AdAgrA 2019: True Success

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AdAgrA: Adventist Agriculture Association

Intensive: Advanced Soil Science

Michael Trevizo

Advanced Soil Science - Part 1

Our Heavenly Father, we want to thank You once again for giving us the opportunity to be here and to be able to discuss and present these topics.

And Father, we pray that You would please be with us this morning and that You would be with me and that you would help me to convey this information in a way that would be beneficial to everyone that's here.

I thank you father for this opportunity and I pray asking this in Jesus name, Amen.

All right so I have a chance to meet some of you guys already today or well not today but since yesterday and For those of you that don't know me.

I'm Michael Trevizo I Will be presenting on soil science today, and I wanted to Talk a little bit more on some I want it I know the subject has been discussed quite a bit already in previous agri-conventions.

And if any of you guys have actually gone on and heard any of the audio that's been put on AudioVerse from the last years, a lot of what they said was kind of a repetition.

They're really trying to make certain points.

I didn't want to just repeat what has already been said.

So I will discuss some of those things, but I wanted to kind of get into cation exchange capacity soils and what exactly they are and kind of give you guys an understanding of what that is And then we'll talk about balancing nutrition and how we may be able to manage it and how You know the importance it plays when we actually look at doing soil tests and then of course when you get a soil test done maybe what type of soil test you want to look for and why you want to look for it.

So let's see there's a couple other things I want to discuss I think I talked about ion exchanges in soils.

I also wanna talk about, let's see, different nitrogen, phosphorus, and sulfur cycles when we start looking at some of the anions and how we ought to consider or what we ought to consider when we want to manage those nutrients because those nutrients aren't held by colloids.

They're anions, which means that they cannot be, they're not cations.

In other words, they have a negative charge instead of a positive charge.

Therefore, they're not gonna be on your soil colloids or they're gonna be very, there is some anion exchange capacity on your colloids in your soil, but it's very insignificant.

So we don't really wanna focus, or we don't usually focus on that and we don't really bother testing for that, because the amount that's held is very insignificant.

So I'll start with the functions of agricultural soil.

So what is the purpose of the soil, besides walking on it and putting things on it.

Some of the important parts that the plant plays is the fact that it anchors the roots, so it's a physical structure, a place to, a foundation for the plant to be.

Of course, it supplies water to plants and roots, provides air for plants and roots.

Well, your average pore space in any soil is 50%.

And it's ideal to have 25% of your pore, or actually 25% of that 50%, which is half of that 50%, moisture, straight moisture.

So when we start thinking about moisture content, we're talking about the pore space in soil.

So if I say that you're fully saturated, that means that 100% of your pore space is full of water.

So that means that that 50% is completely full of water.

That's not a condition you really want to have.

It's ideal to be at 25% air, 25% water, and then the other 50% being the actual mineralogy in the soil.

Okay, of course, releasing water with low levels of nutrients.

Now, I'm sure everybody in here is familiar with hydroponics, right?

Does anybody not know what hydroponics is?

Okay, we all got a pretty good grip on what that is.

So when we're growing in hydroponic soils, what they do, or not hydroponic soils, I'm sorry, when we're growing in a hydroponic production system, what they do is that they take the minerals that normally the soil provides for the plants and they look for ways to put it into an aqueous, which means water solution, that they can feed to the crop.

And essentially you're spoon feeding your crop.

Well, when you're growing in soils, what is referred to as a soil solution is similar to hydroponics in the sense that it is water that has nutrients available to the crop.

However, the nutrients that are in that soil solution come from your colloids and also come from your organic matter that's being decomposed and worked on by microorganisms.

So those nutrients in the soil are applied in a method that is very complex and different than a hydroponic system.

So when you're growing in the soils, there are certain mineralogy and certain nutrients that you can expect to be there that you cannot expect to find in a hydroponics.

In hydroponics, you don't usually have that because you're growing in coca coir or you're growing in beads or some other substrate that has no capacity to hold moisture because the pore spaces are too big.

And compared to soils where you have tiny pore spaces that where the water can adhere through the forces of cohesion and adhesion onto these small particles of soil and are allowed to be available to the plant throughout different parts of the day through periods of dryness when there's no moisture coming in.

So this is why in hydroponics, if the pump breaks, the crop is done.

So I spoke about soil air being 25%, water, oh of course, of the mineralogy in the soil, that 50%, you want 5% of that typically to be organic matter.

And a desirable soil condition would look like this.

There are a few instances in coastal regions, in Alaska as well, where your organic matter is extremely high, maybe 25%, 50% even.

And these type of conditions, in fact, the soils where they harvest phagnum peat moss are typically about 50% to 60% organic matter.

I mean, it's just a ton of organic matter.

And that's usually found, again, in soils that freeze, where that organic matter, where the microbes cannot work on that organic matter and break it down.

