Iron oxide nanoparticles as iron micronutrient fertilizer—Opportunities and limitations

Iron (Fe) is necessary for plant growth and development. Iron deficiency disrupts major metabolic and cellular activities such as respiration, DNA synthesis, and chlorophyll synthesis. Iron also activates various metabolic pathways and is vital to numerous enzymes. Iron is widely distributed in soil, but plants do not readily absorb it. In addition to neutral pH, Fe also forms insoluble Fe complexes under alkaline conditions. The fundamental cause of Fe chlorosis is an imbalance between the solubility of Fe in soil and the demand for Fe by plants. Various Fe fertilizers, including organic, chelated, and inorganic, are administered to the soil and leaves to treat Fe deficiency and chlorosis. Currently, used Fe fertilizers are expensive, easily adsorb on soil particles, and cause Fe to leach out of the soil with water, thereby diminishing their efficiency. They also need to be applied repeatedly, resulting in an excessive Fe fertilizer concentration in the soil that can cause harm to the plants. The usage of Fe nanofertilizers in agricultural production has expanded to address the disadvantages of existing Fe fertilizers. The advantages of nanosized Fe fertilizers include their physical and chemical characteristics, such as the high surface area to volume ratio that aids in easy absorption by plants’ roots and leaves. Controlled-release iron oxide nanofertilizers supply the regulated release of nutrients in a way that is coordinated with the nutritional needs of the crops. This improves the accumulation of nutrients in the plant, filling in the gap of nutrient deficiency and lowering environmental risks due to leaching. The possibility of iron oxide nanoparticles as Fe micronutrient fertilizers, their uptake and mechanism of action, advantages, and limitations are critically highlighted in this review article.