Pathways of soil N2O uptake, consumption, and its driving factors: a review

Process Rate Estimator: A novel model to predict total denitrification using natural abundance stable isotopes of N2O

“…In comparison, data for total denitrification reported in the literature is poorly constrained and varies widely across studies, in part due to methodological limitations in quantifying total denitrification rates. In a global synthesis, denitrification rates, defined as N2O+N2 fluxes, were found to range between 0.001 and 20 kg N ha -1 day -1 (Pan et al, 2022). When calculating mean daily gross N2O production in our 144-day experiment, we find rates between 0.03 and 1.06 kg N ha -1 day -1 , well within but on the low end of the range observed in the literature.…”

“…As such, the soil in this experiment behaved, to some extent, as a sink of N2O. While it is generally accepted that soils are net sources of N2O, it is well known that soil can act as a sink under certain conditions (Chapuis-Lardy et al, 2007;Liu et al, 2022). Main direct controls on N2O consumption include microbial community structure, soil oxygen concentrations, forms and concentrations of N sources, residue or other amendments, soil pH, and copper and iodide concentrations (Liu et al 2022).…”

“…In relation to the potentially available N from fertilizer and initial soil NO3 -, the denitrification loss over the course of the experiment in our study ranged between 1 % and 35 %. Similarly, Pan et al (2022) found that fertilizer N losses from denitrification across studies ranged between 0.5 % and 40%. This range aligns well with findings from N budget studies using 15 N tracers, where the percentage of N that is unaccounted for was on average 38% (Gardner and Drinkwater, 2009).…”

“…On a global scale, total N2 emissions from denitrification were estimated to range between 67 to 130 million tons N per year, with roughly half of this N removal attributed to agricultural soil (Scheer et al, 2020). Daily gross denitrification rates from soil ranged between 0.001 and 20 kg N ha -1 day -1 across studies, correlating positively to soil water-filled pore space, nitrate (NO3 -) content, and temperature, and negatively with soil oxygen content (Pan et al, 2022). When studying denitrification, potential emissions of the potent greenhouse gas and ozone depleting substance nitrous oxide (N2O) need to be considered (Ipcc, 2013;Ravishankara et al, 2009), as N2O is an intermediate compound formed during the reduction of NO3to N2 by denitrifiers (Zumft, 1997).…”

“…In this context, a commonly used metric is the ratio of N2O:(N2O+N2), where a lower ratio indicates a greater importance of gross N2O consumption or total denitrification in an ecosystem (Schlesinger, 2009;Stevens et al, 1998). Ratios of N2O/(N2O+N2) were found to increase with soil oxygen content but decrease with soil organic carbon (C), C:N ratio, soil pH and soil water filled pore space (Pan et al, 2022). Furthermore, total denitrification was shown to not only be affected by the quantity of organic C added or present in the soil, but also its biochemical composition (Henry et al, 2008;Morley and Baggs, 2010).…”