So you grow, and then you freeze, and then you grow, and you freeze.

You get into the deserts, into the tropics, and you have very low organic matter, typically, in the soil.

You might have some in the surface, but very little in the actual soil because it's always warm and microactivity is constantly working on that, breaking that down so you don't have this ability to buffer it.

And then of course, in organic production systems or agricultural production systems, sometimes you don't even have 5%.

You're lucky if you have 1% or 2% because we plow them and we break that ground down and we push it so hard that we rip everything out of that organic matter and you lose it.

So when they coined the term organic agriculture, the reason why they went with the word organic and not some other thing, sustainable or whatever other word, phrase, perhaps hip phrase you could think of is simply because their focus was on keeping healthy organic matter.

They did this through composting and other methods that have become popular over the years, but essentially, really, what they were looking at is how have we traditionally farmed over the last multiple millenniums, and how is that different from what we've been doing once machines got involved, as well as chemicals and other genetics.

And they use an awful lot of organic matter, and they really try to keep no less than 5%.

So anyhow, that's where that term came from.

So when we start looking at soil texture, a lot of times I'll talk with farmers and they'll tell me, oh, well, you know, alfalfa really likes to be grown in a silt loam and this is a clay loam and that's why my alfalfa doesn't do very well.

Well, that's not really a good practice to have, a good idea, because when you start talking about silt loam and clay loam and sandy loam, I didn't put a soil triangle in this thing, but anyhow, really, you're just talking about different portions of the soil and how much of it is actually clay, silt, and sand.

And when we look at this, sand, These are the size of particles from 0.1 to 0.002 inches, which is rather large.

So sand is actually a very large particle.

The bigger the particle, the bigger the pore space, which means the bigger the pore space, the lower the moisture retention capacity of that soil is.

So this is why sandy soils drain well and don't hold moisture.

Well, if we look at silt, you see it's 0.002 all the way to 0.001 inches.

This is considerably smaller, but even smaller yet is clay, which is .001 inches and below.

And, you know, clay is actually very light compared to sand, to silt or sand.

But the reason why we tend to think as farmers that clay is heavier is because it's so small, it has such tiny pore spaces that the moisture comes in there and it doesn't leave.

So the heaviness comes from the water that's in the clay and not the actual clay.

So that's how those clay soils are so sticky and heavy even though the clay is actually light.

So here's a soil structure and when we start looking at organic matter and the role it plays, now we talked about these 3, sand, silt, and clay, and it doesn't really matter whether you have sand, silt, or clay.

There's this thing called soil aggregates.

Soil aggregates is the icky gooey stuff in your soil that holds it all together and gives your soil structure.

When you pick that soil up and you feel it and it crumbles nicely on you or it stays together so it doesn't fall apart and get blown by the wind or get washed off through erosion when the rain comes, that is soil aggregates.

And soil aggregates comes from decomposing or decomposed organic matter.

And that organic matter can be anything from your old dog Skip to your great-great-grandfather to deer that you may have killed, or the weeds that were there, or anything that was ever alive that has died is organic matter in the soil.

So when we look at the organic matter in the soil, and everything that was ever alive, that means that at some point it had the nutrients it needed to be alive.

It had the amino acids it needed, it had if it had bones, it had the calcium and the phosphorus it needed, whatever that organism had while it was alive, it gives up when it dies.

From the dust we came to the dust we shall return.

Everything that has ever been alive will return to the soil.

So whatever it takes to make something, when it dies, mineralization of nutrients is the fancy term that soil scientists use to say, the building blocks that once made that living thing are now breaking, coming apart, and are being made available for the next generation of living organisms.

So, it's in organic matter where we really focus to control our anion exchange capacity, if you will.

We don't normally talk or refer to it that way, but essentially With organic matter, you have different cycles.

I'll get into that a little bit later, but a lot of your nutrients, nitrogen in the form of nitrate, phosphorus in the form of orthophosphate, and sulfur in the form of sulfate tend to come from your organic matter.

So when you want to manage those nutrients, you really got to pay attention to your organic matter.

And now not all organic matter is created equal.

There's Typically 3 different fractions of organic matter.

Advanced Soil Science - Part 2

Now I want to talk about base saturation, what that is, percent base saturation, and then of course soil nutrient balancing, or should we say percent base saturation balancing.

Now If you get this book right here, it talks a tremendous amount about base saturation balancing.

That's Michael Listera's book, The Ideal Soil Handbook.

So we spoke earlier about cation exchange capacity, soil nutrients in the soil solution, and these nutrients exchanging with the plant roots.

So, base saturation is the measure of total bases in the soil.

So when you go back and you look at this and you take that sample, we're going to say how many bases.

Does anybody remember from chemistry class what a base is?

