"What the...?" Part 1

Once upon a time, I started to write a blog post that went like this:


Recently I went to, according my zero research, the world's largest antique fair(!!!) in Round Top, TX.  Fried pickles, fried mushrooms, funnel cake, fresh fried pork rinds, and popcorn may or may not have been devoured ravenously.

We may or may not have found the perfect vintage accessories.

While in town, in a pine forest, I also happened upon a cut in the soil that showed the native clay a few inches below. It had weird yellow veins going through it.  The veins were very fine grained, like a flour-fine powder.  I dug deeper to see if they thinned out, but after several inches of digging through dry clay, the veins were still there.  Can you see them below?

You don't see the yellow veins?  Let's try again, with "magnification."

OK? 
OK.

"What the...?" I was being SoilDuck's good kind of stupid: stupid yet curious.

Internet research was boring, so I checked in with my fellow twits, to see what they thought.  Here were some ideas:

• Fungus.
• But the location (deep) and orientation (horizontal) look wrong.  
• Sulfur.
• But sulfur precipitates as gypsum, and gypsum is white (ahem, it can actually come in different colors).
• Pollen.
• But the powder goes preeeeeetty deep into the cracks...
• Microscope it!
• Oh yeah, and I work at a high school, so this is feasible...
• Do you know the series?
• Maybe.

 I forgot to mention that there was something else interesting too: a white crystalline crust on the outer surface of the clay.

Here is your first official look at the '"mystery of nature" observed under a stereoscope.

See? It is right there, under the stereoscope.

(Thank you, young scientist, Manuel Lopez for taking this picture.

Thank you Mr. Moldyenhaur for setting up the learning apparatus.

Thank you Eastside Memorial HS for hosting this scientific inquiry.)

Actually, were looking at the white crystalline crust here, not the yellow vein powder. Our computer screen is showing a blurry version of it.


But then I hit a stopping point.  I hit Publish anyway.  I hope this post finds you well, and if we don't chat sooner, Happy Mother's Day!  Thank you to both Granny Sharon and Mother Earth.

Join us next time, in "What the...?" Part 2, How do you identify a mystery substance?

Six Degrees of Separation: Smectite Style

Hello, my dearest little poblano peppers!

How are you today?  Where are you today?  You know, I clicked on something according to my research, there are twelve whole readers of you out there. TWELVE of you that lovingly indulge me with a subscription!  I thank our usual suspects, Dr. Doyle, Soilduck, GonferalinID, and Layla.  And you others aren't my mom or dad (well, two of you are, but you don't actually subscribe, LOVE YOU!), so... who are you? Please let me know, so instead of me talking about soils I encounter, we can talk about our soils.  For example, uno de mis amigos vive en un ultisol importante, y otro vive sobre de  roca y un poco suelo (his guest post here).

So please, will you comment and introduce yourself?  Or what you want to hear about next? Or a random thought? I'll pause and wait, to give you a moment to do that....

Waiting for you to comment gives me similar existential issues as those confronted by Grover and Telly Monster in "Waiting for Godot Elmo" by Sesame Street's Monsterpiece Theater. 

Moving on, I have this little "6 degrees of soil separation" game going on in my head all the time.  I believe you can link anything back to soil, just like Kevin Bacon.  So today I am going to relate annoying small toads to the chemical structure of smectite*. I know, it's magic!  Thank you ;-)

First of all, let us let us focus our attention on a gentle, young, unsuspecting Bufo valliceps toad.

Actually, he indeed suspects, see why below.

According to my research hubs, this toad is a Bufo Valliceps. I like to water my foundation, catch them, and gawk at them adoringly.  I pour water onto the side of my house and they all come jumping out from the crack between the foundation and the soil. 

You see, when it doesn't rain, my clay shrinks to provide these naifs space to cuddle in a nice, moist resting area. 

And when it doesn't rain, I water my foundation to get rid of the very same crack in which they reside (Does it help your foundation stability for reals? No idea).

You see, this toad and my humble abode are located upon a smectite clay. I'm obsessed Perhaps you have heard of this soil here, here and here.  Anyways, the crystal pattern for smectite involves adjacent planes, or sheets of oxygen (among other elements).  And adjacent oxygens don’t “bond” with each other very strongly compared to say, hydrogen bonding [the polarity of water: discuss].  This means that when precipitation (rain) percolates into the soil, fresh soil water molecules have an opportunity to get all up in between the tetrahedal layers, which pushes the layers apart and increases the soil volume(!!!).  Yes dude, the soil gets bigger, and in an annoyingly uneven way.  "Le sigh," says my house.

Imagine, the soil under your house is a smectitic, and whenever it rains, the clay under your house expands, and shrinks when it doesn't.  It is like building on ... some other slowly flowing (viscous) material.  Your walls may crack, your door jams stick.  Anyways, we water it in a futile? effort at keeping soil moisture nice and even at all times, which should supposedly preserve our foundation's integrity.  And this is where the toads come in again.

In conclusion, our 6 degrees of Kevin Bacon separation:

1. I pour water onto the soil next to my house foundation so that it will expand to close the crack between the two.  Toads hop out of the crack, annoyed (and then I catch them!).  You see,
2. Maintaining near constant soil moisture levels may preserve our foundation located on a smectite clay. 
3. Smectites change volume depending on soil moisture, 
4. Cuz their adjacent tetrahedral layers are only bonded by oxygen bonds and 
5. Water is more electrostatically attracted to the oxygens in between the tetrahedral layers than the oxygens are to each other.  
6. Once hydrated, the smectite clay mineral expands with the added molecules.

Ta da!  You too, can use your soil science expertise to mildly inconvenience small animals!

PS These smectitic soils are characterized by high base saturation, partially explained here and here.  

