How does soil compaction alter nitrous oxide fluxes? A meta-analysis

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Reclamation of coastal wetland to paddy soils alters the role of bacteria and fungi in nitrous oxide emissions: Evidence from a 53-year reclamation chronosequence study

Increased N2O emissions by the soil nematode community cannot be fully explained by enhanced mineral N availability

Abstract. Fertilised soils are a significant source of nitrous oxide (N2O), a highly active greenhouse gas and a stratospheric ozone depleter. Nitrogen (N) fertilisers, while boosting crop yield, also lead to N2O emissions into the atmosphere, impacting global warming. We investigated relationships between mineral N fertilisation rates and additional manure amendment with different crop types through the analysis of abundances of N cycle functional genes, soil N2O and N2 emissions, nitrogen use efficiency (NUE), soil physicochemical analysis and biomass production. Our study indicates that N2O emissions are predominantly dependent on the mineral N fertilisation rate and enhance with an increased mineral N fertilisation rate. Crop type also has a significant impact on soil N2O emissions. Higher N2O emissions were attained with the application of manure in comparison to mineral fertilisation. Manure amendment also increased the number of N cycle genes that are significant in the variations of N2O. The study indicates that N2O emissions were mainly related to nitrification in the soil. Quantification of nitrogen cycle functional genes also showed the potential role of denitrification, comammox (complete ammonia oxidation) and dissimilatory nitrate reduction to ammonium (DNRA) processes as a source of N2O. Our study did not find soil moisture to be significantly linked to N2O emissions. The results of the study provide evidence that, for wheat, a fertilisation rate of 80 kg N ha−1 is closest to the optimal rate for balancing biomass yield and N2O emissions and achieving a high NUE. Sorghum showed good potential for cultivation in temperate climates, as it showed a similar biomass yield compared to the other crop types and fertilisation rates but maintained low N2O emissions and N losses in a mineral N fertilisation rate of 80 kg N ha−1.

Chapter 10 - Impacts of nitrogen deposition on soil nitrous oxide emissions in global forests

We assessed the seasonal dynamics of N2O emission in ant nests soils in secondary tropical Millettia leptobotrya forest of Xishuangbanna by using the static chamber-gas chromatography method, and determined the lin-kages between ant-mediated changes in soil properties (e.g., carbon pool, nitrogen pool, and temperature and humidity) and N2O emission. The results showed that ant nesting significantly affected soil N2O emission. The ave-rage soil N2O emission (0.67 mg·m-2·h-1) in ant nests was 40.2% higher than that in the control (0.48 mg·m-2·h-1). N2O emission in ant nests and the control showed substantial seasonal variation, with higher rate in June (0.90 and 0.83 mg·m-2·h-1, respectively) than that in March (0.38 and 0.19 mg·m-2·h-1, respectively). Ant nesting significantly increased the values (7.1%-74.1%) of moisture, temperature, organic carbon, total nitrogen, hydrolytic nitrogen, ammonium nitrogen, nitrate nitrogen, and microbial biomass carbon, but decreased pH (9.9%) compared with the control. Results of structural equation model showed that soil N2O emission was promoted by soil C and N pool, temperature, and humidity, but was inhibited by soil pH. The explained extents of soil nitrogen pool, carbon pool, temperature and humidity, and pH for N2O emission changes were 37.2%, 27.7%, 22.9% and 9.4%, respectively. Therefore, ant nesting regulated N2O emission dynamics by changing nitrification and denitrification substrates (e.g., nitrate and ammoniacal nitrogen), carbon pool, and micro-habitat (temperature and moisture) of soil in the secondary tropical forest.

Identification of nitrous oxide (N2O) and carbon dioxide (CO2) emissions from soils amended with different types of compost is needed for appropriate use of manure in agriculture. This study aimed at investigating the interaction effects of compost type and soil properties and effects of moisture contents on N2O and CO2 emissions, with identification of relative abundances of functional ammonia-oxidizing genes. Laboratory tests were conducted using cattle manure compost (CC) or mixed compost (MC) (cattle, poultry, and swine manure) amended Kochi (from a greenhouse) or Ushimado (from a paddy field) soils (3% by weight) with controls (no compost). Initial moisture contents were adjusted to 60% water-holding capacity (WHC) for Kochi soil and 70% WHC for both soils. The samples were aerobically incubated at 25°C. Emissions of N2O and CO2 and contents of ammonium N (NH4 +-N) and nitrate N in soils were measured continuously until day 42. The abundances of ammonia-oxidizing bacteria (AOB) and archaea genes were estimated to evaluate nitrifying activities. Cumulative N2O and CO2 emissions were significantly higher (p < 0.05) in MC than those in CC treatments probably due to higher NH4 +-N content and lower C/N ratio, which facilitated faster N mineralization and C decomposition. Emissions of N2O and CO2 were higher in compost-amended Kochi soil (70% WHC) with high total C and N, mineral N, and clay contents than those in less fertile Ushimado soil. Interestingly, interactions of compost type and soil properties on N2O emissions were significant (p < 0.05) only in Kochi soil because the addition of decomposition resistant CC increased N2O emissions only from this soil with high C and N contents. Higher soil moisture contents increased N2O and CO2 emissions significantly (p < 0.05) in Kochi soil. Emissions of N2O until day 15 were mainly due to activities of AOB amoA genes (R2 = 0.91). This study suggests that N2O emissions are increased by high NH4 +-N contents and a low C/N ratio in compost and high total C and N, mineral N, and clay contents in soil. The application of compost with less decomposable C increases N2O emissions only from nutrient-rich soil.

