FePO4 NANOPARTILCES AS SOURCE OF NUTRIENTS: EFFECTS ON THE PLANT-SOIL SYSTEM AND EVI-DENCE FOR A SAFE AND SUSTAINABLE NANO-FERTILIZATION

In the last decade, nanotechnology became a consistent part of the technological progress in modern agriculture, with applications in agri-food technology, nano-biosensoring, plant defence and plant nutrition. Nanomaterials which can provide one or more macro/micro-nutrient to the plant are commonly referred as nanofertilizers. Nevertheless, in the scientific literature there are still few evidence of a successful utilization of nanomaterials as fertilizers. In a previous work, it has been shown that iron phosphate (FePO4) nanoparticles (NPs) can provide either iron (Fe) or phosphate (P) to plants grown in hydroponic. The present study is aimed to highlight the effect of FePO4 NPs used as nanofertilizer in the whole plant-soil system, and to determine if they can represent a safe and effective alternative to conventional fertilizers. To investigate the plant early transcriptomic responses to FePO4 NPs exposure, microarray expression analyses have been performed in maize and cucumber roots grown in hydroponic for 24 hours. Responses of the plants treated with FePO4 NPs were shown to be associated mainly to biotic and abiotic stress, cell wall modulation and regulation of transcription, and triggered a different pattern of responses that was dependent on the nano-size. To evaluate the possibility to apply FePO4 NPs to the soil as fertilizer, two different bare soils were treated. Soil enzyme activities, CO2 respiration and DGGE analyses showed that there was not negative impact of FePO4 NPs onto soil microbial community and metabolic functions, neither toxic effects. Further, FePO4 NPs provided available P in bare soil in respect to triple superphosphate (TSP), even though the efficacy was dependent on the soil characteristics. Moreover, FePO4 NPs represented a source of available P for plant, which grown in soil in controlled condition without significant differences in respect to TSP, although P availability in the bare soil resulted lower for NPs than TSP. Microbial community associated to rhizosphere was not negatively affected by NPs and a stimulatory effect on enzyme activity was observed. In this work it was shown that FePO4 NPs can be applied to the soil without any negative consequence for the environment, enhancing plant growth and providing nutrients. These results encourage the hypothesis that the nanoparticulate nature of fertilizers could contribute to rationalize the chemical inputs in agriculture and increasing nutrient use efficiency