Primed N₂O emission from native soil nitrogen: A ¹⁵N‐tracing laboratory experiment

Abstract

Soils can naturally be a source of the potent greenhouse gas nitrous oxide (N 2 O). By contrast, the largest anthropogenic source of N 2 O is the application of nitrogen (N) fertilizer on agricultural soil, but it is unclear if fertilizer-supported N 2 O emission only originates from the fertilizer N directly or through additionally stimulated N 2 O production from native soil N. Even though native soil N also includes mineral N already in soil before fertilizer application, organic N is the principal native N pool and thereby provides for mineral N cycling and N 2 O emission. Here, we tested (1) the contribution of native soil N to N 2 O emission after mineral N fertilizer application and (2) whether it is affected by different soil organic matter (SOM) contents by conducting a laboratory 15 N-tracing experiment with agricultural soil from a long-term field trial with two treatments. Both field treatments are fertilized with mineral N, whereas only one of the two receives liquid manure causing higher SOM content. Soil sampling was conducted in March 2016 shortly before fertilizer application in the field. The application of 15 N-labeled fertilizer more than doubled the N 2 O production from native N sources compared to the non-fertilized control incubations. This primed N 2 O production contributed by 5-8% to the fertilizer-induced N 2 O emission after one week of incubation and was similar for both field treatments regardless of liquid manure application. Therefore, further research is needed to link N 2 O priming to its potential production pathways and sources. While the observed effect may be important in soils, the amount of applied N fertilizer remains the largest concern being responsible for the majority of N 2 O emission.

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

“…(2018) and Schleusner et al. (2018) documented low primed SOM contributions to N 2 O production, which were probably constrained by the much lower organic C in their soils (Figure 3). Guardia et al.…”

“…At 100 kg N ha −1 , Schleusner et al. (2018) had two field treatments: with and without liquid manure (LM+ and LM−). For Buckthought et al.…”

“…Hence, it can be hypothesized that the priming effects of N 2 O derived from SOM interact and shift with differences in soil moisture; however, there is a paucity of information regarding this. To date, reports assessing the sources of N 2 O production in controlled experiments have been conducted only at a single soil moisture content (Schleusner et al., 2018; Zhu‐Barker, Doane, & Horwath, 2015). Therefore, to better understand and accurately predict how moisture affects N 2 O priming, there is a need to evaluate a range of soil moisture contents that are relevant to real field scenarios.…”

Field Application of Organic Fertilizers Triggers N2O Emissions From the Soil N Pool as Indicated by 15N-Labeled Digestates

“…However, the experimental setup does not allow for a differentiation between nitrification and denitrification. Therefore, we can only conclude that the first N 2 O peak was mainly derived from soil N. The high share of soil-borne N suggests that the addition of OM positively affected microbial activity which further enhanced the turnover of native soil-N, as also stated by Schleusner et al (2018).…”

“…This sum was then divided by the amount of 15 N applied by the digestate as described by Pfab (2011). Schleusner et al (2018), the amount of primed N 2 O-N lost by fertilizer application was calculated by a simplified approach accounting for cumulative N 2 O-N emissions of the unfertilized control treatment (Equation 4), without considering other gaseous losses via NH 3 or N 2 .…”