基施硅肥对土壤镉生物有效性及水稻镉累积效应的影响

为研究硅肥对土壤Cd生物有效性以及水稻累积重金属Cd的影响,模拟土壤低Cd污染水平(Cd总量为0.72mg·kg~(-1))和土壤高Cd污染水平下(Cd总量为5.08 mg·kg~(-1)),土壤基施0、15、30、60 mg·kg~(-1)的硅肥,进行水稻盆栽种植实验.结果表明,施用15~60 mg·kg~(-1)硅肥能提升水稻各生育期土壤的pH值,降低土壤交换态Cd含量和TCLP提取态Cd含量24.2%~43.7%,12.7%~46.8%,土壤中Si能与Cd形成Si-Cd复合物,降低土壤Cd的生物有效性,且降低效果在土壤低Cd污染水平时优于高Cd污染水平.硅肥提升水稻地上部的生物量尤其是产量.土壤低Cd污染水平下,Si对土壤Cd向水稻地上部的转运有促进和阻碍两种作用,施用量过低(Si 15 mg·kg~(-1))或过高(Si 60 mg·kg~(-1))时均促进土壤Cd向水稻地上部转运,施用量为30 mg·kg~(-1)时则阻碍Cd向上转运.随着Si施用量的增大,糙米Cd含量先上升后下降,范围为0.07~0.15 mg·kg~(-1),均低于0.2 mg·kg~(-1).土壤高Cd污染水平下,Si阻碍Cd向水稻地上部的转运,糙米、谷壳、茎叶的Cd含量分别降低38.7%~48.5%、35.7%~70.7%、30.9%~40.7%,糙米Cd含量范围0.23~0.28 mg·kg~(-1).综合考虑产量和糙米Cd含量,土壤低Cd污染水平下,建议施用30 mg·kg~(-1)的Si;高Cd污染水平下,建议施用Si 15~60 mg·kg~(-1).

Impacts of Silicon Fertilizer as Base Manure on Cadmium Bioavailability in Soil and on Cadmium Accumulation in Rice Plants

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.