behavior, and N sustained-release performance were also measured. And the sustained-release mechanism was discussed by using a kinetic model of dissolution and release. It was found that the prepared composited fertilizer could enhance the water retention capacity of soil, and the maximum swelling rate of N @ CoSP/LoGP in water and 0.9 wt. % NaCl solution were 263.2 g/g and 62.5 g/g, respectively. Its swelling rate kept to 80 % than that of the initial value after 6 cycles, the water holding capacity of soil, containing 2 wt. % of N @ CoSP/LoGP, reached more than 25 days. Furthermore, the promoting plant growth action of N @ CoSP/LoGP was tested through pot experiments of corn. It indicated that the pre-pared composited fertilizer could effectively promote the germination and growth of corn crop as it released 60.6 % of nutrients within 45 days. In summary, a strategy for reutilization of agricultural waste and low-cost loess was explored, and the obtained composited fertilizer has great potential application in agricultural production.