Agriculture Reference
In-Depth Information
6.5
Control
A. caliginosa
A. longa
A. trapezoides
5.5
*
*
*
*
*
4.5
3.5
0-2.5 cm
2.5-5 cm
5-10 cm
10-15 cm
15-20 cm
Soil Depth
FIGURE 14.4
) at varying depths within field cages containing different earthworm
species. Cages were maintained in a pasture on a sandy loam at Strathdownie, Victoria. There were 45
earthworms added per cage. All treatments had an equivalent of 4 t lime added to the soil surface. Soil pH
was measured approximately 5 months after adding earthworms and lime. Asterisks indicate significant
differences compared with data for the control treatment (no earthworms) at the same soil depth. Soil pH in
the absence of lime is indicated by horizontal dashed lines. (Data redrawn from Baker et al. 1999a.)
Average soil pH (in CaCl
2
Optimal use of key plant nutrients is central to sustainable agricultural production and catchment
health, particularly the development of systems that maximize the uptake of applied fertilizer into
plants and the recycling of nutrients from plant residues; minimizing off-site losses and nontarget
impacts through leaching and surface runoff is viewed by farmers and the broader community as
a high priority. Research in New Zealand (Sharpley et al. 1979) has shown that earthworms can
bury surface organic matter in pastures rapidly and reduce N and P loss (leached out of the dead
organic matter) from sloped agricultural fields (by factors of 4 to 8). Similar research to that in
New Zealand has not been done in Australia, but it seems likely that similar benefits would accrue
through the retention of nutrients on farms if earthworm communities were managed well. Certainly,
opportunities exist for earthworm treatments to be imposed on surface-runoff trials that are currently
under way in Australian pastures to test for impacts.
EFFECTS OF AGRICULTURAL MANAGEMENT PRACTICES
ON EARTHWORMS
It is well known worldwide that agricultural management practices such as drainage, irrigation,
lime, fertilizer and slurry application, pesticide use, stocking rate, tillage, crop rotation, and stubble
retention can influence earthworm populations and biomass (Lee 1985; Lavelle et al. 1989; Curry
1994; Fraser 1994; Edwards and Bohlen 1996).
Rovira et al. (1987) demonstrated that populations of earthworms in a red-brown earth soil in
S.A. were doubled by the direct drilling of cereals, in contrast with those under conventional
cultivation. Fewer earthworms were found in soils under a lupin-wheat rotation than under a pasture-
wheat rotation. Haines and Uren (1990), Buckerfield (1993b, 1994), Buckerfield and Wiseman
(1997), and Mele and Carter (1999a) provided further evidence that tillage reduces earthworm
populations in Australia and that pastures in rotation with cereals and the retention of stubbles can
increase earthworm abundance.
