Agriculture Reference
In-Depth Information
Figure 5.4
Example of shallow-burrowing earthworms collected from a moist, organic-rich
soil.
pH, will markedly increase earthworm numbers. In general, earthworms are most
abundant under permanent grass cover in cool, humid climates because there they
are undisturbed, their food supply is plentiful, and living conditions are most
favorable. Numbers may then exceed 250 worms/m
2
or a staggering 2.5 million
worms/ha. Their biomass (live weight) can be as much as 3000 kg/ha.
Through earthworm activity, organic matter from the surface is mixed into the
topsoil. Burrowing earthworms create pores, called biopores, as large as 5 mm in
diameter that promote excellent soil drainage and aeration. Thus soil with a healthy
earthworm population quickly drains to its field capacity after rain or irrigation.
Arthropods
Arthropods are a heterogeneous group of reducers that includes wood lice, mites
and springtails, insects (beetles and their larvae, ants, bees, and wasps), centipedes,
and millipedes. Many mites and springtails feed on plant residues and fungi in the
litter, especially where thick mats build up under trees or undisturbed grassland.
Predatory adult mites and springtails feed on other mites and nematodes, whereas
the juveniles feed on bacteria and fungi. For example, predatory mites are effec-
tive in controlling rust mite and bud mite in several wine regions in southeastern
Australia. Such biological control methods can remove the need for chemical pes-
ticides and hence reduce the environmental side effects of viticulture.
Wood lice prefer dark, damp places and are exclusively saprophytes. Although
many beetles and insect larvae that live in soil are saprophytes, others feed on
living tissues and can be serious pests of grapevines. Bees, some wasps, and ants
