Effects of combined application of Se and ammonium fertilizers on the growth and nutritional quality of maize in Hg-polluted soil under two irrigation conditions and its health risk assessment

The interactive effects of Se (Na₂SeO₃) and ammonium fertilizers ((NH₄)₂SO₄ and NH₄Cl) on the growth and quality of maize (Zea mays L.) in mercury (Hg)-contaminated soil were studied under different water conditions. This study determined how two nutrient sources (Se and NH₄⁺-N) interacted to improve the yield, quality, and safety of maize to ensure food security and quality assurance under the stress of heavy metal Hg. The experiment was conducted under two irrigation conditions: W1 (complete irrigation condition, 60–70% of water-holding capacity) and W2 (restricted irrigation condition, 40–50% of water-holding capacity). The combined treatment of Se and ammonium fertilizers significantly improved the growth of maize and the quality of grain in Hg-polluted soil. When Na₂SeO₃ and (NH₄)₂SO₄ were combined, the growth and quality of maize increased the highest among all treatments. The interaction between Na₂SeO₃ and ammonium fertilizers significantly affected the available Hg/methylmercury (MeHg) content in soil and the Hg/MeHg concentration in maize. NH₄Cl significantly increased the content of available Hg/MeHg in soil and increased the accumulation of Hg/MeHg in maize tissues due to Cl⁻. However, the treatments containing Na₂SeO₃ or (NH₄)₂SO₄ significantly reduced the content of available Hg/MeHg in soil, reduced the accumulation of Hg/MeHg in maize tissues, and significantly reduced the possible health risks to human beings. The treatments containing Na₂SeO₃ or (NH₄)₂SO₄ promoted maize growth by increasing the Se content in maize tissues and reducing the Hg/MeHg content, relieving the stress induced by Hg, and increasing the nutrient content. The combined treatment of Na₂SeO₃ and (NH₄)₂SO₄ had the best effect in this experiment. This study also showed that this strategy is helpful in reducing the opportunities for consumers to accumulate Hg/MeHg by eating maize and its derivatives, thus ensuring food safety. Se and ammonium fertilizer can be used together to increase maize yield and develop agricultural production in Hg-polluted areas, which may have a significant impact on global food production. In addition, this simple method can help farmers manage soil affected by heavy metal pollution.