Earthworms are the best soil builders on earth.
In fact, all the great agricultural soils of the world were created with the help of these industrious creatures. Among other things, earthworms aerate the soil, improve its water holding capacity, keep it loose, improve its texture, bring minerals from the subsoil, break up hardpans, create fertile channels for plant roots and homogenize soil elements. Best of all, the improvements earthworms make in soil is permanent. For outside flower beds and gardens, use 3-5 lbs. Castings feed plants from seed germination to harvest.