Physicochemical properties of amended soils Table 1 shows selected physicochemical properties of amended soils. The texture of commercial soil (C0) was loam. However, some amended soil became clay loam after being treated with various organic amendments such as SL, SLBM, SLVC, LCM, and LBM. Loam is a soil texture that contains high levels of nutrients, moisture, and humus, making it ideal for agricultural plantations16. Organic amendments were able to modestly raise the pH of some amended soils, e.g., SL, SBM, SLBM, LBM, BMVC, BMCM, and BMBM; pH 6-7.3, while only SLVC and LCM had a slight reduction in pH (5.5 and 5.8, respectively). Leonardite in SLVC, LCM, and LBM has the potential to lower soil pH, affecting plant growth and productivity. As a result, leonardite is usually mixed with other organic or inorganic amendments to achieve the desired soil pH for plant cultivation17. Electrical conductivity values in some amended soils were relatively high, exceeding the regulatory limit of 2 dS m−1, e.g., SL, SLVC, LCM, BMCM, and BMBM; 2.1 to 2.5 dS m−1. This indicated that the soils had excessively high salt levels, which could affect plant growth18. Organic amendments can raise EC contents to dangerously high levels, making it vital to maintain a note of any changes in plant symptoms that can alter the survival rates of the study plants19. When compared with C0 soil, the addition of various organic amendments resulted in an increase in OM of 1.3 to 1.5 times. The CEC values in some amended soils, such as SBM, BMVC, BMCM, and BMBM, decreased slightly, which could be due to the dilution effects of the organic amendments5. Higher soil pH values in some amended soils may be linked to the increased negative charge that develops on OM and microbial activity as a result of enhanced nutrient availability20. When compared with the identical product of commercial soil in a related study, the C0 soil in this study had higher contents of essential nutrients (N, P, K); however, it had lower amounts of Ca and Mg15. Organic amendments increased essential nutrient concentrations such as total N, Ext. P, Ext. Ca, and Ext. Mg, although Ext. K content was somewhat lower in practically amended soils, with the exception of T8 soils (3,960 mg kg−1) or higher than 1.4 times compared with C0 soil.
Table 1
Physicochemical properties of the amended soils
| Parameter | Units | Soil |
C0 | SL | SBM | SLBM | SLVC | LCM | LBM | BMVC | BMCM | BMBM |
| Texture | | Loam | Clay loam | Loam | Clay loam | Clay loam | Clay loam | Clay loam | Loam | Loam | Loam |
| Sand | % | 44.8 | 42.4 | 43.4 | 42.4 | 40.2 | 39.6 | 42.2 | 44.0 | 48.2 | 48.2 |
| Silt | % | 37.6 | 28.2 | 31.2 | 28.2 | 29.2 | 32.2 | 28.2 | 30.2 | 28.0 | 28.0 |
| Clay | % | 17.6 | 29.4 | 25.4 | 29.4 | 30.6 | 28.2 | 29.6 | 25.8 | 23.8 | 23.8 |
| pH | | 5.9 | 6.6 | 7.3 | 6.9 | 5.5 | 5.8 | 6.0 | 6.8 | 6.9 | 7.3 |
| EC | dS m−1 | 1.5 | 2.2 | 1.8 | 1.9 | 2.1 | 2.5 | 1.8 | 2.0 | 2.5 | 1.7 |
| OM | % | 6.8 | 9.4 | 9.0 | 8.6 | 9.9 | 9.8 | 8.9 | 9.6 | 8.5 | 8.5 |
| CEC | cmol kg−1 | 13.4 | 21.5 | 11.8 | 15.6 | 22.1 | 20.2 | 17.0 | 12.9 | 11.9 | 10.8 |
| Total N | % | 0.34 | 0.47 | 0.45 | 0.43 | 0.49 | 0.49 | 0.44 | 0.48 | 0.43 | 0.42 |
| Ext. P | mg kg−1 | 467 | 441 | 5928 | 4375 | 866 | 715 | 2302 | 5676 | 6363 | 5975 |
| Ext. K | mg kg−1 | 2749 | 2586 | 2478 | 2391 | 2305 | 2723 | 2085 | 2530 | 3960 | 2679 |
| Ext. Ca | mg kg−1 | 1375 | 3948 | 3682 | 4447 | 2832 | 2244 | 2874 | 3640 | 2928 | 3768 |
| Ext. Mg | mg kg−1 | 463 | 561 | 511 | 547 | 708 | 702 | 514 | 667 | 690 | 532 |
Cd concentrations measured in soils prior to planting |
| Total Cd | mg kg−1 | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
| Ext. Cd | mg kg−1 | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
Cd concentrations measured in soils after plant harvest |
J. curcas | Total Cd | mg kg−1 | - | 2.7±1.2bA | 2.9±1.2bA | 2.5±1.3 bA | 2.0±0.9 bA | 2.3±1.1abA | 3.1±1.1bA | 3.7±1.3bA | 3.1±1.4aA | 2.6±1.2abA |
| Ext. Cd | mg kg−1 | - | 0.7±0.2bA | 0.7±0.2bA | 0.5±0.2 bA | 0.4±0.2 bA | 0.7±0.2abA | 0.4±0.2bA | 0.7±0.2bA | 0.7±0.2aA | 0.4±0.2abA |
M. esculenta | Total Cd | mg kg−1 | - | 0.6±0.3bcB | 1.0±0.3aB | 0.6±0.3abcB | 0.4±0.2cB | 0.4±0.2cB | 0.5±0.0cB | 0.6±0.4bcB | 0.4±0.cB | 0.9±0.6abB |
| Ext. Cd | mg kg−1 | - | 0.5±0.1bcdB | 0.6±0.1aA | 0.5±0.1bcA | 0.5±0.1bcdA | 0.4±0.1deB | 0.3±0.1eA | 0.4±0.1cdeB | 0.5±0.1abB | 0.4±0.1bcdA |
