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Slownickel lounge, pull up a chair. CEC interpretation
- Thread starter slownickel
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The numbers at Spectrum are reported in meq/100 grams of soil. Please explain.
caterpillar710
Member
Proof is in the pudding
So you are thinking you could have up to 4 times more of every thing?
The good thing is that the proportions would be the same.
The good thing is that the proportions would be the same.
I gave up trying to adjust micros a long time ago. I just apply proportional dosages every other irrigation or so. Seems to work better. No surprises that way.
Let's see if we can get the guys at the lab to give us back some density data.
Let's see if we can get the guys at the lab to give us back some density data.
caterpillar710
Member
Let's send them a scale
Here is Humphrey Davy's take on the subject:
From a soil perspective.....
CEC refers to the number of negative sites, expressed in meq/100g, or how many cations it will hold per 100 grams of soil.
say your soil has a CEC of 10. It holds 10 meq/100 g of soil. So if all the sites were taken by Ca, that would means that 100 grams of soil could hold 200 mg of Ca. My point is, meq weight of calcium is constant.
Also when they refer to lb/acre, just view the "acre" term as 2 million lbs (the assumed density of field soil, 1 acre 6" deep weighs 2 millions lbs)
So into the wormhole even deeper...
Labs test a specific volume of the soil and assume it's density.
Labs take a set volume of your soil, they assume they're dealing with say 100 grams, when really they have say 25 grams. So if they say your CEC is 15, that means it can hold 15 meq/100 grams of soil. However, it's actually 15 meq/25 grams of soil, which in CEC would mean 60 meq/100 grams of soil.
Bottom line, the ratios they give you in your reports are correct, it's just that they assume your soil per weight hold less of everything than what it does. However in C:N tests they actually do take your density into consideration.
As MIlky knows, Ive created an excell program that takes your soil test results and corrects the difference in density and factors in many things such as ph and suggests amendments and even shows you the percent of target levels each element is at before and after your amendments. You can input your own desired C:N ratio, Ca%, Mg%, and the volume of soil you plan to amend. It also takes into consideration application limits and notifies you when they've been reached. I mainly started it to save me hand work, but then I went a little crazy and wanted more out of it, took a LOT of time but it works very well."
I plan to ask them tomorrow if they will weigh my sample.
From a soil perspective.....
CEC refers to the number of negative sites, expressed in meq/100g, or how many cations it will hold per 100 grams of soil.
say your soil has a CEC of 10. It holds 10 meq/100 g of soil. So if all the sites were taken by Ca, that would means that 100 grams of soil could hold 200 mg of Ca. My point is, meq weight of calcium is constant.
Also when they refer to lb/acre, just view the "acre" term as 2 million lbs (the assumed density of field soil, 1 acre 6" deep weighs 2 millions lbs)
So into the wormhole even deeper...
Labs test a specific volume of the soil and assume it's density.
Labs take a set volume of your soil, they assume they're dealing with say 100 grams, when really they have say 25 grams. So if they say your CEC is 15, that means it can hold 15 meq/100 grams of soil. However, it's actually 15 meq/25 grams of soil, which in CEC would mean 60 meq/100 grams of soil.
Bottom line, the ratios they give you in your reports are correct, it's just that they assume your soil per weight hold less of everything than what it does. However in C:N tests they actually do take your density into consideration.
As MIlky knows, Ive created an excell program that takes your soil test results and corrects the difference in density and factors in many things such as ph and suggests amendments and even shows you the percent of target levels each element is at before and after your amendments. You can input your own desired C:N ratio, Ca%, Mg%, and the volume of soil you plan to amend. It also takes into consideration application limits and notifies you when they've been reached. I mainly started it to save me hand work, but then I went a little crazy and wanted more out of it, took a LOT of time but it works very well."
I plan to ask them tomorrow if they will weigh my sample.
plantingplants
Active member
So K is ridiculous, Ca is low...
Anyone have opinions? I'm confused.
Also, why in the world do LABS, scientific LABS, assume the weight of every soil is the same?! Is this just complete idiocy or am I missing something.....
