Hire some earthworms. They're dirt cheap. All they ask for is some decaying organic matter to eat and undisturbed soil.
And, boy, will they work!
They will tunnel through your soil to get to the food sources on top — decayed roots, leaves and stems, nematodes, bacteria and fungi.
Their actions aerate the soil, bringing needed oxygen to the roots of plants, an extremely important function in our oxygen-poor, heavy clay soils.
Charles Darwin, who made earthworms the subject of his last book, speculated that every particle of soil on earth had been ingested by a worm at least once, a theory never proven.
His final research, which his contemporaries felt an unworthy subject for a renowned scientist, showed how important earthworms are in maintaining soil quality for healthy plants.
"Earthworms are as important to the soil as bees are to pollination," says Dr. John Bradley, vice president of technical support for FBSciences and former director of the University of Tennessee Experiment Station in Milan, Tenn., a research center for no-till farming practices.
Earthworms eat 30% to 50% of their weight each day and excrete 80% of what they eat, he adds.
The nutrients in their excretions or castings are more easily absorbed by plant roots because they have been converted to a more readily available form, Bradley says. Without their work, many nutrients would stay chemically "locked up" in compost or mulch applied on top of the soil.
Their castings increase the organic matter in soil. As they travel through the soil to get to food, they create tunnels that serve several functions.
"I call the tunnels 'bio-holes,'" Bradley says. "They provide passageways for added fertilizers to go deeper into the soil."
They also funnel oxygen to roots and allow the soil to hold water, thus reducing runoff and erosion.
Worms move organic matter from one place to another. It's estimated that an acre of good garden or farm soil will contain 2 million to 3 million earthworms or 10 to 50 per square foot.
Bradley, a longtime proponent of no-till farming techniques, said earthworms can rarely be found in fields or gardens where the soil is disturbed by tilling or plowing.
Through years of observing the no-till method on various crops, he found many benefits in leaving the soil undisturbed and allowing stubble from crops to remain on the surface.
The decaying stubble feeds earthworms so their populations increase even when synthetic herbicides are used.
"The worms actually break down the herbicides in the soil," Bradley says.
Farmers who have adopted no-till techniques tell Bradley their fields have gone from being practically without worms to teeming with them.
During one of the station's field days, Bradley pulled three cotton plants out of the soil to show farmers the health of the plants. He remembers how surprised the farmers were when they saw earthworms clinging to the root balls.
Compared to soil that has not been through an earthworm, worm castings have seven times the phosphate; 10 times the potash; five times the nitrogen; three times the usable magnesium; and 1.5 times the calcium.
While almost everyone who grows plants is bullish on worms, there are some places in Minnesota and Canada where overpopulations of non-native earthworms introduced by fishermen have been detrimental to forested areas.
But there is no harm in beefing up the worms already in your soil.