NITROGEN PROTOXIDE EMISSIONS ON COLZA PLO TS

Nitrous oxide (N2O) emissions were measured under rapeseed cultures su bjected to two levels of N fertilisation and compared with two types o f fallow in three different pedological situations in North-East and E ast-Central France. The results showed i) a very marked effect of soil properties, particularly the water filled pore space and the ability of the soil microflora to reduce N2O to N-2; ii) a stimulating effect of nitrate availability on N2O emission. The emission increase due to N fertiliser was in accordance with the predictions based on the relat ionship determined by Bouwman (1996). As rapeseed is generally cultiva ted in well drained soils and if N fertilisation is correctly adjusted to the crop requirements, average N2O emissions from rapeseed in Fran ce should be in the lower part of the range usually given in the liter ature.