MANHATTAN, Kan. – Earthworm populations generally become reduced in cultivated agricultural fields, said Peter Tomlinson, K-State Research and Extension environmental quality specialist.

Several explanations for the decline and loss of earthworms have been proposed, he said.

“It could be that tillage implements cause physical injury to earthworms, resulting in mortality. Also, reductions in residue and soil organic matter associated with long-term tillage restrict the earthworms’ food supplies,” Tomlinson said

“A change in soil temperature resulting from the loss of insulation provided by the vegetation could also be reducing earthworm populations. Another possibility is increased predation from birds when the soil is turned over,” he added.

It is likely a combination of these factors leads to reduced earthworm populations, the K-State agronomist said.

In studies comparing adjacent cultivated and uncultivated soils, population reductions are wide-ranging, he said. In one five-year study, the population was reduced by 70 percent by tillage but in a different series of 25-year studies the population was only reduced between 11 and 16 percent, he said.

When tillage practices are reduced or eliminated as a result of conversion to a minimal or no-till system, earthworm populations generally begin to increase, Tomlinson said.

“Earthworms play an important role in no-till systems as they redistribute organic matter. They are important in soil fertility, and their burrows play an important role in soil aeration and drainage,” he concluded.



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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by: Steve Watson
swatson@ksu.edu
K-State Research & Extension News

Peter Tomlinson is at 785-532-3198