NITROGEN MINERALIZATION AND REORGANIZATION IN CASTS OF THE GEOPHAGOUS TROPICAL EARTHWORM PONTOSCOLEX-CORETHRURUS (GLOSSOSCOLECIDAE)

被引:90
作者
LAVELLE, P [1 ]
MELENDEZ, G [1 ]
PASHANASI, B [1 ]
SCHAEFER, R [1 ]
机构
[1] INIAA,ESTAC EXPT SAN RAMON,YURIMAGUAS,PERU
关键词
EARTHWORM; PONTOSCOLEX-CORETHRURUS; NITROGEN MINERALIZATION; MICROBIAL BIOMASS; CASTS; ULTISOL;
D O I
10.1007/BF00336302
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
Mineral N concentrations ranged from 133.1 to 167.8-mu-g g-1 dry soil in fresh casts of the endogeic earthworm Pontoscolex corethrurus fed on an Amazonian Ultisol; this was approximately five times the concentration in non-ingested soil. Most of this N was in the form of NH4+. N also accumulated in microbial biomass, which increased from a control value of 10.5-11.3 to 67.5-74.1-mu-g g-1 in fresh casts. During a 16-day incubation, part of the NH4+-N was nitrified and/or transferred to the microbial biomass. Total labile N (i.e., mineral + biomass N) decreased sharply at first (ca. 50% in the first 12h), and then more slowly. The exact fate of this N (microbial metabolites, denitrification, or volatilization) is not known. After 16 days, the overall N content of the casts was still 28% higher than that of the control soil. Incubation of the soil before ingestion by the earthworms significantly increased the production of NH4+ in casts. We calculate that in a humid tropical pasture, 50-100 kg mineral N may be produced annually in earthworm casts. Part of this N may be conserved in the compact structure of the cast where the cast is not in close contact with plant roots.
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页码:49 / 53
页数:5
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