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The fertilization regimes of combining manure with synthetic fertilizer are benefits for crop yields and soil fertility in cropping systems as compared to sole synthetic fertilization, but the responses of nitrous oxide (N 2 O) emissions to these practices are inconsistent in the literatures. We hypothesized that it is caused by different proportions of nitrogen (N) applied as manure and various soil properties. Here, we conducted a microcosm experiment, and measured the N 2 O emissions from control (no N) and five manure substitution treatments (supplied 100 mg N kg−1 using the combination of urea with manure) with a range of proportions of N applied as manure (0, 25%, 50%, 75%, and 100%) in three different soil types (fluvo-aquic soil, black soil, and latosol) under aerobic condition. The stimulated effect on N 2 O emissions was more pronounced after manure application in an alkaline soil with high nitrification rate, due to relatively rapid soil DOC depletion and N mineralization of manure. N 2 O emissions from partial substitution of urea with manure were significantly higher than manure-only addition under high soil pH due to abundant labile C from manure. However, there was no difference between manure substitution treatments under acid soils. Nitrification inhibitor substantially decreased N 2 O emissions with increasing soil pH, but it was less effective in mitigating N 2 O emissions with larger proportion of manure. This is likely due to the slow nitrification under low soil pH, and denitrification derived N 2 O increased with increasing manure application rate. Collectively, our study shows that the application of manure substitution to alkaline soils requires careful consideration, which might have rapid nitrification potential and hence trigger significant N 2 O emissions. The knowledge gained in this work will help the decision-makers in optimizing a sound N fertilization regime interacted with soil properties for sustainable crop production and N 2 O mitigation. [Display omitted] • Partial manure substitution triggered significant N 2 O emission under high soil pH. • Manure substitution did not enhance substantial N 2 O emissions under low soil pH. • The availability of N and DOC mediated the response of N 2 O emissions to manure substitution. • Nitrification inhibitor was less effective in mitigating N 2 O emissions with larger proportion of manure. [ABSTRACT FROM AUTHOR]

Digestate is considered as an option for recycling resources and a part of the substitution for chemical fertilizers to reduce environmental impacts. However, its application may lead to significant nitrous oxide (N 2 O) emissions because of its high concentration of ammonium and degradable carbon. The research objectives are to evaluate how N 2 O emissions respond to digestate as compared to urea application and whether this depends on soil properties and moisture. Either digestate or urea (100 mg N kg−1) was applied with and without a nitrification inhibitor of 3,4-dimethylpyrazole phosphate (DMPP) to three soil types (fluvo-aquic soil, black soil, and latosol) under three different soil moisture conditions (45, 65, and 85% water-filled pore space (WFPS)) through microcosm incubations. Results showed that digestate- and urea-induced N 2 O emissions increased exponentially with soil moisture in the three studied soils, and the magnitude of the increase was much greater in the alkaline fluvo-aquic soil, coinciding with high net nitrification rate and transient nitrite accumulation. Compared with urea-amended soils, digestate led to significantly higher peaks in N 2 O and carbon dioxide (CO 2) emissions, which might be due to stimulated rapid oxygen consumption and mineralized N supply. Digestate-induced N 2 O emissions were all more than one time higher than those induced by urea at the three moisture levels in the three studied soils, except at 85% WFPS in the fluvo-aquic soil. DMPP was more effective at mitigating N 2 O emissions (inhibitory efficacy: 73%–99%) in wetter digestate-fertilized soils. Overall, our study shows the contrasting effect of digestate to urea on N 2 O emissions under different soil properties and moisture levels. This is of particular value for determining the optimum of applying digestate under varying soil moisture conditions to minimize stimulated N 2 O emissions in specific soil properties. [Display omitted] • N 2 O emission ratios of digestate to urea were all more than 1 except at 85% WFPS in alkaline soil. • High soil moisture triggered an exponential increase in N 2 O emissions from digestate amendment. • The greater increase in alkaline soil was due to high net nitrification rate and transient nitrite accumulation. • Nitrification inhibitor significantly reduced digestate-induced N 2 O emissions under high soil moisture conditions. [ABSTRACT FROM AUTHOR]