Anyone have opinions? I'm confused.
Also, why in the world do LABS, scientific LABS, assume the weight of every soil is the same?! Is this just complete idiocy or am I missing something.....
GreenHands13
Active member
Jidoka if you don't mind me asking where is all the zn coming from zn sulfate dosings? The reason I ask is I had one plant in a garden this year that I confirmed had a zn def it had 16 ppm zn and 700 lbs/acre P. the plant right next to it had 25 ppm zn and 700 lbs/acre P and was healthy. I'll post a pic of the plant. I have zn sitting around 30 ppm in my greenhouse with 600 lbs/acre P and can't see anything I recognize as a deficiency are you shooting for 100 plus ppm zn?
GreenHands13
Active member
Crazy thing is the plant still grew as big as the healthy ones. It flowered a little weird but ended up finishing ok. The tips of every branch was clustered and strange looking but the buds below the Tips were fine
plantingplants
Active member
GreenHands, how do you know that's a Zn deficiency? Did you see a P deficiency in the low Zn pot?
Nice greenhouse.
Nice greenhouse.
H
HazyBulldog
Dont forget the super low Cu and Mn, very important for proper bud formation and mildew resistance. The Mg is low also, a reason why you guys see such a response from Sea Crop. That boron I was taught should be at toxic levels, but some of my crop was as high as 6 and no signs of Boron burn. That Ph needs to come down also.
Milky, did you have plants that had mildew? What if any were symptoms of your soil being off? With that ca so low, were you getting hallow stems? Bud rot?
So I chased a Zn def for two yrs and never got it solved. I got really aggressive through the soil on a few plants to try and solve it. Turns out if you start em wrong you cant ever catch up. imo the first soil you put them in is the one you ought to have the most dialed. Give them young uns a good start
On the K...I got greedy. The plants were so healthy that once they had all their trichs and could protect themselves that way I tried some KNO3 in the soil. I needed the N and figured wtf...definitely overdid the K. If I recall they started with not enough K to really finish the crop
But something else is going on. K should not be able to replace Ca on a cec site. If I had used Logan I would at least see which way stuff actually moved regardless of if the numbers are right or not. There is something to be said for picking a lab and staying with it. Consistency probably means more than accuracy
If Spectrum will actually weigh my samples I will switch labs. If they won't ima stick with Logan just cause I have 4 orr 5 yrs of data. And I learned something from it because I improve every yr.
Never stop learning
On the K...I got greedy. The plants were so healthy that once they had all their trichs and could protect themselves that way I tried some KNO3 in the soil. I needed the N and figured wtf...definitely overdid the K. If I recall they started with not enough K to really finish the crop
But something else is going on. K should not be able to replace Ca on a cec site. If I had used Logan I would at least see which way stuff actually moved regardless of if the numbers are right or not. There is something to be said for picking a lab and staying with it. Consistency probably means more than accuracy
If Spectrum will actually weigh my samples I will switch labs. If they won't ima stick with Logan just cause I have 4 orr 5 yrs of data. And I learned something from it because I improve every yr.
Never stop learning
GreenHands13
Active member
Thanks man. No P def. I fed zinc sulfate to it and it stopped curling after about 10 days.
Bull...my stems were rock solid. On the Logan test Si was like 93 ppm and Ca was 60%, combined with enough B that created the pathway.
If you look at ppm Ca my numbers are right there where Slow talks about albeit in a slightly higher cec soil. Maybe there is something to the Si and the sufficiency theory v the exact %s.
As far as pH I shoot for 6.8. I do not rely on sulfuric acid like conventional ag, I count on carbonic acid exudates to dissolve minerals and make them available. I posted Microbeman's take on that earlier in this thread.
They got sprayed with plenty of Mn (accelerate) to form bud.
I saw my first piece of bud rot on still running plants this week. For at least the last two years the only place I see it is where bud rubs against Hortinova.
This year I had perfect weather through Oct...last yr shitty cold and rain. So I don't know what to think other than Si is awesome
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