Estimation of N2O fluxes under rape for biological fuel production, bare soil and grass fallow

Abstract

The excessive use of nitrogenous fertilizers on biofuel-producing crops could substantially increase agricultural emissions of N 2 O and hence eliminate the beneficial effects of recycling CO 2. N 2 O fluxes were estimated from a soil in France under four treatments: (1) bare soil; (2) unfertilized grassland fallow; (3) soil cropped to rapeseed and fertilized at rate of 180 kg N/ha per year; and (4) as for (3) but fertilized at 280 kg N/ha per year. Measurements were made using the static chamber method throughout spring and summer 1994. No beneficial effect on N 2 O production was observed under fertilized rapeseed. Fluxes in the order of 1 kg N/ha per year were measured under rape fertilized at 180 kg N/ha per year. The amount of fertilizer applied to rape has a significant effect on the amount of N 2 O released. Bare soils constitute a risk in terms of N 2 O release as a 'hot spot' was observed after the harvest. Grass fallow seemed to be best adapted to limiting N 2 O release.