EFFECTS OF GRASSLAND MANAGEMENT ON THE EMISSION OF METHANE FROM INTENSIVELY MANAGED GRASSLANDS ON PEAT SOIL

Methane (CH4) is the most important greenhouse gas next to CO2 and as such it contributes to the enhanced greenhouse effect. Feat soils are often considered as sources of CH4. Grasslands on the other hand are g enerally considered to be a net sink for atmospheric CH4. The aim of t his study was twofold: (i) to quantify the net CH4 emission of intensi vely managed grasslands on peat soil in the Netherlands; and (ii) to a ssess the effects of grassland management, i.e. drainage, nitrogen (N) fertilization, and grazing versus mowing, on CH4 emission rates. Net CH4 emissions were measured weekly or biweekly for one year with vente d closed flux chambers at two sites, one with a mean ground water leve l of 22 cm below surface and one with a mean ground water level of 42 cm. On each site there were three treatments: mowing without N applica tion, mowing with N application, and grazing with N application. The d ominating species was perennial ryegrass (Lolium perenne L.). Net CH4 emissions were low, in general in the range of -0.2 to 0.2 mg CH4 m(-2 ) d(-1). In the relatively warm summer of 1994, consumption of atmosph eric CH4 peaked at 0.4 mg m(-2) d(-1). On an annual basis, the sites w ere net consumers of atmospheric CH4. However, the consumption was sma ll: 0.31 to 0.08 kg CH4 ha(-1) yr(-1). Effect of mean ground water lev el was significant, but small. There were no significant effects of wi thholding N fertilization for some years and grazing versus mowing on net CH4 emissions. We conclude that grassland management of intensivel y managed grasslands on peat soil is not a suitable tool for reducing net CH4 emissions.