Measurement of gaseous emissions from denitrification of applied N-15 .I. Effect of cover duration

Abstract

Measurement of gas emissions from denitrification of applied N has been restricted because of the lack of a convenient method. Recently a method using an electric are to measure 15N contents of dinitrogen (N2) and nitrous oxide (N2;O) in air has been developed. Gas emissions from denitrification of applied 15N were determined using this method for gas analysis of the 15N2 and 15N2O captured beneath an air-tight soil cover. Loss of 15N was calculated from gas emission measurements by two methods, accumulation of daily emissions and from the peak 15N emission value by assuming linear increase and decrease over the period of emissions. Losses estimated at low emissions with incomplete soil saturation were similar (1.9 - 5.6% 15N applied) for the two methods. Losses estimated at higher emissions with complete soil saturation were higher when calculated using peak emission values (14.8 - 28.5%) rather than accumulated daily emissions (9.5 - 18.7%). Losses estimated by emissions were compared with 15N loss estimated by mass balance at the completion of two successive soil saturations. As daily cover duration was shortened, gas emission estimates of loss more closely approximated total gaseous 15N as estimated from unaccounted for 15N in the15N balance. With shortest cover duration (15 min day-1) there was close agreement (94% estimated from peak emissions) with 15N loss estimated by 15N balance. A strategy for quantitatively estimating 15N loss by emission measurements is suggested.

Influence of temperature and soil water content on bacterial, archaeal and denitrifying microbial communities in drained fen grassland soil microcosms

“…Biological processes respond positively to temperature upshift and several studies have confirmed that this is also true for the denitrification process. In experiments addressing both N 2 O production and reduction to N 2 , the product ratio (N 2 O/N 2) has been found to increase with decreasing temperature (Bailey & Beauchamp, 1973; Keeney et al , 1979; Avalakki et al , 1995). One possible explanation might be that N 2 O reduction has higher activation energy than N 2 O production.…”

Emission of the Greenhouse Gases Nitrous Oxide and Methane from Constructed Wetlands in Europe

“…Biological processes respond positively to higher temperatures within a range where the enzymes are stable and retain full activity; this has also been shown for the denitrification process (Holtan‐Hartwig et al, 2002). The product ratio (N 2 O/N 2 ) has, however, been found to increase with decreasing temperatures (Keeney et al, 1979; Avalakki et al, 1995). Most factors that slow down the overall rate of denitrification appear to cause an accumulation of N 2 O as the major end product (Firestone and Davidson, 1989).…”

Measurement of gaseous emissions from denitrification of applied N-15 .2. Effects of temperature and added straw

“…Each pot was covered every day for 3 h and a sample of 15N (Nz +NzO) gas evolving beneath the cover was collected into a pre-evacuated arc vessel, as described previously (Avalakki et al 1995). Gas samples for total NzO analysis were also taken into 10 mL pre-evacuated vials.…”

“…Analysis for the 1 5~ content of NzO and Nz emitted beneath the cover was carried out as described previously (Strong et al 1991). Measurement of N2O by gas chromotography has been described previously (Avalakki et al 1995).…”