A. mangium | Total Cd | mg kg−1 | - | 1.5±0.9 bB | 2.4±0.7 bA | 2.5±1.3 bA | 2.3±0.3 bcA | 2.8±0.6abA | 3.2±0.1abA | 3.5±0.3aA | 2.8±0.3abA | 2.9±0.1abA |
| Ext. Cd | mg kg−1 | - | 0.6±0.1 aAB | 0.6±0.0 aA | 0.5±0.0 bcA | 0.4±0.1 cA | 0.6±0.1abA | 0.4±0.1cA | 0.5±0.1abcAB | 0.6±0.1aAB | 0.5±0.1cA |
BDL below detection limits, CEC cation exchange capacity, EC electrical conductivity, Ext. extractable, OM organic matter, C0 commercial soil, SL soil+leonadite (Treatment 1: T1), SBM soil+bone meal (T2), SLBM soil+leonadite+bone meal (T3), SLVC soil+leonadite+earthworm manure (T4), LCM soil+leonadite+chicken manure (T5), LBM soil+leonadite+bat manure (T6), BMVC soil+bone meal+earthworm manure (T7), BMCM soil+bone meal+chicken manure (T8), BMBM soil+bone meal+bat manure (T9) |
Values followed by the same letter did not significantly differ; lower-case letters show the differences in Cd concentrations in the soils within the same plant species (LSD, p < 0.05); while capital letters indicate the differences in total (or Ext.) Cd concentrations in the soils among plant species (LSD, p < 0.05) |
Before planting, total Cd and Ext. Cd concentrations in all soil samples were below detection limits (Table 1), but those values increased somewhat following plant harvest, whereas total Cd concentrations were greater than ext. Cd concentrations. High cadmium accumulation in soil has long been influenced by the Cd content in water and the accumulation period21. The remaining Cd contents in soils after the three-month harvesting period might be attributable to the addition of Cd solution to amended soils and different bioavailability rates of the study plants. When comparing all amended soils, total Cd and ext. Cd contents for individual plants exhibited narrow variations. Total Cd concentrations in all amended soils for jatropha, cassava, and acacia were 2 to 3.7 mg kg−1, 0.4 to 1 mg kg−1, and 1.5 to 3.5 mg kg−1, respectively, whereas ext. Cd concentrations for jatropha, cassava, and acacia were 0.4 to 0.7 mg kg−1, 0.3 to 0.6 mg kg−1, and 0.4 to 0.6 mg kg−1, respectively.
Effects of amendments on plant growth. In this study, jatropha and acacia thrived in Cd soils for three months, with no visible phytotoxic effects in any of the treatments. Cassava also had a 100% survival rate; however, this crop plant showed symptoms of stress such as deformed leaves and yellowing in almost all treatments. During the study period, however, Cassava cultivated in T1 treatment showed no signs of harm. Of three crop plants surveyed, only Cassava was found to be cultivated in Cd and Zn co-contaminated agricultural areas of the Mae Tao River Basin. However, no research publications are available on all of the study plants growing in those locations.
The use of soil amendment had variable effects on plant growth (plant height, root length, and dry biomass production). Furthermore, all of the study plants had considerably improved plant height and root length, as well as enhanced dry biomass production, from planting to harvesting periods (Table 2). Except for jatropha, the GRDB values of the study plants also revealed similar trends to those of plant growth performances, with GRDB values in month 3 slightly lower than month 1. The following is the descending order of growth rate in dry biomass values for the study plants: cassava > acacia > jatropha.
Table 2
Growth performances of the study plants in a pot study for 3 months (n = 4)
Scientific name | Treatment | Month | Height (cm) | Root (cm) | Biomass (g plant−1) | Growth rate in dry biomass |
J. curcas | T1 | 0 | 36.7±0.6aA2 | 0.0±0.0aB3 | 11.0±1.7aA3 | - |
| 1 | 51.3±2.1aB1 | 14.5±1.1aC2 | 27.8±2.3aA2 | 17.4±2.3aA1 |
| 3 | 50.8±5.0bA1 | 20.3±2.7bC1 | 59.9±7.4abA1 | 16.3±2.5abA1 |
T2 | 0 | 36.7±0.6aA2 | 0.0±0.0aB3 | 11.0±1.7aA3 | - |
| 1 | 43.7±4.7abcB2 | 11.4±5.1abB2 | 33.0±5.9aA2 | 22.5±5.9aA1 |
| 3 | 66.1±10.5aA1 | 24.5±4.1abA1 | 62.5±2.5aA1 | 17.2±0.8aA1 |
T3 | 0 | 36.7±0.6aA2 | 0.0±0.0aB3 | 11.0±1.7aA3 | - |
| 1 | 38.8±4.3cB2 | 12.1±6.6abB2 | 25.7±5.6aA2 | 15.3±5.6aA1 |
| 3 | 60.8±2.3abA1 | 29.6±11.3aA1 | 52.4±8.7abcA1 | 13.8±2.9abcA1 |
T4 | 0 | 36.7±0.6aA2 | 0.0±0.0aB2 | 11.0±1.7aA2 | - |
| 1 | 47.6±11.7abB1,2 | 10.6±5.7abB1 | 27.2±12.4aA1,2 | 16.8±12.4aA1 |
| 3 | 55.2±13.4abA1 | 19.3±1.7bB1 | 42.4±16.0bcB1 | 10.5±5.3bcB1 |
T5 | 0 | 36.7±0.6aA2 | 0.0±0.0aB3 | 11.0±1.7aA2 | - |
| 1 | 38.2±6.7cA2 | 7.1±1.6bcB2 | 14.3±4.0bA2 | 3.8±4.0bA1 |
| 3 | 58.9±13.6abA1 | 16.3±5.6bB1 | 46.8±21.1abcA1 | 11.9±7.0abcA1 |
