Overlapping yak excreta patches emit less nitrous oxide than expected
image: The abundances of nitrifying functional gene (AOA amoA and AOB amoA), denitrifying functional gene (nirS, nirK and nosZ) and nir/nos under different yak excreta application treatments.
Credit: Nitrogen Cycling
A research team has found that overlapping yak urine and dung patches in an alpine meadow do not simply add together to increase soil nitrous oxide emissions. Under dry field conditions on the Qingzang Plateau, combined deposition produced an antagonistic response: cumulative emissions were similar to urine alone and far below the theoretical sum of separate urine and dung patches. The finding challenges a common assumption in greenhouse-gas accounting and could improve estimates of livestock emissions around watering points, shelters, and other congregation areas where excreta frequently overlap.
Grazing animals return most consumed nitrogen to grasslands through urine and dung, creating concentrated nutrient patches that stimulate microbial nitrification and denitrification, the main soil processes producing nitrous oxide. Urine supplies readily available nitrogen, while dung contributes organic carbon and moisture, so overlap has often been expected to cause additive or synergistic emissions. Yet previous studies report inconsistent outcomes because soil moisture controls oxygen diffusion, anaerobic microsite formation, and the balance between nitrous oxide production and reduction to nitrogen gas. This uncertainty limits accurate emission inventories for heavily grazed ecosystems.
A study (DOI: 10.48130/nc-0026-0005) published in Nitrogen Cycling on 13 April 2026 by Yanjiang Cai's team, Zhejiang A & F University, shows that urine emitted much more nitrous oxide than dung, whereas combined deposition produced emissions comparable to urine alone.
The researchers conducted an in-situ field experiment at the Zoige Peatland and Global Change Research Station on the eastern Qingzang Plateau in Sichuan Province, China. Using a randomized block design, they established four treatments: an untreated control, urine application, dung application, and combined urine and dung application. Artificial urine matched typical yak urine nitrogen concentrations, while fresh yak dung was collected, homogenized, and applied at realistic field rates. Urine formed 40-centimeter patches, dung formed smaller raised patches, and the combined treatment placed dung directly onto urine patches. Nitrous oxide fluxes were monitored for 73 days with static chambers and gas chromatography, while soil temperature, water-filled pore space, pH, dissolved organic carbon, ammonium, nitrate, enzyme activities, and nitrogen-cycling genes were measured to identify the processes driving emissions. All excreta treatments increased nitrous oxide release relative to the control, with emissions peaking around day 13. Urine produced cumulative emissions of 295.82 grams of nitrogen per hectare, more than four times the 72.29 grams recorded from dung. The combined treatment produced 296.45 grams per hectare, nearly identical to urine alone but well below the theoretical additive total. Its proportional response was 0.84, confirming an antagonistic interaction. Urine stimulated stronger nitrification throughout the experiment, reflected in greater ammonium availability, ammonia-oxidizing bacterial gene abundance, and nitrifying enzyme activity. In combined patches, dung increased carbon availability and altered denitrification, but greater production potential appeared to be offset by enhanced reduction of nitrous oxide to nitrogen gas. Soil moisture stayed below 50% water-filled pore space, indicating dry conditions that likely restricted anaerobic microsites. A comparison with published studies supported the broader pattern: combined excreta tended to be antagonistic under dry conditions and synergistic under wet conditions. The emissions pattern was biphasic, with most release occurring during the first 30 days before stabilizing later.
The study shows that emissions from livestock congregation sites cannot be estimated reliably by adding the separate effects of urine and dung. By revealing how dry soils and microbial nitrogen cycling suppress the expected combined response, the work offers a more realistic basis for nitrous oxide budgets in alpine grazing systems. Further studies across soil types and moisture regimes, using gene-expression and isotope-tracing methods, will be needed to test how widely this effect applies and guide mitigation strategies.
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References
DOI
Original Source URL
https://doi.org/10.48130/nc-0026-0005
Funding information
This research was funded by the National Natural Science Foundation of China (Grant Nos 41877085, 41573070), and the Research and Development Fund of Zhejiang A&F University (Grant Nos 2018FR005, 2018FR006).
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