Document Type
Thesis - University Access Only
Award Date
2009
Degree Name
Doctor of Philosophy (PhD)
Department / School
Agronomy
Abstract
Global demand for food products with high selenium (Se) content is great due to reported anti-cancer and immune system building attributes of Se for human health. It is therefore essential to develop the best agricultural practices for managing food crops grown in high Se areas of the world to ensure a sustainable supply of food naturally enriched with Se. Unfortunately, there is limited scientific information available for managing crops growing on naturally high Se soils in South Dakota. Therefore, the over-arching goal of this research was to investigate Se uptake and accumulation by wheat (Triticum aestivum L.) grown in soils naturally high Se in South Dakota. The specific research objectives of this study were to determine 1) the Se concentration among current wheat varieties grown in South Dakota, 2) the adsorption and desorption properties of Se on South Dakota soils, and 3) the effect of phosphate (PO4-P), sulfate (SO4-S), and nitrate (NO3-N) fertilizer on wheat growth and Se contents in naturally high Se soils. A total of 280 wheat grain samples including eight winter wheat and ten spring wheat varieties, grown in 2005 and 2006 were analyzed to determine grain Se concentration and Se uptake. The mean grain Se concentration over two years was 0.63 μg Se g·1 and grain Se concentrations ranged from 0.10 to 1.94 μg Se g·1 . Grain Se concentration was strongly influenced by geographical location in which different amounts of soil Se bioavailability occurred. Total soil Se was not significantly correlated with grain Se, but plant available (0.1 M KH2PO4 extractable) and conditionally available (4M HCI extractable) Se in soils provided the best relationship with wheat grain Se content. This indicated that these extractions could be used to predict Se bioavailability and grain Se concentration. The wheat grain Se concentration and Se uptake by wheat were not significantly different among the wheat varieties used in this study. However, soil environment factors such as soil pH and available orthophosphate-P content were found to have a greater influence. The adsorption and desorption properties of Se in selected South Dakota soils were determined as a function of pH and the competition effect of PO4-P and SO4-S in soil solution. The adsorption capacity of Se was strongly related to soil pH. The maximum adsorption occurred at a low pH and decreased as pH increased. The maximum Se adsorption capacity corresponded with the specific surface area of the soil. The Freundlich isotherm provided the best fit (R2 ~ 0.94) to describe the Se adsorption behavior compared to the Langmuir isotherm. The presence of PO4-P in solution decreased the amount of Se adsorbed in all soils, although the effect of PO4-P varied depending on the adsorption capacity of the soil. The competition effect between Se and PO4-P was less distinct in soils with high adsorption capacity. However, the presence of SO4-S in solution had little effect on Se adsorption. Desorption of adsorbed Se was also greater with PO4-P addition than with SO4-S addition. This indicates that PO4-P additions could influence soil solution Se and therefore could influence soil Se bioavailability and plant uptake. Field experiments were conducted in 2007 and 2008 to investigate the effect of oxi-anions in fertilizer (Pas triple-superphosphate, Sas gypsum, and N as urea) on wheat growth and Se content when applied to wheat crops grown on naturally high Se soils under field conditions. The fertilizer applications had a significant affect on wheat grain yield, grain Se concentration, and Se uptake. Phosphate, SO4-S, and NO3-N applications significantly decreased Se concentration in wheat grain due to the dramatic increase in yield. Sulfate applications significantly decreased grain Se concentration as well as grain Se uptake due to the competition effect between SO4- S and Se in soil. The ratio of S/Se absorbed was significantly higher in low Se areas and low S application areas. It was also found that Se concentration in soil from a sub-surface depth (15-60 cm) provided a better estimate of grain Se concentration due to the higher concentrations of plant available Se. This study showed that soil chemical properties such as soil pH and available P are important factors for Se uptake and accumulation in plants. In a field study, P influence on grain Se concentration was not clear. Therefore, future research is necessary to determine the best management practices for different soil characteristics (e.g., landscape position). Farmers in high Se soils should know the best locations to produce a high Se grain crop because Se concentration in wheat is more strongly associated with location than with wheat variety or fertilizer management.
Library of Congress Subject Headings
Soils -- Selenium content -- South Dakota
Wheat -- South Dakota
Selenium in agriculture
Selenium in human nutrition
Format
application/pdf
Number of Pages
197
Publisher
South Dakota State University
Recommended Citation
Lee, Sanghun, "Selenium Uptake by Wheat Grown in South Dakota" (2009). Electronic Theses and Dissertations. 1587.
https://openprairie.sdstate.edu/etd2/1587