T6 | 0 | 36.7±0.6aA3 | 0.0±0.0aB3 | 11.0±1.7aA3 | - |
| 1 | 45.3±1.9abcB2 | 11.0±1.7abB2 | 25.6±3.6aA2 | 15.1±3.6aA1 |
| 3 | 58.0±8.9abB1 | 22.5±1.7abAB1 | 57.4±13.3abA1 | 15.5±4.4abA1 |
T7 | 0 | 36.7±0.6aA1 | 0.0±0.0aB3 | 11.0±1.7aA2 | - |
| 1 | 41.7±3.3bcB1 | 6.2±5.0bcB2 | 28.9±7.6aA1 | 18.6±7.7aA1 |
| 3 | 50.3±14.8bA1 | 20.5±5.9bA1 | 42.1±15.0bcA1 | 10.4±5.0bcA1 |
T8 | 0 | 36.7±0.6aA2 | 0.0±0.0aB3 | 11.0±1.7aA3 | - |
| 1 | 38.4±3.0 cA2 | 3.5±1.8cB2 | 23.1±7.2abA2 | 12.7±7.2abA1 |
| 3 | 53.1±12.4abAB1 | 24.1±3.0abA1 | 39.0±10.0cAB1 | 9.4±3.3cA1 |
T9 | 0 | 36.7±0.6aA3 | 0.0±0.0aB3 | 11.0±1.7aA3 | - |
| 1 | 47.0±2.7abA2 | 11.9±5.1abB2 | 23.6±9.6abA2 | 13.1±9.6abA1 |
| 3 | 61.8±1.3abA1 | 23.6±2.5abA1 | 53.3±9.6abcB1 | 14.1±3.2abcB1 |
M. esculenta | T1 | 0 | 35.7±0.7aA2 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
| 1 | 61.1±5.0aA1 | 22.8±3.2abB1 | 19.5±7.4aB2 | 11.2±7.4aAB1 |
| 3 | 60.8±1.9bA1 | 27.3±5.1abcdB1 | 56.7±17.8aA1 | 16.1±5.9aA1 |
T2 | 0 | 35.7±0.7aA2 | 0.0±0.0aB3 | 8.3±1.4aB2 | - |
| 1 | 62.0±7.2aA1 | 17.0±8.7abcAB2 | 21.7±3.5aB2 | 13.4±3.5aB1 |
| 3 | 66.5±8.7abA1 | 33.8±6.3abA1 | 40.7±22.7aA1 | 14.9±7.5aA1 |
T3 | 0 | 35.7±0.7aA3 | 0.0±0.0aB3 | 8.3±1.4aB2 | - |
| 1 | 58.1±3.5abA2 | 13.6±6.3cB2 | 21.1±8.48aAB2 | 12.8±8.5aA1 |
| 3 | 67.5±5.1abA1 | 36.3±13.2aA1 | 51.0±22.9aA1 | 14.2±7.6aA1 |
T4 | 0 | 35.7±0.7aA2 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
| 1 | 65.2±8.2aA1 | 22.9±1.9abA1 | 15.0±5.9aAB2 | 6.7±5.9aA2 |
| 3 | 71.8±2.6aA1 | 28.1±6.4abcdAB1 | 48.0±15.8aA1 | 18.8±4.5aA1 |
T5 | 0 | 35.7±0.7aA3 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
| 1 | 43.9±6.3cA2 | 15.1±8.1bcB1 | 13.0±4.8aA2 | 4.6±4.8aA2 |
| 3 | 70.3±5.3aA1 | 17.6±1.5dB1 | 64.4±7.5aA1 | 18.7±2.5aA1 |
T6 | 0 | 35.7±0.7aA3 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
| 1 | 64.9±4.6aA2 | 25.0±6.3aA1 | 19.4±8.4aAB2 | 11.1±8.4aA1 |
| 3 | 73.1±4.9a A 1 | 19.8±4.1cdB1 | 75.1±41.6aA1 | 22.2±13.9aA1 |
T7 | 0 | 35.7±0.7aA2 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
| 1 | 58.8±1.7abA1 | 20.3±9.3abcA1 | 15.8±4.6aB2 | 7.5±4.6aB2 |
| 3 | 64.1±8.8abA1 | 29.4±10.6abcdA1 | 41.9±7.3aA1 | 16.0±3.9aA1 |
T8 | 0 | 35.7±0.7aA3 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
1 | 50.2±11.4bcA2 | 14.5±3.1bcA1 | 17.5±7.0aA2 | 9.2±7.0aA1 |
3 | 65.0±8.8abA1 | 21.9±4.3bcdA1 | 36.6±17.0aA1 | 17.3±9.9aA1 |
T9 | 0 | 35.7±0.7aA3 | 0.0±0.0aB2 | 8.3±1.4aB2 | - |
| 1 | 45.3±8.4cA2 | 13.4±2.1cB1 | 15.2±3.3aA2 | 6.9±3.3aA2 |
| 3 | 61.1±5.5bA1 | 31.5±19.2abcA1 | 45.0±18.8aA1 | 22.5±3.9aA1 |
A. mangium | T1 | 0 | 17.4±1.7aB3 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 28.3±4.8 abcdC2 | 34.5±6.0aA1 | 9.6±3.4bC2 | 6.1±3.4bB2 |
| 3 | 56.7±10.3 abcdA1 | 40.8±4.1aA1 | 17.8±6.8bcdB1 | 14.3±6.8bcdA1 |
T2 | 0 | 17.4±1.7aB3 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 34.5±6.0 abB2 | 25.8±7.6abA1 | 10.7±2.6bC2 | 7.1±2.6bB2 |
| 3 | 68.9±12.9 abA1 | 29.8±7.8abcA1 | 23.0±9.0abB1 | 19.4±9.0abA1 |
T3 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 37.1±12.2aB2 | 29.2±11.1abA1 | 14.0±4.8abB1 | 10.5±4.9abA1 |
| 3 | 74.1±26.3aA1 | 33.0±11.6abcA1 | 9.6±5.36cdB1,2 | 6.1±5.4cdA1,2 |
T4 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 28.9±5.9abcdC2 | 31.6±8.9abcdA1 | 10.8±4.0bB1 | 7.3±4.0bA1 |
| 3 | 57.8±12.8abcdA1 | 36.6±7.0abA1 | 8.6±3.7dC1 | 5.1±3.7dB1 |
T5 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC1 | - |
| 1 | 18.6±1.4dB2 | 26.6±6.0dA1 | 10.4±3.0bA1 | 6.9±3.0bA1 |
| 3 | 37.1±3.0dB1 | 32.6±6.1abcA1 | 10.9±9.4cdB1 | 9.8±9.7bcdA1 |
T6 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 20.7±3.8cdC2 | 22.6±8.3cdA1 | 13.0±1.9abB1 | 9.4±1.9abA1 |
| 3 | 27.5±3.8cdC1 | 41.4±8.2bcA1 | 11.3±6.2cdB1 | 7.7±6.2cdA1 |
T7 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 30.6±9.8abcdC2 | 25.8±6.3abcdA1 | 14.1±2.2abB1 | 10.5±2.2abAB1,2 |
| 3 | 61.1±21.3abcdA1 | 30.8±8.9abcA1 | 18.7±7.6abcB1 | 15.2±7.6abcA1 |
T8 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC2 | - |
| 1 | 22.6±4.1bcdB2 | 21.3±5.6bcdA1 | 15.6±2.1aA2 | 12.0±2.1aA2 |
| 3 | 45.3±8.9bcdB1 | 22.0±5.9cA1 | 21.7±5.1aA2 | 18.2±5.1abA1 |
T9 | 0 | 17.4±1.7aB2 | 12.9±3.0aA2 | 3.6±0.4aC1 | - |
| 1 | 32.3±17.8abcA1,2 | 24.9±8.0abcA1,2 | 15.8±2.5aA2 | 12.3±2.5aA1 |
| 3 | 64.6±38.4abcA1 | 35.1±12.3abA1 | 27.7±5.9aC1 | 24.2±5.9aA1 |
