Comparison of alternative farming systems. II. Earthworm population density and species diversity

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Abstract
Effects of soil fauna on soil quality are largely unknown. Our objective was to learn whether long-term soil management has significantly affected earthworm species and populations at two Iowa locations. Soil cores were collected in fall 1989, spring 1990, and fall 1990 from a long-term tillage study in Polk County, Iowa, involving monoculture of corn (Zea mays L.) with either no-tillage, fall disking, fall chisel plowing, or fall moldboard plowing. Species found wereLumbricus terrestris(L),Octolasion tyrtaeum(Savigny),Aporrectodea trapezoides(Duges),A. turgida(Eisen), andA. tuberculata(Eisen), withO. tyrtaeumdominant across all treatments. As the amount of tillage increased, the number of earthworms generally decreased. InBoone County, Iowa, we compared the populations of mature and immature earthworms and cocoons on two adjacent fields, one managed conventionally, the other managed with an alternative farming system for more than 20 years. The predominant species was A. tuberculata. Regardless of management practice, the most worms were found in Canisteo soil on the toeslope landscape position.