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Abstract The absence of N 2 flux measurements in liquid manure-amended soils has resulted in a poor understanding of the effect of manure application on gaseous N losses. The aim of this study was to quantify N 2 , N 2 O, CO 2 , N 2 O reduction to N 2 , depth distribution of moisture, water-extractable organic C, NO 3 − , NH 4 + , pH, and diffusivity in a laboratory incubation experiment with an arable silt-loam soil. To quantify N processes and gaseous fluxes, 15 N tracing was applied. An artificial livestock slurry-mixture was added to the soil in various treatments (control, surface or injected application; slurry-application rate: 42.9 kg N ha − 1 ; soil water content of either 40% or 60% water-filled pore space (WFPS)). The soil was incubated for 10 days. The depth distribution of the control parameters was measured twice during the experiment on days 5 and 10. The average increase in N 2 and N 2 O fluxes from denitrification was about 900% in slurry-amended soils. The highest N 2 and N 2 O fluxes from denitrification were measured in the slurry injection, 60% WFPS treatment (7.83 ± 3.50 and 11.22 ± 7.60 mg N m − 2 d − 1 , respectively). The hypothesis that injected slurry at a higher water content enhances denitrification was confirmed. This study provides important insights into the formation, spatial and temporal variation of the manure-soil hotspot and its impact on the denitrification process. The results will form part of a dataset to develop, improve and test manure application submodules of biogeochemical models and will help to understand in detail the effect of hotspots on N-cycling in manure-treated soils.
Grosz et al. (Fri,) studied this question.