Evaluation of Calcium Oxide of Quicklime and Si–Ca–Mg Fertilizer for Remediation of Cd Uptake in Rice Plants and Cd Mobilization in Two Typical Cd-Polluted Paddy Soils

Abstract

Lime and Si fertilizer are effective amendments for alleviating Cd accumulation in crops. In this study, two Cd-polluted typical soils from different regions in China were sampled to conduct a pot experiment. The effects of two soil amendments [calcium oxide of quicklime (SH) and Si–Ca–Mg fertilizer (GF)] on the distribution of Cd fractions in soil with and without rice-planting treatment and on Cd uptake and accumulation in rice were investigated. The results showed that SH and GF application significantly reduced Cd accumulation in rice in YSS and GSS, and that the maximum Cd reduction in GSS reached 319 μg pot−1 with SH treatment. SH and GF significantly decreased and increased, respectively, the proportions of Acid-Cd and Res-Cd in the soil. Rice-planting treatment activated Res-Cd compared with no rice-planting treatment, and SH and GF restrained the remobilization process. Significant positive correlations were found between Res-Cd remobilization rates in soil and Cd content in brown rice. Multiple regression revealed that applying GF at dosages of 1.296 g kg−1 and 1.246 g kg−1 in YCS and GSS, respectively, was an ideal method to control soil acidity. This study highlighted the view that Res-Cd remobilization provoked by rice plays a considerable role in influencing Cd bioavailability in the soil, that soil type should be considered as a factor when applying soil amendments to contaminated soils, and that soil amendment dosages should vary according to soil type.