The application of precipitated silica in agricultural granular fertilizers for anti-caking and adsorption primarily relies on its high specific surface area, porous structure, and surface activity, achieving both physical anti-caking and nutrient slow-release functions.

Anti-Caking Mechanism
Precipitated silica inhibits fertilizer granule caking through the following physical mechanisms:
Moisture Adsorption: Its nano-scale porous structure efficiently adsorbs moisture on the granule surface, blocking the "liquid bridges" formed by capillary action and preventing soft caking caused by humidity fluctuations.
Crystal Bridge Inhibition: It reduces the crystallization and precipitation of salts in the saturated mother liquor of fertilizers (such as urea and ammonium nitrate), preventing "crystal bridges" from adhering to adjacent granules.
Particle Isolation: Fine silica particles are evenly distributed on the fertilizer surface, forming a physical isolation layer, reducing the contact area and friction between particles, and improving fluidity.
Performance Advantages: Compared to traditional anti-caking agents such as diatomaceous earth and fly ash, precipitated silica's anti-caking efficiency is 2–5 times higher, especially for highly hygroscopic compound fertilizers.
Nutrient Adsorption and Slow-Release Effects
Precipitated silica exhibits significant adsorption and slow-release capabilities for nutrients such as nitrogen, phosphorus, and potassium:

Adsorption Mechanism: Its surface is rich in silanol groups (–SiOH), which can bind to ammonium ions (NH₄⁺) and phosphate ions (H₂PO₄⁻) through electrostatic interactions or hydrogen bonds, reducing nutrient leaching.
Slow-Release Function: Under the action of soil moisture, the adsorbed nutrients are slowly desorbed, extending the fertilizer's effectiveness and improving fertilizer utilization.
Synergistic Effect: Combined with controlled-release fertilizer technology, it can reduce the frequency of topdressing. For example, in lettuce cultivation, applying controlled-release blended fertilizer (N-P₂O₅-K₂O=21-7-22) as a one-time base application achieved a fertilizer saving rate of 31.64%, and nitrate leaching was reduced by over 70%. Practical Applications and Technological Potential
Application Areas: Currently, precipitated silica is widely used in agriculture primarily as a pesticide adjuvant, enhancing the dispersion of pesticide solutions and improving leaf adhesion to increase efficacy. In the fertilizer field, its application is still mainly focused on research and experimentation, and standardized commercial products have not yet been developed.
Research Support: Multiple studies have confirmed that it can improve soil porosity, water retention, and the microbial habitat, indirectly promoting root development.
Commercialization Gap: A search on the Baidu Ai Purchasing platform revealed no precipitated silica products specifically designed for granular fertilizers in agriculture, indicating that its market application is still in the technical verification stage and lacks large-scale production and promotion.