Nitrogen fertilizer is essential for modern agriculture, but a substantial share of applied nitrogen can escape from farmland rather than reaching crops. One major pathway is ammonia volatilization, which wastes valuable fertilizer and contributes to air pollution and broader environmental problems.
Researchers in China have now found that adding both biochar and dicyandiamide to organic fertilizer could provide a more effective way to keep nitrogen in the agricultural system. In a two-year rice and wheat rotation experiment, the combined fertilizer reduced cumulative ammonia losses by 27.1% compared with conventional urea fertilization, while maintaining crop productivity despite a 30% reduction in mineral nitrogen input.
"Reducing fertilizer input is only useful if farmers can maintain crop production at the same time," said corresponding author Haijun Sun. "Our results suggest that combining biochar with dicyandiamide in organic fertilizer can help balance these goals by retaining nitrogen, limiting ammonia losses, and supporting crop growth."
The researchers conducted a greenhouse soil-column experiment covering two complete rice and wheat rotations from 2022 to 2024. They compared conventional urea fertilization with three treatments that used less mineral nitrogen: conventional organic fertilizer, biochar-amended organic fertilizer, and organic fertilizer containing both biochar and dicyandiamide.
The biochar and dicyandiamide treatment proved the most consistent. Across the full two-year rotation, it was the only organic fertilizer treatment that significantly reduced cumulative ammonia emissions compared with the conventional urea treatment. Compared with conventional organic fertilizer, adding biochar alone reduced cumulative ammonia volatilization by 5.9%, while adding both biochar and dicyandiamide achieved a much larger reduction of 33.6%.
The researchers linked these improvements to better regulation of nitrogen in soil and the water covering the rice crop. Biochar helped moderate ammonium concentrations and pH, two important controls on ammonia volatilization. Dicyandiamide, a nitrification inhibitor, was associated with altered nitrogen transformation patterns.
Microbial analysis also revealed changes in soil bacterial communities. Biochar-containing fertilizers reduced the abundance of Nitrospirota, a group associated with nitrite oxidation, suggesting that the amendments may influence nitrification-related microbial niches. The authors caution, however, that the microbial analysis was based on taxonomic profiling and does not directly demonstrate specific microbial functions.
Importantly, the environmental gains did not come at the expense of another major greenhouse gas. Cumulative nitrous oxide emissions showed no significant differences among the fertilizer treatments. The combined biochar and dicyandiamide treatment also maintained rice yields at levels comparable with conventional fertilization, whereas conventional organic fertilizer and biochar-only organic fertilizer reduced rice grain yields.
The approach may also offer an economic incentive. Using Monte Carlo simulations, the researchers estimated that the combined treatment could generate potential benefits of approximately 36,600 CNY per hectare per year under the experimental conditions, reflecting reduced nitrogen-related environmental and health costs, fertilizer savings, and other economic factors.
The researchers emphasize that the study was conducted in controlled soil columns rather than commercial fields. Field-scale studies are therefore needed to determine how well the approach performs under variable weather, soil, and farm management conditions.
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Journal Reference: Huang W, Wang L, Gong X, Bian R, Lu X, et al. 2026. Ammonia mitigation and economic gains from dicyandiamide and biochar-amended organic fertilizer: a 2-year rice-wheat rotation study. Agricultural Ecology and Environment 2: e019 doi: 10.48130/aee-0026-0016
https://www.maxapress.com/article/doi/10.48130/aee-0026-0016
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Agricultural Ecology and Environment (e-ISSN 3070-0639) is a multidisciplinary platform for communicating advances in fundamental and applied research on the agroecological environment, focusing on the interactions between agroecosystems and the environment. It is dedicated to advancing the understanding of the complex interactions between agricultural practices and ecological systems. The journal aims to provide a comprehensive and cutting-edge forum for researchers, practitioners, policymakers, and stakeholders from diverse fields such as agronomy, ecology, environmental science, soil science, and sustainable development.
