STUDIES IN-SITU ON NITROGEN FLOWS FROM LUMBRICUS-TERRESTRIS L TO PLANTS

In situ validation of the nitrogen flow through Lumbricus terrestris L. was carried out in an undisturbed natural grassland. This validation was possible thanks to the double labelling of earthworms (coloration + N-15) followed by reintroduction in the field and by a series of recaptures of earthworms for 48 days. Concurrently the nitrogen flow through Lumbricus terrestris L. was measured in the laboratory. Taking into account the Q10, nitrogen flows were similar in the field (16.1% a day at 16.5-degrees-C) and in the lab (14.2% a day at 14-degrees-C). Over a period of 48 days 80% of the earthworms' body nitrogen was excreted into the soil and 24% was taken up by plants. The authors compared the nitrogen flow through another anecic earthworm (Nicodrilus longus longus, Ude) with that measured through Lumbricus terrestris. They showed that the nitrogen flow values were very similar, taking into account the earthworms' biomass, and depended on the temperature only (with Q10 = 1.65). These results allowed validation in the field, in various sites and with two earthworms species, the nitrogen flow measured in microcosms.