Synthesis and mechanism of Mg/Al layered double oxides-silica nanocomposites for sustainable multi-nutrient delivery in agricultural applications

Abstract

Potassium (K), urea (N), phosphate (P), and selenite (Se) are widely used in modern agriculture for improvement of crop yield and quality. However, traditional fertilizer suffers from poor fertilizer utilization efficiency and noncontrollable slow-release behavior. To improve nutrient utilization, we developed a layered double oxides-silica (LDO@Si) based on calcined Mg/Al layered double hydroxide-silica nanocomposites (LDH@Si), for slow release of K, N, P, and Se to crops. In this study, SEM, XRD, FT-IR, XPS, BET, and TGA were employed to analyze the structure, morphology, and microstructures of the samples. Results show that LDH@Si successfully transforms into LDO@Si after calcination, where LDO is mainly connected to silica via M-O-Si bonds. Furthermore, after K, P, and Se loading, the LDH@Si structure was successfully restored, indicating that phosphate and selenite ions have been effectively embedded in the inner layer of LDH. K ions are firmly fixed to the material surface via M-O-K bonds. After urea introducing, the pore structure of the material was completely filled, and excess urea formed a urea layer on the surface of the material. LDO@Si can continuously release nutrients into water through diffusion and LDO@Si dissolution for up to 240 h. Compared with chemical fertilizers, LDO@Si based slow-release fertilizer (CRSF2) significantly improves plant fresh weight, dry weight and chlorophyll content, increasing them by 13.91 %–23.13 %, 18.20 %–34.40 % and 2.24 %–14.81 %, respectively. Furthermore, a modest increase in the levels of nutrients N, P, and K is observed, while the Se concentration in plants treated with CRSF2 demonstrates significant enhancements of 9.57 %, 72.49 %, and 50.97 % compared to control treatments. These results illustrate the potential agricultural application of LDO@Si as a slow-release fertilizer for improving crop yields while minimizing the required amount of fertilizer.