The Nutrient Use Efficiency in intensive agriculture is lower than 50% for macronutrients. This feature results in unsustainable financial and environmental costs. Nanofertilizers are a promising application of nanotechnology in agriculture. The use of nanofertilizers in an efficient and safe manner calls for knowledge about the actual effects of nanoproducts on the plant metabolism and eventually on the carrier release kinetics and nutrient accumulation. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) nanoparticles (nHA) have an interesting potential to be used as nanofertilizers. In this study, the effects of different nHA solutions stabilized with carboxymethylcellulose (CMC) were evaluated on germination, seedling growth, and metabolism of Solanum lycopersicum L., used as model species. Our observations showed that the percentage germination of S. lycopersicum is not influenced by increasing concentrations of nHa, while root elongation is strongly stimulated. Tomato plants grown in hydroponics in the presence of nHA have not suffered phytotoxic effects. We conclude that nHA had nontoxic effects on our model plant and therefore it could be used both as a P supplier and carrier of other elements and molecules.

The Green New Deal requires a profound transformation of the agricultural sector, which will have to become more sustainable and ensure universal access to healthy food. Thus, it will be essential to introduce radical technological innovations. Nanotechnologies have the potential to produce a significant boost to the improvement of the food system. Within this context, in the next years, a strong challenge will need to be faced regarding developing new and more efficient uses of nutrients in agriculture, being the nutrient use efficiency (NUE) paramount in sustaining high crop productivity without depleting biodiversity, and altering both the natural and agricultural systems. Nutrients leaching causes environmental pollution and water eutrophication, while nutrient excess favors pest and weed widespread. Therefore, it will be mandatory to improve plant nutrition efficiency without affecting agricultural productivity and economic sustainability. A promising alternative consists of the introduction of the so-called nanomaterial enhanced fertilizers and plant growth stimulators. Such innovation includes nanotechnological solutions that can improve nutrient delivery for a more finely tuned, accurate, and saving-resources distribution of nutrients. This review provides a critical view of the latest advances in nanofertilizer research, mainly referring to nano-hydroxyapatite, silica nanoparticles, and chitosan-derived nanostructures.