Iron oxides found to unlock phosphorus to become usable by plants

Northwestern University researchers have published new findings in the journal Environmental Science & Technology that challenge the traditional view of iron oxides as simple phosphorus traps in soil. Instead, they have identified these compounds as highly effective catalysts that convert organic phosphorus into a form usable by plants, a discovery with significant implications for agriculture.

Traditionally, it was believed that only enzymes from microbes and plants could convert organic phosphorus into its inorganic form, which is essential for plant nutrition. However, this study builds on previous Northwestern research, which showed that natural iron oxides in soil and sediments could also perform this conversion.

The recent study highlights the efficiency of iron oxides as catalysts, demonstrating their ability to convert organic phosphorus at rates comparable to those of natural enzymes. This finding could lead to better management of the phosphorus cycle in soils, potentially enhancing the effectiveness of fertilizers and contributing to agricultural sustainability.

Phosphorus is a critical element for life, forming the backbone of DNA and playing a key role in cellular energy transfer. The majority of soil phosphorus is organic, derived from the decay of plants, microbes, and animals. Inorganic phosphorus, while a minor component in soils, is vital for plant growth and is the primary form used in agricultural fertilizers.

Ludmilla Aristilde, the lead researcher and an associate professor of environmental engineering at Northwestern, emphasized the importance of understanding phosphorus dynamics in the environment to support global food security. The study involved detailed experiments with different iron oxides—goethite, hematite, and ferrihydrite—and their interactions with ribonucleotides, components of RNA and DNA, to understand the catalytic processes involved.

With the research, scientists advance their understanding of soil chemistry and point to the potential development of synthetic catalysts that could recycle phosphorus, thereby sustaining its availability as natural reserves dwindle. With phosphate rock reserves concentrated in only a few global locations, such innovations are critical in addressing the long-term sustainability of food production.