A recent study published in Environmental Pollution investigated how the application of peanut straw biochar affects soil pH and cadmium (Cd) availability in paddy soils, and how these changes influence Cd absorption in various rice varieties. The researchers found that soil pH increases during submergence due to reduction reactions involving iron, manganese, and sulfate, which reduces available Cd. Conversely, drainage decreases soil pH and increases Cd availability due to the oxidation of iron, manganese, and sulfur compounds.

The application of peanut straw biochar was shown to stabilize soil pH, preventing its decline during drainage and thus reducing the availability of Cd. This effect was observed to decrease Cd absorption in the roots, shoots, and grains of rice plants. Notably, indica rice varieties absorbed more Cd than japonica varieties, and Cd-sensitive varieties accumulated more Cd than tolerant ones.

Overall, biochar application resulted in lower Cd levels in rice grains, bringing them below the national food safety limit of 0.2 mg/kg. The study suggests that using biochar in combination with planting japonica rice varieties in Cd-contaminated soils can effectively mitigate Cd uptake, thereby protecting human health from Cd toxicity. This research highlights the potential of biochar as a practical solution for managing heavy metal contamination in rice cultivation.