On the role of fertilizer concentration in bicontinuous structures stabilized by nanoparticles for the controlled delivery of urea

A bicontinuous structure made of a biodegradable polymer with an easy production process without tensides or solvents, and enriched by the presence of hydroxyapatite, can change the traditional use of molecules added in agriculture. The main peculiarity of these systems resides in the presence of two incompatible domains, one hydrophilic and one hydrophobic, stabilized by hydroxyapatite nanoparticles that can work simultaneously as stabilizer and source of phosphorus. The possibility of loading hydrophilic and hydrophobic molecules during materials production can reduce the costs and maximize the loading capacity. Here, fertilizers, in particular urea, are considered at different concentrations to understand their role in the design of urea delivery systems. The release rate from these devices is tested in liquid and solid releasing media. The release is quicker in water (3 days) and slower moving to solid media (15 days), strongly dependent on urea concentration. Then experiments on plant growth underlined that the addition of PCL-U is associated with better performances in terms of size and height with respect to the control group (pure urea). The use of PCL-U is responsible for the higher length of both characteristics with respect to the corresponding control groups, underlining that these systems can be very promising in agriculture.