Fertilizers based on urea, provide plants with the amount of nitrogen necessary for their growth. In soils, urea is degradated into ammonium by ureases. Next, ammonium is oxidized to nitrite, then to nitrate in the nitrification process. This last ion is fundamental for plant nutrition. However, this artificial input induces many ecological disturbances due to nitrogen loss in the atmosphere and groundwaters. This is why urease as well as nitrification inhibitors, which balance the presence of different forms of nitrogen in soils, are challenging targets for an efficient and responsible agriculture. Within the project AZOSTIMER, we were interested in improving the efficacity of MBT, a nitrification inhibitor, and NBPT, a urease inhibitor. Firstly, we set out to improve the water solubility, and therefore, the biodisponibility of the MBT and the analogous MBI, by applying the concept of pro-drug. These molecules were bound to sugars by glycosidic synthesis and a set of glycosylated inhibitors were produced. The physicochemical (solubility, stability) and biological (ecotoxicity, inhibition activity) properties were later evaluated, as well as the behavior of these molecules in soils (degradability, mobility). Secondly, we wanted to extend the activity of NBPT in acidic soils by lowering its degradation, developing either new formulations based on encapsulation of the bioactive molecule or by designing new chemical modulations. Many formulations of NBPT were created and assessed (stability in acidic media, inhibition activity in soils). Phosphoramides were synthesized and evaluated in order to highlight correlations between the structure, and the stability or the activity.
Development of new inhibitors of ureases and nitrification for a phytosanitary use