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 agroecosystems in southern Germany. From 1996 to 1998, we regularly determined the gas fluxes (closed chamber method) and associated environmental parameters. 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 uptake. CH4-C fluxes ranged from 1.3 to -0.2 mg m(-2) h(-1) and were not significantly different from 0 at both plots. We budgeted an annual net emission 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 topsoil prevents N losses and the inhibition of CH4 oxidation.