Here’s What Happens When You Add Earthworms to Your Garden

January 30, 2018 at 5:16 pm





Earthworms build topsoil from scratch and increase food production up to 75 percent, meta-analysis finds


In order to “meet the challenge of feeding a growing world population,” soil scientists from the Netherlands have published a report on what they believe is one the most important factors effecting crop production — earthworms.

A meta-analysis of earthworm studies found earthworm presence in agro-ecosystems leads to an average 25-percent increase in crop yield and-23 percent increase in soil volume.




The report included research conducted in New Zealand and Tasmania, where the introduction of earthworms into perennial pastures increased pasture growth by 70–80 percent initially and by 25 percent over the long-term.

It also included research conducted in Australia, where wheat production increased up to 75 percent after adding earthworms to various fields there.

The studies includes the three main global staple crops (maize, rice and wheat), pastures, and many other food crops.

Researchers believe earthworms stimulate plant growth “predominantly through releasing nitrogen locked away in old crop residue and soil organic matter.”

In addition to nitrogen, worm castings are rich in other nutrients, like phosphorus. The phosphorus levels in worm castings are four times higher than in the surrounding soil.

Also, the worms’ burrows allow plant roots to reach deeper into the soil to access more water and other nutrients.

Earthworms are often termed “ecosystem engineers,” as they are the very creators of soil, the scientists say.

In one trial, earthworms built a 7-inch layer topsoil from scratch in just 30 years.

After creating soil through their castings, they also help maintain its structure and prevent erosion.

Earthworm burrows aerate the soil and allow the the drainage of water up to 10 times faster than soils without earthworms.

Soils with high populations of earthworms have up to 6 times greater water infiltration than cultivated soils.




Plowing or tilling the soil destroys earthworms, along with billions of other microorganisms per square inch.

If you’re tilling to aerate compacted soil, or to bring nutrients up from below, you’re better off to let worms do the job.

One hectare of land can support up to 7 million worms, which in favorable conditions can turn over 50 tons of soil per year.

RELATED: The No-Till Gardening Revolution: Why Farmers are Putting Down their Plows