An effective planting model to decrease cadmium accumulation in rice grains and plants: Intercropping rice with wetland plants

Cadmium (Cd) pollution affects plant growth and poses a serious threat to food safety and human health. Cadmium-contaminated rice is assumed to be the main source of Cd exposure to humans, with grave health risks. Phytoremediation is an efficient, cost-effective, and eco-friendly approach to minimize Cd accumulation in rice. However, research on the effect of rice intercropping with wetland plants that exhibit great capacity for phytoremediation in decreasing Cd concentrations in paddies is limited. A pot experiment in greenhouse was conducted to evaluate the effect of rice intercropping with two wetland plants (Pontederia cordata and Canna indica) under different soil Cd levels (0, 1, 10, and 25 mg kg-1) on rice growth and Cd accumulation and translocation. The results showed that rice intercropping with the two wetland plants significantly improved plant height, tiller, and biomass of rice, but reduced Cd bioconcentration factors (BCFs) and Cd concentrations in rice and wetland plants. Compared with rice monocropping, the BCF in rice grain under 25 mg kg-1 soil Cd level significantly decreased by 54.39% and 59.65% in the systems of rice intercropping with C. indica and P. cordata, respectively. In addition, intercropping inhibited the increase in BCFs in rice and wetland plants under increasing soil Cd levels. In conclusion, the systems of rice intercropping with P. cordata and C. indica can be considered two new and effective approaches for ameliorating Cd pollution in paddies, as well as minimizing Cd accumulation in rice and improving food safety. Of the two intercropping systems, rice intercropping with P. cordata performed better than intercropping with C. indica.