Dynamic influence of S fertilizer on Cu bioavailability in rice (Oryza sativa L.) rhizosphere soil during the whole life cycle of rice plants
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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.
Materials and methods
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.
Results and discussion
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.
KeywordsBioavailability Cu Paddy rice Speciation S fertilizer
The work was supported by the National Natural Science Foundation of China (11179025, 41422107, U1532103), National Key Research and Development Program of China (2016YFD0800401), Shanghai Sailing Program (18YF1421100), and Excellent Team Program of Shanghai Academy of Agricultural Sciences (Nongkechuang 2017(A-03)). We would like to express our great gratitude to Lirong Zheng at the beamline 1W1B and Lei Zheng at beamline 4B7A of Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences for their generous help in Cu and S K-edge XANES collection and analysis, respectively.
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