Long-term tillage and crop residue management in the subarctic: fluxes of methane and nitrous oxide

Abstract

Long-term tillage and crop residue management in the subarctic: fluxes of methane and nitrous oxide. Can. J. Soil Sci. 77: 565-570. Methane and nitrous oxide are important radiatively active gases that are influenced by agricultural practices. This study assesses long-term tillage, crop residue management, and N fertilization rates on the flux of these two gases at a high latitude site representing the northern fringe of large-scale agriculture. Cumulative methane uptake for the summer was higher from no-tillage plots than tilled plots. This was associated with lower soil water contents with tillage. Thus, the reduction in CH 4 uptake was attributed to water stress on methane oxidizers. At planting, soil water contents were near field capacity, and the no-till plots had the lowest uptake which was attributed to restricted diffusion of methane to active sites. A similar pattern of methane uptake to soil water content was found with the residue management treatments. Removing the straw lowered the soil water content and for most of the season methane uptake was also lower than where the straw had been left on the plots. Nitrogen fertilizer rate had little effect on methane uptake over the summer, but high N rates lowered consumption during the time of active nitrification early in the season. This corresponded to the time of maximum efflux of nitrous oxide. Nitrous oxide efflux was greatest at the high N rate where straw was retained on the plots. L'absorption cumulative de méthane durant l'été était plus abondante à partir des parcelles en régime de culture sans travail du sol que dans celles travaillées selon les méthodes classiques. Cette plus forte absorption était associée à l'abaissement de la teneur en eau du sol par les façons culturales répétées. Ainsi la moins forte absorption de CH 4 en régime de travail classique était attribuée au stress hydrique exercé sur les oxydants du méthane. Aux semailles, époque où la teneur en eau du sol est presque à la capacité au champ, ce sont les parcelles conduites en culture sans labour qui manifestaient la plus faible absorption, ce qui s'expliquait par une diffusion réduite du méthane vers les sites d'activité. Un rapport similaire de l'absorption du méthane avec la teneur en eau du sol était observé dans les traitements de gestion des restes de culture. L'enlèvement de la paille provoquait l'abaissement de la teneur en eau du sol, et pour la plus grande partie de la saison, l'absorption du méthane était elle aussi plus faible que là où la paille était laissée sur place. La dose de fumure N n'avait que peu d'effet sur l'absorption du méthane pour la totalité de l'été, mais la dose supérieure causait une réduction de la consommation de méthane dans la phase de nitrification active du début de la saison de végétation, qui coïncidait avec celle d'efflux maximum d'oxyde nitreux. L'efflux de N 2 O était particulièrement abondant à la dose supérieure de fumure N lorsque la paille était laissée sur place.

Greenhouse gas contributions and mitigation potential of agricultural practices in northwestern USA and western Canada

“…Soil uptake of CH 4 was 8.7 g C ha À1 d À1 under grass sod, 7.7 g C ha À1 d À1 under NT, and 6.8 g C ha À1 d À1 under moldboard plow in western Nebraska (Kessavalou et al, 1998a). Cochran et al (1997) also found that increased tillage intensity decreased CH 4 uptake within the subarctic region of Alaska. Fertilization with N generally reduced CH 4 uptake by 0.3 AE 0.5 g C ha À1 d À1 , possibly from the interference of excess NH 4 + on the activity of methanotrophic bacteria in soil (Bronson and Mosier, 1994).…”

Effects of straw carbon input on carbon dynamics in agricultural soils: a meta‐analysis

“…Also, the increase in microbial biomass under straw return may have positive consequences in C fluxes. A number of studies have demonstrated that CH 4 emission was largely influenced by the input of organic substrates under anaerobic conditions (Cochran et al, 1997;Naser et al, 2007;Ma et al, 2008). Additionally, increases in soil moisture due to straw return might accelerate CO 2 emission, as suggested by Jabro et al (2008).…”

Effects of organic matter incorporation on nitrous oxide emissions from rice-wheat rotation ecosystems in China

“…Such a management technique has been shown to support high grain yields and soil fertility, as well as to reduce soil bulk density in rice-wheat systems (Aulakh et al 2001). On the other hand, some studies have shown that the incorporation of crop residues generally increases the readily available C and N in soils, and therefore affects N 2 O production and emissions from soils (Aulakh et al 1991;Cochran et al 1997;Flessa and Beese 1995;Lemke et al 1999). For instance, Zou et al (2005) reported that the application of rapeseed cake together with N fertilizer increased N 2 O emissions, but that a combined wheat straw and N fertilizer application had the potential to decrease N 2 O emissions.…”