Biofunctional Microgel-Based Fertilizers for Controlled Foliar Delivery of Nutrients to Plants

Foliar application of micronutrients (e.g. Fe³⁺ ) onto plants over an extended time is challenging and often not possible due to insufficient rainfastness. Smart delivery systems which enable micronutrient release over several weeks would offer innovative and sustainable options to improve plant health and food production. Herein, we report a novel foliar fertilizer delivery system based on functional pH-responsive biohybrid microgels that have orthogonal functionality as carriers of micronutrients and employ peptides (termed anchor peptides) as foliar adhesion promoters. The anchor peptides bind to hydrophobic surfaces and the waxy "islands" of plant leaves. Our system requires no auxiliaries and is loadable, storable, and applicable from aqueous dispersion. We report the synthesis and functionalization of microgels, their loading with Fe³⁺ ions, and a proof of concept for the biofunctional microgel-based fertilizer system is demonstrated for iron-deficient cucumber plants.