Values followed by the same letter did not significantly differ; lower case letters indicate the differences in growth performance among treatments within the same plant species and growth period (LSD, p < 0.05); capital letters indicate the difference in growth performance among plant species within the same treatment (LSD: p < 0.05); and numbers indicate the difference in growth performance among growth periods within the same plant species and treatment. |
After harvest, BMBM in T9 treatment promoted the best growth performance in acacia (dry biomass 27.7 g plant−1, GRDB 24.2), followed by LBM in T6 treatment for Cassava (dry biomass 75.1 g plant−1, GRDB 22.2). Bone meal and bat manure are more widely used as a P source in commercial fertilizer because of their high P content (7 to 12% and 1 to 9%, respectively). Bone meal has an NPK of 3-15-0 on average, making it a rich source of P for plants. Bat manure, commonly known as "Guano," is an important organic source of nitrogen that also contains minerals like struvite and magnesium, making it useful for fertilizing crops to some extent22. Leonardite is an end-product of lignite coal and mined pits at Mae Moh mine in Lampang Province, which has a high total N concentration (0.6%) but low Cd and Zn contents (0.7 mg Cd kg−1 and 40 mg Zn kg−1, respectively)1. It has been employed as organic amendment mixtures to promote crop plants, particularly Thai commercial rice cultivars, indicating that it provides a highly effective soil amendment5. In this study, the treatment that received both bone meal and bat manure supplements had 1.2 times higher dry biomass after harvest than treatment that just received bone meal. Some research also indicated that a combination of amendment supplements could increase extractable essential micronutrients and soil enzymatic activity23. However, jatropha preferred bone meal alone, as shown by the T2 treatment having the highest biomass and GRDB compared with the other treatments (p < 0.05; 62.5 g plant−1, GRDB 17.2).
The other treatments (T3, T4, T5, T7, and T8) exhibited lower growth performances, particularly in jatropha and acacia, indicating that a specialized soil amendment, such as bat, bone meal/or leonardite alone, would be more beneficial. The combination of chicken manure or vermicompost with leonardite or bone meal was unable to support the growth of the study plants until they had attained substantial values of dry biomass production and GRDB (Table 2). In Thailand's agricultural areas, vermicompost and chicken manure are important soil organic amendments. They were reported to be successful in replacing chemical fertilizer and stimulating plant growth when combined with other organic amendments or materials, e.g., rice husk charcoal24. Because numerous research studies have suggested that chicken manure alone at high concentration may achieve targeted plant growth, the lower growth performance of the study plants might have been due to insufficient amounts of the organic amendment25,26. Furthermore, the growth performances of Cassava did not differ significantly across treatments after harvest (p > 0.05). This means that the combination of chicken manure or vermicompost with leonardite or bone meal as soil organic amendments for cassava is a suitable alternative amendment for planting.
The results clearly demonstrated that jatropha and acacia had lower R/S ratios than cassava (Fig. 1). The R/S ratios of the study plants were observed in ascending order as follows: jatropha (0.04 to 0.06) > acacia (0.16 to 0.8) > cassava (0.59 to 3). According to Meeinkuirt et al.27 (2013), a high R/S ratio value indicated Cd toxicity in plants, and so increasing Cd concentration in plant media is thought to harm the study plants. Substantial root/shoot ratio values were seen in all treatments for Cassava, particularly in T5 and T6 treatments, which might be linked to increased plant stress (3 and 2.63, respectively).
Cadmium concentrations in plant tissues. Because soil amendments had varied impacts on different plant tissues, amended soil treatments in this study revealed varying levels of Cd accumulation and uptake depending on the crop plant species (Table 3). Furthermore, the study plants accumulated Cd primarily in their roots after one month of growth, with average values of 2.4 to 6.2 mg kg−1, 4 to 15 mg kg−1, and 3.3 to 4 mg kg−1 for jatropha, cassava, and acacia, respectively. T5 treatment resulted in the maximum Cd accumulation in cassava (15 mg kg−1), whereas T2 treatment resulted in the lowest value for acacia (3.3 mg kg−1).
