Why Do Earthworms Come Out When it Rains?

I’ve always wondered why earthworms come out of the ground when it rains.  I don’t know about you, but after a rain I can always find them on driveways and roads. Sometimes I’ll see thousands of them on a short stretch of road as if they are having some kind of mass annelid exodus from a field on one side of the road to the other. So what gives?

At times I’ve wondered if a hard surface like concrete or asphalt provides a source of relative warmth over wet soil.  As it turns out the answer is pretty simple. They can’t breathe underground when the soil is saturated.  The air pockets in the soil fill up with water and worms basically breathe through their skin.  Teri Balser is an associate professor of soil and ecosystem ecology at UW-Madison and she says, “Oxygen from air or water passes directly from their outer cuticle into their blood vessels. Normally, soil has a mix of air and water — about 50 percent of the pore space in soil is air, the rest is water. Oxygen diffuses easily through air, and the soil stays aerobic because oxygen comes in from the surface.”

So that’s all there is to it, and now I know better. Rather than suffocate, the worms move elsewhere. I’d probably do the same thing. Hopefully, I won’t lay in the middle of a road and get squished though.

BUT!!

Another article claims they may reveal themselves in such great ffnumbers following a rain for a number of other reasons.  Stemming from the possibility that “they can even survive several days fully submerged in water” some experts believe pounding rain may mimic the vibrations of worm eating predators causing the worms to surface.  Another thought is they may be using the wet conditions to travel longer distances overland than they could underground.  Since the surface is wet they don’t have to worry about drying out in the hot sun.

What’s your worm experience?  Why do you think the come out on a rainy day?

This post was orignally shared on The Farmer’s Life on April 6th, 2013.  View it now at “Why Do Earthworms Come Out When it Rains?”

What is No-Till?

I recently posted this picture of amassed corn stalk residue on my The Farmer’s Life facebook page with the description “Water has caused crop residue to accumulate in some areas creating a thick mat. In our no-till fields. We may have to burn a few of these to assist the planter in placing seed correctly.”  The first comment on the photo resulted in the post you are reading right now.  That comment read “What’s a no till field? Why would you not till a field?”  A great question.  There are many kinds of tillage including not tilling at all.

What is No-Till? No-till is just what is sounds like.  A true no-till system avoids disturbing the soil with tools like chisel plows, field cultivators, disks, and plows.  Not all of our acres are no-till, but we have been doing less tillage as of late including putting more acres into no-till.  I’m 32 years old and I’ve never actually ran a moldboard plow over a field aside from the single acre we took turns playing on a few years ago in our 1956 John Deere 70 Diesel and three-bottom plow.  I might lose some farmer points here, but I don’t even know how to plow a field properly.  Lack of experience I guess.  A plow could be considered the polar opposite of no-till.  A plow flips over the top layer of soil incorporating nearly all residue into the soil.  No-till relies on natural processes to break down residue from the previous crop.   Advantages

• Reducing fuel, labor, and equipment costs are the most quantifiable benefits of not doing any tillage.  Our current tillage system normally includes a fall chisel plow pass to manage residue followed by a pass, or two, with a field cultivator to prepare a seed bed for planting.  This system would be called minimum or conservation tillage by some, but right off the bat a no-till plan cuts at least two trips across our ground out of our budget.  If we quit doing tillage over our whole farm we’re looking at removing a couple of gallons per acre of fuel from our expenses.  Take the price of diesel today times our just over 2,000 acres of farmland and you’ll get a fairly substantial number.  That’s also fewer hours on a tractor meaning more value at trade-in time, and less wear and tear on tillage tools.  In fact I believe if we went 100% dedicated no-till we could sell off all our tillage tools and downsize one tractor from our lineup.   We’ve recently purchased a John Deere 2623VT vertical tillage tool, but let’s keep things simple for now.
• Improved soil structure is another big benefit.  Tillage disrupts the natural structure of soil and releases some of the carbon soil organisms thrive on.  Soil biology plays an important role in providing crops with the water and nutrients they need.
• Potential for erosion can be reduced by leaving more residue on the surface in the months when there are no crops growing.  Residue allows for rainwater and snow melt to infiltrate the soil rather than causing surface run off that will carry away topsoil and nutrients.  Of course if enough rains falls on already saturated soils you’ll have some runoff no matter what.  We are experiencing those conditions right now.
• Reducing soil compaction is a great benefit.  Soil gets compacted any time equipment drives over the surface.  The weight of farm equipment compacts the air and water pockets present in soil that allow for the movement of water, crop roots, and soil organisms.  Combines and grain carts are the worst offenders because they are very heavy.  Since no-till reduces the amount of equipment a field sees the threat of compaction is reduced.  Compaction cannot be avoided completely, but it can be managed by limiting field traffic to certain areas.  Subsoilers and cover crops can also correct compaction issues.