State of Science :: Commentaries
Organic Farming, Worms, and No-till
Author(s): Klaas Martens
Note -- A posting to the "Odairy" email list asserted that tillage-dependent organic farming systems are hard on soil structure and earthworms. Klaas Martens responded and discusses the impact of organic and no-till systems on earthworm populations.
Odairy List, March 20, 2006.
I've heard that story about earthworms many times. The good news is that the earthworms have not. My direct observation has been that earthworm populations explode after plowing in a good immature cover crop.
I am convinced that many farmers are really just starving their earthworms to death. Just like any other animals, The worms, arthropods, protozoans, etc. in the soil need food, water, air, and a favorable environment to thrive. I
would contend that the scorched earth chemical no-till that is so heavily promoted falls down on at least two and often on all of those factors.
Old dead crop residue is pretty poor quality food for animals. The chemical nitrogen, herbicides, fungicides, and insecticides needed to keep the crop alive make for a poor environment for animals to grow in. Lack of oxygen is far more harmful to many soil organisms than tillage is.
I agree that we should reduce tillage whenever it is possible while still maintaining healthy soil conditions and high yields. I have seen first hand though, that on many soils, using straight no-till is a disaster. Many of
our neighbors have observed: "no-till no corn" That's not theory. That's simple field observation. I even tried going ahead and continuing to no-till for a few more years on one field where it was not working in hopes
of the soil finally straightening itself out if we stopped tilling it long enough. I ended up with soil so hard that all the water from fast rains ran off causing more erosion downstream. There were no earthworms left in that field. The soil was so hard they had all suffocated or starved to death.
Why do you think farmers pull 'zone builders' ahead of their no-till planters? It's not because they enjoy buying those $30,000 to $40,000 machines that take a 200+ horsepower tractor to pull. I have a little trouble understanding why the government calls that no-till. Sure they leave the residue on top, but they are also often tilling 18" deep with a
zone builder tooth and then churning up the slot with multiple wavy coulters ahead of the "no-till" planter.
There are some excellent no-till systems out there like Steve Groff's and the Rodale roller. There are also some really destructive ones.
There are soils in the world that have been under intensive cultivation for literally many thousands of years that are in still in excellent condition today and there are soils that have been ruined by farmers using poor
practices in just a generation.
I am confident that our organically farmed soils will be in better shape when our children take them over than they were when we transitioned them.
I see more and more acres of chemically farmed soil, mostly minimum till or no-till degraded to the point where farmers can't make a living on them anymore.
Our organic matter content is at least 50% higher now than when we transitioned despite our soil being farmed with a plow. We have also seen
aggregate stability doubled on fields after moldboard plowing. (Those observations were made by Cornell researchers working on our farm).
Yes, tillage oxidizes the soil and burns organic matter. It does so by stimulating biological activity. Active soil organisms help build stable aggregates. A soil where very little organic matter is being used up is a
dead soil. As long as we add more organic matter than we consume and keep the soil healthy and full of life, it(the soil) is improving. It's only when we take out more than we return that the soil declines. Chemical nitrogen burns up organic matter too but it returns nothing of value in the process.