[Impacts of Silicon Fertilizer as Base Manure on Cadmium Bioavailability in Soil and on Cadmium Accumulation in Rice Plants].Huan Jing Ke Xue. 2017 Dec 08; 38(12):5299-5307.HJ
The impacts of silicon (Si) on cadmium (Cd) bioavailability in soil and Cd accumulation in rice plants were investigated in pot experiments with rice (Oryza sativa L.) cultivation. Silicon fertilizer as the base manure (Si 0, 15, 30, and 60 mg·kg-1) was added in simulated slightly Cd-contaminated soil (total soil Cd of 0.72 mg·kg-1) and severe Cd-contaminated soil (total soil Cd of 5.08 mg·kg-1). It indicated that the application of 15-60 mg·kg-1 Si before the rice was transplanted improved soil pH values and reduced the contents of exchangeable-Cd and TCLP extractable-Cd in the soil by 24.2%-43.7% and 12.7%-46.8%, respectively, during the rice growing stages. The reduction in soil Cd bioavailability resulted from the complexing of Si and Cd, and the reduction followed the order:slightly Cd-contaminated soil > severely Cd-contaminated soil. It was obvious that silicon fertilizer improved rice biomass above ground, especially for rice grain yield. In the slightly Cd-contaminated soil, Si both promoted and restrained soil Cd transportation from the rice root to the shoot; the low application (Si 15 mg·kg-1) and high application (Si 60 mg·kg-1) of Si both promoted Cd transportation, but the medium application (Si 30 mg·kg-1) restrained Cd transportation. With increasing silicon fertilizer application, Cd contents in brown rice increased first and then decreased, ranging from 0.07-0.15 mg·kg-1, remaining lower than 0.2 mg·kg-1. In the severely Cd-contaminated soil, Si restrained the soil Cd transportation from the rice root to the shoot. The Cd contents in brown rice, husk, and straw were reduced by 38.7%-48.5%, 35.7%-70.7%, and 30.9%-40.7%, respectively, and Cd contents in brown rice were 0.23-0.28 mg·kg-1. Considering rice grain yields and Cd contents in brown rice, it was recommended that the Si application be 30 mg·kg-1 of Si in the slightly Cd-contaminated soil and Si 15-60 mg·kg-1 in the severely Cd-contaminated soil.