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Field experiments were conducted in two consecutive rice-wheat cropping seasons on a yellow clay soil to assess the efficacy of organic and inorganic amendments for cadmium (Cd) and lead (Pb) immobilization. Amendments were applied alone and in combinations to compare their efficacy for metals immobilization. Composite amendment of GSA-4 (Green Stabilizing Agent) and biochar resulted in higher biomass and grains yield for both rice (Oryza sativa L.) and wheat (Triticum aestivum L.). Liming, DEK1 (Di Kang No. 1) or GSA-4 amendment increased soil pH from 6.34 to 7.35, 7.20 and 7.15, respectively. Soil amendments significantly reduced DTPA extractable Cd and Pb in soil at wheat harvest. Cadmium and Pb fractionation showed a significant decrease in the extractable fractions by the amendment of biochar (34% and 25%) or GSA-4 (35% and 26%, respectively). GSA-4 and biochar amendment enhanced metals immobilization and reduced their uptake by plant and subsequent accumulation in the grains of rice and wheat, particularly with GSA-4. These results indicate that GSA-4 and biochar, especially their combination, have great potential for application to remediate Cd and Pb contaminated soils.

Phytoremediation is a valuable technology for mitigating soil contamination in agricultural lands, but phytoremediation without economic revenue is unfeasible for land owners and farmers. The use of crops with high biomass and bioenergy for phytoremediation is a unique strategy to derive supplementary benefits along with remediation activities. Sunflower (Helianthus annuus L.) is a high-biomass crop that can be used for the phytoremediation of polluted lands with additional advantages (biomass and oil). In this study, 40 germplasms of sunflower were screened in field conditions for phytoremediation with the possibility for oil and meal production. The study was carried out to the physiological maturity stage. All studied germplasms mopped up substantial concentrations of Pb, with maximum amounts in shoot > root > seed respectively. The phytoextraction efficiency of the germplasm was assessed in terms of the Transfer factor (TF), Metal removal efficiency (MRE) and Metal extraction ratio (MER). Among all assessed criteria, GP.8585 was found to be most appropriate for restoring moderately Pb-contaminated soil accompanied with providing high biomass and high yield production. The Pb content in the oil of GP.8585 was below the Food safety standard of China, with 59.5% oleic acid and 32.1% linoleic acid. Moreover, amino acid analysis in meal illustrated significant differences among essential and non-essential amino acids. Glutamic acid was found in the highest percentage (22.4%), whereas cysteine in the lowest percentage (1.3%). Therefore, its efficient phytoextraction ability and good quality edible oil and meal production makes GP.8585 the most convenient sunflower germplasm for phytoremediation of moderately Pb-contaminated soil, with fringe benefits to farmers and landowners.

Phytoremediation coupled with crop rotation (PCC) is a feasible strategy for remediation of contaminated soil without interrupting crop production. The objective of this study was to develop a PCC technology system for greenhouse fields co-contaminated with Cd and nitrate using hyperaccumulator Sedum alfredii. In this system, endophytic bacterium M002 inoculation, CO2 fertilization, and fermentation residue were continuously applied to improve the growth of S. alfredii, and low-accumulator Ipomoea aquatica and low-accumulator Brassica chinensis were rotated under reasonable water management. These comprehensive management practices were shown to increase S. alfredii biomass and Cd uptake and reduce Cd and nitrate concentration in I. aquatica and B. chinensis. This crop rotating system could remove 56.5% total Cd, 62.3% DTPA extractable Cd, and 65.4% nitrate, respectively, from the co-contaminated soil in 2 years of phytoremediation, and is an effective way of remediating moderately co-contaminated soil by Cd and nitrate.