Objectives Huanghuai Plain is a major wheat-producing region in China, and the selenium content in wheat grains significantly affects the selenium nutrition of the population. We investigated the effects of selenium fertilization on enhancing wheat selenium levels and the fate of applied selenium under traditional irrigation and integrated water-fertilizer management practices., thereby providing a theoretical basis and technical support for optimizing selenium fertilization and enhancing selenium biofortification in wheat in the Huang-Huai wheat region.

Method  Field surveys were conducted from 2023 to 2024 across four locations at Qishan (Shaanxi), Yiyan (Henan), Cixian (Hebei), and Qihe (Shandong) to assess soil available Se and grain Se content. A field experiment under traditional irrigation was with Se application rates of 0, 100, 200, 300, and 400 g /hm² (Na₂SeO₃ was selected as the Se fertilizer) was carried out in Qishan and Qihe, and wheat yield was recorded. From 2024 to 2025, multi-site field experiments were implemented at four locations. Treatments included: basal applying Se 0 and 400 g/hm² under traditional irrigation (TC, and TB); no Se application, basal applying Se 400 g/hm², and topdressing Se 400 g/hm² under fertigation (DC, DB, and DT). At maturity, grain and straw yields were measured; Se contents in different grain fractions and straw were analyzed; Se harvest index and Se use efficiency were calculated. Soil samples from 0–100 cm depth were collected to determine available Se content in each 20 cm layer.

Result  (1) Investigation revealed that the Se content in wheat grains across four sites in the Huanghuai wheat region ranged from 10.8 to 234.2 μg/kg, with an average of 42.5 μg/kg. The soil available Se content varied between 2.1 and 19.2 μg/kg, indicating that both grain and soil are deficient in Se. (2) Se rate trials demonstrated that wheat yield increased with higher Se application rates. The maximum yield of was achieved at Se 300 g/hm², representing a significant increase of 22.8% compared to the non-Se treatment (P< 0.05). (3)Under different irrigation and Se application methods, Se treatments did not significantly affect wheat yield but significantly enhanced Se contents in grains, flour, and bran. The Se content in grains, flour, and bran of TB treatment reached 291.7, 244.3, and 373.5 μg/kg, respectively, and those in DB were 316.8, 313.8, and 404.9 μg/kg, respectively, and were 313.2, 244.6, and 339.3 μg/kg in DT treatment, respectively. No significant differences were observed in Se distribution among grain components between DB and DT treatments. Notably, flour Se content was lower than that in bran in Shaanxi, Hebei, and Shandong, whereas the opposite trend was found in Henan. The overall recovery efficiency of Se fertilizer across the four sites was low, averaging only 0.63%. Se application increased the Se harvest index (HI) by 67.6% in TB treatment, 71.9% in DB treatment, and 66.3% in DT treatment. Consequently, the Se allocation index in flour increased from 44.7% to 51.1%, with no significant difference between DB and DT treatment. Furthermore, Se application significantly increased available Se content in the 0–20 cm soil layer by 38.2%–199%, with varying degrees of increase observed in deeper layers; however, no significant differences were found between traditional irrigation and integrated water-fertilizer management within the same soil layers. Under traditional irrigation, the soil layers with significantly increased available Se extended to 0–60 cm in Shaanxi and Henan, 0–100 cm in Hebei, and 0–40 cm in Shandong.

Conclusions  The Huanghuai wheat region exhibits prevalent Se deficiency due to low soil available Se (2.1–19.2 μg/kg). Although Se fertilization significantly enhances grain Se levels, its efficiency remains low and is highly dependent on environmental and management factors. Notably, while integrated water-fertilizer management did not compromise Se content in grain products compared to traditional irrigation, it exacerbated Se leaching to deeper soil layers. Consequently, we recommend adopting basal Se application combined with reduced application rates under integrated water-fertilizer management to mitigate leaching risks and optimize Se utilization efficiency.