Definiciones:

Smectite: A mineral found in great quantities in vertisols, which are known for their shrink swell capacity due to expanding 2:1 lattice clays (source).
Phyllosilicates: Silicates (atomic structures featuring silicon) that combine to form planar sheets.
P.S. They discovered phylosilicates on Mars.  

Vertisols, veritably difficult.

Once upon a time, I took a class on tropical soil management (SOS 5132) by Dr. Hugh Popenoe, at the University of Florida.  Each day, we would get a slide show of pictures from farms all over the world that highlighted low-input agriculture.   It wasn't my typical technical science class; we learned from stories.  This post is on one of the many cool things I learned. 

I got this photo from here

According to the USDA-NRCS, vertisols are high shrink/swell content clays that have deep wide cracks in the dry season. They shrink (to the point of cracking) when drying and swell when absorbing moisture.  Also according to the USDA-NRCS, I live on a classic vertisol, the Houston Black Clay (associated sob story and fun fact).  The state soil of Texas.

According to my class notes, vertisols typically have a wavy, bumpy surface due to all of their shrinking and swelling.  They are usually dark brown, and are located on flat or low slope soils.  Although they have a high exchange capacity (ability to hold nutrients), their massive* structure makes it easy to erode.  


The shrinking and swelling can damage roots, and the soil is hard to plow unless it has just the right soil  moisture (what that magic number is, I can't tell you, it's magic).  If you plow it when it is too wet, you will be creating clods that harden as they dry, almost to the strength of  rocks.  


So how can you manage it? The notes say two things: 1) "Well, annuals, pasture and rice do best on the soil."  This makes sense to me since my soil developed with prairie vegetation from a parent material of calcareous clays and marls  2) "You must manage soil moisture, and cultivate at right moisture content."  


I have a third tip.  If you build a house on it, enjoy the options of either watching grass grow or the cracks on your wall grow**!!  They are about the same :-l

By the way, remember my post on the five soil forming factors?  Well, vertisols and alfisols (a better drained soil order) are both found in same climactic zone, with the same type parent material, but different topography. They both developed from and found on basic parent materials like andecite, limestone, and basalt.

Links for further study:

Agroclimatology of the Vertisols and vertic soil areas of Africa

Networking on Vertisol management concepts, problems and development

Improved Cropping Systems for the Deep Vertisols of the Indian Semi-arid Tropics

*massive in this case means structureless
** from your house foundation shifting

Basic soil physics lesson plan up and running

Hey guys,
I'd like share a lesson plan with you that I wrote for school-aged kids.  I don't see a way to post a PDF on blogspot, so I put it up here instead.  It is about one of my favorite soil topics- soil porosity and water storage!  After you read it, you can consider yourself better versed in basic soil physics!

Thoughts on the lesson plan? I'm thinking of writing up more, in hopes that I can put them to use in "real life" one day.
Thanks!
Amanda

UPDATE!  This USGS link is awesome and also teaches us about capillary action.

Compost teaser

Indeed, my compost smells like roses.

A commenter recently asked how to get started on compost.  I haven't gathered all the necessary information yet, but I wanted to give you a quick factoid to get you interested. The time that it takes to transform your compost into usable nutrients for your plants can vary from days to years, depending on environmental conditions and contents of your compost.  The fastest way to get nutritive use from your compost  (there are other uses!) is to create the following conditions:

• temperatures between 77 and 95 degrees Fahrenheit (25-35 degrees Celsius),
• a pH close to neutral,
• good soil moisture(within your volume of soil, about 60% of the void space is filled with water instead of air), AND
• good aeration (reference).

Why you wait to walk on wet soil

Our gardens love the rain! But be careful, wet soil is more vulnerable to compaction, especially clayey soils. The physical damage from compaction can

• increase bulk density, where soil pores are now too small to accommodate the root cap's growth
• increase soil's ability to resist deformation (soil strength), and prevent root penetration.
• crushes natural soil aggregates and associated macropores, thereby preventing adequate water and air flow.

All this means reduced root growth and therefore less overall vigor of a plant, from your garden plants to large trees! Clay soils are more vulnerable to having their structure damaged due to their increased plasticity and cohesion. Try not to walk too much on your wet soils; perhaps make a permanent path in your garden to help you remember.

Here are some definitions:

Bulk density: weight per volume of soil
Soil Strength: ability of a soil to resist deformation (change in shape)
Plasticity: ability of a soil to be molded or deformed by pressure
Cohesion: stick/stay together
Soil aggregates: soil particles that are held together in one mass
Macropores: soil pores large enough to allow for air and water flow, and even some small animals (some animals make macropores!)
(reference)

When clay soil and cast iron pipes meet

My house is among the many houses built in East Austin in the late 1950s (and maybe other places) that used a unique type of iron pipes for the sewer pipes leading from the house to the city sewer mains in the street. Typically houses are built with cast iron pipes, but this iron was centrifugally spun to create the hole in the center instead of in a cast (info courtesy of our plumber). Somehow this makes them more vulnerable (not sure of the details). Anyways, over time, the chemicals we pour down our drain can damage any iron pipes. Also, in the case of our house, if you don't have enough slope in your pipes, standing water can them rust away. It is possible that over time, corrosion of your pipes will accumulate such that you get a hole in your pipe, and instead of waste water being delivered to your city sewer system, you are also watering the ground underneath your house with chemicals (shampoo, household cleaners etc.) and other gross human goo. Another reason these pipes may be seeing their last days is that they reside in clay soil. Clay soil retains water very well, and we all know what happens when you mix water and iron: rust! Anyways, it is 2010 and this is a picture of the pipes that are now being excavated from our soil not a moment too soon.