Nitrous oxide emissions from a New Zealand cropped soil: tillage effects, spatial and seasonal variability

Abstract

Agricultural practices are believed to be the major anthropogenic source of enhanced nitrous oxide (N 2 O) gas emissions in New Zealand. Studies conducted in New Zealand generally suggest low N 2 O emission from pasture; however, there is little information for arable farming systems. This paper evaluates tillage and land use effects on N 2 O emissions using a closed chamber technique at an Ohakea silt loam (Gleyic luvisol) where winter oats (Avena sativa L.)/fodder maize (Zea mays L.) was double-cropped for 5 years. The tillage types included conventional tillage (CT) and no-tillage (NT) systems, and a permanent pasture (PP) was used as a control.Spatial variability in all treatments showed large inherent variations in N 2 O fluxes (a mean CV = 119%), which reflected natural soil heterogeneity, and perhaps the measurement technique used rather than the real differences due to the tillage and cropping systems evaluated. On an annualised basis, N 2 O emissions measured from December 1998 to September 1999 from the PP (1.66 kg N 2 O-N/ha per year or 19 g N 2 O-N/(m 2 h)) were significantly lower than the CT and NT fields averaging at 9.20 (or 105) and 12.0 (or 137) kg N 2 O-N/ha per year (or g N 2 O-N/(m 2 h)), respectively. However, there were no differences in N 2 O emission rates between the CT and NT treatments. Seedbed preparation using a power harrow which followed within a few days of first ploughing the CT field reduced N 2 O emissions by 65% within the first hour after power harrowing. However, N 2 O emission rates returned to the pre-power harrowing levels at the next sampling period, which was 1 month later.There was a strong relationship between log-transformed data of soil water content (SWC) and N 2 O emissions in all treatments with r = 0.73, 0.75 and 0.86 for the PP, CT and NT treatments, respectively. Seasonal variations in N 2 O emission from the PP were in the order of winter = autumn > summer. Although fluxes in the CT were higher in winter than in the autumn season, there were no differences between the summer and autumn data. The seasonal variations in N 2 O emission in the NT treatment were in the order of winter > autumn = summer.

Estimation of N2O emissions from agricultural soils in Canada. I. Development of a country-specific methodology

“…Another model, NCGAS, predicted higher emissions from no-till situations with a stronger effect in drier environments (Mummey et al 1998). In comparative field studies, N 2 O emissions under no-till were greater than (Aulakh et al 1984;MacKenzie et al 1998;Ball et al 1999;Baggs et al 2003;Yamulki and Jarvis 2002;Koga et al 2004), smaller than (Jacinthe and Dick 1997;Kessavalou et al 1998;Lemke et al 1999;Kaharabata et al 2003;Del Grosso et al 2005) and approximately equal to (Lemke et al 1999;Robertson et al 2000;Choudhary et al 2002;Kaharabata et al 2003) emissions from tilled soils. Contrasting effects of no-till on N 2 O fluxes have also been observed depending on the N fertilizer type that was applied (Venterea et al 2005).…”

Mitigation of postharvest nitrous oxide emissions from soybean ecosystems: a review

“…Other studies have found no significant effect of tillage on N 2 O production from soybean crops (Parkin and Kaspar 2006;Jantalia et al 2008). Results from previous studies on the effects of tillage on soil N 2 O production are thus contradictory (Ball et al 1999;Choudhary et al 2002). A review article by Rochette (2008) concluded that a notillage treatment increased N 2 O emissions in poorly-aerated soils, whereas the same treatment resulted in the decrease in N 2 O emissions in well-aerated soils.…”

The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

“…N 2 O fluxes are believed to be driven primarily by the availability of nitrogen compounds in the soils (ammonium and nitrate) (Davidson et al, 2000) as well as physical properties of the soil such as WFPS, aerobic extent, soil type, temperature and compaction (Ball et al, 2008;ButterbachBahl et al, 2013;Choudhary et al, 2002;Davidson et al, 2000;Turner et al, 2008). The collection of these data on a temporal/spatial scale which would allow these models to be applied is not often logistically possible or affordable.…”

“…Chatskikh and Olesen, 2007;Merbold et al, 2014;Omonode et al, 2011;Pinto et al, 2004;Yamulki and Jarvis, 2002), whereas others have shown a zero (i.e. Boeckx et al, 2011;Choudhary et al, 2002) or potentially negative effect of tillage (−0.88 kg N ha −1 ; Tan et al, 2009). There is little consensus among these studies on the relative effect of different drivers of N 2 O production.…”