THE ROLE OF EARTHWORMS IN STRAW DECOMPOSITION AND NITROGEN TURNOVER IN ARABLE LAND IN IRELAND

Under favourable conditions conventionally tilled arable land can support substantial earthworm populations which can significantly influence soil fertility. Eleven species were present in a winter wheat field in County Kildare, Ireland; the mean density and biomass were 408 ind. m-2 and 61 g m-2 respectively. The population was estimated to mineralize 3.2 g N annually through excretion and tissue turnover, and a further 3.3 g through enhanced mineralization in faeces. The decomposition rate of straw which was accessible to earthworms in the soil was increased by 26-47% within an 8-10 month period compared with that of straw from which earthworms were excluded.