ABSTRACT
Selenium (Se) biofortification depends on Se content in the soil or exogenous applications of Se to the plant. The transformation of Se in soil determines its availability for plant absorption. Straw amendment will enhance soil-dissolved organic matter (DOM) and affect Se availability through the formation of DOM-Se, which involves hydrophilic acid-bound Se (Hy-Se), fulvic acid-bound Se (FA-Se), humic acid-bound Se, and hydrophobic organic matter bound-Se. The straw derived DOM affected selenite availability in soil due to its composition and functional groups. Among the three DOM components, HA can easily incorporate with selenite and thus HA-Se became one of the important forms to reflect the availability of selenite. Additionally, the aromaticity of straw-derived DOM was enhanced with straw input and thus reduced Se availability. The DOM-Se was found pre-dominantly in the Hy-Se and FA-Se fractions, ac-counting for 62.7– 89.8% and 18.9–22.1% of total Se in soil solution at initiation of aging.
