Selenium uptake and its content in soybean grains are affected by Se application methods. This study evaluated the impact of Se foliar application combined with a multi-nutrient fertilizer (MNF) on soybean, establishing a Se threshold to better understand the relationship between Se content in grains and yield of two genotypes (58I60 Lança and M5917). Two trials were conducted in a 4 × 2 factorial design: four Se rates (0, 10, 40, 80 g Se ha⁻¹) and two methods of foliar Se application (Se combined or not with MNF). Foliar fertilizers were applied twice, at phenological stages of beginning of pod development and grain filling. Grain yield increased with the application of MNF, yet Se rates increased Se contents linearly up to 80 g Se ha⁻¹, regardless of the use of MNF. Lança and M5917 genotypes had grain Se critical thresholds of 1.0 and 3.0 mg kg⁻¹, respectively. The application of Se favored higher contents of K, P, and S in grains of genotype Lança and higher contents of Mn and Fe in grains of genotype M5917. Our findings highlight the importance of addressing different Se fertilization strategies as well as genotypic variations when assessing the effects of Se on soybean yield and grain quality.

Selenium is beneficial to plants and is essential for animals and humans, which justifies any efforts for producing Se-enriched wheat grains worldwide. This study aimed to (i) verify if wheat is an efficient species to be used for Se biofortification in tropical agroecosystems and (ii) assess the influence of Se on the physiological and biochemical parameters of wheat plants. Selenium was applied as sodium selenate (Na₂SeO₄) at different doses (12, 21, 38, 68, and 120 g ha⁻¹) in soil. The dose of 120 g ha⁻¹ of Se resulted in Se contents of 7.98 and 2.27 mg kg⁻¹ in the leaves and grains, respectively. The supply of 38 g ha⁻¹ of Se increased the total soluble sugar content by 50%, with reducing sugars increasing by 17% and sucrose augmenting 53%, compared with that in the control. The doses of 12, 68, and 120 g of Se ha⁻¹ promoted a significant increase in catalase activity. In addition, Se application increased carbohydrate and nutrient contents. Our findings indicate that wheat is a good species for agronomic biofortification with Se via soil application in tropical agroecosystems. Selenium proved to be a valuable element for plants since it provides physiological and biochemical benefits.

Rice (Oryza sativa L.) is a crucial crop for biofortification that is widely consumed and is cultivated in soils with low levels of selenium (Se) and zinc (Zn). The study evaluated how upland rice genotypes can increase Se and Zn in grains with foliar fertilization and analyzed the impact on agronomic characteristics and protein and amino acid contents. Experiments in Lambari and Lavras used a 5 × 4 factorial design with five genotypes (BRS Esmeralda, CMG 2188, CMG ERF 221-16, CMG ERF 221-19, CMG ERF 85-15) and four treatments (control, without Se; 5.22 g Se ha⁻¹; 1.42 kg Zn ha⁻¹; and combined Zn+Se) with three replicates. The study showed that CMG ERF 85-15, with Se fertilization, increased grain yield in Lambari. In Lavras, adding Zn to CMG 2188 and CMG ERF 85-15 improved grain yield. In Lambari, most variables were grouped with Zn+Se, except grain yield and free amino acids in the grain. In Lavras, variables associated with Se, proteins, free amino acids in the polished grain, hulling in whole and polished grain, and milling yield were grouped under the treatment Zn+Se. We recommend the genotype CMG ERF 85-15 based on the results for foliar biofortification with Zn+Se.