Nanoscale Selenium Spray Boosts Rice Photosynthesis, Cuts Fertilizer Use and Emissions

Rice feeds more than half of the world's population, but common cultivation practices carry heavy environmental costs. Flooded rice paddies consume large amounts of nitrogen fertilizer that often runs off into waterways, while anaerobic soils emit methane and other greenhouse gases.

Small dose, big effects

Researchers from the University of Massachusetts Amherst and Jiangnan University report a promising, low-dose intervention: applying nanoscale selenium directly onto rice leaves and stems. Their field study, published in the Proceedings of the National Academy of Sciences, found that minute aerial sprays of selenium can strengthen plants, improve nutrition and cut pollution — while reducing the need for nitrogen fertilizer.

The Green Revolution massively boosted agricultural output during the middle of the last century. But that revolution is running out of steam. We need to figure out a way to fix it and make it work.

In replicated field trials the team used drone-mounted sprayers to deposit very small, nanoscale quantities of selenium onto rice canopies. That treatment increased leaf photosynthesis by more than 40 percent, enabling plants to take up additional carbon dioxide and to develop deeper, healthier root systems.

Stronger roots fostered beneficial soil microbes that helped the plants access more nitrogen from the soil. As a result, farmers could reduce nitrogen fertilizer application by nearly one third while maintaining or improving plant growth.

Measured benefits

• Higher photosynthetic rates (over 40%).
• Nearly one-third reduction in nitrogen fertilizer needs in trial plots.
• Up to 45% lower field emissions and pollution outputs in treated plots.
• Increased protein and essential amino-acid content in grain.
• Approximately 40% greater profit per ton of grain in the study's economic comparison.

Because rice cultivation accounts for a substantial share of global nitrogen fertilizer use and related runoff, the authors say this approach could reduce environmental impacts and make nutrient use in rice production more efficient — if it can be scaled safely and economically.

Caveats and next steps

While results are encouraging, the researchers and independent experts note several important caveats. Selenium is an essential micronutrient at low doses but can be toxic at higher concentrations; long-term monitoring of soil and grain selenium levels is necessary. Additional trials are required across different climates, rice varieties and management systems to confirm safety, persistence and cost-effectiveness. Regulatory review and guidelines would also be needed before widespread adoption.

Overall, the study offers a potentially simple tool to boost rice productivity and nutrition while lowering pollution — but responsible scaling and further research are essential before farmers adopt the method broadly.

Study source: Proceedings of the National Academy of Sciences. Research led by teams at UMass Amherst and Jiangnan University.