Soil trace elements (TEs) contamination has become a worldwide problem in arable lands and poses great risk to human health via food chain. Intercropping of hyperaccumulator and cash crops is now proposed as a promising alternative phytoremediation technique to address the issue. However, the effect of intercropping in different soil types and field-scale benefits evaluation are rarely reported. A greenhouse pot experiment and a field trial were therefore designed to explore the effects of intercropping Sedum alfredii (hyperaccumulative population) and oilseed rape on Cd phytoextraction potential, Cd transport and crop production, as well as establishing a feasible assessment framework on the basis of benefits evaluation in contaminated soils. Compared with oilseed rape monoculture, intercropping with S. alfredii significantly and consistently increased biomass, seed yield and Cd accumulation in oilseed rape in five typical soil types. Accumulations of Cd varied with soil types, ranging from 22.8 to 4000 μg pot-1. Stepwise multiple linear regression analysis (SMLRA) showed Cd concentrations in plants were related to available phosphorus (AP), pH, soil organic matter (OM), available potassium (AK), silt and sand; R2 values varied from 0.834 to 0.994 (P < 0.05). A field trial also verified that intercropping could significantly enhance Cd phytoextraction. The highest index for comprehensive benefits evaluation was 0.61 observed in the S. alfredii and oilseed rape intercropping system. This system presented higher Cd phytoextraction potential and comprehensive benefits index whilst allowing ongoing agricultural activities in slightly and moderately Cd-contaminated soils. These results provide a possible technical approach for phytoremediation practice and give new insights into theoretical reference for development of Cd phytoextraction and benefits evaluation.
Keywords: Cadmium; Comprehensive benefits evaluation; Intercropping; Phytoextraction; Soil types.
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