Table 3
Cd accumulation and uptake, bioconcentration factor for root (BCFR) and translocation factor (TF) among the study plants in a pot study (n = 4)
Scientific name | Treatment | Month | Cd accumulation in plants (mg kg−1) | Cd uptake (mg plant−1) | BCFR | TF |
Leaf | Stem | Root | Cassava tuber | Seed | Whole plant |
J. curcas | T1 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.3±1.0aA2 | 3.4±1.2aA1 | 5.9±1.5aA1 | - | - | 4.2±0.6aA1 | 120.1±20.4aA2 | 6.3±1.2abA1 | 0.6±0.1cdA1 |
3 | 4.4±0.8bA1 | 2.3±0.8bcB2 | 3.2±2.2abA2 | - | - | 3.3±0.8aAB2 | 197.0±22.8abA1 | 1.2±0.3abB2 | 0.8±0.3cdA1 |
T2 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
1 | 3.3±1.0aA2 | 3.1±1.2abA1 | 4.0±1.1cA1 | - | - | 3.5±0.5bcA1 | 116.2±21.7abA2 | 3.6±0.8abcA1 | 0.8±0.3bAB1 |
| 3 | 4.4±0.8bA1 | 2.5±0.7abcA2 | 3.5±1.6abA1 | - | 0.6±0.3a | 3.5±0.6aA1 | 217.0±13.1aA1 | 1.2±0.1abcB2 | 0.7±0.1bA1 |
T3 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
1 | 2.8±1.0aA2 | 2.9±1.1bA1 | 3.9±1.9cAB1 | - | - | 3.0±0.8cdAB2 | 79.1±17.7abcA2 | 9.1±2.3abcA1 | 0.8±0.2bcA1 |
| 3 | 4.8±1.0abA1 | 2.2±0.7cB2 | 3.2±1.7abA1 | - | - | 3.4±0.8aA1 | 177.8±32.4abA1 | 1.3±0.3abcB1 | 0.7±0.1bcB1 |
T4 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.9±1.1aA2 | 2.9±1.1bA1 | 6.0±1.3aA1 | - | - | 3.6±0.9abcA1 | 102.4±53.3abA1 | 11.3±6.2aA1 | 0.5±0.0dB2 |
3 | 4.2±0.8bA1 | 2.6±0.9abcA1 | 3.9±1.9aB2 | - | 0.5±0.1a | 3.3±1.0aAB1 | 147.6±74.5abA1 | 2.0±0.3aB1 | 0.7±0.1dAB1 |
T5 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.3±1.3aA1 | 3.2±0.8abA1 | 5.0±1.0bB1 | - | - | 3.4±0.8abA1 | 54.8±12.0cAB2 | 3.8±1.6bcA1 | 0.6±0.0bcdB1 |
3 | 4.4±1.0bA1 | 2.6±0.8abcA1 | 2.2±1.7bB2 | - | - | 3.0±0.9aA1 | 145.2±68.8abA1 | 1.0±0.5bcB1 | 1.3±0.8bcdA1 |
T6 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.0±1.0aA2 | 2.9±1.2bA1 | 2.4±0.5dB1 | - | - | 2.7±0.4dB2 | 71.3±11.3bcA2 | 1.3±0.5cA1 | 1.2±0.1aA1 |
3 | 4.6±0.8abA1 | 2.5±0.9abcA1 | 2.9±1.7abB1 | - | - | 3.4±0.5aA1 | 193.3±46.8abA1 | 1.0±0.3cB1 | 0.9±0.2aA2 |
T7 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.2±1.1aA2 | 2.9±0.8bA1 | 5.1±0.9bA1 | - | - | 3.2±0.8abA1 | 109.5±24.1abA1 | 4.8±0.8abcA1 | 0.6±0.0cdB2 |
3 | 5.1±1.2aA1 | 2.7±0.7abA1 | 3.4±1.7abB2 | - | - | 3.5±0.8aAB1 | 151.9±68.4abA1 | 0.9±0.1abcB2 | 0.8±0.1cdA1 |
T8 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.1±0.9aA2 | 3.1±1.3abA1 | 6.2±1.8aA1 | - | - | 3.5±1.3aA1 | 101.4±47.4abA1 | 7.5±1.1abcA1 | 0.5±0.1aB1 |
3 | 4.5±0.8abA1 | 2.7±0.9abcA1 | 2.9±2.1abA2 | - | - | 3.2±1.0aA1 | 127.8±60.3bA1 | 1.3±0.2abcB2 | 0.7±0.1dA1 |
T9 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.9±1.0aA2 | 3.0±1.0abA1 | 4.9±1.2bB2 | - | - | 3.4±0.8bcA1 | 83.8±41.9abcA2 | 6.3±2.1abcA1 | 0.6±0.1cdA2 |
3 | 4.6±0.9abA1 | 2.9±0.8aAB1 | 3.1±1.6abB2 | - | - | 3.5±0.7aA1 | 187.9±32.9abA1 | 1.2±0.3abcA1 | 0.9±0.1cdA1 |
M. esculenta | T1 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.5±0.9abB1 | 1.8±1.1dC2 | 5.7±2.4bA1 | - | - | 3.3±0.6bB1 | 53.6±18.2aB2 | 2.2±0.4abB2 | 0.3±0.0cB2 |
3 | 1.8±0.5cdC2 | 3.1±0.5aA1 | 3.9±1.4abA2 | - | - | 2.9±0.6bcB1 | 154.7±51.7aA1 | 10.2±3.5abcdA1 | 0.8±0.0bA1 |
T2 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.8±0.6aA1 | 2.3±1.1abcB1 | 4.0±1.8bA1 | - | - | 3.0±0.4bA1 | 72.4±20.1aB1 | 1.5±0.3bB2 | 0.6±0.2aB1 |
3 | 2.5±0.5aB1 | 2.8±0.7aA1 | 3.4±1.6bA1 | 1.6±0.3b | - | 2.9±0.6bcdB1 | 126.9±41.4aB1 | 3.6±0.6dA1 | 0.8±0.2bA1 |
T3 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.7±0.9aA1 | 2.8±0.9aA1 | 4.2±1.4bA1 | - | - | 3.2±0.3bA1 | 68.4±29.2aA1 | 1.2±0.3bA2 | 0.7±0.1aA2 |
3 | 2.4±0.5aC1 | 3.2±0.4aA1 | 3.4±1.7abA2 | - | - | 3.0±0.7abB1 | 119.1±62.0aA1 | 5.6±1.5bcdA1 | 0.9±0.1abA1 |
T4 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.5±1.1abA1 | 2.6±1.1abcA1 | 4.6±1.3bB1 | - | - | 3.2±0.3bAB1 | 46.1±16.2aB2 | 1.9±0.2bA2 | 0.6±0.1aAB2 |
3 | 1.9±0.6bcdB2 | 3.0±0.6aA1 | 3.8±1.6abB1 | 6.0±4.9ab | - | 2.9±0.6bcdB1 | 152.6±40.4aA1 | 11.2±5.2abA1 | 0.8±0.1bA1 |
T5 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 1.9±1.2bB1 | 2.6±0.9abB1 | 15.0±10.2aA1 | - | 5.4±3.5aA1 | 67.1±36.8aA2 | 6.4±2.5aA1 | 0.2±0.1cC2 |
3 | 2.3±0.6abB1 | 2.9±0.5aA1 | 2.7±1.6cB2 | - | - | 2.6±0.6cdA1 | 132.5±30.0aAB1 | 8.5±3.4abcdA1 | 1.1±0.2aA1 |
T6 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.7±0.7aAB1 | 2.3±1.2bcdB1 | 4.6±1.5bA1 | - | - | 3.2±0.3 bA1 | 62.2±26.4aA1 | 1.4±0.3bA2 | 0.5±0.0abC1 |
