Hi, I am Francisco Arriaga, I’m a soil and water management specialist with the UW-Extension
and also a faculty member in the Department of Soil Science at the University of Wisconsin–Madison.
Today, we are in beautiful Arlington, Wisconsin and we have the opportunity to come to the
soil pit that has been dug long-term near a long-term tillage experiment that Dr. Joe
Lauer, corn agronomist with the Department of Agronomy with UW-Extension, has been managing
for the last 25-30 years.
What we want to show you today is a couple of demos.
First, is an infiltration test, we’re going to compare a conventional tillage system which
consists of a chisel operation done in the fall, followed by a disking operation in the
spring, and then a no-till system.
Again, like I mentioned, the systems have been in place for 25 years.
First, we’ll add water to the infiltration disc.
I have about half a gallon, 1500 MLs, of water and I’m just going to pour it slowly here,
carefully trying not to disturb the soil surface too much.
We will track the infiltration as we continue to talk about this test.
We’ll fill it up all the way to the rim.
We have a little that we’ll start so we get an idea of the time.
I’ll head over to the other side where we have the no-till system and do the same amount
of water.
These rings were actually inserted into the soil, the same amount, so the amount of ring
under the soil surface is actually the same as the amount of ring above the soil surface.
So what we’re trying to determine is differences in infiltration rates between these two systems
long-term tillage management systems.
Again, I’ll fill it up to the rim and we’ll let it infiltrate while we go and show you
what’s called a slate test.
So, what we have here is aggregates from three different management systems.
Over here, this is some surface aggregates from the conventional tillage system that
we just talked about.
In the middle we have the opportunity to take some aggregates from one of the alleyways,
and what that allows us is to show what 2-5 roto-till operations during the growing season
will do to your soil structure and your organic matter.
Finally, we have the long-term no-till system, so we’ll start by inserting the soil into
this container and continue on.
You can see how quickly the soil that was in the roto-till is just disintegrating.
It’s not really holding up, so those aggregates have very, very little integrity–they’re
not very stable.
This is what the slate test shows you.
On the right is a conventional till, so again we have the no-till system long term, 25 plus,
the roto-till alleyway, so 2-5 times roto-till during the growing system, you can see those
aggregates have no stability whatsoever, and we so on the right the conventional tillage
system.
So what’s happening with the slate test is that as we introduce these aggregates into
the water, the aggregates are actually dry, so water gets drawn into the soil.
Water in the soil is actually held under a suction, under a tension, and so this water
gets drawn into the aggregate and what’s happening is that there’s air that gets
trapped inside that aggregate and you get to the point that the pressure is too much
and that air needs to come out.
At some point it will burst out, and that’s the action that we’re seeing here, and so
it gives us an idea, it’s a great test because we can do it in the field and demonstrate
how stable these aggregates are.
And so why are aggregates so important is because we have spaces between these aggregates
in the soil that we call macropore, so these are large pores.
That’s where we get most of our infiltration and so when we get a rainfall event, that’s
what’s going to allow that rainfall to penetrate into the soil and recharge that soil profile.
In Wisconsin, a corn crop, even a soybean crop, requires about 24 inches of water–of
rainfall–to grow.
These soils, like I mentioned earlier, they’re prime soils, plain soil series, they hold
about 11 inches of water.
So, that means over half of the water that your crop needs to grow in Wisconsin needs
to come from either an irrigation or a rainfall event that happens during the growing season.
So you want to improve that infiltration and have the best infiltration capacity that you
can, to make sure that that water gets into your soil profile, recharges the soil profile
and is available for your crop to use.
So we go back, it’s been about three minutes since we started the infiltration test, close
to 4.
We can see here on the conventional side, very little infiltration of this water, still
pretty much where we left it at the beginning.
And if we go and look back at the no-till, it has gone down a little bit more, not quite
substantially, so one of the issues with this test is that it takes a long time, but we
can see that infiltration happening at a little bit faster rate.
Again, going back to the slate test, it’s been going on now for a couple of minutes.
We can see a tremendous difference.
I’ll tap these, and obviously the aggregates are not immune to breaking down, so if we
tap them, we can see that they’ll break down even in no-till.
But you can see that the integrity of the no-till system, it’s much, much greater.
If you have any questions, you can please contact me through my website, or you can
contact your local UWEX agent.