Base, those are the positively charged, the cations.

So when we say base saturation of the soil, we're asking how many bases, cations, how many cations are in that soil.

When we say percent base saturation, that is the percent of the soil's cation exchange capacity that is occupied by a given nutrient, say calcium or magnesium, etc.

Base saturation and percent base saturation are not necessarily the same thing in the literature.

I'm going to focus mostly on percent base saturations because base saturation usually does not include aluminum and hydrogen because well of course what is pH?

The negative log of the concentration of hydrogen ions.

So pH is just a measure of either the hydrogen or the hydroxides.

If we're less, or really it's actually most of the hydrogens.

So if we have a pH less than 7, then that means we have more hydrogen ions than we have hydroxide ions floating in our solution, right?

Which is in this case, our soil solution.

If we are greater, a pH is greater than 7, then we have more hydroxides than we have hydrogens.

Okay, so we don't really focus on hydrogen because we consider it an acid.

And aluminum drives acidity, like I talked about earlier.

Now, here is a soil sample taken from a field in New England.

This was taken at Logan Labs Soil Report back in 16 from a field in New England.

In other words, it's just been a pretty lawn for the better part of 20 years, maybe.

It has a pH of 6.4, which is a critical thing a lot of people usually look at.

I'm sorry, it has a cation exchange capacity of 6.4, which is right here in the center you see 6.24.

And then we see our calcium, magnesium, potassium, and then sodium.

And then these are referred to as our exchangeable cations.

Then you have your anions, which is sulfur and phosphorus.

Then you have your base saturation percent.

Now, we talked about the percent base saturation.

What we're talking about, like I said, is here in this example, we have 42.22% calcium.

That means when they look to see how many, you see value found, which is right here, 1, 404 pounds to the acre, they concluded at a depth of 8 inches that 1, 404 pounds to the acre of calcium was enough to saturate 42.22% of this soil's cation exchange capacity.

So when we look at magnesium, we see 9.22%.

The same case for magnesium, when they say it's 9.22% base saturation, that means that the value found, 184 pounds, was 9.2%, saturated 9.22% of that 6.24 on top.

Now, you could have, now every soil has a different cation exchange capacity.

You never know what it's gonna be until you test it.

So when you come up to me and you ask me questions, anything along the lines of what do you think it is, or I got a farm over somewhere, any idea what my CEC is?

You come and you ask me questions about, I have this problem or that problem, what could it be?

Until I see something like this, I really don't know what to tell you.

And the thing is, when you get your soils tested, folks, a lot of the exchange universities and some of the other laboratories, they don't test them like this and they don't give you all that information.

And when you don't get this much, you look at it, you think, that's a lot of information.

But really, if you don't get this information, then you don't really know.

They're giving you incomplete information, and it's hard to make decisions.

Some of the labs I've had tested in the past, or some of the samples that I had tested in the past from different laboratories, but they'll do something like maybe just test calcium, and then maybe magnesium and potassium.

You see this in this example, they say that they found 27 pounds and then they tell us that our base saturation of sodium is 0.69.

That's very, very little, very, very little.

But if you just told me, if you don't even bother to test it, and say this soil was from the coast somewhere, and it's getting a lot of sea water on it, and you don't even bother to test for sodium, sodium could have been 40% of your base saturation.

And all you look at is how much calcium, magnesium, and potassium you have, then you're not doing yourself a favor, are you?

If you're in a desert and saline soils, you could have the same thing.

The soil is not considered sodic until it's more than 10% base saturation, 10 to 15%.

But they don't usually Describe it that way.

They'll say more than 100 pounds or 200 pounds to the acre, whatever number they give you.

But really, that's not what's so important as much as it is what's your base saturation.

Because if you have 200 pounds of sodium to the acre, but you have a base saturation, I mean, a cation exchange capacity of 90, then that's not really a big deal.

Because your percent, I mean, I'm not going to do the math.

I'm just going to throw a number out there, for example.

It could be 2% or it could be 3% base saturation, which is not a big deal.

So you see what this is about is balancing your percents of base saturation that is here.

Albrich's approach was not have this many pounds and you'll always be good no matter what.

No, it was balancing the available nutrients in the soil but in order to balance that you need to know what the soil can carry.

The first off this this 1 was taken in New England right?

About 40 inches of annual rainfall and I don't know what they're supposed 15 feet of snow or whatever it is so they get a lot of precipitation every year.

Alright so low pH, so my argument here is that low soil pH is something I wanted to get to a lot of times a Tremendous amount of the literature that you read from extension agents and everywhere else really argue and really push pH Oh, I got to get my pH down or I got to get it up or oh the pH needs to be this and the pH Needs to be that I handed out some books yesterday on production guides, and they'll tell you, hey, you want to grow strawberries, you need a pH of 6.5.

