Iron oxide nanoparticles in soils: Environmental and agronomic importance

The iron (Fe) oxide particles affect a wide range of important environmental processes related to soil fertility and plant growth. They often occur as aggregates, mineral nanoparticles or as nanoscale coatings on other grains in the soil, where they may also control the fate and transport of nutrients such as phosphate, sulfate, molybdate and pollutants (arsenic or chromium). Solubilization of Fe from minerals control iron availability for plant growth; this process is regulated by chemical mechanisms (pH and dissolution-precipitation), sometimes mediated by biological interactions at rhizosphere scale, of both Fe crystalline and poorly ordered Fe oxide minerals. In cold and temperate climate the organic carbon storage and the Fe minerals are highly correlated, possibly because the interactions of nano-size iron oxide particles with humic substances. The aims of this review are to summarize the main findings and the classical iron soil chemistry and to propose chemical and biological relationships with the hope of stimulating new model in soil fertility.