Grazing animals return most of the nitrogen they consume back to the land through urine and dung. In grasslands, these nutrient-rich patches can become hotspots for nitrous oxide, or N₂O, a powerful greenhouse gas and ozone-depleting substance. But what happens when urine and dung overlap in the same place, as often occurs where animals gather near shelters, water points, or resting areas?
A new field study published in Nitrogen Cycling provides an unexpected answer. Researchers found that combined yak urine and dung deposition in an alpine meadow on the Qingzang Plateau did not simply add together to create higher nitrous oxide emissions. Instead, overlapping patches showed an antagonistic effect, meaning the measured emissions were far below the theoretical sum of urine-only and dung-only patches.
"Our results show that excreta patches cannot always be treated as independent sources of greenhouse gas emissions," said corresponding author Yanjiang Cai. "In yak-grazed alpine meadows, the interaction between urine and dung can change the soil microbial processes that control nitrous oxide production and reduction."
The team conducted an in-situ field experiment in a typical alpine meadow on the Qingzang Plateau, a region that supports millions of yaks and contains vast areas of grazing grassland. The researchers compared four treatments: no excreta addition, yak urine application, yak dung application, and combined urine plus dung application.
The results confirmed that urine deposition was a much stronger driver of soil N₂O emissions than dung deposition. Cumulative emissions from urine-treated plots reached 295.82 g N ha⁻¹, more than four times the emissions from dung-treated plots, which reached 72.29 g N ha⁻¹. The researchers linked this difference to higher nitrogen availability, increased soil pH, and stronger nitrification activity following urine deposition.
However, the combined urine and dung treatment produced 296.45 g N ha⁻¹, nearly the same as urine alone. This was surprising because the theoretical additive value of urine plus dung was much higher. The team calculated a proportional change value of 0.84, indicating an antagonistic interaction rather than an additive or synergistic one.
The study suggests that the combined treatment may have created a balance between two competing processes. On one side, the added nitrogen and carbon could stimulate N₂O production. On the other side, the presence of dung may enhance the soil's capacity to reduce N₂O further to harmless nitrogen gas. Under the relatively dry conditions of the experiment, this balance may have prevented emissions from rising as much as expected.
"This finding is important for greenhouse gas accounting in grazing systems," Cai said. "If models assume that urine and dung emissions are simply additive, they may overestimate emissions from some alpine meadow environments."
The study also highlights the importance of soil moisture. By comparing their results with published studies from other regions, the authors found that combined urine and dung deposition tended to show stronger synergistic effects under wet conditions, while dry conditions were more likely to produce non-additive or antagonistic outcomes.
The findings provide new insight into how yak grazing affects nitrogen cycling and greenhouse gas emissions in fragile alpine ecosystems. They also suggest that more field-based studies are needed to improve emission models for livestock systems, especially in regions where animal behavior, soil moisture, and microbial processes interact in complex ways.
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Journal Reference: Fan B, Jiang W, Wang Y, Liang H, Chen H, et al. 2026. Co-application of yak urine and dung deposition antagonistically affected soil nitrous oxide emissions in an alpine meadow. Nitrogen Cycling 2: e018 doi: 10.48130/nc-0026-0005
https://www.maxapress.com/article/doi/10.48130/nc-0026-0005
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About Nitrogen Cycling :
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.
