Mineral nitrogen fertilizers have supported agricultural productivity for decades, but excessive application can cause soil acidification, inefficient nitrogen use, nutrient losses, and increased N₂O emissions. Organic manure is increasingly used to replace part of the mineral fertilizer input because it releases nitrogen gradually, adds carbon, and stimulates soil microorganisms. Nevertheless, its environmental effects are complex: manure can improve nutrient retention and soil structure, but readily available carbon and nitrogen may also promote microbial processes that generate N₂O. These uncertainties are particularly important in the acidic, organic-matter-poor red soils used for tobacco production, where the effects of different manure types on individual nitrogen-transformation and N₂O-production pathways remain insufficiently understood.
A study (DOI: 10.48130/nc-0026-0008) published in Nitrogen Cycling on 13 May 2026 by Zhengqin Xiong's team, Nanjing Agricultural University, shows that partial organic substitution strengthens soil nitrogen turnover while reducing cumulative N₂O emissions relative to mineral fertilizer alone.
The researchers conducted a randomized field experiment in Qujing, Yunnan Province, using four nutrient-management treatments: mineral nitrogen fertilizer alone (SN); commercial organic manure replacing 15% of mineral nitrogen (NC); farmyard manure replacing the same proportion (NF); and bio-organic manure inoculated with T. viride replacing 15% of mineral nitrogen (NT). After the tobacco harvest, soil from the upper 20 cm was collected for physicochemical analysis and laboratory incubation. To trace nitrogen movement, the team added either ^15N-labelled ammonium or ^15N-labelled nitrate to soil microcosms maintained at 25 °C and 60% water-filled pore space. Samples collected over 144 hours were analyzed for ammonium, nitrate, organic nitrogen, N₂O concentrations, and ^15N abundance. Gas chromatography and isotope-ratio mass spectrometry were used to distinguish N₂O originating from autotrophic nitrification, heterotrophic nitrification, denitrification, and co-denitrification. Quantitative PCR further measured genes involved in nitrification and denitrification, while statistical and correlation analyses connected soil properties, microbial functions, nitrogen transformations, and emissions. Compared with SN, all three organic treatments increased gross nitrate production from 6.00 to 6.43–7.43 mg N kg⁻¹ soil day⁻¹, ammonium production from 0.88 to 1.01–1.37 mg N kg⁻¹ soil day⁻¹, and ammonium consumption from 6.14 to 6.50–6.96 mg N kg⁻¹ soil day⁻¹. Farmyard manure produced the highest gross nitrate production and ammonium consumption rates, whereas bio-organic manure generated the greatest ammonium production and nitrate consumption. Autotrophic nitrification supplied 63.0%–74.8% of nitrate production and accounted for 62.6%–79.2% of ammonium consumption across the organic treatments. It also remained the largest source of N₂O, contributing 59.7%–65.4% of emissions, while co-denitrification contributed little. Despite stimulating nitrogen turnover, every organic treatment produced significantly lower cumulative N₂O emissions than mineral fertilizer alone, with emissions ranked SN > NF > NC > NT. The bio-organic treatment therefore showed the lowest emissions, although differences among the three organic treatments were not statistically significant. Because the tracer dose exceeded typical field nitrogen pools, the measured transformation rates represent potential rather than strictly in-field rates.
Overall, the study demonstrates that carefully designed organic substitution can intensify beneficial nitrogen cycling without increasing N₂O losses. Different manure products regulated individual pathways in distinct ways, but all reduced cumulative emissions compared with exclusive mineral fertilization. The results identify bio-organic manure as especially promising and show that fertilizer evaluation should consider not only total emissions but also the microbial pathways producing them.
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References
DOI
10.48130/nc-0026-0008
Original Source URL
https://doi.org/10.48130/nc-0026-0008
Funding information
This research was carried out with financial support from the Science and Technology Project of Yunnan Provincial Branch of China National Tobacco Corporation (2023530000241025) and from the National Natural Science Foundation of China (Grant No. 42377292).
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Nitrogen Cycling (e-ISSN 3069-8111) is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.