[blkantha]

Looks like slow has taken a backset... Hopr he will be back soon.. If not let us know where to subscribe to learn more or ask Q

[growingcrazy]

Originally Posted by paradoxlost

Its just a question of math. Whatever rock dust or sand or inorganic material that is making up the rest is swinging the average down.

That or spectrums sum of bases inherently measures less than the CEC cause assuming 100% base saturation is a poor assumption

What change occurs to a mediums cation exchange capacity with an increase of pH?

What CEC value have you witnessed from a bale of premier peat or equivalent?

I ask only to learn.

[EastBayGrower]

Originally Posted by growingcrazy

What change occurs to a mediums cation exchange capacity with an increase of pH?

What CEC value have you witnessed from a bale of premier peat or equivalent?

I ask only to learn.

Plain peat

TEC - 14.38
pH - 4.3
O-matter - 91.38
S - 8 ppm
P2O5 - 25 lbs/acre
Ca - 1155 lbs/acre
Mg - 423 lbs/acre
K - 62 lbs/acre
Na - 20 lbs/acre
Ca% - 19.47
Mg% - 11.89
K% - 0.54
Na% - 0.30
H% - 59.00
B - 0.22
Fe - 26
Mn - 9
Cu - <0.2
Zn - 0.71

[growingcrazy]

Originally Posted by EastBayGrower

Plain peat

TEC - 14.38
pH - 4.3
O-matter - 91.38
S - 8 ppm
P2O5 - 25 lbs/acre
Ca - 1155 lbs/acre
Mg - 423 lbs/acre
K - 62 lbs/acre
Na - 20 lbs/acre
Ca% - 19.47
Mg% - 11.89
K% - 0.54
Na% - 0.30
H% - 59.00
B - 0.22
Fe - 26
Mn - 9
Cu - <0.2
Zn - 0.71

Fantastic! Now explain the CEC of 14.

[jidoka]

Is the real trick to move that H% down to around 10 with what you want then fertigate the rest? Or use a fertilizer with its own cec...compost or biotic?

There may be a reason why the tom hill mix worked so well

[growingcrazy]

With a TCEC of 10, what level would you put calcium at?

[jidoka]

If we are going there change threads...i promised

[paradoxlost]

Originally Posted by growingcrazy

Fantastic! Now explain the CEC of 14.

So at such a low pH the CEC sites start being taken over by hydrogen and aluminum. The reason why the aluminum is such a problem at low pH is that it goes from aluminum oxide to trivalent aluminum, which takes over CEC sites and leaches out other bases. TCEC is not equivalent to CEC, it's is much much lower. This is because sites occupied by hydrogen and aluminum will not removed by any other single ion, you need a change in the chemical environment. What would want to do there is raise the pH with lime. This will give an actually CEC number.

[jidoka]

So check the cec of Promix, which has been pH adjusted with dolomite and get back with us.

[paradoxlost]

Originally Posted by growingcrazy

What change occurs to a mediums cation exchange capacity with an increase of pH?

What CEC value have you witnessed from a bale of premier peat or equivalent?

I ask only to learn.

the CEC would increase, which I have experienced myself. But this also is affected by other factors, including carbonate content as carbonate will precipitate calcium carbonate, which will lower CEC, for example. There are certainly other factors than can affect CEC over a range of pH, such as iron and aluminum content, etc.


Sphagnum peat moss, according to university of Idaho, has a CEC of 100 to 200. Also they are reporting a pH of 4.4. But they are using the BaCl2 method of CEC determination, which is like the amonium acetate test at a high pH.

Let's take a look at the coots mix. One part aeration, one part peat, one part compost, plus various amendments. Let's say the CEC of both the compost and the moss are 100 meq/100 g soil. The aeration is most likely basically 0 meq/100 g soil. Probably has some residual CEC that's less than a meq. That mix would be 60 meq/100 g soil. We recently made a mix loosely based off the coots mix and at a pH of 7 it had a CEC of 24 than at pH 8.2 it had a CEC of 83. There were some other things going on, but right now iits looking fantastic. Just popped two of The One backcross and they look great. This makes sense though. We used very little carbonates in it. The compost we used was the same CEC at pH 7 and only a CEC of 43 at pH 8.2. This indicates the peat moss having most of it's CEC being realized at higher pHs.

Idk why peat moss is so acidic and whatnot, but it's following a reasonable trend.

But jidoka, you mentioned that you were requesting labs weigh samples when they test. This is good practice and should also be done by you before you send in a test. Also retest things from other labs to confirm they aren't making wild assumptions. Universities may not offer the variety of tests a private lab does, but if it confirms their melich 3 numbers you can probably assume they did it right.