Selenium adsorption and desorption capacity and its influence on selenium uptake by green spinach

Abstract

Selenium is important to human health and must be consumed in adequate amounts through a variety of food sources, particularly vegetables. In order to identify availability of soil Se to crops, Se adsorption-desorption process in soil must be understood. In this study, an adsorption-desorption study of inorganic Se in soils of various textural classes was performed with the following concentration of Se (0–2 mg L−1) applied as Se(VI) and Se(IV). A glasshouse experiment was then conducted in a factorial (2 × 5) completely randomized design, with two Se form—Se(IV) and Se(VI)—and Se at five rates (0–60 g ha−1 Se in solution form) to green spinach. First, soil texture appeared to be the main factor controlling Se adsorption in soils. Selenite was adsorbed more, however, Se(VI) was desorbed at higher rate compared to Se(IV). Contrary to other soil types, in peat, Se(IV) was desorbed at higher level compared to Se(VI), where more than 70% was retained. Higher retention of Se(IV) was found in clayey soil. Meanwhile, from glasshouse experiment, Se uptake was higher in plants when treated with Se(VI) than with Se(IV). However, higher dry matter and antioxidant activity of green spinach was observed when Se(IV) was applied. Selenium applied as Se(IV) had greater benefits to spinach yield and antioxidant activity than Se(VI) or conventionally grown spinach (0 g ha−1), even though plants treated with Se(VI) had greater Se uptake.