• ISSN 1008-505X
  • CN 11-3996/S
GAO Jin-tao, WANG Xiao-yue, ZHOU Xing, LU Yan-hong, LIAO Yu-lin, NIE Jun, SUN Bo. Soil conditioners with Chinese milk vetch reduce Cd bioavailability in paddy soil[J]. Journal of Plant Nutrition and Fertilizers, 2022, 28(10): 1828-1839. DOI: 10.11674/zwyf.2022069
Citation: GAO Jin-tao, WANG Xiao-yue, ZHOU Xing, LU Yan-hong, LIAO Yu-lin, NIE Jun, SUN Bo. Soil conditioners with Chinese milk vetch reduce Cd bioavailability in paddy soil[J]. Journal of Plant Nutrition and Fertilizers, 2022, 28(10): 1828-1839. DOI: 10.11674/zwyf.2022069

Soil conditioners with Chinese milk vetch reduce Cd bioavailability in paddy soil

  • Objectives This study evaluated the effects of combining application of milk vetch (Astragalus sinicus L.) and different soil conditioners (lime or biochar) on the bioavailability of cadmium (Cd) in paddy soil and its accumulation and translocation in rice, in order to provide a theoretical and technical support for the restoration of Cd contaminated paddy fields and the cleaner production of rice in China.
    Methods A pot experiment was carried out in Hunan Province, using moderate Cd contaminated paddy soil (Total Cd 1.27 mg/kg, available Cd 0.15 mg/kg). The four treatments included the control with single cropping rice (CT), and three treatments of milk vetch incorporation as milk vetch alone (GM), milk vetch + lime (GL), and milk vetch + biochar (GB) in a milk vetch-rice rotation. At the tillering and matured stages of rice, soil properties and available Cd content were measured, and the absorption and accumulation of Cd in various parts of rice as well as rice yield were analyzed.
    Results 1) GM increased the available Cd content in soil and Cd enrichment coefficient in rice roots at tillering stage, but GM decreased the Cd content in stems and leaves at tillering stage, and had no significant effect on Cd content in grain. 2) Both GL and GB significantly increased soil pH, decreased soil Cd activation rate and available Cd content, and the two treatments reduced the average Cd accumulation in rice roots by 55.4% and 57.8% at tillering stage, respectively. Compared with GM, GL reduced the accumulation of Cd in grain, while GB increased the Cd enrichment coefficient in the roots of rice at maturity and Cd transport coefficient from stem and leaf to grain, resulting in a significantly higher Cd content in grains (0.08 mg/kg), but lower than the national standard permitted for rice Cd content. 3) Redundancy analysis (RDA) and random forest model predictions showed that soil pH, soil soluble organic carbon (DOC), and available phosphorus (AP) were the most important factors in determining the bioavailability of Cd at 0–15 cm paddy soil depth.
    Conclusions The application of milk vetch combined with lime or biochar effectively reduces soil available cadmium by increasing soil pH thus improving rice yield. Milk vetch combined with lime reduces the content of Cd in rice, while the addition of milk vetch and a large amount of biochar increases the risk of Cd contamination in rice.
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