Exploiting Biological Nitrogen Fixation: A Route Towards a Sustainable Agriculture

For all living organisms, nitrogen is an essential element, while being the most limiting in ecosystems and for crop production. Despite the significant contribution of synthetic fertilizers, nitrogen requirements for food production increase from year to year, while the overuse of agrochemicals compromise soil health and agricultural sustainability. One alternative to overcome this problem is biological nitrogen fixation (BNF). Indeed, more than 60% of the fixed N on Earth results from BNF. Therefore, optimizing BNF in agriculture is more and more urgent to help meet the demand of the food production needs for the growing world population. This optimization will require a good knowledge of the diversity of nitrogen-fixing microorganisms, the mechanisms of fixation, and the selection and formulation of efficient N-fixing microorganisms as biofertilizers. Good understanding of BNF process may allow the transfer of this ability to other non-fixing microorganisms or to non-leguminous plants with high added value. This minireview covers a brief history on BNF, cycle and mechanisms of nitrogen fixation, biofertilizers market value, and use of biofertilizers in agriculture. The minireview focuses particularly on some of the most effective microbial products marketed to date, their efficiency, and success-limiting in agriculture. It also highlights opportunities and difficulties of transferring nitrogen fixation capacity in cereals

Phosphate coatings on magnesium alloy AM60: Part 2: Electrochemical behaviour in borate buffer solution

International audienceA zinc phosphate coating was formed on the surface of magnesium alloy AM60 by immersing the specimen in a phosphating bath. Corrosion potential measurements, anodic polarisation curves and electrochemical impedance spectroscopy (EIS) were used to assess the corrosion protection of the coating. The electrochemical measurements were performed in borate solution at pH=9.2. This slightly alkaline solution was chosen because it can be used to differentiate the electrochemical behaviour of phosphated and non-phosphated magnesium alloys. The phosphate coating considerably slowed down the metal dissolution process. Measurements performed on phosphated and non-phosphated specimens in borate solution showed that the phosphate coating afforded considerable protection against corrosion. From the results obtained, it was deduced that the optimum phosphating time was 10 min. The results were fitted to an equivalent electrical circuit

Oxidative conversion of lignin over cobalt-iron mixed oxides prepared via the alginate gelation

The depolymerization of polymer lignin model to low molecular weight products was studied in water, at 200 °C under 100 MPa of 10% O2 using cobalt-iron mixed oxides as catalysts. These nanostructured oxides with different Co/Fe ratios were prepared via alginate gelation. X-ray diffraction, scanning electron microscope, and size exclusion chromatography were used to study the influence of the Fe/Co ratios on the structure and the proprieties of the oxides as well as the morphology, the structure, and the composition of the obtained degraded products. The results showed that the oxides used in this study were versatile catalysts with a high catalytic activity for lignin depolymerization. Furthermore, these oxides demonstrated high yield and high selectivity towards aromatic compounds