Fabrication of pH-Controlled-Release Ferrous Foliar Fertilizer with High Adhesion Capacity Based on Nanobiomaterial

Iron deficiency is a worldwide problem in modern agriculture, which causes leaf chlorosis and severe declines in crop yield. Therefore, improving the utilization efficiency (UE) of ferrous fertilizer is an urgent need. This study developed a pH-controlled-release ferrous foliar fertilizer (PCRFFF) composed of ferrous sulfate (FeSO4·7H2O), microcrystalline cellulose (MC), and attapulgite (ATP). Therein, MC was oxidized to form carboxyl cellulose (CC) that possessed plenty of carboxyl groups (-COOH) on the surface and could effectively chelate Fe2+ [Fe(II)] to form CC–Fe(II) microfibers. Then the CC–Fe(II) microfibers were tightly coated by abundant ATP nanorods through hydrogen bonds to produce PCRFFF. Under acidic conditions, the chelated Fe(II) became isolated and the ATP coating became loose, which facilitated the release of Fe(II) from PCRFFF. Thus, the release of Fe(II) could be efficiently controlled by pH. In addition, PCRFFF displayed high adhesion capacity on a crop leaf surface. This technology could effectively decrease the loss and improve the UE of Fe(II), thereby promoting the growth of crops.