17.5 Cracking The Code Of Salty Soils

We break down what “salty soil” really means and why salinity and sodicity demand different fixes. We share how to properly diagnose a soil as saline, sodic, or saline/sodic through soil sampling and testing, to avoid turning a manageable patch into concrete.

We also discuss....
• defining normal, saline, sodic, saline-sodic with soil test EC and sodium results
• why salinity causes drought-like stress without wrecking structure
• how sodicity drives clay dispersion and pore collapse
• when salts keep clays flocculated in saline-sodic soils
• risks of leaching or tiling without a sodicity management plan
• sampling depths: 0–6, 6–12, 12–18 inches for diagnosis
• using pH as a supporting clue for sodicity
• prioritizing amendment before drainage to prevent sodic blowups

More information on management of salty soils here: https://www.ndsu.edu/agriculture/extension/publications/managing-saline-soils-north-dakota

Tune in next time for a Tiny Byte of knowledge from GK Technology, where we have a map and an app for that.

https://gktechinc.com/

Chapters

• 0:00 Naming Salt-Affected Spots
• 0:41 How To Sample And Test
• 2:09 Defining Normal, Saline, Sodic, Saline-Sodic
• 3:21 Why Salinity Mimics Drought
• 4:13 Sodic Soils And Clay Dispersion
• 6:09 Saline-Sodic Behavior And Risks
• 7:36 Management Order And Sampling Depths
• 8:43 Wrap-Up And Next Steps

Transcript

Sarah: 0:00

And now it's time for a Tiny Byte of knowledge.

Jodi: 0:13

Gumbo. White spot. Krusty. Alkali. Gumbo. Saline. Kosha patch. These are all terms I've heard people call areas and fields that are salt-affected, but they aren't all created equally. There are some differences here, and we're going to talk about those on these salt-affected areas of our fields.

Sarah: 0:40

That's right, Jodi. There are three major types of salt-affected soils that we can really talk about and think about. We're going to break that all down in this episode of Tiny Bites. First of all, I think it's important for everybody to know that if you want to try to, by the numbers, identify and define a salty soil, you have to soil sample with that in mind. And it's important that you pull soil samples zero to six, six to twenty four, sample. You can even go down and partitions and take a look at soil cores and six-inch increments and have these parameters analyzed. But make sure that you're getting those soils tested for electrical conductivity on a one-to-one basis, as well as the extractable sodium percentage. You need to have those two parameters. pH can also be a helpful indicator in some instances.

Jodi: 1:37

Getting these soil test numbers are crucial for diagnosing and determining what's actually going on and what the best plan of attack for management is going to be. That's right.

Sarah: 1:49

And just backing up a little bit, there are three major types of salt-affected soils. There are saline soils, sodic soils, and saline sodic soils. We also have another category that we'll lump into there that we can call normal. In other words, a non-salt-affected soil. So let's just break that down. What is a normal soil?

Jodi: 2:17

Yeah, so just using like routine soil test data number. So a routine soil test back that's got EC, it's got percent sodium. Um, what you're gonna look for is it's gonna be considered a normal soil if the EC levels are less than one and the percent sodium number is less than five percent. We start to move into that saline category once we get over E or once we get ECs over one, and then a sodium percentage less than five percent. And then on the sodi side, we're looking at soils that have an EC less than one, a percent sodium number greater than five. And then we have the third category, which is a combination of both, when we have both high salts or ECs over one, and high percent sodiums with percent sodiums of five or greater.

Sarah: 3:09

So that is definitely the breakdown of those three categories. And again, a saline soil is a soil that, by the characteristics and how that acts, Jodi just went through the numbers. That is a soil that is highly affected by salts. And what that means is in that scenario, it's going to be hard for a plant. It's going to be difficult for a plant to actually take up the soil solution. Salt-affected fields actually sometimes act as if they're almost in a drought situation because it's just so hard for that plant to take up moisture and the soil solution in that scenario. However, the actual physical properties of the soil don't change that much. So you can still have somewhat aggregation. Usually they do tend to be a bit more saturated, just again, because plants aren't able to take up that much moisture in that scenario. So they might be a little bit wetter. But generally speaking, the soil physical parameters don't change a whole lot. Now, in a sodic soil, something that's very interesting is that often we might even see soil pHs greater than 8.5 in that sodic soil scenario. Also, sodium-affected soils tend to have some very interesting soil physical properties that go along with them. Sodic affected soil has what's called clay dispersion occurring in the soil. What that means is that the individual clay particles actually disperse or break away from the main aggregate. Now, clay particles are actually really small. You can only see clay particles with a micron microscope. So they're very tiny. So when you have those actually dispersing and breaking away from the main aggregate, the soil solution tends to look very cloudy. And what happens then is that when that soil dries out, after those clay particles have dispersed, those clay particles will collapse on top of each other without aggregating or flocculating back together again. And then all of the pore space becomes clogged in that soil and water is not able to infiltrate through. So in this instance, that soda affected soil, after it dries out again like that, actually almost becomes as hard as concrete. And it's very indicative sometimes when you see that soil, that sodium affected soil out there. The whole field might be dry for a long time. But that one place that had that change in the physical properties of the soil, there might just be a little bit of water sitting there because it absolutely cannot infiltrate through. So the soil physical properties can be greatly affected by a purely sodic soil. Saline sodic soil is very interesting because it has both the saline component as well as the soda component. What's interesting is that in this scenario, those clays are not able to disperse as they would in a purely sodic situation. And so what happens is the physical properties of that soil maintain and water can actually still infiltrate through because it's the salts from the staline component that keep those clay particles, what we call flocculated or maintained together in the little aggregates. If you have a scenario, the non-sodium salts are able to leach through the system, then you get left behind with just the sodium, at which point in time that can take over as a sodium-affected soil. And the soil physical properties again can change to have that dispersion issue. And again, where the clays can collapse upon themselves and not allow for water to infiltrate through.

Jodi: 7:14

That is such a great way to describe that third category, the saline sodic. It took a long time for me to wrap my head around that concept that when you have both salinity and sodicity, you might only see the salinity showing itself. But yeah, if you leach away all that groundwater that has those salts in it, those salts kind of buffer and help that dispersion to not be there. And that's why it's so important to get your soil tested so that you don't end up, you know, putting tile in place, leaching those, those salts, salts that are helping to flocculate or keep that sodic soil together, leaching those away and just having the sadicity left behind. So it's so important to have those numbers to help you figure out, you know, what order can I do? What, how can I address the situation and avoid ending up with just a sodic soil in the end, which is very hard to manage. Okay, what we think of as the three major types of salt-affected soil are going to be our saline soils, our sodic soils, and our saline-sotic soils. Again, saline, that's going to be high ECs and not a high percentage of sodium. Sodic soils, high percentage of sodium, but not a high EC. And then, of course, our saline-sodix, which are a mix of both. So if you think you've got one of these areas, go out, take a soil sample. Like Sarah said, zero to six. Um, it's even helpful to do zero to six, six to twelve, twelve to eighteen to figure out where these levels are.

Sarah: 8:42

Well, with that, I don't have a lot more to say about salts. Maybe it's time for us to disperse. Tune in next time for a tiny bite of knowledge from GK Technology, where we have a map and an app for that.