Abstract
The earthworm population in a winter cereal field in Ireland was studied over a 3-year-period and its effects on soil and N turnover were assessed. The mean annual population density was 346–471 individuals m-2 and the mean biomass was 56.9–61.2 g m-2. Twelve species were recorded, the most abundant being Allolobophora chlorotica followed by Aporrectodea caliginosa, and 242 mg at 5°C to 713 mg at 10°C in the case of juvenile Lumbricus terrestris. Gut contents (dry mass of soil) comprised 6.7–15.5% of the A. caliginosa live mass, and 9.7–14.7% of the Lumbricus terrestris mass. Annual soil egestion by the field population was estimated as 18–22 kg m-2. Tissue production ranged from 81.7 to 218.5 g m-2, while N turnover resulting from mortality was calculated as 1.5–3.9 g m-2 depending on the year and the method of calculation. Earthworms were estimated to contribute an additional 3.4–4.1 g mineral N to the soil through excretion, mucus production, and soil ingestion. Independent estimates of N output via mucus and excretion derived from 15N laboratory studies with Lumbricus terrestris were 2.9–3.6 g m-2 year-1.
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