What is missing to advance foliar fertilization using nanotechnology?

An urgent challenge within agriculture is to improve fertilizer efficiency in order to reduce the environmental footprint associated with an increased production of crops on existing farmland. Standard soil fertilization strategies are often not very efficient due to immobilization in the soil and losses of nutrients by leaching or volatilization. Foliar fertilization offers an attractive supplementary strategy as it bypasses the adverse soil processes, but implementation is often hampered by a poor penetration through leaf barriers, leaf damage, and a limited ability of nutrients to translocate. Recent advances within bionanotechnology offer a range of emerging possibilities to overcome these challenges. Here we review how nanoparticles can be tailored with smart properties to interact with plant tissue for a more efficient delivery of nutrients. Recent advances within bionanotechnology pave the way for development of biocompatible foliar nanofertilizers with superior nutrient use efficiency.Emerging evidence shows that nanoparticle physicochemical properties and formulation are key for effective penetration of all major plant barriers, including the cuticle, stomata, cell walls, and plasma membrane.Nanoparticles can be targeted to specific cell organelles and be programmed to release their nutrients in a time-dependent manner or as a response to cellular stimuli.Nanoparticles can translocate from exposed leaves to unexposed tissue. This highlights a clear potential for designing phloem-mobile nanofertilizers, containing nutrients that are currently immobile. Manipulating the phloem mobility of nutrients would constitute a major landmark within plant science.