Tea gardens, being a key agroecosystem type, are an important source of nitrous oxide (N2O) emissions. However, main factors that regulate N2O emissions following urea and organic matter amendments have yet to be clarified. To investigate the influence of different fertilization management measures on N2O emissions in tea garden soil, a 50-day laboratory incubation experiment was conducted. Five treatments were designed for this experiment: control (CK), urea (U), rapeseed cake (R), urea + rapeseed cake (2:1, UR1), and urea + rapeseed cake (1:2, UR2). N2O emission flux in the R treatment peaked at 14.12 μg kg−1 h−1 on day 19, which occurred later than the UR1, UR2, and U treatments. Cumulative N2O emissions from the R and UR2 treatments were 6073 and 4296 μg kg−1, respectively, which were greater by a factor of 11.2 and 7.9, respectively, compared to the U treatment. Moreover, N2O emissions of the UR1 and UR2 treatments were significantly lower than the R treatment. Additionally, N2O emissions were also significantly positively correlated to pH levels and microbial biomass carbon (MBC) content. MBC content had the most direct and greatest influence on soil N2O emissions, indicating that MBC could be the key limiting factor for N2O emissions in this experiment. A single application of rapeseed cake caused an increase in N2O emissions, whereas the combined application of rapeseed cake and a synthetic N fertilizer (urea) caused a decrease in N2O emissions. Results from this study offer potential strategies to mitigate soil N2O emissions from tea garden agroecosystems through improved field fertilization management.

Biochar application to soil has drawn much attention as a strategy to sequester atmospheric carbon in soil ecosystems. The applicability of this strategy as a climate change mitigation option is limited by our understanding of the mechanisms responsible for the observed changes in greenhouse gas emissions from soils, microbial responses, and soil fertility changes. We conducted an 8-wk laboratory incubation using soils from PASTURE (silt loam) and RICE PADDY (silt loam) sites with and without two types of biochar (biochar from swine manure [CHAR-M] and from barley stover [CHAR-B]). Responses to addition of the different biochars varied with the soil source. Addition of CHAR-B did not change CO and CH evolution from the PASTURE or the RICE PADDY soils, but there was a decrease in NO emissions from the PASTURE soil. The effects of CHAR-M addition on greenhouse gas emissions were different for the soils. The most substantial change was an increase in NO emissions from the RICE PADDY soil. This result was attributed to a combination of abundant denitrifiers in this soil and increased net nitrogen mineralization. Soil phosphatase and N-acetylglucosaminidase activity in the CHAR-B-treated soils was enhanced compared with the controls for both soils. Fungal biomass was higher in the CHAR-B-treated RICE PADDY soil. From our results, we suggest CHAR-B to be an appropriate amendment for the PASTURE and RICE PADDY soils because it provides increased nitrogen availability and microbial activity with no net increase in greenhouse gas emissions. Application of CHAR-M to RICE PADDY soils could result in excess nitrogen availability, which may increase NO emissions and possible NO leaching problems. Thus, this study confirms that the ability of environmentally sound biochar additions to sequester carbon in soils depends on the characteristics of the receiving soil as well as the nature of the biochar.

