Hi, my name is Francisco Arriaga, I’m the soil and water management specialist for UW-Extension
and also faculty member in the Department of Soil Science in the University of Wisconsin–Madison.
Today, we are in Arlington, Wisconsin. We are right next to a long term silt experiment
that Dr. Joe Lauer, corn agronomist for UW-Extension, had been maintaining for the past few decades.
What we have here is a system where we have a conventional tillage system that is chiseled
in the fall, followed by … in the spring. Then we also have a continuous no-till system
that has been under no-till for over 25 years. A third system that we’re going to compare,
kind of as an extreme will be the alleyway which has been roto-tilled 2-5 times during
the growing season. Obviously, very little vegetation growing in the alleyway. So, we
have the extreme where we have very little organic matter residue going into the soil.
What I want to talk to you about is actually organic matter. What are the differences between
organic matter and between the systems and what’s happening? So, typically when we
do a tillage operation, we’re incorporating air and oxygen into the system, which the
oxygen tends to be a limiting factor for microbial activity. Microbes, they actually feed on
the organic matter in the soil, so when you introduce that oxygen, that air, as you do
the field abrasion, the microbes start growing and multiply. They chew on–basically they
feed on–that organic matter. That carbon gets released–carbon dioxide, CO2–into
the atmosphere.
On the no-till system, we still have what we call the soil respiration, that process
that I just explained, but it happens at a lower rate relative to a conventional system.
Now, in a roto-till system, we have an extreme, where we’re incorporating a lot of air,
in this case many times during the growing season. We can see that the structure of the
soils, which the structure is held by the organic matter stabilized by the organic matter,
is very weak compared to the other systems. I want to show you a little demo that kind
of mimics a little bit of this oxidation that microbes do, so we can kind of get an idea
and see the relative difference in organic matter in the soils in these three systems.
We’ll start by showing you here. First one to my right, it’s a soil that I took from
the conventional tillage system, just from the surface. In the middle is the roto-soil.
On the left is the no-till system. What we are going to do is add some hydrogen peroxide.
This hydrogen peroxide is not the same hydrogen peroxide that you can get at your local pharmacy,
it’s quite a bit higher concentration at 30 percent hydrogen peroxide. We have the
same amount of hydrogen peroxide and the same amount of soil in this cup, so we’re just
going to add it in. Basically, what’s going to happen is that instead of the microbe subsiding
the organic matter in the soil, it is actually the hydrogen peroxide reacting to that organic
matter and oxidizing that soil organic matter–that carbon, organic carbon. This is actually quite
a strong reaction. It’s exothermic. You can see bubbles being created. If I were to
touch these cups, you can tell that they’re getting quite hot, sometimes to the point
that you can barely touch it. By looking at this reaction, how aggressive they proceed,
we can kind of gage visually and get a n idea of the organic matter content on the systems.
We can see that the one on the right, the commissional tillage, started very vigorously
and it’s starting to kind of wind down a little bit. Similarly, we see the same thing
with the roto-till soil. Then finally, here on the left, it is the no-till system and
you can see that reaction is still going pretty strong. You can see that CO2 being released,
you can see those bubbles where that CO2 is being released.
So what we can conclude from here is that under no-till system, we’re going to have
a greater amount of carbon accumulation, and all the benefits realized that having a greater
carbon in the soil and soil organic matter, all the benefits of fertility, chemical properties,
and especially physical properties relative to a conventional tillage system.
For more information you can visit my website or you can contact your local UWEX agent.