Use of Biogenic Silica in Porous Alginate Matrices for Sustainable Fertilization with Tailored Nutrient Delivery

Population growth coupled with significant pressure for clean agricultural practices puts a heavy burden on conventional crop treatments that target high yields with minimal cropland expansion. Optimization of fertilization systems is required as part of the solutions to current megatrends. Herein, we present a sustainable strategy to achieve controlled release formulations for nitrogen fertilization. Specifically, we used interfacial engineering to design alginate-based matrices that incorporated biogenic silica particles to achieve increased interfacial area for dynamic entrapment and release of ammonium nitrate. The incorporation of biogenic silica in the alginate matrix provided a porous architecture spanning length scales from the micro- (within particles) to the macrosize (within the polymeric matrix) levels, leading to tunable patterns of nitrogen release. Alginate-biogenic silica granules approached the European requirements of "slow-release" compositions. At optimized silica content, 15% of the nitrogen was released within 24 h and 56% over 28 days. The complete nitrogen dissolution was achieved after 60 days. The experimental results and kinetic models provided insights on the mechanisms driving the nitrogen release from the alginate-silica matrix as a function of the pore-polymer hybrid architectures.