Agriculture Reference
In-Depth Information
2.In the southeastern states, native earthworms (e.g., Megascolecidae), although rarer than
the introduced Lumbricidae, can still constitute 40% on average of the earthworm fauna
(and in many instances, the majority). We know virtually nothing of the agricultural
importance of this Ñresource.Ò
3.Although a substantial amount is known about the biology of the exotic earthworms in
southern pasture systems, ecological linkages between these and other soil biota (with
the exception of root diseases), aboveground pests, and beneficial invertebrates (e.g., via
nutrient flows) remain unstudied (cf.
Scheu et al
.
1999 and
Wurst and Jones
2003). If
current aspirations toward establishing and harnessing improved functional biodiversity
in these soils is to succeed, such linkages need to be understood far better.
4.
Optimal use of water and key nutrients such as N and P, particularly in the development
of systems that optimize uptake by agricultural plants while minimizing off-farm eco-
nomic losses and environmental degradation through leaching and surface runoff, are
high-priority topics across a wide range of agricultural industries, including those that
are pasture based. Previous studies throughout the world have suggested that earthworms,
if managed properly, can contribute to substantial improvements in efficient usage of
nutrients on the farm (Lee 1985; Edwards and Bohlen 1996; Lavelle et al. 1999).
Earthworms need to be utilized as Ñsoil engineersÒ Ð as taxa that can substantially create
the soil architecture that determines water and nutrient movements through profiles and
the abilities of plant roots to access these. Like other macrofauna, such as dung beetles,
it needs to be realized that earthworms can be, and have been elsewhere, manipulated
in agricultural landscapes.
Earthworms are the most obvious element of the macrofauna in pasture soils in southern
Australia. The earthworm fauna in pastures in this region is similar to that of several other countries
with temperate or mediterranean climates. The fauna is dominated by introduced Lumbricidae from
Europe, particularly
A. caliginosa
,
A. trapezoides,
and
A. rosea
. Population numbers and species
diversity are usually low. The geographic distributions of the most common species are patchy.
Earthworm population abundance is correlated with a number of climatic and edaphic variables,
most notably rainfall. The common species are most active in the top 10 cm of the soil profile
during winter-spring. Deep-burrowing (anecic) species are rare, particularly in mainland Australia.
A number of studies have shown that earthworms can improve soil properties, help offset soil
degradation (e.g., burial of lime to reduce soil acidity), and increase pasture productivity in southern
Australia. Different species differ in these abilities to improve soil fertility. The paucity of anecic
species in mainland Australia may be partially compensated by introduction of the highly beneficial
species
A. longa
from Tasmania. Recent research has developed means to mass rear this species
and predict where it might best be established.
Agricultural management practices can markedly influence earthworm populations and biomass.
Examples given in this chapter include tillage, drainage, irrigation, lime and fertilizer application,
stocking rates, and pesticide use. The use of earthworms as biological indicators of the sustainability
of agricultural practices has been suggested by some authors. However, the patchy distributions of
earthworms in space and time present very significant hurdles for the successful adoption of such an
approach.
REFERENCES
Abbott, I. and Parker, C.A. 1981. Interactions between earthworms and their soil environment,
Soil Biol.
Biochem
., 13, 191Ï197.
Andrewartha, H.G. and Browning, T.O. 1961. An analysis of the idea of ÑresourceÒ in animal ecology,
J.
Theor. Biol
., 1, 83Ï97.
