Influencing factors on bioavailability and spatial distribution of soil selenium in dry semi-arid area

Authors: FAROOQ, MUHAMMAD RAZA - University Of Science And Technology Of China; ZHANG, ZEZHOU - Anhui Agricultural University; YUAN, LINXI - Liverpool University; LIU, XIAODONG - University Of Science And Technology Of China; REHMAN, ABDUL - University Of Science And Technology Of China; Banuelos, Gary; YIN, XUEBIN - Anhui Agricultural University

Submitted to: Agriculture
Publication Type: Review Article
Publication Acceptance Date: 2/20/2023
Publication Date: 2/27/2023
Citation: Farooq, M., Zhang, Z., Yuan, L., Liu, X., Rehman, A., Banuelos, G.S., Yin, X. 2023. Influencing factors on bioavailability and spatial distribution of soil selenium in dry semi-arid area. Agriculture. 13(3):576. https://doi.org/10.3390/agriculture13030576.
DOI: https://doi.org/10.3390/agriculture13030576

Interpretive Summary: The natural distribution pattern of selenium (Se) in the soil can be designated as high (seleniferous) to deficient in different regions of the world. Generally, bioavailable Se in soil influences Se content in crops and thereby human intake of Se from plant-based products. In Central China, geological surveys have identified a low Se region belt extending from Northeast to Northwest China. Consequently, crops grown in this region have lower Se concentrations and inhabitants living within this region also have a lower intake of Se. In our attempt to understand the relationship between soil Se, crops, and Se content in humans, we investigated the distribution of Se and its bioavailability in high alkaline soils under semiarid conditions in Northwestern China, a region famous for producing agricultural crops. Soil analyses from this region showed that geology controls the soil formation and concentrations of bioavailable Se, and eventually determines the Se content in the food chain. Total soil Se content depends on parent soil material, while bioavailable Se depends on physical-chemical parameters like contents of organic matter, iron/aluminum oxide and soil pH. Data showed that the bioavailability of Se in soil declined with the increase of pH in an acidic environment, and Se bioavailability increased with an increase of the alkaline environment. Future efforts should evaluate strategies for increasing Se intake by manipulating physicochemical properties in the soil and thereby influencing bioavailability of Se for plant uptake. Increasing bioavailable Se should result in a higher Se content in crops and a higher intake of Se for the population consuming Se-enriched food product. This study highlights the need to understand the roles that total Se content and bioavailable Se play in determining Se concentration in crops grown in Se deficient soil.

Technical Abstract: Selenium (Se) is a natural-occurring trace element, whose concentration varies worldwide under natural conditions. It is essential micronutrient for human and animals. Generally, geology and parent soil control the total soil Se concentrations and the related soil physiochemical parameters determine the amount of bioavailable Se in the soil. Importantly, bioavailable soil Se contrats Se content in crops, which influences Se intake by humans. To understand the relationship between soil Se and plant Se content, the main objectives of this study were to utilize an expansive soil survey and preform soil analyses to (I) determine the spatial distribution of soil Se content and estimate Se bioavailability at different soil depths; and 2) analyze the relationships between Se bioavailability, and key soil physicochemical properties that influence crop Se content. Results showed that approximately 42 % of collected soil samples were marginal to deficient in soil Se present in Zhongwei, Central China. Total soil Se ranged from 0.01 to 0.55 mg/kg, while Se content (mg/kg DM) in plants averaged in vegetables (0.005), rice (0.002), potato (0.054) and grains (0.044). The total soil Se and bioavailable Se were significantly (p<0.01) influenced by physiochemical factors, such as pH, CaC03, and organic matter. Total Se and bioavailable Se in the soil ranged from 0.01 to 0.55 mg/kg and 16%, respectively, and bioavailable Se was significantly (p<0.01) correlated to organic matter (OM) and CaC03. in the soil. We also observed at some soil locations that where there was a high Se bioavailability, sufficient to moderate Se- enriched crops were produced. We observed that total soil Se content and soil physicochemical properties were the main influential factors related to soil Se bioavailability and plant uptake of Se. Our results highlight a need to manipulate bioavailable Se in highly alkaline soil to increase plant Se content by introducing soil amendments or performing additional agronomic management practices, e, g., adding soil amendments. We conclude that if bioavailable Se fractions in Se -deficient soil sites, as a result, then Se-enriched crops can be efficiently and importantly consistently produced in Southwest China.