TABLE 7.
Effect of biochar on remediation of Cd-contaminated soils.
| Plant species | Feed stock | Applied rate | Experiment type | Soil type | Heavy metals | Effects | References |
| Rice (Oryza sativa) | Rice Straw (450°C) | 0, 3, and 5% (w/w) | Pot | Sandy clay loam | Cd | Biochar application significantly decreased the Cd uptake (38%) along with a considerable increase in plant growth. | Hafeez et al., 2019 |
| Pak choi (Brassica chinensis) | Rice straw (550°C) | 0, 2.5 and 5% (w/w) | Pot | Alfisol | Cd | Application of biochar reduced the Cd uptake in root (29.23%) and shoot (42.49%), while increased the plant production together with enhanced enzymatic antioxidant activity. | Kamran et al., 2019 |
| Saffron (Crocus sativus) | Beeswax waste (400°C) | 0, 1.5, 3 and 6% (w/w) | Pot | Cd | The Cd uptake was reduced up to 24% in corm and 33% in leaf coupled with increased plant biomass with biochar application. | Moradi et al., 2019 | |
| Spinach (Spinacia oleracea) | Cotton stalk, Rice straw (450°C) | 0, 2 and 5% (w/w) | Field | Cd | Both the biochar applications minimize the Cd uptake in plants up to 66% and enhanced the fresh biomass of spinach and phosphorous concentration in the soil. | Qayyum et al., 2019 | |
| Spinach (Spinacia oleracea) | Cotton stalk, Rice straw (450°C) | 0 and 2% (w/w) | Pot | Cd | The treatments of both rice and cotton biochar considerably increased the fresh mass and reduced the Cd uptake (61%). | Qayyum et al., 2019 | |
| Maize (Zea mays) | Common reed (550°C) | 0 and 1% (w/w) | Pot | Alkaline soil | Cd | Application of biochar enhanced the plant biomass, root length, and root volume in addition to reduced Cd uptake (57%). | Rafique et al., 2019 |
| Pak choi (Brassica chinensis) | Platanus orientalis branches (650°C) | 0, 0.5, 1, 2, and 4% (w/w) | Pot | Loamy soil | Cd | Biochar application reduced the Cd availability (80%) and malondialdehyde concentration in the shoot. | Chen et al., 2019 |
| Garden lettuce (Lactuca sativa) | Rice husk (500°C) | 0 and 5% (w/w) | Pot | Cd, Pb, As, Ni, Cr | Application of biochar reduced the bioavailability of Cd (31%), Pb (20%), and As (22%) in addition to increased P, total nitrogen, and total carbon contents in the soil. | Ibrahim et al., 2019 | |
| Wild mint (Mentha arvensis) | Mentha arvensis waste (450°C) | 0, 2, and 4% (w/w) | Pot | Sandy loam soil | Cd, Pb | Biochar enhanced the Cd and Pb tolerance by decreasing Cd (50%) and Pb (25%) uptake in mint along with an increase in photosynthetic pigments and stomatal activity. | Nigam et al., 2019 |
| White willow (Salix alba) | Carpinus betulus waste biomass (400°C) | 0, 2.5, and 5% (w/w) | Pot | Sand | Cd, Cu, Pb | Biochar treatment increased the plant height, root length, leaf area, photosynthetic pigments, CO2 assimilation rate, and intracellular CO2 concentration in addition to reduced cd, Pb, and Cu availability. | Mokarram-Kashtiban et al., 2019 |
| Lebbek tree (Albizia lebbeck) | Farmyard manure (450°C) | 0, 3, and 6% (w/w) | Pot | Sandy loam | Cd | Application of biochar enhanced the growth and gas exchange characteristics by lowering the absorption rate of Cd in root, shoot, and leaves up to 34, 33, and 50% respectively. | Yousaf et al., 2019 |
| Rice (Oryza sativa) | Rice straw (450°C) | 0 and 1% (w/w) | Pot | Cd | Biochar treatment significantly decreased the Cd uptake in root (29%) and shoot (45%) along with a considerable increase in shoot and root dry weight of plant and chlorophyll-a concentration. | Rizwan et al., 2019b | |
| Rice (Oryza sativa) | Sugarcane bagasse (500°C) | 0 and 3% (w/w) | Pot | Fragile sandy soil | Cd | Application of biochar alleviates the ROS and decreased the bioavailability of Cd in fragile soil along with an increase in growth of plant root and photosynthetic pigments. | García et al., 2020 |
