Phosphorus

[muddstopper]

Originally Posted by Smallaxe

Cation Exchange Capacity. Simply put it is where a nutrient molecule latches onto a particle and the root is able to extract it for use. How many places for a molecule to latch onto defines its capacity.

Not just any molecule. CEC is a measure of the "Positive" (cations) molecule, and how they are Adsorbed and not Absorbed by the "Negative" (anion) nutrient molecules. Adsorbed being that the molecules are attached on the outside of the negative molecules where thay can be easily detached, rather than being absorded, where s they are surrounded by negative molecules and rather hard to dislodged for plant uptake. To many negative results in a absorbsion of Cations, rather than adsorbsion and to many Cations, will result in absorbsion of Anions, whereas a correct balance of Cations and Anions will result in more readily availability of both types of nutrient molecules.

Hydrogen being the major acid causeing Cation where the positive charge of the hydrogen molecule is used to dislodge the other positive charged molecules from the negative molecules. Further, as hydrogen is found in abundance in water solutions, this same hydrogen molecule is used to exchange negative nutrient molecules with the plants. Ph being one measure of how much hydrogen is in the soil.

[Kiril]

CEC = measure of electrical charge per unit mass of soil, typically expressed as meq/cmol or cmolc/kg.

Soils adsorb

Plants absorb


A short review

http://www.soils1.cses.vt.edu/MJE/sh...n1.1/cec.shtml

[Smallaxe]

Originally Posted by muddstopper

Not just any molecule. CEC is a measure of the "Positive" (cations) molecule, and how they are Adsorbed and not Absorbed by the "Negative" (anion) nutrient molecules. Adsorbed being that the molecules are attached on the outside of the negative molecules where thay can be easily detached, rather than being absorded, where s they are surrounded by negative molecules and rather hard to dislodged for plant uptake. To many negative results in a absorbsion of Cations, rather than adsorbsion and to many Cations, will result in absorbsion of Anions, whereas a correct balance of Cations and Anions will result in more readily availability of both types of nutrient molecules.

Hydrogen being the major acid causeing Cation where the positive charge of the hydrogen molecule is used to dislodge the other positive charged molecules from the negative molecules. Further, as hydrogen is found in abundance in water solutions, this same hydrogen molecule is used to exchange negative nutrient molecules with the plants. Ph being one measure of how much hydrogen is in the soil.

Great additional comments - A little more detailled than my 'simply put' context.
2 followups.

Are all nutrients anion molecules?
Is compost mainly positively charged Cations, due to it high Carbon content?

[Kiril]

Originally Posted by Smallaxe

Are all nutrients anion molecules?

No

Originally Posted by Smallaxe

Is compost mainly positively charged Cations, due to it high Carbon content?

No, and I am not even sure where you are going with this.

[Smallaxe]

Kiril,

What are the exceptions?
Why does compost have a lot more CEC than regular topsoil?

There are too many factors - to be sure... One example - simply put - is useful.

[growingdeeprootsorganicly]

kiril, thanks for the new link, great info...!


smallaxe, if you read kiril's link and link to the other links/pages there it explains why some clay's have more CEC then others, if you look at OM, and it's humic fraction it becomes sort of more
obvious why humus has more CEC then clays, it's not just the carbon, think oxygen and hydrogen too for that matter

[growingdeeprootsorganicly]

i find interesting how pH is such a major factor on what type of phosphate is in majority in solution and how water soluble some phosphates can be at different pH

[Kiril]

Originally Posted by Smallaxe

What are the exceptions?

Exceptions to what???

Originally Posted by Smallaxe

Why does compost have a lot more CEC than regular topsoil?

It doesn't necessarily have more. Remember OM has pH dependent charge/CEC, and it increases at a faster rate than clay as pH moves towards neutral.

[JDUtah]

Originally Posted by Smallaxe

Great additional comments - A little more detailled than my 'simply put' context.
2 followups.

Are all nutrients anion molecules?
Is compost mainly positively charged Cations, due to it high Carbon content?

What are the exceptions?
Why does compost have a lot more CEC than regular topsoil?

There are too many factors - to be sure... One example - simply put - is useful

I think I know what you are looking for, and think I have some good and bad news. I am working on a reply, but it might take a few days to get it all together.

[Smallaxe]

Originally Posted by Kiril

Exceptions to what??? ....

The train has derailed.