Grasslands are important water-regulating agro-ecosystems. Their ability to store and retain water is of vital importance under the current trend of increasing peak rains and droughts, which are events that can result in economic damage to infrastructure and crops. The presence of the anecic earthworm Lumbricus terrestris has a positive effect on the water regulation of the soil. This earthworm creates semi-permanent burrows with a depth of up to 2 m, which increase the water infiltration rate and capacity of the soil. The burrows can also facilitate plant root penetration into deeper soil layers, thus increasing drought resistance. The objective of this research was to explore the ability of L. terrestris to survive and reproduce after introduction into grasslands on sandy soils where they had been absent.
We introduced L. terrestris into mesocosms on sandy soil under permanent grassland at two dairy farms in the Netherlands. Results showed that while L. terrestris was able to survive and produce cocoons, survival rate was low (32% after seven months, 6% after fifteen months) and the number of juveniles was low (2.6 and 2.7 ind. m− 2 after seven and fifteen months, respectively). The causes of this low survival rate may be related to the life history of the earthworms introduced, the effects of soil moisture, interspecific competition for food with the native population of epigeic earthworms, and the risk of predation.
We conclude that L. terrestris can survive and produce cocoons after introduction into permanent grassland on sandy soil, but only further experimental trials over greater time spans and in non-enclosed plots will determine whether there is realistic potential for L. terrestris to develop a stable population.