[Ecological responses of Brassica juncea-alfalfa intercropping to cadmium stress].

A pot experiment was conducted to study the effects of cadmium (Cd) stress on the soil-plant system under Brassica juncea-alfalfa intercropping, and to evaluate the Cd feed safety of alfalfa. Comparing with monoculture, when the soil Cd content was in the range of 0.37-20.37 mg x kg(-1), intercropping decreased the B. juncea biomass by 0.4%-11.8% while increased the alfalfa biomass by 55.3%-70.0%. Soil available Cd was mainly determined by soil total Cd and plant species, and less affected by planting pattern. Comparing with monoculture, when the soil Cd content was in the range of 0.37-5.37 mg x kg(-1), intercropping increased the Cd content in above-ground part of B. juncea by 14.5%, but decreased the Cd content in above-ground part of alfalfa by 57.1%. The Cd contents in the above-ground parts of alfalfa under monoculture and intercropping were 0.21 and 0.09 mg x kg(-1), respectively, neither of them being over the feed safety standard (0.5 mg x kg(-1)). When the soil Cd content was in the range of 10.37-20.37 mg x kg(-1), though the Cd contents of mono-cultured and intercropped alfalfa were both over the standard, the Cd contents in the above-ground parts of alfalfa and B. juncea under intercropping were decreased by 2.8%-48.3% and 1.1%-48.6%, respectively. Under both monoculture and intercropping, the Cd transport coefficient of B. juncea was far greater than that of alfalfa.