Gage County
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Beatrice NE 68310
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News Column

Paul C Hay, Extension Educator

No-Till is For the Worms

At every no-till conference and most crop production meetings today, one of the speakers will tell you the benefit of earthworm populations. When farmers ask how many earthworms they should have, there is a vague sort of reply and some reference to a Canadian study which showed 10-12 earthworms per cubic foot of soil in long-term no-till fields. This spring I set out to find out just how many earthworms we actually have in Southeast Nebraska tilled and no-till fields.

The worm species I found in my explorations of 77 sites on 19 fields were Red Wriggler, "Lumbricus rubellus", which is an earthworm commonly used in worm farms. They are a smaller worm which are commonly found in permanent cover crop areas. The most common worm found was "Lumbricus terrestis" commonly called "nightcrawlers". These are common in wetter, cooler areas of lawns, and other grassed areas.

Earthworm populations are important in soil structure, nutrient flow, organic material breakdown and organic matter formation. In the process of burrowing through the soil and feeding on crop residues, earthworms bring soil up from lower depths to the surface, help form stable soil particles (peds), and create burrows which allow for air spaces, aid in water movement, and provide root channels. Some no-tillers back east report all their soybean residue is devoured by earthworm activity. This is not the case in Nebraska for several reasons. The three most important are drier soils, lower organic matter levels, and warmer soils.

So what did I find in the sampled fields?

The 12 no-till fields have been no-tilled for 5 to 20 years. Individual counts of earthworms in a one cubic foot hole ranged from 0 to 39 earthworms. Fields counts made up of four sample locations varied from 1 to 117 worms. The average no-till field had 6 worms per cubic foot and 5.4 earthworm cocoons per cubic foot. The soil structure ratings in these samples was excellent and very good. The structure refers to how the soil peds are laid together. Soil with excellent structure fractures easily and the surface will show more than four blockly ped surfaces per inch.

The 7 regularly tilled fields had individual hole counts ranged from 0 to 7 earthworms per cubic foot. Fields counts made up of four sample locations varied from 0 to 20 worms. The average tilled field had 1 worm per cubic foot and 0.4 earthworm cocoons per cubic foot. The soil structure ratings in these samples was good, fair, and one site had a poor rating. Poor soil structure would have no blockly ped surfaces and basically the whole sample would come out as one block which is very hard to break when dry. Just like the clods we used to push aside with out planter furrow openers so we could get the seed in the ground. They later dissolved in rain to form crusts 2 inches deep which forced us to replant.

If farmers want more organic matter, better structure, and whatever magic the earthworm can do for the soil, no-till appears to offer the better possibilities.

View other Gage County News Columns & News Letters: http://gage.unl.edu/news/news.htm

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