Survey results are in. We’re seeing more and more earthworms in the Prairies than we saw before, and we sure don’t like them in our gardens
In the October 22, 2012 issue of Grainews we talked about earthworms and the impact our current farming system has had in developing viable populations in farm fields. It had been my observations that earthworms were rare in farm fields with our old farming system of fallow and mainly cereal crops with little fertilizer. The change to continuous cropping, zero or minimum till, crop rotations with legumes and generous fertilizer use has changed all that.
The October issue included a short survey form and a request for input from readers with their experience and observations with earthworms.
Sincere thanks to the 23 readers who responded in spades — four from Manitoba, 13 from Saskatchewan and six from Alberta. The locations ranged from Winnipeg, Manitoba to Fairview in the Peace River Country of Alberta, so all soil zones were included. A special thanks to the gardeners who made it very plain that earthworms are not all good.
Many of the responses echoed what I had already concluded. Respondents saw few earthworms in the old half and half wheat/fallow days but they see lots now.
The most common rotation includes cereals, oilseeds and pulses but even rotations without legumes still observe viable populations of earthworms.
It’s not all good news: Beware, gardeners!
When I penned the first column our fearless editor Leeann asked if it is all good news. “Are there any negatives?”
I did recall Soil Science Professors at University of Saskatchewan — in my student days — discussing ways to get rid of earthworms in their city gardens. They said the worms made the soil hard and “ruined” the garden.
Wow, was that an understatement. Many gardeners have a big hate on for earthworms and would like to know how to get rid of them. There were two responses from Saskatchewan and one each from Alberta and Manitoba.
John Morriss, Winnipeg-based associate publisher and editorial director of Grainews said, “Are the worms helping or hurting the organic content? Is their presence simply the result of the increased organic matter from zero or minimum till attracting an invasive species?… Don’t get me started on the night crawlers in my other lawn in Winnipeg. It’s literally hard to walk on it because of the castings on the surface.”
Sandra Wasyiciw of the Peace River Country said, “… 100 per cent of the women of this area would strongly disagree that earthworms do anything other than destroy the soil. If I dug a spade full of soil in my garden I would turn up a five-inch ball of hard soil that looks like Swiss cheese.”
Evelyn Johnson of Spiritwood, Sask., agreed with that. “All the organic material has been removed by the earthworms and all that remains is hard clay lumps that look like Swiss cheese.”
I owned a quarter section of land at Spiritwood for 30 years so phoned Evelyn and we had a good visit.
Allan Baker of Mantario, Sask. (near Kindersley), wrote: “In 1960 I broke up an old hog yard. A wonderful garden — could even walk in it after a rain. My brother brought some earthworms from town. After a few more years, no more garden, just hard chunks… They’ve moved half a mile into crop land. Don’t seem to cause harm. There’s less humus — not so thick.”
Darlene McWilliam of Blackie Alberta reported seeing earthworms in 30+ year continuous crop zero/minimum till but also had this to say, “… earthworms eat organic matter and leave the ground crumbly. Only good for fish bait. I wish I had none.”
Earthworms and Anhydrous Ammonia
In the October 22, 2012 article I said, “When anydrous ammonia first came out in the 1970s naysayers said the NH3 would kill the worms. ‘What worms,’ said I at that time. On my Dundurn farm, anhydrous ammonia is my main form of nitrogen, applied three years out of four (not on peas). So, obviously anhydrous is not hurting the worms.”
Jeff Elder of Wawanesa, Manitoba, quit using NH3 10 years ago and thinks earthworm numbers have improved in that time.
Editor Leeann forwarded an Internet exchange between a Wisconsin farmer and one in Alberta. The fellow from Wisconson made the following comment online. “… as for using NH3, your earthworm population will return and your soil will respond over the next three to five years, it takes time.”
The Albertan responded, “funny you should say that! The earthworms in Alberta must be hardier than the ones you guys have because after 40 years of NH3 in our operation we still have lots of them.”
I contacted an earthworm specialist in U.S. who was very surprised to find that NH3 did not kill earthworms.
Anydrous ammonia is not a fumigation. The gas is adsorbed in a fairly tight ball of “light bulb” shape and does not permeate the whole soil — only a small fraction. So, it makes sense to me that earthworms would survive anhydrous.
Earthworms and flax
“Flax is like ice cream to earthworms.”
That is a quote from Ernie Hall of Wynyard, Sask. Frank and Alex Russell of Lethbridge agree.
Jill Capperton, formerly of Agriculture and Agri-Food Canada at Lethbridge also concluded that flax and canola were two favourite foods of earthworms.
It seems that the flax part should be of interest to flax growers that have struggled with tough flax straw for years.
Remember the basics
In the October article I talked about three groups of earthworms:
1. Surface feeders. This type feeds on the soil surface on leaves and other plant materials. They are found in places like under fallen trees, etc. Their casts (feces) form part of the surface soil.
2. Deep drillers. These produce single burrows from the soil surface to depths of two metres or more. They consume surface litter and mix it with soil and can bring subsoil to near surface. Lumbricus terrestris is a deep driller.
3. Topsoil dwellers. These worms work in the topsoil (at about six inches depth) and produce roughly horizontal burrows. They live off surface litter and mix it with soil.
I suspect we have few or none of the surface feeders, that deep drillers dominate gardens and that topsoil dwellers dominate our field soils.
There are many more excellent responses that I could quote — but based on the 23 responses I conclude the following:
1. After 20+ years of continuous cropping, crop rotation and zero/min till — we now have a viable population of earthworms over millions of acres that previously had few or none. Perhaps they are mostly topsoil dwellers.
2. It is not all good news. Earthworms are a menace in many gardens.
3. Some respondents wondered if there is such a thing as too many earthworms.
4. We have no good answer for many of the questions about earthworms. It is my hope that with the great help from readers I may be able to encourage some keen young scientist to take on the topic and answer our questions.
Thanks to readers who took time to write — I am greatly impressed with the information provided. †