Wheat straw fibre based semi-IPN composite: Preparation and evaluation as a matrix for water and fertilizer release and in slope reinforcement

To improve the utilization rate of fertilizer and reduce environmental pollution, the effective management of water and fertilizer is extremely significant for the development of modern agriculture. Herein, using agricultural wastes (wheat straw fibre, WS) and phosphoric acid-based geopolymers (PGs) as eco-friendly materials, a novel wheat straw fibre composited polymer/PGs (WS-Po/PGs), was prepared by in-situ graft polymerization strategy, and a kind of nutrient-water carrier with semi-IPN was formed. Its structure and morphology were revealed by XRD, FT-IR, BET and SEM. Its water-retaining and controlled release behavior, and the nutrient release model were studied, while the effects on plant growth and loess slope of WS-Po/PGs were further investigated. The results illustrated that the obtained nutrient-water carrier had excellent water absorption (270.27 g/g) and salt tolerance (131.58 g/g) as straw fibres were mixed into polymer networks and formed semi-interpenetrating structures (semi-IPN). Comparing with controls, the WS-Po/PGs significantly improved the water retention capacity and N release longevity (30 d, 66.2%). Its nutrient release fitted the Fickian diffusion model (n < 0.5). Furthermore, the WS-Po/PGs could remarkably enhance the erosion resistance and stability of the loess slope, regulate the pH of the soil, and promote the germination rate of slope vegetation. In summary, by using agricultural wastes straw and loess as resources, the obtained WS-Po/PGs presented excellent slow-release behavior, salt tolerance and slope reinforcement function, and this kind of semi-IPN nutrient-water carrier could provide an insight for agriculture and slope protection.