SOILS - Earthworms

Fallen leaves can be composted, composted leaves can be added to gardens, and in the garden they can feed earthworms as well as provide many other benefits to the soil. Dr. Joseph R. Heckman, Rutgers specialist in Soil Fertility explains why "earthworms [are a] soils best friend."

Soil health is often associated with the presence of an ample population of earthworms. The feeding, casting and burrowing activity of earthworms can significantly improve soil quality. Listed below are some of the many direct and indirect benefits attributed to earthworms:

Channels created by earthworms aid air and water flow as well as root development. Soil, air and water relationships are thus improved. Night crawlers create large vertical channels which increase water infiltration under intense rainfall. The channels also aid root proliferation into the subsoil. The cast material produced by earthworms has a higher availability of plant nutrients that bulk soil. Earthworms improve overall soil structure and tilth. Their activities partially replace the work of tillage implements. In reduced tillage systems, earthworms help to mix organic residues and nutrients with soil.

There are thousands of species of earthworms. In agricultural soils they can be grouped into two major classes: shallow soil dwellers ('redworms, greyworms, fishworms'). They live and burrow randomly throughout the topsoil layer; deep burrowers ('nightcrawlers'). They build large, vertical, permanent burrows that may extend 6 ft. deep or more. They also construct middens over the mouth of their burrows.

Soils can be managed to encourage a build-up of the earthworm population. Many of the practices that are considered best agricultural management practices are also favorable to earthworms:

Management practices beneficial to earthworms are: leaving plant residues on the soil surface; mulching with organic materials; adding organic matter to soil; maintaining soil pH between 6.0 and 7.0; 'seeding' earthworms into areas with low populations.

Management practices harmful to earthworms are: use of anhydrous ammonia which is toxic; use of carbamate insecticides which are highly toxic; use of certain fungicides which are toxic; using nematicides which, in general, are highly toxic Most herbicides are harmless or only slightly toxic.

While earthworms are almost always beneficial when present, they are not essential to soil productivity. They are usually not present in very sandy soils. Application of manures and organic waste materials help to build earthworm populations. Populations also vary depending on time of year, weather conditions and food availability.