Methane and nitrous oxide exchange in differently fertilised grassland in southern Germany

We examined the effect of fertilisation (200 kg cattle slurry-N ha(-1) year (-1)) on the exchange of N2O and CH4 in the soil- plant system of meadow ag roecosystems in southern Germany. From 1996 to 1998, we regularly determine d the gas fluxes (closed chamber method) and associated environmental param eters. N2O and CH4 fluxes were not significantly affected by fertilisation. N2O fluxes at the unfertilised and fertilised plots were small, generally between 50 and -20 mug N m(-2) h(-1). We identified some incidents of N2O u ptake. CH4-C fluxes ranged from 1.3 to -0.2 mg m(-2) h(-1) and were not sig nificantly different from 0 at both plots. We budgeted an annual net emissi on of 15.5 and 29.6 mg m(-2) N2O-N and an annual CH4-C net emission of 184. 2 and 122.7 mg m(-2) at the unfertilised and fertilised plots, respectively . Apparently, rapid N mineralization and uptake in the densely rooted topso il prevents N losses and the inhibition of CH4 oxidation.