Life · 10 authors, 3 centres
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Applying 600 kg/ha of selenium-containing organic fertilizer (SOF) significantly increased wheat yield by up to 15.3% and reduced cadmium content in grains by up to 67.3%. Selenium accumulated most in roots, and the distribution in wheat plants ranked root > grain > spike-stalk > glume > leaf > stem. These findings support using SOF to produce selenium-enriched wheat with lower cadmium levels, improving food safety and nutrition.
**Background:** Selenium (Se) is an essential trace element for humans and animals, with roles in immune function and detoxification. Se deficiency is widespread, affecting 72% of China's land area, and is linked to diseases such as cancer and cataracts. Wheat is a major dietary staple in China, providing over 70% of daily calories. Exogenous Se application can increase Se content in wheat, but excessive Se can be toxic. Cadmium (Cd) is a common soil contaminant that accumulates in crops and poses health risks. This study aimed to evaluate the effects of different rates of selenium-containing organic fertilizer (SOF) on wheat yield, mineral nutrient content (Ca, Mg, Fe, Mn, Cu, Zn), Cd content, and Se distribution in wheat plants.
**Methods:** Field experiments were conducted from October 2021 to June 2022 in Mengcheng (MC) and Dingyuan (DY) counties, Anhui Province, China. The soil in MC had pH 5.19, organic matter 37.2 g/kg, total Se 0.18 mg/kg, and total Cd 0.29 mg/kg; in DY, pH 5.85, organic matter 28.7 g/kg, total Se 0.15 mg/kg, and total Cd 0.16 mg/kg. Wheat varieties were Huaimai 33 (MC) and Yangmai 25 (DY). Five treatments were applied: Se0 (1200 kg/ha OF, no SOF), Se1 (900 kg/ha OF + 300 kg/ha SOF), Se2 (600 kg/ha OF + 600 kg/ha SOF), Se3 (300 kg/ha OF + 900 kg/ha SOF), and Se4 (0 kg/ha OF + 1200 kg/ha SOF). The SOF contained 256.96 mg Se/kg. Each treatment was applied to a 5 m² plot without replication. At maturity, three 1 m² samples per treatment were harvested to measure yield components (spike number, kernel number per spike, 1000-kernel weight). Wheat plants were divided into grains, glumes, spike-stalks, leaves, stems, and roots. Total Se was determined by hydride atomic fluorescence spectrometry after microwave digestion. Cd, Ca, Mg, Fe, Mn, Cu, and Zn in grains were measured by atomic absorption spectrometry. Statistical analyses used one-way ANOVA with Duncan's multiple range test (p < 0.05) and linear regression.
**Key Results:** - **Wheat yield:** Yield increased then decreased with SOF application. Maximum yields were 9979.78 kg/ha in MC and 8868.97 kg/ha in DY under Se2 (600 kg/ha SOF), representing significant increases of 14.6% and 15.3% compared to Se0. Under Se4, yields significantly decreased by 8.18% in MC and 8.09% in DY. Spike number per hectare and 1000-kernel weight increased under Se2 (11.7% and 4.7% in MC; 6.5% and 6.9% in DY), while kernel number per spike did not change significantly. - **Mineral nutrients:** Ca content increased significantly with SOF, reaching maximums of 342.98 mg/kg (Se3, MC) and 337.31 mg/kg (Se4, DY), increases of 12.1% and 102.9% vs. Se0. Mg content decreased, with minimums of 672.99 mg/kg (Se4, MC) and 531.33 mg/kg (Se2, DY), reductions of 5.1% and 36.9%. Fe content showed opposite trends: in MC, it decreased by 43.5–52.9%; in DY, it increased up to 147.5% (219.69 mg/kg under Se4). Mn content decreased by 26.5–34.5% in MC and 21.7–40.6% in DY. Cu content in MC decreased by 62.9–65.7% under Se1–Se3 but increased 19.8% under Se4; in DY, Cu decreased by 50.6% under Se1 (minimum 3.91 mg/kg). Zn content decreased by 3.2–10.8% in MC and 13.5–30.1% in DY. - **Cadmium content:** Cd content in grains was significantly and negatively correlated with SOF application (R² values not provided, p < 0.01). Reductions ranged from 24.4% to 30.1% in MC and 40.2% to 67.3% in DY. Minimum Cd levels were 32.38 μg/kg (MC) and 13.73 μg/kg (DY) under Se4. - **Selenium distribution:** Se content increased in all organs, with the greatest increase in roots (4.6–13.3 times in MC, 3.7–12.1 times in DY vs. Se0). Under SOF, Se distribution ranked root > grain > spike-stalk > glume > leaf > stem in both locations, whereas under Se0, root > glume > spike-stalk > grain > stem > leaf in MC and root > spike-stalk > grain > stem > glume > leaf in DY.
**Clinical Implications:** This study demonstrates that moderate application of selenium-containing organic fertilizer (600 kg/ha) can enhance wheat yield and grain selenium content while significantly reducing cadmium accumulation, a toxic heavy metal. The reduction in Cd (up to 67.3%) is clinically relevant because chronic Cd exposure is linked to bone disease, cancer, and kidney damage. Increasing Se in wheat may help address widespread Se deficiency, which is associated with increased risk of cataracts, cancer, and other diseases. However, the effects on mineral nutrients were mixed: Ca increased, but Mg, Mn, Cu, and Zn decreased, and Fe showed site-dependent changes. These nutrient shifts could have implications for overall dietary mineral intake, particularly in populations relying heavily on wheat. The optimal Se application rate (77.10 mg sodium selenite per plot) balances yield improvement and Cd reduction without causing Se toxicity. Future studies should confirm these findings with replicated trials and assess long-term effects on soil health and human nutrition.