Straw-based biochar and smart irrigation help maize thrive with less water and fertilizer

A new study has revealed that the lasting effects of biochar depend strongly on the material it is made from, with straw-derived biochar offering clear advantages for maize productivity under limited-water conditions. The research, published in Biochar, shows that combining wheat-straw biochar with an alternate partial root-zone drying irrigation system can boost crop yield and resource efficiency for at least two growing seasons after a single biochar application.

Biochar, a carbon-rich material produced by heating plant residues, has long been recognized for improving soil fertility and structure. Yet most studies have focused on its immediate effects. Researchers from Northwest A&F University in China and the University of Copenhagen set out to understand how different biochar types continue to influence soil and plant performance over time.

In greenhouse experiments conducted in 2021 and 2022, the team compared softwood and wheat-straw biochar applied once to maize plants grown under three irrigation strategies: full watering, deficit irrigation, and alternate partial root-zone drying, in which only half of the root system is watered at a time. This alternating approach helps plants adapt to periodic drying while maintaining productivity.

The findings revealed strong contrasts between the two biochar types. Under water-saving irrigation, wheat-straw biochar enhanced total maize biomass by up to 30 percent, increased water use efficiency by 27 percent, and improved nitrogen use efficiency by about 10 percent compared with untreated soil. These benefits were linked to greater microbial activity and higher soil nitrogen availability, which stimulated root growth and nutrient uptake even under stress.

In contrast, softwood biochar initially reduced microbial respiration and nitrogen availability, leading to smaller root systems and lower yields in the first year. However, these negative effects gradually declined in the following season as the soil microbial community adapted to the woody biochar’s more stable carbon structure.

The study also confirmed that alternate partial root-zone drying irrigation itself significantly improved nitrogen mineralization and water use, particularly when paired with straw-based biochar. By promoting cycles of drying and rewetting, this irrigation method stimulated soil microbes to release nutrients and supported deeper, more efficient root systems.

“Our results show that one-time applications of straw-derived biochar can deliver multi-year benefits when combined with precision irrigation,” said lead author Heng Wan. “This approach helps maintain soil fertility and crop productivity while reducing water and fertilizer use.”

The researchers suggest that integrating crop-residue biochar with water-saving irrigation could form part of sustainable soil-water-nutrient management strategies in dryland agriculture. The findings provide valuable guidance for farmers and policymakers seeking to enhance food security and resource efficiency in regions facing growing water scarcity.

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Journal Reference: Wan, H., Hong, M., Fang, L. et al. Contrasting residual effects of different biochar types on maize nitrogen uptake, biomass accumulation, water and nitrogen use efficiency under alternate partial root-zone drying irrigation. Biochar 7, 115 (2025). https://doi.org/10.1007/s42773-025-00518-3  

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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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