Selenium Spray Could Turn Sorghum Into a Hidden Nutrition Powerhouse

Selenium is one of those nutrients most people never think about until something goes wrong. It sits quietly at the heart of antioxidant enzymes, supports the immune system, and protects organs from damage, yet nearly one billion people worldwide do not get enough of it. The problem is rarely the diet itself but the soil beneath it: crops grown in selenium-poor regions pass that deficiency straight into the human food chain. Now a large field experiment in Brazil suggests that a simple foliar spray, timed to the right moments in the growing season and matched to the right crop variety, could transform grain sorghum into a vehicle for delivering this missing micronutrient to hundreds of millions of people.

Sorghum is an unlikely hero in the story of global nutrition. It is the world’s fifth most cultivated cereal, a drought-tolerant C4 grass that thrives where maize and wheat struggle, and a staple source of protein, carbohydrates, vitamins, minerals, and antioxidants for food-insecure populations across Africa and Asia. In Brazil, more than 500 million people worldwide depend on sorghum directly or indirectly, and the country harvested roughly 2.5 million tons of the grain across nearly 900,000 hectares in 2021, mostly for animal feed. If that grain could be enriched with selenium without sacrificing yield, the implications for selenium-deficient regions would be enormous.

That is precisely what a team of Brazilian researchers set out to test. In a study published in the journal Plant and Soil, Patriciani Estela Cipriano of the Federal University of Lavras and colleagues grew eight commercial sorghum genotypes across two contrasting field environments in the state of Minas Gerais, spraying the plants with selenium at a rate of just 10 grams per hectare. The twist was the chemistry: alongside the industry-standard sodium selenate, they tested two novel selenium compounds, potassium hydroxy-selenide and acetylselenide, whose behavior inside plants has never been properly characterized. The question was whether these alternatives could match or beat the conventional source, or whether the old standby would prove unbeatable.

The two field sites were chosen deliberately rather than for convenience. In Lavras, the soil was a Dystrophic Red-Yellow Latosol, an Oxisol in international classification, dominated by sandier textures and lower macronutrient fertility but richer in iron. In Lambari, the crop grew on a Melanic Gleysol, a Histosol, with roughly ten times more available phosphorus and potassium, a clay-dominated profile, and higher organic matter. Both locations share a subtropical Cwa climate with dry winters and hot summers, but their soils could hardly be more different. By running identical experiments at both sites, the researchers could determine whether the response to selenium biofortification is a general property of the treatment or something shaped by local conditions.

The experimental design was rigorous. Each site hosted a randomized block experiment with a 4 by 8 factorial layout: four selenium treatments, including an unsprayed control, crossed with eight genotypes named BM737, BRS310, Enforcer, K200, Nugrain320, Nugrain420, Nugrain430, and SHS410. That meant 128 plots per location, each with four rows of plants. The selenium was applied twice, first at flowering and again during grain filling, using a pressurized carbon dioxide sprayer with a surfactant to help the solution stick to leaves. The team then measured grain yield, thousand-grain weight, crude protein, and the concentrations of eleven elements, from nitrogen and phosphorus to iron, zinc, copper, manganese, and selenium itself, using inductively coupled plasma optical emission spectrometry and graphite furnace atomic absorption spectrometry, with certified reference materials confirming the accuracy of every batch.

The headline result was unambiguous: sodium selenate won the selenium race decisively. Spraying with selenate significantly increased selenium concentrations in both grain and shoots at both locations, with grain levels ranging from 0.31 to 1.01 milligrams per kilogram and shoot levels from 0.76 to 2.45 milligrams per kilogram. The two novel compounds, by contrast, produced selenium concentrations in grain and shoots that were indistinguishable from the unsprayed control, often falling below the detection limit of the analytical equipment. The reason is likely rooted in plant physiology: selenate enters plants through well-described sulfate transporters and is translocated efficiently to the grain, whereas neither hydroxy-selenide nor acetylselenide has a characterized transport pathway. In wheat and rapeseed, mobility follows the order selenate, then selenomethionine, then selenocysteine, and sorghum appears to behave the same way.

