This study describes the behavior of potential slow-release fertilizers (SRF), prepared by the mechanochemical activation of calcined Mg₂Al-CO₃ or Mg₂Fe-CO₃ layered double hydroxides (LDH) mixed with dipotassium hydrogen phosphate (K₂HPO₄). The effects of LDH thermal treatment on P/K release behavior were investigated. Characterizations of the inorganic composites before and after release experiments combined X-Ray diffraction (XRD), Fourier-transform infra-red spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The best release profile (<75% in 28 days and at least 75% release) was obtained for MgAl/K₂HPO₄ (9 h milling, 2:1 molar ratio, MR). Compared to readily used K₂HPO₄, milling orthophosphate into LDH matrices decreases its solubility and slows down its release, with 60% and 5.4% release after 168 h for MgAl/K₂HPO₄ and MgFe/K₂HPO₄ composites, respectively. Mechanochemical addition of carboxymethylcellulose to the LDH/K₂HPO₄ composites leads to a noticeable improvement of P release properties.

A detailed structural investigation of a promising bio-based polymer, polyglycerol citrate polyester, obtained by the bulk polycondensation of glycerol (Gly) against citric acid (Cit) under mild reaction was performed. The reaction in conditions with and without catalyst use (sulfuric acid, H₂SO₄) was investigated, showing evidence that it is possible to modify the polymer solubility according to the ratio and catalyst utilization. ¹³C and ¹H NMR indicated that synthesis catalyzed with Cit excess leads to higher esterification degrees of citrate groups. In contrast, the Gly moieties are more prominent in catalyzed polymers regardless of the excess monomers. Overall, a successful conversion of Gly and Cit into polyesters was attained even without catalysis, enabling a simple route for the large-scale production of this green material to be used as a coating material. This polymer has been shown to be well-suited for coating seeds and might be a promising material for similar agricultural applications. Tests on soybean seed coating with a PGCit solution of 75% indicated that the seed quality and germination rate were not affected by the PGCit coating, concluding that this polymer is suitable for this application.