Bm. Doube et al., SHORT-TERM EFFECTS OF TILLAGE AND STUBBLE MANAGEMENT ON EARTHWORM POPULATIONS IN CROPPING SYSTEMS IN SOUTHERN NEW-SOUTH-WALES, Australian Journal of Agricultural Research, 45(7), 1994, pp. 1587-1600
The effects of tillage and stubble management on the population distri
bution of earthworms were examined under wheat on a red-earth soil at
Harden and under canola on a red-brown earth at Temora in the wheatbel
t of southern New South Wales. At Harden, a five-year pasture had been
followed by a conventionally cultivated oat crop in the year before t
he experiment. At Temora, a six-year pasture immediately preceded the
experiment. Tillage treatments at Temora, and tillage and stubble trea
tments at Harden, were established during February-May 1990 and earthw
orm populations were measured in September. A number of earthworm spec
ies (Aporrectodea trapezoides, Microscolex dubius and M. phosphoreus)
were present at both localities, but the introduced species A. trapezo
ides made up 97-99% of the earthworms collected. Earthworms were subst
antially more abundant at Temora (425 m(-2)) than at Harden (122 m(-2)
). At Temora there was no effect of the intensity of tillage (4, 1 or
0 passes prior to sowing) on earthworm numbers. Earthworm densities we
re reduced in waterlogged soil. At Harden the direct-drill (DD) plots
had a greater population density and biomass of earthworms and cocoons
than the tilled plots. The size (mean weight) of adult earthworms, an
d the number of cocoons per adult, were also greater in the DD plots.
However, no differences in earthworm populations were detected between
minimum tillage (one cultivation prior to sowing) and stubble incorpo
ration (three cultivations prior to sowing). On DD plots, burning stub
ble resulted in significantly smaller adult earthworms, a lower densit
y of cocoons and a lower mean number of cocoons per adult than in the
unburnt plots, but the differences in numerical abundance and in bioma
ss were not statistically significant. Similarly, plots which had stan
ding stubble contained fewer and smaller adults than those in which st
ubble was bashed and in close contact with the soil. There was a stron
g positive correlation between earthworm biomass and the amount of stu
bble present on the surface of the plots at the beginning of the winte
r (r(2) = 0.64, P < 0.01). The contrasting effects of tillage at the t
wo sites and the impact of stubble management on earthworms are discus
sed in terms of the effects of recent paddock history and management p
ractices on the amount, quality and distribution of suitable organic f
ood for earthworms. The influence of these factors is reflected in the
number, biomass and reproductive performance of the earthworms.