I've been following your posts and hope you will give me some advise ...
In a DWC system using GN's FloraNova Grow/Bloom, temps 76-82, 400HPS,and humidity 45-57%
I keep my pH between 5.5-6.5 usually hovering around 5.8, not usually changing much between reservoir changes every 2 or 3 weeks .
I was keeping my TDS around 1200ppm,but kept experiencing nutrient damage .
I now keep it around 900ppm.
I use hydroton as my medium and wonder if there is any Cation Exchange Capacity.
First off an explantation of Hydroton.
Hydroton is made up of small red clay marbles. Another variety is not rounded marbles but irregular-shaped small red clay pebbles.
Most artificial mediums retain positive ion charges, called cations. These positive charges change the electrical balance in the nutrient solution, affecting the entire workings of nutrients on plants, and the effect is not easy for a grower to detect until production starts to drop off.
Experiments have shown that after 4 weeks in a nutrient solution, the Hydroton absorbs 12-15% calcium cations (Ca++) and a proportional amount of potassium cations (K+). It takes about 4 weeks in pure water to wash out the Ca ++ and a lot longer to flush out the K+.
Hydroton claims its pellets are made out of a neutral pH clay and therefore the claim is that they have an extremely low cation exchange capacity.
[Cation-exchange capacity is defined as the degree to which a soil can adsorb and exchange cations.
A cation is a a positively charged ion (NH4+, K+, Ca2+, Fe2+, etc...)]
There is only one clay type that is not a Polar charged clay (negative charged) clay and that is a mixture of Ilites/chlo rites and Daigenesis clay which can be a Dipolar Clay blend made up of both negative and postive charged clay particles. To say it has extremely low cation exchange capacity is a bit of a far reach however. Clays have a range of CEC rated in MEQ with the range being typically being described as between 0 and 100. The mixed clay has an average MEQ between 20 and 60. Organic soils usually have a CEC of 50 to 100. So does Hydroton really have an extremely low CEC?
So in reality Hydroton is just a inert mediun as in it provided no nutrients through its decomposition as does organic matter in soil, however it still has catonic exchange capacity but in genearl only half of that of a rich organic soil or peat moss medium. Just not as much as soil or peat moss. Basically put Hydroton is not a good hydroponic medium, nor is peat moss. They are essentially like a nutritionless soil in too many aspects.
Q#1, after reading in other threads ,I wonder if I should mix 1part FNGrow and 3 parts FNBloom together as my blooming formula, to keep my nitrogen levels up to keep my older leaves healthy ?
I will discuss that after the Tap Water issue when answering the Flora-Gro question.
Q#2, My water analysis .....
TDS 470 mg/L
Hardness as CaCo3 270 mg/L
Chloride 77mg/L
Chlorine 4.6 mg/L
Cu .00065 mg/L
Fe 0.02 mg/L
Mn .0024 mg/L
Na 54 mg/L
Sulfate 190 mg/L
Zn 0.01 mg/L
pH 7.69
The water analysis does not show much except to show that the water is hard water. Water hardness is principally made up of calcium and magnesium. It is always better when you can obtain the alkalinity and either the calcium amount or the magnesium amount or both. With your Hardness readings though it can very likely be assumed yhough that yu water contains quite abundant amounts of both calcium and magnesium.
However what is alarming about your water is the level of sodium and chloride. The total of the combination of the two together shouldnever get to 300 ppm in your reservoir. It is also reported that the sodium should not exceed 60 ppm. And that is with plants in general. So essentially using your tap water is like adding Botanicare Cal-Mag but without the nitrate and iron that is in the Cal-Mag.
How much of this water can I use in my mix with RO water ...
I'm thinking 25% would be safe .
Cal-Mag is 200 ppm Nitrogen, 320 ppm Calcium, 120 ppm Magnesium, 156 ppm sulphur and 1 ppm iron. Essentially your hardness is going to be neraly all alkalinity so it will be mainly calcium and magnesiunm so figure 240 ppm combined. Typically in natural water the calcium is double the magnesium so figure your straight tap water will add 160 ppm of calcium and 80 ppm magnesium and 300 ppm sulfur and negligible copper.
GH is known for not needing supplemental calcium or magnesium though. If you need it though I would consider that botatnicare suggests that their Cal-Mag be used at 400 to 1. That would sugeest if your wanting to consider using your tap water as a replacement for Cal-Mag supplementation that 25% would be tops.
Q#3 If I change to Dyna-Gro Foliage-Pro will I have water or pH issues that I don't have now?
That is a loaded question. It depends. If used when the plants are in early veg under low lighting it will acuse more ammonium to be taken up than the nitare ratio is set up for so pH drops will be karge. If the temperature are low more ammonium will be taken up and the pH will be large. If the plants are bushy this will provide low lighting intensity to many of the leaves causing incraesed levels of ammonium to be taken up and the pH declines will bee large. If the grow area is set up with reflected wall paint or milar and therefore reflective lighting is provided to the sides of the plants the pH drops will be large. Even side lighting less intnse that the top lighting means incaresed ammonium uptake than nitrate and that causes large pH drops.
What this all boils down to is if there is low lighting any where the ammonium uptake will be larger than the Nitrate take up so the pH will drop. If there temp is low then this will have the same effect.
On the other hand if those conditions do not exist then the nitare will be taken up morethan the ammonium and the pH will rise. Typical formulas have much less ammonium than the FoilagePro and it is common for the pH to drop during budding. However Foliage Pro contains about 5 times the average levels of ammonium contained in MJ specific formulas for hydro.
If you have packed closet type grow in SOG with a very full canopy then there is no low intensity lighting just high intensity lighting of the canopy so no ammonium uptake so the pH will rise. If you have lollipopped plants the pH will rise.
So it all depends. Also if you have high humidity the pH will drop.
As for the mixing of the Grow and Bloom at 3 part Bloom to 1 part Grow. That would only increase the Nitrate to 4.75 % The bloom contains at 4 and the grow is 7. So [4*(3/4) + 7*(1/4)] = 4.75%. That would likely make little difference.
Thanks Fatman I'm looking into creating my own nutrient mix ,just not there yet .