Cadmium contamination in agricultural soils poses a significant threat to global food safety, crop yields, and human health. Rice plants possess a strong physiological tendency to absorb and accumulate cadmium from soil, allowing the toxic heavy metal to readily migrate into edible grains. Traditional soil amendments often struggle to simultaneously lock up heavy metals and provide sufficient essential nutrients required for robust crop growth. To address these dual challenges, researchers investigated the application of micro-nanoscale bone char derived from waste pork bones pyrolyzed at 400 degrees Celsius and 600 degrees Celsius followed by ball-milling. In a comprehensive 140-day full-life-cycle greenhouse study published in the journal BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, authors Anqi Liang, Yi Hao, Zeyu Cai, Weitao Wu, Xinxin Xu, Weili Jia, Yini Cao, Lanfang Han, Luca Pagano, Marta Marmiroli, Elena Maestri, Nelson Marmiroli, Jason C. White, Chuanxin Ma, and Baoshan Xing evaluated how micro-nanoscale bone char influences rice productivity, grain quality, metal transport, and rhizosphere genetics in cadmium-polluted soil.

The full-life-cycle trial revealed that micro-nanoscale bone char pyrolyzed at 600 degrees Celsius increased rice grain yield per pot by 49.72 percent compared to the cadmium-only control treatment. Similarly, bone char pyrolyzed at 400 degrees Celsius enhanced the number of effective tillers per pot by 23.08 percent over cadmium-exposed plants. Both bone char treatments drastically restricted cadmium transport into edible plant parts, lowering cadmium levels in polished rice by 65.0 to 68.7 percent, in bran by 63.7 to 66.7 percent, and in hulls by 74.5 to 75.0 percent.

Soil chemistry analyses indicated that bone char amendments effectively fixed cadmium within the soil matrix, notably during the aerobic growth phase where acid-soluble cadmium proportions decreased by 31.56 to 35.51 percent. Concurrently, reducible cadmium proportions increased by 75.02 to 84.74 percent, confirming a transition toward less bioavailable metal forms. Bone char application also raised soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More to approximately 6.49 and increased total soil phosphorus levels to nearly 3.82 times those of untreated controls, significantly boosting plant-available acid-soluble phosphorus.

Grain metabolomic profiling revealed that micro-nanoscale bone char positively altered the nutritional profile of mature rice grains. Bone char treatment slowed down the metabolic conversion of carbohydrates and branched-chain amino acids into simple sugars or polyols, protecting grains against quality degradation usually triggered by heavy metal stress. Furthermore, treatment at 600 degrees Celsius significantly enriched linoleic acid metabolic pathways in the grains.

Metagenomic analysis of the soil rhizosphere demonstrated that bone char reshaped soil microbial communities across different irrigation phases, enhancing the relative abundance of key carbon-, nitrogen-, and phosphorus-cycling phyla such as Actinomycetota and Cyanobacteriota. Bone char treatments significantly upregulated crucial phosphorus-cycling genes, including phoB and phoR, while increasing the overall complexity and connectivity of the soil phosphorus gene network. A financial cost-benefit assessment confirmed that applying micro-nanoscale bone char delivered a net economic benefit of 60,215.47 Chinese Yuan per hectare by recovering lost yield and ensuring grain safety, highlighting micro-nanoscale bone char as a highly effective, sustainable amendment for heavy-metal-contaminated farmlands.

Source: Liang, A., Hao, Y., Cai, Z., Wu, W., Xu, X., Jia, W., Cao, Y., Han, L., Pagano, L., Marmiroli, M., Maestri, E., Marmiroli, N., White, J. C., Ma, C., & Xing, B. (2026). Micro-nanoscale bone char alters Cd accumulation and rhizosphere functional genes to enhance rice yield and quality. Biochar, 8(1), 45.