Layered double hydroxide for slowing selenium fertilizer release and improving selenium utilization efficiency in vegetables

Selenium (Se) is a beneficial plant micronutrient, and the application of Se fertilizers can promote plant growth and enhance the Se content in crops. However, traditional soluble Se fertilizers have low utilization efficiency of Se due to adsorption or leaching. Here, selenite (SeO ₃ ²⁻ ) -intercalated Mg/Al layered double hydroxide (Se-Mg/Al) for SeO ₃ ²⁻ slow-release was synthesized by co-precipitation and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Se-Mg/Al possessed a typical lamellar structure, combining with selenite by electrostatic interaction in interlayer and chemisorption on the surface. The release mechanism of selenite in distilled water from Mg/Al layered double hydroxide (Mg/Al LDH) was Fickian diffusion with gradually released 97.86% after 20 h (Over 90% within 2 h for sodium selenite). At pH range 4.0–8.0, Se-Mg/Al had a stable slow-release ability. And, the sulfate and phosphate anions could effectively trigger the release of selenite through anions exchange. The pot experiments showed that Se-Mg/Al increased Se content of vegetables, more than twice that of directly using sodium selenite. Compared with control treatment, the average stem height and fresh weight per 10 plants with Se-Mg/Al treatment improved approximately 1.48 times and 2.34 times, respectively. This work provides a feasible way for achieving crops selenium supplementation and improving selenium utilization efficiency.