Ecological effects of intercropping Brassica parachinensis and Sedum alfredii on the remediation of cadmium-contaminated farmland
In order to investigate the effect of intercropping the cadmium(Cd)low-accumulator Brassica parachinensis(B.parachinensis)and the Cd hyperaccumulator plant Sedum alfredii Hance(S.alfredii)in remediating Cd-contaminated soils,a simulation control experiment was conducted at the ecological farm of South China Agricultural University.The rhizosphere soil of B.parachinensi and S.alfredii were collected for study under monoculture and intercropping conditions.The results showed that intercropping significantly increased the biomass of plants,with the shoot and root biomass of S.alfredii increasing by 79.05%and 50.00%,and that of B.parachinensis increased by 110.96%and 125.00%,respectively,compared to monoculture.Intercropping resulted in an increase of 7.61%and 70.73%for Cd content in the shoot and root of the S.alfredii,respectively,while the Cd content in the shoot of B.parachinensis decreased by 27.21%compared to that of monoculture.The main subcellular structure storing Cd in the stems and leaves of S.alfredii was the cytosol in vesicles,accounting for up to 90%of storage,which is much higher than the Cd content in organelles and cell walls.Intercropping significantly increased the pH of the soil,with an increase of 0.39 and 0.28 compared to monoculture with S.alfredii and B.parachinensis,respectively.Intercropping reduced the availability of Cd in the rhizosphere soil of B.parachinensis,which was 19.23%lower than that of monoculture.In addition,intercropping resulted in a significant increase in the total amount of soil microorganisms and invertase activity,with the number of actinomycetes increasing by 27.95%and 24.28%respectively compared to monoculture with B.parachinensis and S.alfredii,and the sucrase activity increasing by 164.89%and 88.48%respectively.Meanwhile,it can be concluded that the cadmium extraction rate from the soil of intercropped S.alfredii was 1.88 times higher than that of monoculture.In conclusion,intercropping of a low Cd-accumulating vegetable(B.parachinensis)with a high Cd-accumulating remediation plant(S.alfredii)not only improves the safety of B.parachinensis production,but also increases the efficiency of soil Cd extraction by S.alfredii,which is an economical,effective and less risky model of remediation during production.
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