Arsenic contamination is a growing global threat that harms crops and threatens human health. Now, scientists have found an eco-friendly solution to reduce arsenic’s toxic impact on rice, a staple food for more than half the world’s population. A recent study from Jiangxi Agricultural University, China, reveals that combining biochar—a charcoal-like substance made from plant material—and melatonin—a natural plant hormone—can dramatically improve rice growth and yield in arsenic-polluted soil.
This breakthrough brings hope for safer and more productive rice cultivation, especially in areas where arsenic-contaminated water and soil pose a serious challenge.
What is Arsenic Contamination and Why Does It Matter?
Arsenic is a toxic element naturally present in soil and water but its concentration has increased sharply due to human activities such as mining, industrial pollution, and excessive use of certain fertilizers. High arsenic levels in soil can be absorbed by crops like rice, entering the human food chain and causing health problems including cancer, cardiovascular issues, and neurological disorders affecting millions worldwide.
Arsenic toxicity harms plants by:
- Damaging roots and leaves
- Reducing photosynthesis and chlorophyll production
- Increasing oxidative stress that leads to cell damage
- Decreasing water retention and nutrient uptake
- Cutting crop yield and quality
Finding effective ways to reduce arsenic uptake by crops while boosting their growth is crucial for food safety and agricultural sustainability.
How Biochar and Melatonin Work Together
Biochar is produced by heating organic materials such as coconut fiber without oxygen, resulting in a porous, carbon-rich substance. When added to soil, biochar:
- Absorbs and binds arsenic, reducing its availability to plants
- Improves soil structure and nutrient retention
- Supports beneficial microorganisms
Melatonin, a natural hormone found in plants, helps activate stress tolerance mechanisms by:
- Enhancing antioxidant defense to fight harmful reactive oxygen species caused by arsenic
- Regulating gene activity related to stress and nutrient uptake
- Promoting root and shoot growth
The study tested rice plants grown under arsenic stress with biochar (2% soil concentration), melatonin foliar spray (100 µM), and a combination of both.
Key Findings: Dramatic Improvement in Rice Growth and Health
The arsenic alone severely stunted rice growth, cutting root length by over 50%, reducing biomass and grain yield by about 35%, and causing chlorophyll loss of up to 90%. Plants also showed high levels of harmful oxidative molecules, indicating cell damage.
Adding biochar or melatonin individually improved growth and reduced arsenic uptake, but the combined application had synergistic and significantly greater benefits:
- Soil arsenic content decreased by 74%
- Root and shoot arsenic concentrations dropped by more than 50%
- Rice root length, biomass, and grain yield increased by 22-48%
- Chlorophyll levels and leaf water content increased by 40-70%
- Antioxidant enzyme activities rose by over 55%, reducing oxidative stress markers dramatically
- Important nutrient levels like nitrogen, phosphorus, potassium, calcium, and magnesium increased in the plant, supporting healthier growth
- Genes linked to arsenic uptake were strongly downregulated, while antioxidant and melatonin synthesis genes were upregulated
Table 1: Impact of Treatments on Rice Growth and Yield under Arsenic Stress
| Treatment | Root Length (cm) | Plant Height (cm) | Grain Yield (g/pot) | Biomass Yield (g/pot) | Arsenic in Roots (mg/kg) | Arsenic in Shoots (mg/kg) |
|---|---|---|---|---|---|---|
| Control (No As) | 35.04 | 101.67 | 18.06 | 156.81 | 0 | 0 |
| Arsenic Only | 14.74 | 79.33 | 13.36 | 117.65 | 46.00 | 25.15 |
| Arsenic + Biochar | 28.32 | 91.00 | 15.67 | 135.67 | 28.00 | 14.50 |
| Arsenic + Melatonin | 16.63 | 86.00 | 14.71 | 127.33 | 31.00 | 17.00 |
| Arsenic + Biochar + Melatonin | 31.31 | 97.33 | 20.93 | 148.31 | 20.53 | 9.26 |
Table 2: Effect on Soil Arsenic and Nutrient Availability After Treatment
| Treatment | Soil Arsenic (mg/kg) | Soil pH | Soil Nitrogen (g/kg) | Available Phosphorus (mg/kg) | Available Potassium (mg/kg) |
|---|---|---|---|---|---|
| Control (No As) | – | 5.62 | 1.72 | 53.70 | 128.63 |
| Arsenic Only | 54.46 | 5.58 | 1.12 | 35.43 | 92.27 |
| Arsenic + Biochar | 37.23 | 5.94 | 1.49 | 42.73 | 109.54 |
| Arsenic + Melatonin | 45.43 | 5.60 | 1.38 | 40.30 | 98.37 |
| Arsenic + Biochar + Melatonin | 31.27 | 6.12 | 1.61 | 45.50 | 119.26 |
What This Means for Farmers and Food Security
The combined use of biochar and melatonin provides a natural, cost-effective, and scalable way to:
- Reduce arsenic uptake by rice, making the grain safer for consumption
- Improve rice growth and yields even in contaminated soils
- Enhance soil health and fertility for sustainable farming
- Potentially reduce the need for harmful chemical interventions
This strategy can help vulnerable farmers grow more nutritious rice, safeguard public health, and contribute to global food security—especially in countries where arsenic contamination is widespread.
Next Steps and Recommendations
While promising, further studies are needed to test this approach across different soil types, climates, and arsenic contamination levels. Additionally, integrating biochar and melatonin treatments into existing agricultural practices will require training and support for farmers.
Reference: here
Other Interesting Articles:
