Pm. Mele et Mr. Carter, Impact of crop management factors in conservation tillage farming on earthworm density, age structure and species abundance in south-eastern Australia, SOIL TILL R, 50(1), 1999, pp. 1-10
Cropping practices commonly used in conservation tillage can potentially im
pact on earthworm abundance and distribution. Management practices associat
ed with conservation tillage fanning for cereals such as stubble retention
and management, greater utilization of herbicides, and soil acidity amelior
ation were assessed for their influence on earthworm density, age structure
, and species abundance at a total of seven sites on Chromic Luvisols in no
rth-eastern Victoria, Australia. Earthworms were sampled from the surface s
oil (0.1 m(2) x 0.1 m deep) at the end of the cool wet season (August-Septe
mber) when species tend to concentrate at this soil depth. In three six-yea
r experiments, crop management practices that retained stubble as a surface
mulch for successive years supported consistently higher densities of eart
hworms, followed by retained stubble left standing, burning stubble, and in
corporation of stubble. The latter reduced earthworm densities by an averag
e of 53%, compared to the mulched system. This trend was consistent across
texturally different soils. Autumn application of postemergent herbicides f
or two consecutive years, at double recommended rates, was associated with
significant increases in earthworm densities (by 10-124%) the following spr
ing, compared to the recommended rate. Herbicide application had no influen
ce on earthworm species richness, Although the effect of increasing soil pH
on earthworm numbers was variable, lowering the pH consistently lowered ea
rthworm densities (by 60%). No clear trend was observed in earthworm popula
tion age structure at any of the sites. Overall, reduced soil disturbance a
nd increased inputs of crop residue at the soil surface, although having li
ttle effect on diversity of species, are conducive to increasing earthworm
populations in conservation tillage cropping practices in north-eastern Vic
toria. (C) 1999 Elsevier Science B.V. All rights reserved.