Types of Soil for Nightcrawlers

Preferred Soils

• Nightcrawlers prefer moist soil, rich in organic material, with temperatures between 68 degrees Fahrenheit and 77 F. They can survive in soils with pH ranging from 4.2 to 8.0, but they are happiest in soils with a pH of 7.0. Earthworms thrive in soil with moisture content of approximately 30 percent; damp and crumbly, but not soggy. Soils with some form of decaying organic matter are best. Although earthworms can live in areas with low oxygen, they can die if conditions are completely anaerobic, and thus prefer well-aerated soils. Anaerobic soils can also contain bacteria that produce substances harmful to earthworms.

Beneficial Roles

• Nightcrawlers, like most worms, are beneficial animals. They tunnel through soil to depths of 12 feet, aerating the soil and producing a high quality fertilizer as they digest and excrete food. Their tunnels aid root growth in plants, and they are natural soil tillers, bringing minerals up from subsoil and breaking down organic material. Earthworm castings contain a number of nutrients vital for plant growth, such as phosphorus, nitrogen and potassium. A healthy earthworm population will produce approximately 18.5 tons of natural fertilizer per acre, every year.

As a Lawn Pest

• Although earthworms offer many benefits to soil and plant life, a number of their habits have led people to classify them as lawn pests. When temperatures are moderate and nights are humid, earthworms come out of their burrows to forage on the surface of the soil, dragging small pieces of organic material back under the surface to feed. This results in small mounds of twigs, leaves or other plant material, which some consider unsightly on well-manicured lawns. Nightcrawlers also deposit their excrement, known as worm castings, on the surface surrounding their burrow, which can lead to small mounds of dirt scattered throughout a yard. Although there are no ill effects on plants, the small hills can give well-kept lawns an undesirable appearance and texture.

Effects of Chemicals

• Some chemicals used in yards and gardens have the potential to harm earthworms, especially if applied incorrectly. Chlorpyrifos and diazinon have been shown to reduce worm populations, and intensive application of synthetic fertilizers can also harm worm populations. Reducing worm populations can slow the decay of organic material, leading to problems with thatch buildup, reduced plant health and soil degradation. Apply pesticides or other garden chemicals in spot applications only when absolutely necessary, and use organic fertilizers in smaller amounts or slow-release formulations, to cultivate a soil friendly to worm populations.