Sources and priming of nitrous oxide production across a range of moisture contents in a soil with high organic matter

Abstract

Adding nitrogen fertilizers to agricultural soils contributes to increasing concentrations of nitrous oxide (N2O) in the atmosphere. However, the impacts of N addition on soil organic matter (SOM) turnover, SOM availability, and the ensuing SOM‐derived N2O emissions remain elusive. Within this context, the net change in direction and rate of SOM‐derived N2O production triggered by added N is termed the N2O priming effect. This incubation study examined the sources and priming of N2O production as a function of urea addition and multiple moisture contents in a soil with high SOM (55 g organic C kg−1). We assessed four water‐filled pore space (WFPS) conditions: 28, 40, 52, and 64%. Relative to controls receiving no N, urea addition increased N2O production by 2.6 times (P < .001). Cumulative N2O production correlated well with nitrification rates (r = .75; P = .03). We used 15N‐labeled urea to trace the added urea into N2O. Of the N added via urea, the recovery as N2O–N shifted from 0.02 to 0.17% when WFPS increased from 28 to 64% (P < .05). We also partitioned the N2O production into urea vs. SOM sources. More N2O was sourced from SOM than urea, with 59 ± 2% N2O originating from SOM. The magnitude of SOM‐derived N2O under urea was larger than that of the control, revealing that positive N2O priming was triggered by urea addition. Upon subtracting the controls, the primed N2O was a consistent 19 ± 2% of the total N2O produced by urea‐amended soils. Nevertheless, the priming magnitude rose sharply with increasing moisture by more than one order of magnitude from 4 to 48 μg N2O–N kg−1 soil and in exponential mode (R2 = .98). Soil moisture, SOM, and nitrification interacted to drive the sources and priming of N2O.

Organic Matter Composition of Digestates Has a Stronger Influence on N2O Emissions than the Supply of Ammoniacal Nitrogen

“…Consequently, it can be concluded that, in the case of dried solid, the addition of easily degradable C in combination with soil-derived NO 3 − triggered the N 2 O production and release. This notion is consistent with previous findings, based on experiments with 15 N-labeled manures [40,47,57,58]. It highlights the complexity of the presented issue and the importance of additional determination of the responsible N source.…”

“…Since the proportion of recalcitrant fractions, such as lignin, was lower in concentrate (Table 2), it can be assumed that the presence of degradable C influenced bacterial growth and activity and, thus, triggered the N 2 O emissions. The addition of labile C can also induce N 2 O emissions derived from soil mineral N [47,57,58], which might have enhanced this effect in the case of concentrate (Figure 2b). Furthermore, a part of initial labile N applied with separated liquid was probably immobilized by soil microflora immediately after fertilization [59], which mitigated the total amount of N 2 O emitted from this treatment.…”

Increased N2O Production from Soil Organic Matter Following a Simulated Fall-Freeze-Thaw Cycle: Effects of Fall Urea Addition, Soil Moisture, and History of Manure Applications

“…2a). This interpretation is consistent with previous studies that evaluated the driving effects 484 of increasing moisture on N2O peak emissions , Roman-Perez and Hernandez-Ramirez 2021. Increasing moisture and microbial activity immediately after soil thawing can have led to the depletion of O2 concentrations in the soil microsites, and hence mediating an increased N2O production from denitrification (Yanai et al…”

Reduced Nitrous Oxide Emissions From Drained Temperate Agricultural Peatland After Coverage With Mineral Soil

“…Priming effects are defined as short-term changes of SOM mineralization in response to external stimuli, for example, exogenous N addition, and they alter the subsequent N 2 O production from SOM-N (Kuzyakov et al, 2000;Daly and Hernandez-Ramirez, 2020;Thilakarathna and Hernandez-Ramirez, 2021). Priming may affect N 2 O emissions positively or negatively, depending on soil moisture and SOM content (Roman-Perez and Hernandez-Ramirez, 2020). Former studies revealed positive N 2 O priming effects to be associated with wetter soil conditions (WFPS >60%) and higher SOM content (Schleusner et al, 2018;Thilakarathna and Hernandez-Ramirez, 2021).…”