But the story did not end there, and this is where the findings become genuinely surprising. Although the novel compounds failed to enrich the grain with selenium, they were far from physiologically inert. Grain yield responses to selenium fertilization were strongly genotype-dependent and were not restricted to the inorganic source. In Lambari, the Enforcer genotype produced yield increases of 32.28 percent under selenate, 28.28 percent under potassium hydroxy-selenide, and 21.79 percent under acetylselenide compared with the control. In Lavras, K200 achieved a striking 88.34 percent yield increase under acetylselenide relative to selenate, while Nugrain320 gained more than 25 percent under acetylselenide compared with the control. The novel compounds also boosted phosphorus, potassium, calcium, magnesium, iron, and zinc concentrations in specific genotype and site combinations, with increases frequently ranging from 10 to 40 percent.

The researchers used principal component analysis to untangle these patterns, and the results revealed strong three-way interactions among selenium source, genotype, and environment. In Lambari, the first two principal components explained 27.09 and 19.19 percent of total variance, while in Lavras they accounted for 26.72 and 16.64 percent. BRS310 separated clearly from the other genotypes at Lambari, associated with elevated concentrations of calcium, manganese, iron, magnesium, nitrogen, sulfur, and phosphorus in shoots, suggesting superior nutrient absorption and translocation. Nugrain420 and Nugrain430 clustered with grain nutritional enrichment traits, while Enforcer was associated with thousand-grain weight and shoot selenium. Notably, acetylselenide and sodium selenate broadened the dispersion among genotypes at both sites, meaning these treatments amplified the underlying genetic differences rather than flattening them.

The soil context proved equally decisive. Lavras produced higher grain yields and thousand-grain weights, with some genotypes exceeding 6,000 kilograms per hectare even without selenium, well above the Brazilian national average of 2,821 kilograms per hectare recorded in 2021. Lambari, with its more fertile, organic-rich soil, produced higher crude protein and higher concentrations of nitrogen and sulfur in grain, reflecting the interdependent assimilation of these two elements into amino acids. Selenium itself follows the sulfur assimilation pathway, converting into selenomethionine and selenocysteine that are incorporated into proteins, which helps explain why protein-rich environments and selenium enrichment are so closely linked. The team is careful to note that the study covered a single growing season, so interannual climatic variability remains untested, and the mechanisms behind the mineral responses to the novel compounds, whether a sub-detection-limit selenium effect on the antioxidant system or properties of the compounds themselves, cannot yet be distinguished without oxidative-stress biomarkers.

What emerges from this work is a practical roadmap rather than a single prescription. For selenium biofortification in sorghum, foliar sodium selenate applied at around 10 grams per hectare during flowering and grain filling is the most consistent and effective scheme, echoing dose ranges of 10 to 30 grams per hectare reported across wheat, rice, and maize. For yield enhancement and broader mineral gains, the choice of genotype matters as much as the choice of compound, with Enforcer, Nugrain420, Nugrain430, and BM737 showing consistently superior performance across sites. The broader message resonates far beyond Brazilian fields: biofortification is not a one-size-fits-all intervention but a negotiation between chemistry, genetics, and environment. As agricultural production must rise by 60 to 70 percent by 2050 under intensifying climate pressure, getting that negotiation right could quietly deliver one of the cheapest and most scalable public health interventions available, one grain of sorghum at a time.

Subject of Research: Selenium biofortification of grain sorghum through foliar fertilization with novel selenium sources across contrasting tropical soils

Article Title: Optimizing grain sorghum selenium biofortification through foliar fertilization: integrating novel selenium sources, genotype, and contrasting tropical soils

Article References: Cipriano, P. E., Martins, F. A. D., da Silva, D. F., de Oliveira, C., de Lima, A. B., Celante, G., Archilha, M. V. L. R., Botelho, M. F. P., Brunetto, G., Faquin, V., dos Santos, A. A., & Guilherme, L. R. G. (2026). Optimizing grain sorghum selenium biofortification through foliar fertilization: integrating novel selenium sources, genotype, and contrasting tropical soils. Plant and Soil. https://doi.org/10.1007/s11104-026-09017-1

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09017-1

Keywords: selenium biofortification, sorghum, foliar fertilization, sodium selenate, tropical soils, grain yield, mineral nutrition, genotype environment interaction, micronutrient deficiency, food security, plant physiology, Brazil