Quantification of nitrogen excretion rates for three lumbricid earthworms using 15N |
| |
Authors: | J. K. Whalen R. W. Parmelee S. Subler |
| |
Affiliation: | (1) Soil Ecology Laboratory, Ohio State University, Columbus, OH 43210, USA, US |
| |
Abstract: | Nitrogen excretion rates of 15N-labeled earthworms and contributions of 15N excretion products to organic (dissolved organic N) and inorganic (NH4-N, NO3-N) soil N pools were determined at 10 °C and 18 °C under laboratory conditions. Juvenile and adult Lumbricus terrestris L., pre-clitellate and adult Aporrectodea tuberculata (Eisen), and adult Lumbricus rubellus (Hoffmeister) were labeled with 15N by providing earthworms with 15N-labeled organic substrates for 5–6 weeks. The quantity of 15N excreted in unlabeled soil was measured after 48 h, and daily N excretion rates were calculated. N excretion rates ranged from 274.4 to 744 μg N g–1 earthworm fresh weight day–1, with a daily turnover of 0.3–0.9% of earthworm tissue N. The N excretion rates of juvenile L. terrestris were significantly lower than adult L. terrestris, and there was no difference in the N excretion rates of pre-clitellate and adult A. tuberculata. Extractable N pools, particularly NH4-N, were greater in soils incubated with earthworms for 48 h than soils incubated without earthworms. Between 13 and 40% of excreted 15N was found in the 15N-mineral N (NH4-N+NO3-N) pool, and 13–23% was in the 15N-DON pool. Other fates of excreted 15N may have been incorporation in microbial biomass, chemical or physical protection in non-extractable N forms, or gaseous N losses. Earthworm excretion rates were combined with earthworm biomass measurements to estimate N flux from earthworm populations through excretion. Annual earthworm excretion was estimated at 41.5 kg N ha–1 in an inorganically-fertilized corn agroecosystem, and was equivalent to 22% of crop N uptake. Our results suggest that the earthworms could contribute significantly to N cycling in corn agroecosystems through excretion processes. Received: 12 April 1999 |
| |
Keywords: | Earthworm Nitrogen excretion rate 15N Agroecosystem Stable isotopes |
本文献已被 SpringerLink 等数据库收录! |
|