"What the...?" Part 2; How to identify a mystery substance.

Hey guys,
Where did we leave off? Oh yeah, there were two "mysteries of nature" that I was trying to solve:

1. A yellow flour-like powder veins in the clay; and a 
2. Very thin white crystalline crust on the soil surface.  

So I sampled them both.

Freestyle soil sampling.

Here is Mystery #1 in the field.  See the yellow powder, look how fine it is.  Can you see it spread on my fingers?

Here is Mystery #1 by microscope magnification. I think it is pollen!

They appear circular, but I can't quite tell due to their small size.
I'm gonna try and get some mineral oil magnification soon.

Here is Mystery #2 in the field.  To obtain the crystalline crust,  I dug out a chunk, which revealed fresh clay (you see the yellow veins, Mystery #1, very clearly).  The rest has that thin layer of white crystal crust on it.

Here, I'll "magnify" again, using my special magnifying lens.

Here is Mystery #2 magnified under the microscope and at various angles.

Thank you Eastside Memorial Green Tech and Mr. Moldenhauer for hosting my curiosity! 

Here are my future plans (if I can acquire a few supplies with limited effort on my part, ahem):

• Mystery #1 (yellow "flour" powder): Access a microscope with greater magnification and hopefully identify the pollen.  
• You see, each type of pollen looks different when you get up close.
• Mystery #2 (tiny white crystalline crust): Attempt to dissolve the crystals in water.  Then, add acetone to see if there is any precipitation reactions. 
• Why? I'm testing to see if it is gypsum.  I think it is gypsum because gypsum is a very common white evaporite. Also, the presence of gypsum indicates arid environments (like where I was standing at the time).

UPDATE: I haven't found a higher resolution microscope yet.  Also, I tried the acetone experiment, but I don't believe I had enough crystal sample to get significant results; it's a very thin layer.  Alas, the mystery continues... 

Have a great weekend, everyone!

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.  

Plants care about soil pH

Fact: Soil pH* affects the availability of nutrients for plants.

Here is a figure that shows the relationship of soil pH with nutrient availability to plants.  The thicker the color, the greater the availability of that nutrient to the plant.  For the most part, plants can get the most nutrition at pH values between 6-7.

Link to image source.

Question: Why?

Answer: Well, one could write a book on this, a looooooong book, but this is a blog post, so let us settle with the main idea...supply and demand!

For the most part, soil has a negative charge.  Negative charges attract positive charges (or cations*).  Hydrogen has a positive charge...

• ...and when there is  a lot of positively charged hydrogen (i.e., less basic, lower pH), there is more of it available to bind to the negatively charged soil.  When more hydrogen is bonded to the soil, there is less of a chance for other positively charged nutrients to bind to the soil.  Without binding to the soil, they have a chance to nourish the plant, but they are also more easily leached away (like when it rains).

• ...and when there is less hydrogen (i.e., more basic, high pH), there is less of it available to bind to the soil.  When less hydrogen is bonded to the soil, there is more of a chance for other positively charged nutrients to bind to the soil instead of being allowed to nourish the plant. (Link to reference)

More learning resources:

In case you ever found yourself in front of a classroom of middle schoolers, and all you had were test tubes, plugs, scoops, pipettes, graduated cylinders, universal indicator solution, beakers, three different soil types, a stop watch, a color chart pH scale, and nothing to talk about, I propose this lesson plan for you: Measuring pH in soil.  I found this at the University of Texas Environmental Science Institute.  It also has other learning resources for teachers and students.

Also,  I found a webpage with great links to nutrient management teaching modules.  Although they might be easier to read if you have some science background, I am still impressed with their clarity.

*Definiciones:

Soil pH: a measure of the soil’s acidity, or hydrogen (H+) concentration.  

pH = -log[H+], 

where [H+] = the hydrogen ion concentration. 

Because of the negative sign in the definition for pH, low pH soils have more hydrogen than high pH soils.  

Acidic soil: a soil with pH values <7 (high hydrogen concentration)

Alkaline soil: a soil with pH >7 (low hydrogen concentration)

Cations: We defined cations here.  They are ions that carry a positive charge of electricity.

Cation Exchange Capacity: the total negative charge on soil, which is a good measure of the ability of a soil to retain and supply nutrients to a crop.

Link to image source

The Skinny on Pine Needles

Pine needles were recently thrust into my consciousness by two friends. So, if you don't mind, let's discuss the skinny on pine needles, shall we?

But before we delve, side note! I did learn one consideration in its sustainability of use during my internet perusing.  Harvesting pine needles off the ground, like harvesting any other crop, ultimately reduces the nutrients in the soil, so conscientious pine needle collectors may want to give something back for the taking.

Moving on, did you know how awesome they are? They are a pretty good mulch! Look at all these reasons! Particularly on hillsides, since they interconnect with each other and stay put. But many people believe that pine needles, as mulch, add acidity. Perhaps they read this link (look under wheat straw). But what if you didn't think it was acidic at all, because you read this link? Or what if you were like, who cares, I read this pine needle apologist! So I asked the expert who wrote this, where he originally writes that pine needles should be put on acid-loving plants. He is Dr. Don Rakow, Executive director of Cornell Plantations at Cornell. He explained his text succinctly:

Pine needles have been shown to be slightly acidic, usually in the range of pH 6.0 – 6.5. This is not very different from average rainfall pH. The acidity is related to the presence of hydrogen ions in the volatile terpenes in the needles. For a review of a somewhat rigorous series of experiments that examined this subject, check out: Pine Straw (Pine Needle) Mulch Acidity: Separating Fact From Fiction Through Analytical Testing by Scott Jacobs.

So there you have it, it is acidic, but only temporarily and not enough to worry about. So all the supposedly conflicting information from reliable sources out there, were all right in their own way. So I guess this is another YES WE CAN, agree moment, heee.

By the way, you may be curious about terpenes.  They are "compounds produced by plants from isoprene, a hydrocarbon that has its five carbon atoms arranged in a branched chain." They smell really good, and in the leaves of a conifer tree suffering from air pollution, they change in chemical composition and amount (more evocative terpene-talk here, from where I got this info). Wow.

Pine needles by any other name would still smell like terpenes.

(P.S. One day I'll read the instruction manual on my camera, and maybe get a better pic for you)
(P.P.S. Speaking of soil myths and mulch, here are some interesting tidbits on mulch selection from an Australian soil blogger)

What are cations, why do I care.

Soil is so interesting, it makes me want to stare into space.

What are cations? 
They are ions that carry a positive charge of electricity (Reference 4). The common soil cations are calcium (Ca+2), potassium (K+), magnesium (Mg+2), sodium (Na+), and hydrogen (H+) (What is an ion, you ask.  An atom or molecule that has lost or gained a charge -by losing or gaining an electron).
Why do we care?
Many of these cations are nutrients for plants.  Different soils have a different capability to hold these nutrients (and other non-nutrients e.g. aluminum Al+3) and store them. This is quantified by cation exchange capacity.  The higher the exchange capacity, the less likely your favored cations will leach away from your beloved plant roots (and in tangential news, the lower your "base saturation", the less likely the mineral will give that cation up and let it go into the soil water solution for roots.  What is base saturation? I'll get back to you with an eloquent reminder, just... remind me).