| Wheat (Triticum aestivum) | Farm yard (500°C) | 0, 2.5, and 5 g/kg of soil | Pot | Alkaline soil | Cd | Biochar application reduced the Cd concentration in plant root (71–92%), shoot (82–92%), and grain (90–96%) in addition to enhanced wheat yield. | Ijaz et al., 2020 |
| Rapeseed (Brassica napus) | Woodchip (300°C) | 0, 1, and 2% (w/w) | Pot | Cd, Pb, Ni, Cu | The concentration of Cd (44%), Pb (51%), Ni (59%), and Cu (45%) were decreased along with an increase in fresh root and shot biomass, total chlorophyll, and enzymatic antioxidant activity under biochar application. | Kamran et al., 2020 | |
| Quinoa (Chenopodium quinoa) | Wheat straw (350°C) | 0, 1, and 2% (w/w) | Pot | Cd | The treatment with biochar enhanced the overall growth, pigments, and gas exchange parameters by limiting the Cd accumulation in root (30%), shoot (25%), and grain (45%) of quinoa. | Naeem et al., 2020 | |
| Wheat (Triticum aestivum) | Rice husk (400–500°C) | 0.4, 3 and 5% | Pot | Cd, Pb | Biochar application showed a promising decrease in shoot Cd (77%) and Pb (50%) availability in the soil and increased the plant growth and grain yield. | Zhang S. et al., 2020 | |
| Cotton (Gossypium hirsutum) | Cotton straw (550°C) | 0 and 3% (w/w) | Pot | Cd | Application of biochar considerably enhanced the chlorophyll contents, gas exchange parameters, and the activities of SOD and POD by decreasing the Cd uptake in both root (17.8%) and stem (15%). | Zhu et al., 2020 | |
| Radish (Raphanus sativus) | Wheat feedstock (500°C) | 0 and 0.5% (w/w) | Pot | Paddy soil | Cd | Biochar application showed a prominent increase in the activity of antioxidant enzymes and mineral contents along with a clear reduction of 92% in Cd uptake through roots. | Dad et al., 2020 |
| Rice (Oryza sativa) | Platanus orientalis branches (650°C) | 0 and 3% (w/w) | Pot | Silty clay loam | Cd, As, Pb | Application of biochar reduced the bioavailability of Cd (37%) and Pb (23%) along with a considerable increase in catalase activity and grain yield. | Wen et al., 2020 |
| Oak (Quercus castaneifolia) | Rice husk (500–550°C) | 1, 3, and 5% (w/w) | Pot | Loamy soil | Cd | Biochar treatment improved the oak growth and decreased the bioavailability of Cd up to 67%. | Amirahmadi et al., 2020 |
| Wheat (Triticum aestivum) | Dry maize (700°C) | 0, 1.5, and 3% (w/w) | Pot | Cd | Plant fresh and dry biomass, root length, and root surface area were increased along with reduced Cd uptake in root (51%) and shoot (48%). | Jan et al., 2020 | |
| Tobacco (Nicotiana tabacum) | Tobacco stem (450°C) | 0, 1, and 2% (w/w) | Pot | Cd | Application of biochar decreased the absorption, accumulation, and concentration of Cd in root (81%), stem (68%), and leaves (80%) along with increased plant biomass. | Yao et al., 2021 | |
| Sweet basil (Ocimum ciliatum) | Mulberry wood residues (530°C) | 0, 1, and 2% (w/w) | Pot | Sandy loam | Cd | Biochar application reduced the Cd uptake in leaf up to 40% along with an increase in photosynthetic pigments, morphological traits, and catalase activity. | Mehdizadeh et al., 2021 |
| Tobacco (Nicotiana tabacum) | Corn Cob (500°C) | 0 and 1% (w/w) | Pot | Clay loam | Cd | Biochar treatment considerably reduced the Cd contents in shoot (32%) and improved the plant growth. | Erdem, 2021 |
| Wheat (Triticum aestivum) | Bamboo biochar (750°C) | 0, 0.1, 1, and 5% (w/w) | Pot | Cd | Cd uptake was reduced in root (34.06%), straw (21.57%), and grain (23.33%). | Ma et al., 2021 | |
| Tobacco (Nicotiana tabacum) | Peanut-shell waste (400°C) | 0 and 1% (w/w) | Pot | Cinnamon soil | Cd | Photosynthetic pigments, gas exchange attributes, and activity of enzymatic antioxidants were increased along with a decrease of 14.8% in leaf Cd absorption. | Ren et al., 2021 |