Vacuum infiltration for priming of soybean seeds: optimization and particle tracking using fluorescent silica nanoparticles

Agrochemical delivery is highly inefficient, and novel application methods are necessary to promote crop health and yields while reducing environmental impact. In this work, a vacuum infiltration seed priming strategy was developed to incorporate silica nanoparticles into soybeans. Although successful in initial greenhouse and field studies, little is known about the amount of nutrient being delivered and the conditions for optimum accumulation. Herein, various infiltration conditions were evaluated using fluorescent silica nanoparticles and confocal microscopy, including nanoparticle surface charge and concentration, infiltration time, infiltrate ionic strength and pH, and seed presoaking. Negative nanoparticle surface charge, higher nanoparticle concentration, shorter infiltration time, and potassium-based salts resulted in greater nanoparticle infiltration. Seed coat elemental analysis complemented fluorescence data and highlighted the co-delivery of beneficial macronutrients including potassium and magnesium under ionic salt infiltration conditions. Overall, these findings illustrate a new strategy to biofortify nanoscale nutrients into soybean seeds that can be expanded into other agrochemical targets and crop species to promote sustainable agriculture.