Effects of Mineral-Based Potassium Humate on Cadmium Accumulation in Rice ( Oryza sativa L.) under Three Levels of Cadmium-Contaminated Alkaline Soils

Shuangshuang Li, Xianmin Huang, Guangxian Li, Ke Zhang, Liyong Bai, Huan He, Shibao Chen () and Jiulan Dai ()
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Shuangshuang Li: Environment Research Institute, Shandong University, Qingdao 266237, China
Xianmin Huang: Shandong General Station of Agricultural Environmental Protection and Rural Energy, Jinan 250100, China
Guangxian Li: Shandong Academy of Agricultural Sciences, Jinan 250100, China
Ke Zhang: Environment Research Institute, Shandong University, Qingdao 266237, China
Liyong Bai: Environment Research Institute, Shandong University, Qingdao 266237, China
Huan He: College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
Shibao Chen: Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Jiulan Dai: Environment Research Institute, Shandong University, Qingdao 266237, China

Sustainability, 2023, vol. 15, issue 3, 1-22

Abstract: Humic acid amendments in the remediation of soils contaminated with heavy metals have received widespread attention. However, the impacts and related mechanisms of mineral-based humate substances on the remediation of alkaline paddy soils with different levels of cadmium (Cd) contamination are still unclear. Pot trials with four mineral-based potassium humate (MBPH) doses (0, 0.25%, 0.5%, 1%, w / w ) and three Cd rates (slightly, moderately, and highly, 1, 2, and 4 mg Cd kg −1 ) were conducted to evaluate the effects of MBPH on rice. Results showed that the application of MBPH effectively reduced brown rice Cd concentrations of all Cd rates by 46.82–65.04%, 44.02–59.21%, and 15.84–43.99%, such that Cd in brown rice fell within the safe edible standards in the highly contaminated soils with the 0.5% and 1% MBPH applications. The application of MBPH significantly alleviated Cd toxicity by increasing soil solution pH, dissolved organic carbon (DOC), and potassium (K) and decreasing free Cd and the bioavailability of rhizosphere soil Cd, as reflected by promoting rice plant growth, photosynthesis, F v /F m , and antioxidant enzymes activities. Additionally, high dose applications (0.5% and 1%) of MBPH significantly reduced the translocation factor of Cd from flag leaf to brown rice. Furthermore, the application of MBPH enhanced the accumulation of mineral elements (iron, manganese, copper, zinc, potassium) in brown rice. Stepwise regression analysis revealed that soil solution K at maturity stage and soil solution DOC at tillering and filling stages were the most important factors affecting Cd accumulation in brown rice under slightly, moderately, and highly Cd-contaminated soils, respectively. Therefore, MBPH application on slightly and moderately Cd-contaminated alkaline soils contributed to achieving rice grains rich with mineral elements but Cd free and Cd safe in highly Cd-contaminated soil.

Keywords: mineral-based potassium humate; cadmium; rice; antioxidant enzymes; bioavailability; photosynthetic characteristics (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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