3 | 1.6±0.5dC2 | 2.8±0.6aA1 | 3.3±1.6bcB2 | 5.1±1.1bc | - | 2.6±0.5dB2 | 154.9±86.6aA1 | 6.8±1.3bcdA1 | 0.9±0.4abA1 |
T7 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.5±1.1aA1 | 2.5±1.0abcA1 | 4.5±1.3bB1 | - | - | 3.2±0.4bB1 | 51.9±17.0aB2 | 1.5±0.3bB1 | 0.6±0.1aB2 |
3 | 2.3±0.5abB1 | 2.9±0.6aA1 | 3.3±1.5bcB2 | 4.9±0.4bc | - | 2.8±0.6bcdB2 | 129.8±26.1aA1 | 12.4±8.6abcA1 | 0.9±0.1abA1 |
T8 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.7±0.8 aA1 | 2.4±1.0abcB2 | 6.5±3.0bA2 | - | - | 3.9±0.8abAB1 | 64.9±18.0aA2 | 2.3±0.7abA2 | 0.4±0.1bcB2 |
3 | 2.5±0.5 aB1 | 3.3±0.7aA1 | 4.1±1.8aA1 | 7.5±0.6a | - | 3.3±0.7aA1 | 145.5±58.9aA1 | 14.4±6.6aA1 | 0.8±0.1bA1 |
T9 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.3±1.0abA1 | 2.1±1.3cdB1 | 4.2±1.6bA1 | - | - | 2.9±0.4bB1 | 40.0±12.8aB2 | 1.5±0.3bA2 | 0.5±0.2abA2 |
3 | 2.1±0.4abcB1 | 2.7±0.4aB1 | 3.5±1.4abB2 | - | - | 2.8±0.6bcdB1 | 175.1±28.5aA1 | 4.1±1.2cdA1 | 0.8±0.1bA1 |
A. mangium | T1 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.8±0.3abcAB1 | 2.7±0.6abB1 | 3.6±0.4aB1 | - | - | 3.0±0.2abB2 | 33.4±8.0bcB1 | 3.1±0.5cdB1 | 0.8±0.2bA1 |
| 3 | 2.6±0.7bB1 | 3.1±0.2abA1 | 4.5±0.9abA1 | - | - | 3.4±0.2bA1 | 81.0±38.5abcB1 | 3.8±2.2aB1 | 0.7±0.1abcA1 |
T2 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.2±0.3abA1 | 3.0±0.3aA1 | 3.3±0.1abA2 | - | - | 3.2±0.2aA2 | 35.1±9.7bcC2 | 1.9±0.2dB1 | 0.9±0.1bA1 |
| 3 | 3.9±0.5abA1 | 3.1±0.3abA1 | 4.0±0.2bcA1 | - | - | 3.7±0.1abA1 | 91.2±35.6abB1 | 1.8±0.7bB1 | 0.8±0.1abA1 |
T3 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.7±0.3bcA2 | 2.2±1.2bA1 | 3.4±0.4abB1 | - | - | 2.8±0.3bB2 | 46.4±15.7abA1 | 2.0±0.6cdA1 | 0.7±0.4bA1 |
| 3 | 4.2±0.3aB1 | 2.9±0.4abA1 | 3.5±0.5cA1 | - | - | 3.5±0.2abA1 | 35.0±20.0cB1 | 1.1±0.3abB1 | 0.9±0.2aAB1 |
T4 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.4±0.5cA1 | 2.6±0.3abA1 | 4.0±0.1aC2 | - | - | 3.0±0.2abB2 | 43.2±16.2abcB1 | 5.9±2.2abA1 | 0.7±0.1bA1 |
| 3 | 3.2±0.9abA1 | 3.0±0.2abA1 | 5.0±0.7aA1 | - | - | 3.8±0.2aA1 | 41.7±13.5cB1 | 2.2±0.4abB2 | 0.6±0.1bcB1 |
T5 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.4±0.4aA1 | 3.3±0.4aA1 | 2.7±0.7bB2 | - | - | 3.1±0.4abA1 | 27.1±6.9cB1 | 2.0±0.6cdA1 | 1.3±0.2aA1 |
| 3 | 3.5±0.8abA1 | 2.6±0.5bA1 | 4.7±1.1abA1 | - | - | 3.6±0.5abA1 | 54.1±52.8bcB1 | 1.7±0.6bB1 | 0.6±0.3bcA2 |
T6 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.4±0.5cB1 | 2.7±0.2abA1 | 3.3±1.0abB1 | - | - | 2.8±0.2abB2 | 44.2±16.2abcA1 | 3.0±1.9cdA1 | 0.9±0.3bB2 |
| 3 | 3.0±1.4abB1 | 2.9±0.3abA1 | 4.5±0.2abA1 | - | - | 3.4±0.3bA1 | 49.9±27.1bcB1 | 1.4±0.0bB1 | 0.7±0.1abcA1 |
T7 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 3.1±0.7abA1 | 2.8±0.2abA1 | 3.4±0.4aC2 | - | - | 3.1±0.3abB2 | 47.8±8.3abB2 | 4.1±1.5bcA1 | 0.8±0.1bA1 |
| 3 | 3.9±1.0abA1 | 2.9±0.1bA1 | 5.1±0.1aA1 | - | - | 4.0±0.4aA1 | 94.0±34.7abA1 | 1.5±0.1bB2 | 0.6±0.0cB2 |
T8 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.6±0.3bcA1 | 2.7±0.3abAB1 | 3.6±0.4aB2 | - | - | 3.0±0.3abB2 | 56.2±12.0aA2 | 6.4±2.5aA1 | 0.8±0.1bA1 |
| 3 | 3.2±0.8abB1 | 3.2±0.4abA1 | 4.2±0.3bcA1 | - | - | 3.5±0.1abA1 | 91.1±24.1abA1 | 1.5±0.2bB2 | 0.8±0.1abcA1 |
T9 | 0 | BDL | BDL | BDL | - | - | BDL | BDL | - | - |
| 1 | 2.7±0.3bcA1 | 3.1±0.1aA1 | 3.4±0.4aB2 | - | - | 3.0±0.1abAB2 | 53.8±9.1aAB2 | 3.8±0.6cdA1 | 0.9±0.1bA1 |
| 3 | 3.0±1.0abB1 | 3.5±0.5aA1 | 4.5±0.3abA1 | - | - | 3.6±0.4abA1 | 123.9±23.0aB1 | 1.6±0.1bB2 | 0.8±0.1abcA1 |
Values followed by the same letter did not significantly differ; lower case letters show indicate the difference of values in accumulation and translocation index among treatments within the same plant species and growth period (LSD, p < 0.05); capital letters indicate the difference of values in accumulation and translocation index among plant species within the same treatment (LSD: p < 0.05); and numbers indicate the difference of values in accumulation and translocation index among growth periods within the same plant and treatment. |
