Aquaphobic Soil

AlittleSalt · September 25, 2015

Years ago, I was lurking at some organic gardening site and started reading about soil that would not soak up water. In 2010, we started gardening. The soil was mostly blow-sand/silt. You could run water on the soil and the water would bounce off and run away - leaving it dry.

I read that can happen especially to soils with a high silt content (Blow-Sand) It happens during droughts when the soil goes a long time with no rain or other precipitation.

Below is a picture of what I am to understand being aquaphobic soil. It is silt that we brought inside on our shoes that settled under a throw-rug. I swept it up and put it where I was going to dump 3 gallons of mop water. You see the results after 3 gallons of water was poured on it.

I'm wondering if Aquaphobic soil is what this is actually called? Anyone know anything about this?

kunosoura · September 25, 2015

I think hydrophobic is the more technical term (instead of aquaphobic), but in this case I'd call what you're witnessing more of a wettability problem.

Two of the multiple material characteristics that can affect wettability are the chemical makeup of a surface and/or the structure of a surface.

By chemical makeup I'm talking about the surface energy of the surface - hydrophilic surfaces tend to have higher surface energies whereas hydrophobic surfaces tend to be lower. As soil is made up of materials such as clays and silicates, you would expect them to wet readily. However, some organic components mixed into the soil or even on the soil particles themselves can reduce surface energy. Fungi, for example, are very good at synthesizing carbohydrate layers that can coat soil particles and render them hydrophobic. In fact, on golf courses they even employ soil-wetting agents (surfactants) to help the water wet the root zones of the grass.

The other characteristic I mention, surface structure, can make high surface energy surfaces unwettable. I believe this is because the high surface tension of water... Google the Lotus Effect for examples.

Anyway, there is a chance that either or possibly both of these factors may be at play. Other factors include the tendency of some components (clays) to swell when wetted, hindering the penetration of water into the "balls" of dirt that are swept up when you dump a bucket of water over it; the fine particle size of dirt you'd find under a mat also likely plays a role. Wetting insoluble powders can be a major challenge in industry, and is usually solved by vigorous mixing (sometimes using high shear) and/or surfactants.... which leaves me somewhat surprised that the surfactants in your mop water did help wet the soil.

RayR · September 25, 2015

It's called hydrophobic soil. There are a number of things that can contribute to it but the bottom line is the soil is dry and lifeless. Without bacteria and fungi to bind particles of sand, silt and clay into aggregates just the polar attraction of particles can make it impenetrable. There can also be a buildup of organic waxes and oils on the particles from plant debris, again without the microbes to degrade them they repel water.

AlittleSalt · September 25, 2015

Thanks

Okay Hydrophobic.

The mop water was just bleach and water used to smooth dried tape and joint compound. (Getting a wall ready to paint.)

In that garden back in 2010, I learned to add organic materials to the soil to correct the hydrophobic problem. I has worked very well over the past 4 -5 years.

Worth1 · September 25, 2015

This is the same thing that happens when you try to weld aluminum in a way.
The weld puddle gets thin layer of oxidation on it and the weld puddles wont flow together.
While you are trying to get them to do it the bottom falls out.
Aluminum melts at around 1,200F and the oxidation layer melts at around 3,000F.
To remedy this the surface has to be super clean and you weld on AC currant.
The electron flow of the electricity goes from the weld surface to the TIG tungsten pops the oxidation layer and allows the puddle to flow together.
How does this relate to dry soil.
Rain does the same thing it causes the shearing action and allows the soil and water to mix.
Nature has it all figured out.

Worth

pauldavid · September 26, 2015

Robert, I think all my spring tomatoes were aquaphobic from all the rain! Sorry, I couldn't resist!

feldon30 · September 27, 2015

This is a huge problem when working with peat moss of any kind. I wonder if some sort of surfactant, such as dishwashing soap, would be as beneficial for soil as it is for getting peat to accept water? Obviously you want a soap that is as natural as possible without any chemicals.

Worth1 · September 27, 2015

Quote:

Originally Posted by feldon30

This is a huge problem when working with peat moss of any kind. I wonder if some sort of surfactant, such as dishwashing soap, would be as beneficial for soil as it is for getting peat to accept water? Obviously you want a soap that is as natural as possible without any chemicals.

I would suggest Dawn Dish washing liquid.

