Unit 2:
Soil Organisms
• Soil organism, any organism inhabiting the soil during part or all of its life.
Soil organisms, which range in size from microscopic cells that digest
decaying organic material to small mammals that live primarily on other
soil organisms, play an important role in maintaining fertility, structure,
drainage, and aeration of soil.
• They also break down plant and animal tissues, releasing stored nutrients
and converting them into forms usable by plants.
• Some soil organisms are pests. Among the soil organisms that are pests of
crops are nematodes, slugs and snails, symphylids, beetle larvae, fly
larvae, caterpillars, and root aphids.
• Some soil organisms cause rots, some release substances that inhibit
plant growth, and others are hosts for organisms that cause animal
diseases.
Macro Animals
• Macrofauna, in soil science, animals that are one centimetre or more long
but smaller than an earthworm. Potworms, myriapods, centipedes,
millipedes, slugs, snails, fly larvae, beetles, beetle larvae, and spiders are
typical members of the macrofauna.
• Many of these animals burrow in the soil, aiding soil drainage and
aeration; in addition, some organic material passes into the soil through
the burrows.
• Most macrofauna consume decaying plant material and organic debris,
but centipedes, some insects, and spiders prey on other soil animals.
1. Earthworms
• Earthworms pass organic matter through their bodies, grinding it
with the help of tiny stones in their gizzard.
• The material passes out of the worm's body in the form of worm
castings, which are the richest and finest quality of all humus
material.
• Fresh castings are markedly higher in bacteria, organic material, and
available nitrogen, calcium, magnesium, phosphorus, and potassium
than soil itself.
2. Sowbugs