Italian ryegrass–rice rotation system for biomass production and cadmium removal from contaminated paddy fields

Purpose

Growing energy plants in Cd-contaminated soil to produce bioenergy feedstock and remove excess Cd in the soil is a promising approach to the production of sustainable bioenergy feedstock and safe food. Rice, an important staple food for human beings, is a major source of Cd intake in human beings. Italian ryegrass (Lolium multiflorum Lam) is a potential bioenergy plant with high biomass productivity and high biofuel conversion efficiency.

Materials and methods

An Italian ryegrass and rice crop rotation system would be beneficial for the harvest of bioenergy and phytoremediation. An Italian ryegrass–rice rotation system was established in a moderately Cd-contaminated paddy field. The yield of biomass, amount of Cd removal, and transfer factors for three cropping systems (winter fallow, non-cutting, and cutting) were evaluated over 3 consecutive years of field experiments.

Results and discussion

The total biomass production of the Italian ryegrass–rice rotation system was significantly higher than that of the traditional cropping system. Biomass growth was further promoted by cutting during March. No significant differences were found in yield or Cd concentration of brown rice among the different cropping systems. Total Cd accumulation in rice and Italian ryegrass straw in the rotation cropping system was significantly higher than that in the winter fallow cropping system. Cd was mainly accumulated in the roots, and the ability of Italian ryegrass to transport Cd to the leaves was higher than that of rice.

Conclusions

The Italian ryegrass–rice rotation system is a potential cropping system for Cd-contaminated paddy fields. The average annual yield of biomass was 1656.6 kg km^?2, and the average annual amount of Cd removal was more than 9.8 g Cd km^?2.