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Responses of Soil-Rice Cd to Different Conditioners and their Combinations in a Karst Area with High Geological Background (Vol. 51, No. 3, Tot No. 353 2023) TEXT SIZE: A A A

RAN Gang1,2,3, YANG Hanwen1, WEI Lan1, LIU Xiuming1,3, WANG Shijie1,3

(1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry,Chinese Academy of Sciences, Guiyang 550081, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China;

3. Puding Karst Ecosystem Observation and Research Station, Chinese Academy of Sciences, Puding 562100, China)

Abstract: At present, the application of soil conditioners in the prevention and control of Cd pollution in rice is mainly concentrated in the industrial and agricultural pollution areas such as East China, Central China, and South China, while the application of soil conditioners in the southwest karst area with high geological background of cadmium is less. In this article, an experimental study on the response of soil-rice Cd to NPK compound fertilizer, rapeseed cake fertilizer, cow dung, silicon-calcium- magnesium fertilizer conditioner and their combination was carried out in the karst high geological background area of Luodian, Guizhou, and the results showed that: (1) Compared with before planting, the soil DTPA-Cd content decreased by 21.6% on average, the proportion of reducible Cd content decreased by 5.84%, and the proportion of weak acid-extracted Cd content increased by 5.53% on average. the proportion of oxidizable state and residual state Cd content remained basically unchanged; (2) Compared with the blank, the Cd content of brown rice was reduced by 24.7% on average, and the Cd enrichment coefficient of brown rice was reduced by 20.0% on average under each conditioner and combination treatment except NPK compound fertilizer + rapeseed cake fertilizer; (3) The traditional planting (fertilization) mode of NPK compound fertilizer + cow dung has the best effect, the soil DTPA-Cd content has the largest decrease (28.1%), the Cd content in brown rice is the lowest (0.182 mg/kg), and the Cd enrichment coefficient in brown rice is the lowest. (0.0230), it is worth carrying out a wider range of experimental demonstration and promotion. The response of soil-rice Cd to various conditioners and combinations in this study area is obviously different from that of industrial and agricultural pollution areas in my country, reflecting the characteristics of karst areas: The flooding caused the dominant reducible Cd in the soil to be activated to a certain extent, and the proportion of weakly acid-extracted Cd increased accordingly, However, the calcium and magnesium-rich karst water irrigation drives the passivation mechanism of carbonate and Cd coprecipitation, which generally reduces the bioavailability of soil Cd.

Key words:soil conditioner; cadmium; rice; high geological background of cadmium; karst

EARTH AND ENVIRONMENT Vol.51, No.3, Tot No.353, 2023, Page 330

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