Earthworms can save the world

"If we feed the earthworms, they'll feed the people" - so says John Baker, a soil scientist from New Zealand. He of course is referring to the challenge of feeding 50% more people worldwide by 2050. However what Dr. Baker is really talking about is soil health and increasing soil biological productivity. Earthworms are the most visible indicators of soil health - kind of the poster child for soil health.

So let's start with earthworms then - what can we do to increase populations? It's much like that famous movie - if you build it they will come.

You can build a better earthworm habitat by going to no-till, using longer, more diverse crop rotations, adding organic matter in the form of manure and compost and of course including cover crops.

Cover crops - imagine that! But it takes time right? Well maybe not as much time as we thought. Adam Hayes and I did some earthworm counts last year on our cover crop plots that were established after wheat harvest. These are plots with simple cover crop mixtures like oats, radish and crimson clover. We compared the number of earthworms where there was cover crop to the no cover crop check. The results varied across the plot but there was always more earthworms in the cover crop treatments. Anywhere from slightly more to two to ten times as many earthworms in the cover crop area.

Crop rotation combined with cover crops like red clover can make a difference in earthworm populations even on a coarse sandy soil. Russ Johnston of the University of Guelph had long term crop rotation work near Leamington in the early 1990's that showed significant increases in earthworm populations even on a very coarse sandy soil.

So if you build it - the earthworms will come. Create a habitat and provide food through crop rotation and cover crops to improve earthworm numbers and in turn soil health and soil productivity.

Chart showing more earthworms in cover crop treatments than in fields with no cover crops.

Text version of graph


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