In Central Europe 120 to 140 worms per square metre make
a good population density for cropland.
The approximate number of worms can be roughly estimated
using the following methods, which can be easily used by
practitioners:
A 10 x 10 cm and 25 cm deep spade full of fertile,
medium-heavy loam soil contains in average 2 to 3
worms. This amount corresponds to 100 to 200 worms
per square metre.
The number of worm burrows is also a good indicator of
worm activity in the soil.
When counting the number of casts (worm droppings) on
a 50 x 50 cm area during the periods of earthworm activi-
ty (March to April and September to October) i) 5 or few-
er casts indicate little worm activity, ii) 10 casts indicate
moderate worm activity, whereas iii) 20 or more casts in-
dicate good worm activity with the soil containing many
worms.