A. Basker et al., EXCHANGEABLE POTASSIUM AND OTHER CATIONS IN NONINGESTED SOIL AND CASTS OF 2 SPECIES OF PASTURE EARTHWORMS, Soil biology & biochemistry, 25(12), 1993, pp. 1673-1677
An incubation experiment was conducted using four soils and two specie
s of earthworms viz., Aporrectodea caliginosa and Lumbricus rubellus,
to study the influence of soil ingestion by earthworms on the concentr
ations of exchangeable K+ and other soil cations. Analyses of cast and
soil samples for exchangeable cations revealed that the exchangeable
K+ content of casts of both types of earthworm was significantly highe
r in Tokomaru (rolling phase), Tokomaru (virgin) and Timaru soils, and
that L. rubellus was more effective than A. caliginosa in all the soi
ls studied. In Marton soil, exchangeable K+ concentrations of the cast
s of A. caliginosa were not markedly different from the non-ingested s
oil. Increases in the values of exchangeable K+ content differed with
the types of soil and earthworm used. The multiple regression analyses
revealed that the differences in these values could be predicted sign
ificantly by the exchangeable and step K values of the soils used in t
his study (R2 = 1.00 and 0.998 for A. caliginosa and L. rubellus respe
ctively). The concentrations of exchangeable Ca2+ Mg2+, and Na,+ of th
e casts of both types of earthworm tended to increase compared to the
non-ingested soil. Exchangeable H+ and the cation exchange capacity of
the cast material remained unaltered with respect to non-ingested soi
l.