Linking N2O Production in No-till Soils to Organic Carbon Quality and Microbial Community.

It is well-known that intensive agricultural activities have contributed to the increase in atmospheric concentration of nitrous oxide (N₂O) and the accelerated greenhouse effect. With the growing popularity on no-till (NT) farming, there has been renewed interest in understanding the impact of this practice on N₂O emission. However, past studies comparing N₂O fluxes under NT and conventional tillage (CT) have yielded mixed results. The main source of N₂O in agricultural fields is denitrification, a process controlled by several factors including soil organic carbon (SOC) and soil microbial activity. While tillage-induced alterations in these factors have been reported, only a few studies have linked N₂O production under different tillage systems to SOC quality (carbohydrates, C/N, H/C) and composition of the soil microbial community. To that end and to complement a 2-yr field monitoring of N₂O flux, a laboratory investigation will be presented to compare soils from adjacent CT and NT (up to 48 years) fields. Denitrification activity (with and without glucose addition) will be assessed, and selective inhibition techniques will be applied to determine the bacterial/fungal fraction of the soil microbial biomass. These results will shed light on some of the controversial questions surrounding N₂O dynamics in NT agro-ecosystems.