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| Effects of superfine phosphate rock powders on Pb and Cd uptake and transportation in rice at different growth stages |
| Received:May 30, 2019 |
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| KeyWord:rice;growth period;superfine phosphate rock powder;lead;cadmium |
| Author Name | Affiliation | E-mail | | ZHANG Qing | Institute of Soil and Fertilizer/Land Cultivation Engineering Technology Research Center, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China | | | WANG Huang-ping | Institute of Soil and Fertilizer/Land Cultivation Engineering Technology Research Center, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China | | | KONG Qing-bo | Institute of Soil and Fertilizer/Land Cultivation Engineering Technology Research Center, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China | | | LI Fang-liang | Institute of Soil and Fertilizer/Land Cultivation Engineering Technology Research Center, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China | | | LUO Tao | Agricultural Ecology Institute, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China | luotaofjfz@188.com |
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| Abstract: |
| This study investigates the effects of the application of superfine phosphate rock powders(SPRP) on the absorption and transfer of lead(Pb) and cadmium(Cd) in soils contaminated with these elements during different growth periods of rice. Pot experiments were carried out to analyze the effects of i) different amount of SPRP on rice yields, ii) the absorption and transportation of Pb and Cd in plants, and iii) the forms of Pb and Cd in soils, when SPRP were applied at the pre-transplanting, tillering, and flowering stages of rice. The results showed that the yields of rice increased by between 9.70% to 26.60% with SPRP application, which were significantly higher than of rice yields with unground powders or without powder treatment. The concentrations of Pb and Cd decreased with increased levels of SPRP in all parts of the rice, including the root, stem, hull, and grain. When SPRP were applied at the pre-transplanting stage, the Pb concentrations of rice grains were between 75.7% to 79.1% lower than of those without any powder, and from between 73.5% to 77.3% lower than of those treated with unground powder. The reduction effects of grain Pb concentrations were better than of those at the tillering stage(55.4%~69.1%) and flowering stage(55.9%~61.5%). The application of SPRP at the flowering stage resulted in the grain Cd concentrations being between 44.3%~71.9% and 44.1%~71.8% lower than of those in the control and unground treatments, respectively. The reduction effects at the flowering stage were better than of those at the pre-transplanting stage(33.0%~45.8%) and tilling stage(28.6%~39.9%). With the application of superfine powders, the Pb and Cd concentrations in grain were mostly lower than the limit of 0.2 mg·kg-1 defined in the National Food Health Standard(GB 2762-2017). The application stage of SPRP also had a notable influence on exchangeable heavy metals in soils. The concentrations of soil exchangeable Cd were decreased by between 16.8% to 33.4% at flowering stage, which were better than of those at the pre-transplanting stage(18.0%~27.8%) and tillering stage(11.8%~27.9%). Meanwhile, the reductions in concentrations of soil exchangeable Pb ranged from 143.8% to 193.3% at the pre-transplanting stage, which was better than of those at the tillering stage (103.2%~183.4%) and flowering stage(56.0%~160.6%). The concentrations of exchangeable Cd and Pb in soils were positively correlated with their concentrations in rice grains, with correlation coefficients of 0.856 and 0.946, respectively. The absorption and primary transport coefficients of Cd and Pb decreased with increased dosage of SPRP, and were significantly different from those in the control. Therefore, the application of SPRP led to the passivation of the concentrations of exchangeable Pb and Cd in contaminated soils, a gradual reduction in the uptake and transport of heavy metals by rice, and an increase in rice yields. We conclude that the suggested optimum amount of SPRP is 2 g·kg-1 of polluted soils, which can be applied to soils polluted by Pb or Cd at pre-planting stage or growth boom stage, respectively. For complex soil pollution, we suggest that it is better to apply SPRP before planting in order to achieve improved comprehensive effects and easy operation. |
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