pH-Responsively Water-Retaining Controlled-Release Fertilizer Using Humic Acid Hydrogel and Nano-Silica Aqueous Dispersion

A pH-responsively controlled-release fertilizer was prepared using humic acid (HA) hydrogel, Nano silica aqueous dispersion (NSAD) and sodium alginate (SA). Therein, the NSAD was modified with HA owning a variety of reactive groups and good compatibility by the hydrogen bonding and playing a skeleton supporting role in the entire structural system, SA was soluble in alkaline environments thus releasing the HA. The facts showed that the gel fertilizer had a good controlled release effect and the HA was released organically in alkaline environments through structural characterization and controlled release mechanism experiments. The application test showed that the humic acid sustained-release fertilizer has obvious improvement effect on saline-alkali soil.