You want to grow blueberries, you need a pH of 4.5.

You want to grow tomatoes, they really like it at 6.5 to 7 or whatever, and they tell you all these pHs, but really, what the, it's naked information, and it really doesn't matter.

I'm growing tomatoes and I grow tomatoes very well, very excellent, beautiful tomatoes at 7 to 8.

Because I don't really focus on hydrogen.

All that pH is telling you is what your base saturation of hydrogen is.

Which normally we like to keep around 10% and that usually equals 6.5, a pH of 6.5.

If you're growing in real soils, it gets more complicated.

You've got a 5.2, a 6.1, a 5.9, a 5.2 at the top.

Advanced Soil Science - Part 3

I got a number of different soil samples that were shown to me, but I didn't actually see any that said anything about buffering capacity.

Of course, I didn't look over them thoroughly.

But the old school of thought was you take your soil sample in, you get it tested, they'll tell you what the buffering capacity is.

So I wanted to kind of describe what the buffering capacity is.

But the term buffering capacity is usually associated with the soil's ability to resist changes in pH.

So remember we talked earlier about percent base saturation of hydrogen and how that relates to the pH in the soil as well as the percent base saturation being related to the total cation exchange capacity of the soil.

So if you know the total cation exchange capacity of the soil, we'll say it's a really high number, we'll just exaggerate, we'll say 100.

So that means that if you have a pH of 6.5, then that 10% is the equivalent of a CEC of 10 being saturated with nothing but hydrogen.

So if you want to change that pH, you've got to put a tremendous amount of line down, right?

So you see, when you're using soil mineral balancing, when you use Albrecht's system of soil mineral balancing to work with your soils, buffering capacity becomes really essentially meaningless.

So these old school of thoughts that really go way back, I mean, literally I think it's about a hundred years ago or so that when they started using buffering capacity and they just didn't want to let it go, but that's where that comes from.

Now if you have a soil that you can, maybe it's contaminated with aluminum or it just naturally has high levels of aluminum.

What that aluminum does is that it restricts your, I talked earlier how it pulls those hydrogen ions off of the water.

I'm sorry, the hydroxide ions off of the water, putting hydrogen ions into the soil solution and then increasing the pH.

So another issue in buffering capacity is how much calcium do you need to put in the soil to remove aluminum?

So there's not just the hydrogen that's associated with your pH and your base saturation, but also the aluminum that's in your soil.

So these are the 2 things that you really need to look at.

It's referred to as desorb from the soil exchange sites, et cetera, et cetera.

We look at the actual pH aluminum concentration in parts per million in the soil.

You see as your aluminum increases in parts per million, which is the equivalent of, you know, you multiply that by 2 and you'll get pounds to the acre or kilograms to the hectare.

So if we started at about 0, you usually, it has no real serious effect.

As you start to increase that all the way up to as high as 40 pounds to the acre, you can see that you end up with about pH dropping down to about 3.7 or so, which is a very exaggerated scenario of aluminum toxicity.

Aluminum also, when you put the lime down, again, look at the root system of these seedlings compared to these seedlings in a soil with high levels of aluminum, it's very obvious what's going on with your root system here.

This is where I talked about having healthy roots, having the right calcium level.

It's not necessarily all about aluminum, But because the aluminum drives that acidity, when that calcium comes in, you remove that aluminum, now you have that ability for those bonds to form in the middle lamella of the root cells to make those roots strong.

Because remember, your roots have no epidermal, I'm sorry, they have no cuticles.

They have no waxy cuticles to protect the exterior.

You don't want a waxy cuticle, you need ion exchanges, right?

If you have a waxy cuticle, you're not gonna be able to do that.

So because you don't have that, the only real defense we have is proper mineralogy in our soil solution to give us healthy roots in our crops.

Now okay so the take home on, I didn't really want to talk a whole lot on buffering capacity because I don't feel like there's all that much to say, But let's see here.

The real take home here is that soil with a CEC and low pH will have a higher buffering capacity.

Soils with a high CEC and a low pH will have a higher buffering capacity.

So that means it takes a lot more of lime or whatever nutrient you need to use to change that pH, whether it be dolomitic or calcitic limestone.

So soils with a low CEC and a low pH will have a lower buffering capacity, which means it takes less lime to change that pH.

Okay, so here's an example of where I don't really give pH a tremendous amount of respect.

Now if I told you I had a pH of 8.8 and I told you that I was gonna lime, most of you would think I'm crazy, right?

But in this particular scenario, I looked at it and I said, no way, I need a lime like crazy.

Because when I got down here, the soil nutrient balancing is always more important than pH because when we look at this, 36% calcium, 38% potassium.

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Intensive: Advanced Soil Science

Advanced Soil Science - Part 5

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