Nitrous oxide (N 2 O) emissions comprise the major share of agriculture's contribution to greenhouse gases; however, our understanding of what is actually happening in the field remains incomplete, especially concerning the multiple interactions between agricultural practices and N 2 O emissions. Soil compaction induces major changes in the soil structure and the key variables controlling N 2 O emissions. Our objective was to analyse the ability of a process‐based model (Nitrous Oxide Emissions (NOE)) to simulate the impact of soil compaction on N 2 O emission kinetics obtained from field experiments. We used automatic chambers to continuously monitor N 2 O and CO 2 emissions on uncompacted and compacted areas in sugar beet fields during 2 years. Soil compaction led to smaller CO 2 emissions and larger N 2 O emissions by inducing anoxic conditions favourable for denitrification. Cumulative N 2 O emissions during the crop cycles were 944 and 977 g N ha −1 in uncompacted plots and 1448 and 1382 g N ha −1 in compacted plots in 2007 and 2008, respectively. The NOE model () simulated 106 and 138 g N 2 O‐N ha −1 in uncompacted plots and 1550 and 650 g N 2 O‐N ha −1 in compacted plots in 2007 and 2008, respectively, markedly under‐estimating the nitrification rates and associated N 2 O emissions. We modified the model on the basis of published results in order to better simulate nitrification and account for varying N 2 O fractions of total end‐products in response to varying soil water and nitrate contents. The modified model (NOE2) better predicted nitrification rates and N 2 O emissions following fertilizer addition. Using a fine vertical separation of soil layers of configurable, but constant, thickness (1 cm) also improved the simulations. NOE2 predicted 428 and 416 g N‐N 2 O ha −1 in uncompacted plots and 1559 and 1032 g N‐ N 2 O ha −1 in compacted plots in 2007 and 2008, respectively. These results show that a simple process‐based model can be used to predict successfully the post‐fertilizer addition kinetics of N 2 O emissions and the impact of soil compaction on these emissions. However, large emissions later on during the cropping cycle were not captured by the model, emphasizing the need for further research.

Reclaimed water (RW) is widely used in agricultural systems; however, it affects soil properties and the surrounding environment, thus influencing soil nitrogen transformation and increasing N2O and NO emissions. Understanding the influencing mechanism of N2O production in RW-irrigated soil is very important for water resource utilization and environmental protection, but it is rarely studied. This study investigated the impact of three nitrogen ions (NH4+, NO3−, NO2−) on the nitrogen transformation process and non-biological processes affecting NO and N2O emissions from soil under multiyear RW-irrigated conditions. The results showed that RW effectively increased the abundance of nitrifying and denitrifying functional genes, leading to a significant increase (p &lt; 0.05) in soil NO and N2O emissions under ammonium treatment. Furthermore, RW can reduce the cumulative NH3 emission by 19.11% compared to deionized water (DW). In nitrate treatment, RW can significantly increase (p &lt; 0.05) the nitrate conversion rate by increasing the abundance of denitrifying genes, but not significantly enhance N2O and NO emissions. In NO2− oxidation, RW could increase the abundance of nitrifying genes (AOA-amoA, AOB-amoA), thereby promoting the progression of nitrifier denitrification and leading to a substantial increase (p &lt; 0.05) in soil N2O production. In summary, RW irrigation primarily increases N2O emissions from soil by enhancing soil autotrophic nitrification and heterotrophic nitration. To effectively control soil N2O emissions under agricultural irrigation with RW, it is crucial to carefully manage soil nitrification and adjust the ratio of ammonium and nitrate in the soil.

Partial substitution of manure reduces nitrous oxide emission with maintained yield in a winter wheat crop

Nitrogen oxides (NOx = NO + NO2) are key atmospheric trace gases that affect air quality, oxidation chemistry, and nitrogen deposition. Although anthropogenic NOx emissions have declined due to regulations, natural sources like soil emissions are becoming relatively more important. Biomass burning can alter soil nitrogen cycling and potentially influence soil NO fluxes, yet few controlled studies exist. Here, we examined how prescribed burning affects soil NO emissions in a South Carolina forest using incubation experiments. The study site is a sandhill ecosystem dominated by upland oak and longleaf pine, with fire-adapted understory vegetation including wiregrass. Soil cores were collected before and after burns of varying intensities. Measured soil pH, nitrate, and ammonium showed no consistent differences between pre- and post-burn conditions. NO fluxes, quantified using a custom soil chamber, averaged 0.056 ± 0.068 ng-N h−1 g−1 with no significant burn-related change, and most values remained below the method detection limit of 0.137 ng-N h−1 g−1. However, ammonium nitrate additions triggered significant NO emissions, highlighting nitrogen availability as a key control. Scaling fluxes to the state level, we estimate natural forest soil contributed an estimated 700 ± 800 metric tons of NO during a summer month, which is about 5.0 ± 6.0% of statewide NO emissions. These results suggest that prescribed fire does not enhance soil NO emissions in nitrogen-limited, acidic southeastern U.S. forests, immediately following fire events. Moreover, they indicate that forest soil emissions are likely a minor contributor to regional NO budgets in this region.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-18527-4.

Controlled traffic farming effects on soil emissions of nitrous oxide and methane

Characterization of nitrous oxide and nitric oxide emissions from a full-scale biological aerated filter for secondary nitrification