Worth

kunosoura · September 27, 2015

Worth's suggestion is right on. A little can go a long, long way

If it makes you feel better you could probably go with a castile soap as well.

AlittleSalt · September 27, 2015

This made me think of the Ivory soap commercials being 99% pure (Or something like that) I think I remember seeing it in dish washing liquid form.

lol, I'm tired - brain is taking a break

September 27, 2015	#7
feldon30 Tomatovillian™ Join Date: May 2006 Location: Rock Hill, SC Posts: 5,346	This is a huge problem when working with peat moss of any kind. I wonder if some sort of surfactant, such as dishwashing soap, would be as beneficial for soil as it is for getting peat to accept water? Obviously you want a soap that is as natural as possible without any chemicals. __________________ [SIZE="3"]I've relaunched my gardening website -- [B]TheUnconventionalTomato.com[/B][/SIZE] * [I][SIZE="1"]*I'm not allowed to post weblinks so you'll have to copy-paste it manually.[/SIZE][/I]

September 25, 2015	#2
kunosoura Tomatovillian™ Join Date: Jul 2010 Location: Jupiter, FL (10b) Posts: 97	I think hydrophobic is the more technical term (instead of aquaphobic), but in this case I'd call what you're witnessing more of a wettability problem. Two of the multiple material characteristics that can affect wettability are the chemical makeup of a surface and/or the structure of a surface. By chemical makeup I'm talking about the surface energy of the surface - hydrophilic surfaces tend to have higher surface energies whereas hydrophobic surfaces tend to be lower. As soil is made up of materials such as clays and silicates, you would expect them to wet readily. However, some organic components mixed into the soil or even on the soil particles themselves can reduce surface energy. Fungi, for example, are very good at synthesizing carbohydrate layers that can coat soil particles and render them hydrophobic. In fact, on golf courses they even employ soil-wetting agents (surfactants) to help the water wet the root zones of the grass. The other characteristic I mention, surface structure, can make high surface energy surfaces unwettable. I believe this is because the high surface tension of water... Google the Lotus Effect for examples. Anyway, there is a chance that either or possibly both of these factors may be at play. Other factors include the tendency of some components (clays) to swell when wetted, hindering the penetration of water into the "balls" of dirt that are swept up when you dump a bucket of water over it; the fine particle size of dirt you'd find under a mat also likely plays a role. Wetting insoluble powders can be a major challenge in industry, and is usually solved by vigorous mixing (sometimes using high shear) and/or surfactants.... which leaves me somewhat surprised that the surfactants in your mop water did help wet the soil.

September 25, 2015	#3
RayR Tomatovillian™ Join Date: Jun 2010 Location: Cheektowaga, NY Posts: 2,466	It's called hydrophobic soil. There are a number of things that can contribute to it but the bottom line is the soil is dry and lifeless. Without bacteria and fungi to bind particles of sand, silt and clay into aggregates just the polar attraction of particles can make it impenetrable. There can also be a buildup of organic waxes and oils on the particles from plant debris, again without the microbes to degrade them they repel water.

September 25, 2015	#4
AlittleSalt BANNED FOR LIFE Join Date: May 2014 Posts: 13,333	Thanks Okay Hydrophobic. The mop water was just bleach and water used to smooth dried tape and joint compound. (Getting a wall ready to paint.) In that garden back in 2010, I learned to add organic materials to the soil to correct the hydrophobic problem. I has worked very well over the past 4 -5 years.

September 25, 2015	#5
Worth1 Tomatovillian™ Join Date: Feb 2006 Location: Den of Drunken Fools Posts: 38,539	This is the same thing that happens when you try to weld aluminum in a way. The weld puddle gets thin layer of oxidation on it and the weld puddles wont flow together. While you are trying to get them to do it the bottom falls out. Aluminum melts at around 1,200F and the oxidation layer melts at around 3,000F. To remedy this the surface has to be super clean and you weld on AC currant. The electron flow of the electricity goes from the weld surface to the TIG tungsten pops the oxidation layer and allows the puddle to flow together. How does this relate to dry soil. Rain does the same thing it causes the shearing action and allows the soil and water to mix. Nature has it all figured out. Worth

September 26, 2015	#6
pauldavid Tomatovillian™ Join Date: Mar 2015 Location: NE Louisiana, Zone 8A Posts: 1,179	Robert, I think all my spring tomatoes were aquaphobic from all the rain! Sorry, I couldn't resist!