Cleaner Soil and Better Radish Growth with Treated Biochar

Jenn Hoskins
23rd May, 2024

Cleaner Soil and Better Radish Growth with Treated Biochar

Image Source: Natural Science News, 2024

Key Findings

  • The study by Nagasaki University tested biochar made from cypress wood, treated with calcium hydroxide, to reduce heavy metal contamination in soil
  • Calcium-treated biochar (TCBC) improved soil properties and was more effective than untreated biochar (UCBC) in enhancing plant growth and immobilizing heavy metals
  • TCBC significantly reduced the uptake of zinc and copper by radish plants, and lead uptake was undetectable after its application
Heavy metal contamination in soil is a pressing issue that compromises soil quality, plant growth, and food safety, impacting multiple United Nations Sustainable Development Goals (SDGs). Addressing this problem is crucial for ensuring human health and environmental sustainability. A recent study by Nagasaki University explores a novel solution to mitigate heavy metal contamination by using biochar derived from cypress wood, treated with calcium hydroxide (Ca(OH)2)[1]. The study investigates the effects of untreated cypress biochar (UCBC) and calcium-treated cypress biochar (TCBC) on soil properties and heavy metal uptake by radish plants (Raphanus sativus). Both types of biochar were introduced into pristine and contaminated soils at different rates (3%, 6%, and 9% by weight). The results showed that both UCBC and TCBC improved soil properties such as pH, electrical conductivity (EC), and organic matter (OM) content. However, TCBC demonstrated superior performance in enhancing plant growth and immobilizing heavy metals compared to UCBC. The enhanced chemical adsorption capacity of TCBC is attributed to the presence of nanosized precipitated calcium carbonate particles on its surface. These particles effectively immobilize heavy metals, reducing their bioavailability to plants. When applied at a 9% rate, TCBC significantly decreased the uptake of zinc (Zn) and copper (Cu) by radish roots and shoots. Specifically, Zn uptake in roots decreased by 55% (from 68.3 to 31.0 mg/kg), and in shoots by 37% (from 49.3 to 31.0 mg/kg). Similarly, Cu uptake in roots decreased by 40% (from 38.6 to 23.2 mg/kg), and in shoots by 39% (from 58.2 to 35.2 mg/kg). Notably, the uptake of lead (Pb) was undetectable after the application of TCBC. These findings align with previous research that highlights the challenges of heavy metal contamination in agricultural soils. For instance, a study on Chinese cabbage and radish grown in polluted farmlands showed that heavy metals like Cu, Zn, Pb, and cadmium (Cd) are taken up by plants at varying concentrations depending on the growth stage and type of vegetable[2]. Another study emphasized the phytoavailability of nickel (Ni) in contaminated soils and its accumulation in leafy vegetables, posing potential dietary toxicity risks[3]. Both studies underscore the need for effective soil remediation strategies to ensure food safety. The use of biochar for soil remediation is not new, but the specific approach of treating cypress biochar with calcium hydroxide to enhance its heavy metal immobilization capacity is innovative. Previous research has demonstrated the variability in metal content in polluted soils and the necessity of accurate analytical techniques to assess soil contamination[4]. The current study builds on this knowledge by offering a practical solution that not only improves soil properties but also significantly reduces heavy metal uptake by plants. Furthermore, the study's findings are relevant to the tea industry, where heavy metal contamination in soil can affect the safety of tea leaves. A survey of tea plantations in Yunnan, China, revealed that soil acidification increases the bioavailability of heavy metals, leading to their accumulation in tea leaves[5]. The application of TCBC could potentially mitigate such risks by immobilizing heavy metals in the soil, thereby reducing their transfer to tea plants. In conclusion, the study by Nagasaki University provides a promising solution for addressing heavy metal contamination in soils. By enhancing the chemical adsorption capacity of cypress biochar through calcium hydroxide treatment, the researchers have demonstrated significant improvements in soil properties and reductions in heavy metal uptake by radish plants. This approach not only supports sustainable agriculture but also contributes to food safety and environmental health. Future research should focus on the long-term effects and microbial interactions associated with TCBC application to further validate its efficacy and sustainability.

AgricultureEnvironmentPlant Science


Main Study

1) Heavy metal immobilization and radish growth improvement using Ca(OH)2-treated cypress biochar in contaminated soil.

Published 20th May, 2024

Related Studies

2) A field study on the dynamic uptake and transfer of heavy metals in Chinese cabbage and radish in weak alkaline soils.

Journal: Environmental science and pollution research international, Issue: Vol 23, Issue 20, Oct 2016

3) Nickel uptake in leafy greens from contaminated soil: an investigation into phytoavailability and health risk assessment using in vitro digestion model.

4) Monitoring metal pollution in soils using portable-XRF and conventional laboratory-based techniques: Evaluation of the performance and limitations according to metal properties and sources.

5) Transfer of heavy metals from soil to tea and the potential human health risk in a regional high geochemical background area in southwest China.

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