Abstract
Addition of S fertilizer influences the behavior of metals in soil, the mechanism of which has not been extensively studied to date. We explored the dynamic influence of S fertilizer (S0 and Na2SO4) applied in paddy soils on Cu bioavailability in rice rhizosphere soil during the life cycle of rice plants. Through a microcosm experiment, the speciation of Cu and S in rhizosphere soil was explored by traditional chemical extraction methods and advanced synchrotron-based X-ray absorption near-edge spectroscopy (XANES) techniques. In the vegetative stages of rice plants, sulfur fertilization increased the concentration of bioavailable Cu, as well as the dissolved organic carbon (DOC) concentration in rhizosphere soil. Meanwhile, a higher proportion of Cu-humic substances was found in soil treated with S than that in control soil. However, extended flooding conditions led to the reduction of S fertilizer to sulfide, which provided the substrate for Cu2S formation. Thus, in the reproductive stages of rice plants, a higher proportion of Cu2S formation from +S treatments led to a relatively lower concentration of bioavailable Cu in rice rhizosphere soil than in control soil. The influence of S fertilizer on Cu bioavailability depended on the growth stage of rice plants. Both the DOC and redox potential (Eh) were changed by S fertilization in paddy soils and are critical factors that control Cu speciation in rice rhizosphere soil.
Published Version
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