Effect of soil saturation on denitrification in a grassland soil

Abstract

Abstract. Nitrous oxide (N 2 O) is of major importance as a greenhouse gas and precursor of ozone (O 3 ) destruction in the stratosphere mostly produced in soils. The soil-emitted N 2 O is generally predominantly derived from denitrification and, to a smaller extent, nitrification, both processes controlled by environmental factors and their interactions, and are influenced by agricultural management. Soil water content expressed as water-filled pore space (WFPS) is a major controlling factor of emissions and its interaction with compaction, has not been studied at the micropore scale. A laboratory incubation was carried out at different saturation levels for a grassland soil and emissions of N 2 O and N 2 were measured as well as the isotopocules of N 2 O. We found that flux variability was larger in the less saturated soils probably due to nutrient distribution heterogeneity created from soil cracks and consequently nutrient hot spots. The results agreed with denitrification as the main source of fluxes at the highest saturations, but nitrification could have occurred at the lower saturation, even though moisture was still high (71 % WFSP). The isotopocules data indicated isotopic similarities in the wettest treatments vs. the two drier ones. The results agreed with previous findings where it is clear there are two N pools with different dynamics: added N producing intense denitrification vs. soil N resulting in less isotopic fractionation.

N<sub>2</sub>O isotope approaches for source partitioning of N<sub>2</sub>O production and estimation of N<sub>2</sub>O reduction – validation with the <sup>15</sup>N gas-flux method in laboratory and field studies

“…To determine the isotopic signatures of mineral nitrogen in NA treatments, microbial analytical methods were applied. For nitrate, the bacterial denitrification method with Pseudomonas aureofaciens was applied (Casciotti et al, 2002;Sigman et al, 2001). For nitrite, the bacterial denitrification method for selective nitrite reduction with Stenotrophomonas nitritireducens was applied (Böhlke et al, 2007), as well as for 15 N-enriched samples from 15 N treatments.…”

“…The application of dual-isotope plot SP/N was initially proposed by Yamagishi et al (2007) for ocean waters and by Koba et al (2009) for groundwater studies. In open water bodies, the application of SP/N MAP might be effective due to relatively homogenous distribution of substrates in the sampled water volume and thus not biased by the spatial heterogeneity in 15 N enrichment that can occur in soils due to the fractionation processes in soil microsites (Bergstermann et al, 2011;Cardenas et al, 2017;Castellano-Hinojosa et al, 2019;Lewicka-Szczebak et al, 2015;Well et al, 2012). The δ 15 N isotopic signatures of samples were corrected for NO − 3 substrate only, and for water studies this approach was well justified by the complete conversion of NH + 4 to NO − 3 (Koba et al, 2009).…”

Microplastic fibers affect dynamics and intensity of CO2 and N2O fluxes from soil differently

“…In a given soil with a certain soil texture, parameters of the soil structure such as air permeability, aggregate size distribution, and size and design of pore space seem to play an important role. On the one hand, they have a direct influence on the movement of the gases via mass flow and diffusion in the soil in a variety of ways and thus also the emission of greenhouse gases [33][34][35][36][37][38][39][40][41]. On the other hand, they act indirectly by controlling the availability of oxygen in the soil, which in turn influences the processes of CO 2 and N 2 O formation and N 2 O consumption in many ways [42][43][44][45].…”

The Nitrification Inhibitor Vizura® Reduces N2O Emissions When Added to Digestate before Injection under Irrigated Maize in the Po Valley (Northern Italy)

“…This finding agrees with the effects observed by Reference [54], who found low and stable NO 3 -N concentrations and increasing NH 4 -N concentration over 120 days after the application of DMPP and ammonium sulphate nitrate. Similarly, Reference [55] observed a significant effect of DMPP added to urea in reducing soil NO 3 -N concentrations for 60 days.…”