Earthworms and soil health

Soils contain a diversity of life that is important for the functioning of soil and provision of ecosystem services. Earthworms are a key component of the soil biology that are recognised as indicators of soil health. With an increasing interest in soil health it is timely to recognise the contribution of these underground workers. Earthworms benefit the soil by enhancing both the chemical and physical properties of the soil. They feed on organic matter on the soil surface and within the soil, helping to break down dung pats and incorporate this carbon into the soil. The casts they produce contain a higher concentration of plant available nutrients in comparison to the bulk soil. Earthworms break down organic matter into smaller size carbon fractions, and improve the soils water holding capacity. Simultaneously earthworms burrow through the soil, improving macroporosity and water infiltration. Earthworm burrows aid the growth of plant roots down the soil profile. With all their activity within the soil it is no wonder that earthworms are able to enhance plant growth. Research in both New Zealand and overseas has shown that their presence in the soil increases plant growth by 20%, especially when abundances are over 400/m2.