How Soil Structure Stops Erosion: A 4th Grade Demonstration

0:00 When a raindrop falls out of the sky, it's going about 30 miles an hour. Okay, how many of you would like to get hit by a car going 30 miles an hour? No. Oh, you would? Okay, you may need therapy.

0:20 But a raindrop can be pretty destructive to bare soil. And it actually explodes the soil apart, and then when soil falls apart, water can't get down into it because soil is formed in tiny, tiny little...

0:37 Particles of clay and silt and sand. And when they're put together right, the plant roots and all those animals you saw in that video—all the little bacteria and fungus—they actually produce a glue that helps glue the soil particles together. And when they're glued together, then when water hits it, it doesn't blow apart. And then the water can get down into the soil. And when water gets into the soil, then it's not going to be broken.

1:07 When water can't get into the soil then it just runs off the top. So I've got this is soil from my field that we're going to go out and look at here just a little bit. It's been no-till for quite a few years, probably 15 years, and it's had cover crops on it for a couple of years. I'm going to drop it in this water, and if it's a good soil and it's got a lot of the glues that the roots and the...

1:33 Plant animals put in there it should stay relatively intact and the water can go in it without making the soil fall apart. Okay, I haven't done this before so I don't know what's going to happen, so we may have to delete this video, but we're going to put this in here. Okay, and we're going to see some of it kind of slough off and fall apart.

1:59 Now here, this is soil that is from a field that has a lot of tillage, and when it goes in and we're doing a lot of tillage.

2:10 What happens is those blues break down. We don't have a lot of the roots, we don't have a lot of the animals, and so let's see what this one does. We'll just let these set here. They can bring those other things up here. We'll just kind of watch these, how much of the ground is covered here. None, right, it's just bare, and especially you Hastings kids, and when you drive home, look out your bus windows.

2:50 And look at how much of the ground looks more like this as opposed to this. It's going to be quite a bit. This is from the field that we're going to go look at.

3:03 This has residue from the past two or three crops, and it's also got this green stuff that's growing that's dry. And that's a cover crop.

3:12 So what we're gonna do is Jacob and I are gonna dump water in here. These pans have holes in it so it's going to let

3:18 The water out kind of like a rainfall event. The water is going to hit here, and if it goes through the soil I can soak it into the soil it'll be caught down in this pan. And if it runs off the soil like an erosion event it will come out here and we'll catch it in these pans here.

3:38 So we'll dump dump this in and then how much erosion are we getting from the guy that dissed this field?

4:45 When we started, how much of this water that we dumped in actually got down into my soil? Almost none. Almost zero, it's almost all right here.

5:00 Now this one there was some that ran off because that's a pretty severe rain event, maybe. We got at least three-fourths of that in, if not maybe a little bit more. And where it went, that we've got all this water now went.

5:19 Into my soil, whereas this field that guy got nothing. I think I got nothing. And what's really interesting, you know a lot of times farmers will go out and list their field because they say well I need to disc it so that I can get water to go in. But what's really interesting is they'll have this soil and they'll get a rain, but that water and this was already wet because we had a rain last week. So it's not dry but look there's there's.

6:03 Dry dirt down here that rain did not penetrate at all, it just all ran right off. And so when you don't keep the soil covered, you can't get the water in, and you also get quite a bit of erosion. There's a lot of soil in this, that's why it is so dark.

6:22 And if we come over here, let's look at how our different soils are doing. Now this one had a lot of initial stuff coming off, but then it kind of stopped and I still.

6:31 Got quite a bit of my soil left there. This one is continuing to fall apart. And we'll just leave this and when we come back from looking at the field we'll look to see the difference in the color of the water and we'll look to see how much difference there is in soil. So when you move these out of the way, whoever does that, try not to jiggle them too much.

6:55 We definitely like this better than this, right? Because we want the water to go in the soil because that's going to help our plants to grow. And we definitely want our soil holding together like this as opposed to like this.