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Phytoremediation is a green technology for heavy metal removal from contaminated soil, and its remediation efficiency and economic feasibility in field trial should be evaluated before large-scale application. However, there is still lacking relevant analysis, especially for phytoremediation with different cropping patterns. In the present study, we performed phytoremediation on slightly Cd-contaminated farmland soil via three cropping systems, i.e. Sedum alfredii monoculture, oilseed rape monoculture, and S. alfredii-oilseed rape intercropping. Dry weights of S. alfredii and oilseed rape were both enhanced under intercropping pattern, while the highest total Cd extraction amount (148 g ha -1 ) were observed under S. alfredii monoculture. Furtherly, a cost-benefit analysis via Monta Carlo simulation in a ten-year lifetime was conducted. The benefits of S. alfredii monoculture and intercropping schemes would offset the total costs in 6 and 8 years, respectively. S. alfredii monoculture achieved a higher net present value of 1.88 × 10 4 US$ as compared with intercropping (9.53 × 10 3 US$). These results indicate that S. alfredii monoculture scheme could be a promising phytoremediation strategy for slightly Cd-contaminated soil owing to better remediation efficiency and economic feasibility. Moreover, the enhancement in mechanization level and the reduction of seedling cost could further improve its economic viability., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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; R 2 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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Soil pollution with heavy metals has become a common problem in agricultural ecosystems and poses a threat to food safety and human health. Intercropping is now considered a promising alternative to address this issue. However, our understandings about the influences of intercropping systems on rhizosphere microbiota composition and their association with plant performance are still limited. In this study, rhizobox microcosm experiments were conducted to investigate the influence of cropping regimes (i.e. monoculture and intercropping) on the rhizosphere bacterial microbiota and their linkages with the phytoextraction of cadmium (Cd) by Zhongyouza 19 (Brassica napus L.), Xikou Huazi (Brassica juncea L.) and Sedum alfredii using 16S rRNA gene sequencing. Cadmium accumulation in shoots of B. napus and B. juncea grown under intercropping were enhanced by 370% and 27.8% respectively, as compared to monoculture. Soil compartmentation as a major determinant explained 57.6% of the rhizosphere bacterial microbiota variation, whereas plant species and cropping regime accounted for 26.4% of the variation. The overall abundance of the taxa was Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Verrucomicrobia, and Actinobacteria. Intercropping significantly enriched amplicon sequence variants (ASVs) abundance belonging to Actinobacteria, Bacilli, Deltaproteobacteria while depleting that of Acidobacteria in rhizosphere. Intercropping with S. alfredii influenced more on microbial composition of B. napus rhizosphere. The change in rhizosphere bacterial communities was related to metal availability, soil properties, and plant parameters. The enriched families of Pedosphaeraceae, Ruminococcaceae, Chitinophagaceae, Gemmatimonadaceae, Nitrosomonadaceae, and Parachlamydiaceae were positively correlated with metal concentration in plants. These results indicate that S. alfredii and oilseed rape intercropping could be a promising approach for enhancing the remediation of Cd contaminated soil. Understanding the complex plant-microbe-metal interactions of intercropping system could facilitate the development of remediation strategy for phytoremediation of contaminated soils and sustainable agricultural production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A hydroponic experiment was conducted to investigate the effects of an endophytic bacterium SaMR12 on Sedum alfredii Hance metal ion accumulation, chlorophyll concentration, and the expression of three metal transporter families, zinc-regulated transporters, iron-regulated transporter-like protein (ZIP); natural resistance-associated macrophage protein; and heavy metal ATPase (HMA) at different Cd treatment levels. The results showed that at relatively low Cd conditions (≤25 μM), SaMR12 demonstrated a 19.5-27.5% increase in Fe, a 46.7-90.7% increase in Zn, and a 7.9-43.7% increase in Cu content in the shoot and elevated expression of SaIRT1, SaZIP3, SaHMA2, and SaNramp3 in the shoot and SaZIP1, SaHMA2, SaNramp1, and SaNramp3 in the root. At high Cd conditions (100 and 400 μM), SaMR12 demonstrated a 16.4-18.5% increase in leaf chlorophyll concentration, a 18.9-23.2% increase in Fe, and a 15.4-17.5% increase in Mg content in the shoot and elevated expression of SaZIP3, SaNramp6, SaHMA2, and SaHMA3 in the shoot and SaZIP3, SaNarmp1, SaNarmp3, and SaNarmp6 in the root. These results indicated that SaMR12 can elevate essential metal ion uptake and regulate the expression of transport genes to promote plant growth and enhance Cd tolerance and uptake to improve Cd accumulation up to 118-130%.