Earthworms are visible enough to make soil biology tangible. In a No-Till Farmer conversation with Frank Lessiter, Purdue University soil scientist Eileen Kladivko traces how studying worms in the 1980s and 1990s opened a wider discussion about the organisms influencing soil structure, water flow and nutrient cycling.
Why an applied soil physicist studied worms
Kladivko joined Purdue in 1982 and worked with long-term plots comparing no-till, chisel ploughing, mouldboard ploughing and ridge tillage. Her measurements focused on aggregation, porosity and water movement. Research from Europe, Australia and New Zealand repeatedly identified earthworms as an important part of those physical processes, while relatively few US researchers were studying them in tillage systems.
That connection made earthworms more than a sign of ‘good soil’. Their channels can influence infiltration and aeration, while their feeding and casting interact with residue breakdown and aggregation. Because different species occupy different parts of the profile, counts alone do not tell the whole story.
Management builds or removes habitat
Reduced tillage, surface residue, manure, diverse rotations and cover crops generally give worms food and a less disturbed habitat. Intensive tillage can physically harm worms and repeatedly disrupt their channels. Fertiliser and pesticide choices also matter, but effects depend on product, rate, soil and species.
Kladivko notes that interest has expanded beyond earthworms to the much larger soil food web. Worms remain useful ambassadors: they helped farmers recognise that a field is not just a chemical reservoir and that management changes the living system doing part of the farm’s work.
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Eileen Kladivko, Earthworm Godmother was produced by No-Till Farmer. Credit: Eileen Kladivko, Frank Lessiter and the No-Till Farmer team.