Long term biochar boosts sugarcane growth, soil health, and carbon savings in five year field trial

A five year field study in southern China shows that a single application of biochar combined with reduced nitrogen fertilizer can boost sugarcane growth, reshape soil life around the roots, and cut carbon dioxide emissions from the field for years without additional fertilization.

New way to grow more sugarcane with less fertilizer

Sugarcane provides about 90 percent of China’s sugar, yet farmers often rely on heavy nitrogen fertilization that wastes nutrients and harms soil and water quality. In the new study, researchers tested whether adding biochar, a charcoal like material made from plant waste, could help sugarcane use nitrogen more efficiently and keep soils productive over the long term.​

“Biochar offers a promising way to turn agricultural waste into a tool that supports crops, stores carbon in the soil, and reduces the need for synthetic fertilizer,” said corresponding author Lei Zhang of the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences.​

Five year field experiment

The team set up a five year field trial in a continuously cropped sugarcane plantation with two treatments. One group of plots received conventional basal fertilizer, while another group received the same basal fertilizer plus a one time application of biochar made from biomass residues.​

After the first year, no additional fertilizer was added to any plots, allowing the researchers to track how the initial biochar and nitrogen treatment affected plants, soil, microbes, and carbon dioxide emissions over time. They measured sugarcane growth, root development, soil chemistry, microbial communities, and rhizosphere metabolites at the end of the five year period.​

Stronger plants, finer roots

Compared with plots that received fertilizer alone, the biochar plots produced taller sugarcane with thicker stems and greener leaves, as reflected in a higher nitrogen balance index. Plant height, stem diameter, and leaf nitrogen balance index increased by 10.81 percent, 25.79 percent, and 33.90 percent, respectively.​

Interestingly, total root volume and average root diameter decreased by 31.06 percent and 21.53 percent, indicating a shift toward finer, more efficient roots that can explore soil more effectively. The authors suggest that this finer root system, supported by an improved soil environment, helped sugarcane maintain strong aboveground growth despite the absence of ongoing fertilization.​

Soil and microbes form a lasting support system

Biochar treatment raised the pH of the rhizosphere soil and substantially increased total potassium, while some other nutrient measures such as soil organic matter and available potassium declined relative to the fertilizer only control. Even with these shifts, the plots with biochar retained a clear advantage in long term soil fertility and nutrient use efficiency.​

The biochar plots also showed higher abundances of beneficial bacterial groups in the rhizosphere, including Leptospirillum, Terrimonas, Actinobacteriota, Sphingobacteriia, Chitinophaga, Cyanobacteriia, and Lechevalieria. Metabolites in the root zone were enriched in key pathways related to steroids, fatty acyls, purine nucleotides, indoles, carboxylic acids, and other compounds that can influence plant growth and stress responses.​

Cutting carbon dioxide emissions from fields

Beyond crop performance, the researchers monitored carbon dioxide emissions from the soil to understand how the treatments affected greenhouse gas release. Fields that received biochar with reduced nitrogen had lower carbon dioxide emissions than fields that received fertilizer alone, supporting the idea that biochar can act as a long lasting carbon sink while moderating soil respiration.​

“Sugarcane roots, surrounding soil, and microorganisms form a tightly connected ecological network,” said co corresponding author Chaohua Hu of Fujian Agriculture and Forestry University. “Our results show that even five years after a single application, combining reduced nitrogen fertilizer with biochar continues to support sugarcane growth and soil health while reducing carbon emissions from the field.”​

Implications for sustainable agriculture

The findings suggest that co applying biochar with reduced nitrogen fertilizer could help sugarcane farmers maintain yields, lower fertilizer inputs, and contribute to climate goals in the same fields over many years. Because biochar can be produced from agricultural and forestry residues, the approach also offers a way to add value to local biomass resources while closing nutrient and carbon loops.​

The authors note that similar strategies may be useful for other crops grown in acidic or intensively fertilized soils and that long term trials are essential to understand how biochar, roots, and microbes interact over time. This work provides a practical reference for designing fertilization and soil improvement practices that align productivity with environmental sustainability in major sugar producing regions.​

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Journal Reference: Jia, Y., Zhang, L., Pang, Z. et al. Effects of biochar on sugarcane growth and rhizosphere microecosystem under reduced nitrogen fertilization: a 5‑year field experiment study. Biochar 7, 121 (2025). 

https://doi.org/10.1007/s42773-025-00519-2  

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About Biochar

Biochar is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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