EFFECTS OF EARTHWORMS ON CATION AND PHOSPHATE MOBILIZATION IN LIMED PEAT SOILS UNDER PICEA-SITCHENSIS

Aporrectodea caliginosa was successfully introduced into limed peat mo noliths in field lysimeters under a stand of Picea sitchensis which ha d been fertilised with P and K at 75 and 100 kg ha(-1) 5 years previou sly. Total earthworm biomass was sustained over the 12 months of the e xperiment in the limed treatments, whereas only 3% remained in the tre atment without lime. Earthworm cocoons were produced in the limed trea tments only. Aporrectodea caliginosa in limed soil significantly incre ased leachate fluxes to lower soil horizons of K+ (to 35 kg ha(-1) yea r(-1)), Ca2+ (to 303 kg ha(-1) year(-1)) and Mg2+ (to 19 kg ha(-1) yea r(-1)), compared with untreated controls (19, 8 and 4 kg ha(-1) year(- 1), respectively). These increased leachate Ca2+ and Mg2+ values were also significantly greater than from limed-only soils (56 and 8 kg ha( -1) year(-1) respectively), and treatments in which earthworms alone w ere added (10 and 6 kg ha(-1) year(-1), respectively). Potassium and M g2+ mobilised by the addition of earthworms plus lime appeared to be t aken up by living roots of P. sitchensis. There was no effect of any t reatment on phosphate release.