BOOK OF ABSTRACTS 145 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Thursday, 27 August 2026 / Hall C Soil Organic Matter, Caustobiolites, and Biochar SL70 Cadmium in Contaminated Straw Impairs Carbon Sequestration and Reduces Nitrogen Availability in Paddy Soils Jianming Xu1, Yu Huang2, Zhongmin Dai2 1 Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China. jmxu@zju.edu.cn 2 Zhejiang University While straw incorporation generally enhances carbon (C) and nitrogen (N) storage in paddy soils [1], cadmium (Cd) present in straw from contaminated areas may alter C and N transformation processes [2]. The specific impacts of Cd-containing straw on soil C sequestration and N availability remain poorly understood. This study investigated the dynamics of C and N in paddy soils amended with rice straw at four Cd concentrations (0, 5, 10, and 20 µg g⁻¹) and four application rates (0, 0.5%, 1%, and 3%). The incorporation of Cd-containing straw inhibited straw decomposition, reduced microbial biomass, and increased the mcrA/ pmoA gene ratio. It also lowered total soil organic C and dissolved organic C concentrations. Furthermore, Cd enhanced microbial demand for labile N, intensifying N limitation and reducing both inorganic and dissolved organic N pools. After 91 days of incubation, the addition of 3% straw with Cd concentrations of 5, 10, and 20 µg g⁻¹ decreased soil organic C by 2.2%, 4.4%, and 7.3%, respectively, compared to Cd-free straw. Concurrently, the content of dissolved organic N, NH4⁺-N, and NO3⁻-N declined by 6.6%, 19.1%, and 27.4%, respectively. These findings demonstrate that Cd-contaminated straw reduces both C storage and N availability in paddy soils, particularly when Cd concentrations exceed 5 µg g⁻¹. References 1. X. Liu, H. Liu, Y. Zhang, G. Chen, Z. Li, M. Zhang. 2023. Soil Biology & Biochemistry. 185(2023), 109131. 2. H. Xu, Y. Huang, X. Xiong, H. Zhu, J. Lin, J. Shi, C. Tang, J. Xu. 2023. Changes in soil Cd contents and microbial communities following Cd-containing straw return. Environmental Pollution. 330(2023), 121753. Acknowledgement This work was financially supported by the National Natural Science Foundation of China (42595620), and the China Agriculture Research System (CARS-01).
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