Hyperaccumulators' Diversity Enhances Cd-Contaminated Soil Restoration and Reduces Rice Cd Uptake under an Intercropping System

Cd accumulation in rice-cultivated soils across China is a major problem that needs to be tackled. A plot experiment was carried out using heavy metal (HM) hyperaccumulators Amaranthus hypochondriacus L. and Perilla frutescens (L.) Britt. intercropped with low-accumulation rice to obtain safe edible rice while reducing the soil Cd concentration. It was found that Cd concentration in soil was decreased by 7.43 and 2.86% under rice intercropped with Amaranthus hypochondriacus L. and Perilla frutescens (L.) Britt., respectively, compared to single cropped rice. In addition, enhanced effects were noted under the combination of Amaranthus hypochondriacus L., Perilla frutescens (L.) Britt, and rice in which a 20.35% decrease in soil Cd content was recorded compared to single-cultivated rice soil. In addition, the available Cd in soil was reduced by 4.00 and 5.00% under rice/Amaranthus and rice/Perilla, respectively, and 12.00% under rice/Amaranthus/Perilla mixed culture. Moreover, the concentration of Cd in various parts of rice was under permissible limits. However, rice biomass was decreased by the presence of hyperaccumulators. This study suggests that combining HM hyperaccumulator plants and low-accumulation rice provides efficient Cd extraction results and could be a crucial option for restoring Cd-contaminated soil without reducing rice production.