After harvest, the descending order of Cd accumulation in the plant tissues was generally as follows: leaves > roots > stems for jatropha and roots > stems ≈ leaves for cassava and acacia, respectively. Cd concentrations in roots were higher in acacia across all treatments (3.5 to 5.1 mg kg−1), whereas cassava and jatropha had lower accumulation with narrower ranges (2.7 to 4.1 mg kg−1 and 2.2 to 3.9 mg kg−1, respectively). All amended treatments showed a decrease in Cd accumulation by the roots of cassava to some extent, which could be attributed to the dilution effects of Cd concentration in root tissues and plant biomass. Furthermore, T5 treatment resulted in the largest decrease after three months of growth, which was approximately 5.6 times lower than the first month of growth (p < 0.05). Higher GRDB values in this crop plant species were most likely due to increased plant biomass, which decreased Cd concentrations in roots. All soil amendments increased Cd accumulation by shoots and roots in jatropha and acacia by 1.3 to 1.7 times and 1 to 1.7 times, respectively. Cadmium levels in soil have been demonstrated in numerous studies to rise with time, leading Cd levels in plant tissues to rise as well28. Many studies have also demonstrated that jatropha can be used as an accumulator for a variety of heavy metals; nevertheless, it is an unsuitable accumulator for all heavy metals because it accumulates some heavy metals at extremely low quantities in shoots. Furthermore, other reports claimed that this crop plant may absorb and accumulate substantial Cd concentrations in its roots (3.2 to 8.6 mg kg−1). This might indicate the effects of organic amendments on heavy metal stability in contaminated soil29. In this study, shoots of jatropha showed roughly 1 to 2.6 times higher Cd concentrations than roots when Cd concentrations were compared between plant tissues from all treatments. Plants in the T2, T4, and T9 treatments, on the other hand, showed somewhat greater Cd levels in their roots than in their shoots.
The effects of different organic amendments on Cd accumulation were linked to the physicochemical properties of soils. For example, adding animal manure and biochar to soil reduced Cd mobility and enhanced Cd stabilization in soil because the amendments increased Cd sorption by increasing soil pH and CEC, resulting in decreased Cd bioavailability and translocation in plant tissues30. In this study, leonardite has a low pH (2.6) and a high OM (20.1%); however, it has the potential to decrease Cd mobility because OM has the potential to produce organic ligands that bind heavy metal ions to the surface of soil colloid and form stable complexes1. Compared with other treatments, SLBM in the T3 treatment for acacia exhibited remarkably low Cd concentrations in the roots and stems (3.5 mg kg−1 and 2.9 mg kg−1, respectively); nevertheless, the greatest Cd concentration (4.2 mg kg−1) was found in the leaves (p < 0.05). When the Cd concentrations in whole plant tissues of the study plants were considered, acacia and cassava showed remarkably low Cd concentrations in T3 treatment (3.5 mg kg−1 and 3 mg kg−1, respectively), which followed a pattern similar to the Cd uptake values (35 mg plant−1 and 119.1 mg plant−1, respectively). The T8 treatment, on the other hand, had the lowest Cd uptake value for jatropha (127.8 mg plant−1), as its value was based on Cd content and biomass production of the whole plant tissue. SLVC in T4 treatment for acacia substantially elevated Cd concentrations in roots (5 mg kg−1; p < 0.05); although having a high OM content (9.9%). This might be because leonardite application reduces soil pH, as seen by an acidic soil in the T4 treatment (pH 5.5), resulting in increased Cd mobility in the soil and bioavailability. Despite the fact that BMVC had soil pH near neutral (pH 6.8) and high OM content (9.6%), the Cd concentration in the roots of acacia was greatest in the T7 treatment (5.1 mg Cd kg−1; p < 0.05). To reach the considerably low Cd concentrations in plant tissues found in the T3 treatment, soil pH may need to be adjusted to a slightly alkaline level. However, high OM contents (8.6%) in T3 treatment might be a key factor in reducing the bioavailability of the study plant. If Cd remediation is the main goal, BMBM in T9 treatment may be the best option, because all study plants showed substantial Cd uptake values of 187.9 mg plant−1, 175.1 mg plant−1, and 123.9 mg plant−1 for jatropha, cassava, and acacia, respectively.
