Intercropping with Brassica juncea L. enhances maize yield and promotes phytoremediation of cadmium-contaminated soil by changing rhizosphere properties

Intercropping heavy metal hyperaccumulators and low-accumulating cultivars is a promising strategy for remediating contaminated soils without impeding agricultural production. A field plot experiment was conducted to explore the effects of intercropping maize with Brassica juncea L. on the rhizosphere microecological properties, plant growth and cadmium (Cd) accumulation. The results showed that the Cd bioaccumulation amount per unit area (BCAarea) of the intercropping system was 12.9% lower than that of the Brassica juncea L. monoculture but 87.5% higher than that of the maize monoculture. The grain yield of maize was increased by 10.5% through intercropping, and the land equivalent ratio (LER) was greater than 1. Soil available Cd in intercropped maize was 13.4% lower than that in monoculture maize but was 12.7% higher in intercropped Brassica juncea L. than in monoculture Brassica juncea L. Intercropping significantly increased the contents of malic acid and citric acid in the rhizospheres of maize and Brassica juncea L. The dominant microorganisms were similar in all studied soils but were different in relative abundance between the intercropping and monoculture treatments. These findings suggest that intercropping maize with Brassica juncea L. could be a promising approach for phytoremediation without reducing crop yield in Cd-contaminated soil.