Plants and treated biochar sharply cut heavy metals in maize pot study

The combined treatment lowered metals in contaminated soil and maize grain while increasing growth and grain yield.

Editorial illustration — not from the study.

Researchers tested three plants—Indian mustard, vetiver grass and sunflower—alongside a treated biochar, both separately and in combination, during the first phase of a 120-day pot experiment. The second phase assessed maize grown in the treated soil and compared it with a control.

The combined treatment reduced cadmium, lead, arsenic and nickel in the soil by 93.8%, 94.3%, 94.2% and 94.1%, respectively. Maize plants were taller and produced more biomass and grain in the treated soil, while concentrations of heavy metals in the grain fell by 98.0–98.5% and remained below international food safety standards.

What the treatment changed

The integrated plant-and-biochar treatment improved several measured soil properties. Soil porosity increased by 5.8%, water-holding capacity by 12.9%, organic carbon reached 1.10%, and cation exchange capacity reached 12.0 cmol kg⁻¹.

It also reduced soil concentrations of cadmium by 93.8%, lead by 94.3%, arsenic by 94.2% and nickel by 94.1%. In maize grown afterward, plant height increased from 103 ± 2 cm to 137 ± 3 cm, biomass from 305 ± 5 g to 528 ± 8 g, and grain yield from 4.2 ± 0.2 to 7.1 ± 0.3 tonnes per hectare—a reported increase of 69.0%.

Nitrogen, phosphorus and potassium uptake also increased. Antioxidant enzyme activity improved, while malondialdehyde, a measure of oxidative damage, decreased by 69.1%. Heavy-metal concentrations in maize grain fell by 98.0–98.5% and were reported to remain below international food safety standards.

Why cleaner soil matters

Heavy metals in farmland can reduce crop productivity and create food-safety concerns. In this pot experiment, combining plants with the treated biochar reduced the measured metals in soil and maize grain while improving soil properties and maize yield. The findings support further assessment of this combined approach for contaminated agricultural soils, but they do not establish how it would perform under field conditions.

Evidence and limits

The evidence comes from a 120-day, two-phase pot experiment. The first phase compared three phytoremediation plants, the treated biochar and their combination; the second grew maize in treated soil and compared it with a control. The abstract reports soil, plant-growth, yield, nutrient, enzyme and grain-metal results, but does not provide field-trial evidence. Results from pots may not represent performance across different soils, climates or farm conditions, and the study duration was 120 days.

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