Soils, a sink for N₂O? A review

Abstract

Soils are the main sources of the greenhouse gas nitrous oxide (N 2 O). The N 2 O emission at the soil surface is the result of production and consumption processes. So far, research has concentrated on net N 2 O production. However, in the literature, there are numerous reports of net negative fluxes of N 2 O, (i.e. fluxes from the atmosphere to the soil). Such fluxes are frequent and substantial and cannot simply be dismissed as experimental noise.Net N 2 O consumption has been measured under various conditions from the tropics to temperate areas, in natural and agricultural systems. Low mineral N and large moisture contents have sometimes been found to favour N 2 O consumption. This fits in with denitrification as the responsible process, reducing N 2 O to N 2 . However, it has also been reported that nitrifiers consume N 2 O in nitrifier denitrification. A contribution of various processes could explain the wide range of conditions found to allow N 2 O consumption, ranging from low to high temperatures, wet to dry soils, and fertilized to unfertilized plots. Generally, conditions interfering with N 2 O diffusion in the soil seem to enhance N 2 O consumption. However, the factors regulating N 2 O consumption are not yet well understood and merit further study.Frequent literature reports of net N 2 O consumption suggest that a soil sink could help account for the current imbalance in estimated global budgets of N 2 O. Therefore, a systematic investigation into N 2 O consumption is necessary. This should concentrate on the organisms, reactions, and environmental factors involved.

Nitrogen enrichment and the emission of nitrous oxide from streams

“…Even if stream N 2 O uptake is a common occurrence, the importance of this phenomenon to global budgets is likely to be small. Observed areal N 2 O uptake rates from our study streams are low in comparison to soil uptake rates [Chapuis-Lardy et al, 2007], and streams cover a much smaller area of the landscape than soils. Stream N 2 O uptake rates are also lower than mean emissions from other study streams.…”

“…Periods of net N 2 O consumption have been associated with low ambient NO 3 − concentrations, low O 2 concentrations, low flow, or some combination of these factors [Richey et al, 1988;Hemond and Duran, 1989;LaMontagne et al, 2003;Stow et al, 2005;Rajkumar et al, 2008]. In soils, where N 2 O consumption is more widely documented, factors including temperatures greater than 5°C and low O 2 (or saturation and porosity that drive low O 2 ) have been associated with net N 2 O consumption [Blackmer et al, 1980;Chapuis-Lardy et al, 2007]. In reservoirs, low O 2, low NO 3 − and high organic carbon availability have been cited as factors associated with net N 2 O consumption [Hendzel et al, 2005].…”

Soil pH was the main controlling factor of the denitrification rates and N2/N2O emission ratios in forest and grassland soils along the Northeast China Transect (NECT)

“…Some studies have shown a correlation between denitrification rate and soil pH, but others have failed to establish such a relationship (Drury et al 1991;Watson et al 1994;Xu and Cai 2007). In general, the ratio of N 2 /N 2 O increases with increasing organic carbon (C) content (Weier et al 1993;Miller et al 2008), but decreases in soils with high NO À 3 concentrations (Chapuis-Lardy et al 2007). Numerous studies have reported that soil pH affects the ratio of N 2 /N 2 O, which decreases with decreasing soil pH (Blackmer and Bremner 1978;Firestone et al 1980).…”

Responses of soil nitrous oxide production and abundances and composition of associated microbial communities to nitrogen and water amendment

“…Soil texture regulates soil N 2 O emissions through influencing O 2 availability (Corre et al 1999), because soil texture can affect the size and distribution of soil pores and therefore influence soil aeration and water content (Singurindy et al 2006;Chen et al 2013a). Soil pH has been identified as another key regulator of soil N 2 O emissions (Butterbach-Bahl et al 2013), and product ratios of N 2 O/(N 2 + N 2 O) have a significantly negative relationship with soil pH within the normal range from pH 5 to 8 in agricultural soils (Chapuis-lardy et al 2007). Further, the activity of AMO, NIRK, or NOS is impacted by pH and O 2 availability (Giles et al 2012;Banerjee et al 2016).…”