Jatropha seeds in the field had to wait for roughly 2 to 3 m (height) for harvesting, which is similar to the time frame in this pot study. However, jatropha seeds were only found in T2 and T4 treatments. After harvest, jatropha seeds have been discovered, which are presumed to be edible plant parts; nevertheless, seeds of jatropha are often reported to be toxic. In this pot study, the bone meal in the T2 treatment constituted a suitable soil amendment for promoting growth until seed production. The ability of cassava roots to produce and accumulate starch is dependent on the harvesting period, which is often long or approximately 9 to 12 months in agricultural areas in Thailand. Cassava tubers were found in many pot treatments such as T2, T4, T6, T7, and T8, indicating that many local soil amendments can be applied to promote the growth and production of cassava. However, they were young tubers that could not yet be consumed. Cadmium concentrations in those edible plant parts were similarly found to be low; however, they were higher than the CODEX Alimentarius Commission, Joint FAO/WHO Food Standard Program’s standard threshold (> 0.4 mg kg−1)31.
Phytomanagement of Cd by the study plants. All of the plants examined under various treatments had TF values < 1, with the values changing slightly from the first to the third month of growth (p > 0.05) (Table 3), indicating that Cd was retained in plant tissues from roots to shoots. This may point to a characteristic of the excluder phenotype that makes it suitable for phytostabilization14. From the first to the third month of growth, cassava exhibited 1.6 to 6.3 times higher BCFR values, but jatropha and acacia had lower BCFR values (Table 3). In this study, BCFR values for all study plants from all treatments were typically > 1. Furthermore, the TF value for jatropha in the T5 treatment after harvest was > 1, but the BCFR value was low (0.8). According to related findings, jatropha is a perennial bioenergy crop that can be used for phytoextraction32. This perennial plant cultivated in mining soil mixed with peat moss translocated large amounts of metals from the roots to the aerial portions, which is a crucial characteristic of accumulator and hyperaccumulator crop plants33. However, jatropha in this study cannot be considered a hyperaccumulator of Cd because their TF values are generally less than one and their BCFR values are greater than one, while their Cd accumulation levels did not meet Baker and Brook’s criteria34, which require Cd levels in shoots to be greater than 100. Based on the ability for Cd accumulation in roots or tubers by the study plants, cassava and acacia were classified as Cd excluders, indicating that these plants can avoid importing metals to aerial parts. However, cassava peels may be the primary storage organ for heavy metals such as Pb35.
Plants suited for phytomanagement in heavy metal-contaminated areas may not have a significant capacity to accumulate high levels of heavy metals, but they should have benefits as a product rather than edible purposes. According to Robinson et al.36, phytomanagement strategy is a combination of using the benefits of phytoremediation and crop production. The potential bioenergy crops or non-edible crops, for example, can uptake and accumulate heavy metals in various plant organs; yet, plant tissues and crude extracts have diverse benefits for multi-purposes such as biofuel, fiber, paper and wood. Cassava is another appealing bioenergy crop for the reclamation of metal-polluted soils because this tuber crop is easy to cultivate in tropical and subtropical areas, and cassava tubers contain a high content of starch that could be commercially used as a renewable feedstock to produce ethanol fuel for transportation37. Because jatropha has advantageous properties like quick propagation, rapid growth, and drought tolerance, it can be widely grown in various locations globally38. This crop species offers a great promise for long-term industrial application as a multi-purpose plant whose components could be used as fertilizer, insecticide, soap, medicine, and energy. Despite the fact that cassava or jatropha is not a non-hyperaccumulator, they are non-food bioenergy crops that are grown in a variety of harsh environments, including heavy metal-contaminated areas37. Jatropha demonstrated a great capacity for phytoremediation of several heavy metals (iron (Fe), aluminum (Al), Cr, manganese (Mn), and Cu) from fly ash in greenhouse studies, as it could increase heavy metal uptake by 117% in the roots, 62% in the stems, and 86% in the leaves, respectively37,39. Jatropha and cassava, which may be grown in heavily Cd-contaminated soils and used for renewable energy or biodiesel, are considered suitable for long-term use and rehabilitation of heavy metal-contaminated lands37,40.
The plant growth data of acacia compared with that of other study plants, revealed that this dicotyledon perennial plant had the highest dry biomass and GRDB, as well as low Cd accumulation and no toxicity effects. Because acacia, an N-fixing plant, can fix atmospheric N2 in symbiotic root nodules and it does not have any major pest concerns, and increased plant growth can be expected41. After harvest, acacia wood is very heavy, hard, robust, and durable, meaning it can be used for furniture, doors, and window frames42. Perennial bioenergy crops require fewer nutrient inputs and have higher lignin and cellulose content than annual crop biomass43. Therefore, it could be considered that acacia can be cultivated over a large area such as in a contaminated area and that it has substantial biomass, making it more suitable for use as an energy plant in Cd-contaminated lands.