Quick EC Question?!

[clivemist]

When adding Nutes and other additives..

Do I need to compensate for any additives?

eg. If the EC is 1.8, with all feed and root protector etc, and they need 1.8, am I going to damage them by increasing the load to say 2.4 including everything?

Just figuring out if I should put the additives in first and then take a second reading with the food?

Thanks in advance.

 

[RobMar]

I take my readings with everything in the reservoir

 

[clivemist]

I take my readings with everything in the reservoir

Thanks.

Thats ok then, just had a problem with the nitrogen levels or something? just eliminating problems as I go.

Gunna try out some 60 day wander, and hopefully get some better results next time..

 

[fatman7574]

If you run your EC up to high with the additives simply dilute your nutrient reservoir water with water until it is down to your desired EC. Remember your base additive is the primary nutrient. The additives are extra on top of the base additives so if you must lessen the input of one or the other always give the upperhand to the base nutrients. Especially if your atlking something like Calcium/magnesium or Phosphorus/potash supplements.

In diffusion solutes (molecules) seek to move from the stronger concentration towards the more diluted thus equalizing any possible differences in the concentration. Diffusion of water across a cell wall is called osmosis. In the process of osmosis water diffuses into a solution having a greater solute concentration; but, osmosis is a special case of diffusion because water also diffuses from an area of greater water concentration into an area of lesser water concentration. Plants take in nutrients by osmosis. ie the low concentrate side always diffuses its salts to the high concentrate side. That means for nutrient uptake the nutrients must have a lower concentrate of salts than the plants fluids contain.

 

[patlpp]

If you run your EC up to high with the additives simply dilute your nutrient reservoir water with water until it is down to your desired EC. Remember your base additive is the primary nutrient. The additives are extra on top of the base additives so if you must lessen the input of one or the other always give the upperhand to the base nutrients. Especially if your atlking something like Calcium/magnesium or Phosphorus/potash supplements.

In diffusion solutes (molecules) seek to move from the stronger concentration towards the more diluted thus equalizing any possible differences in the concentration. Diffusion of water across a cell wall is called osmosis. In the process of osmosis water diffuses into a solution having a greater solute concentration; but, osmosis is a special case of diffusion because water also diffuses from an area of greater water concentration into an area of lesser water concentration. Plants take in nutrients by osmosis. ie the low concentrate side always diffuses its salts to the high concentrate side. That means for nutrient uptake the nutrients must have a lower concentrate of salts than the plants fluids contain.

Fatman: Many fine posts!! Your writings force me to break out my chem book every time!! I have an EC question: How do you calculate an estimated EC number when you mix your ferts? Do you need to know the ionic properties of the element? Or is there a mho value of each element mixed in an aqueous solution with a given mole value referenced anywhere? I don't know, I'm so rusty in chem.... thanks for ur time.

 

[fatman7574]

Fatman: Many fine posts!! Your writings force me to break out my chem book every time!! I have an EC question: How do you calculate an estimated EC number when you mix your ferts? Do you need to know the ionic properties of the element? Or is there a mho value of each element mixed in an aqueous solution with a given mole value referenced anywhere? I don't know, I'm so rusty in chem.... thanks for ur time.

Nutrient solutions conduct electricity, and the capacity of any solution to conduct an electric current its Conductivity. Conductivity is measured by a conductivity meter by placing a probe carrying two 5 electrodes into the solution and passing an alternating current through the solution between the electrodes. The current is carried by charged ions (cations and anions) in the solution. Divalent ions (with two charges like (C++ ) carry twice as much current as monovalent ions (like K+ ). The conductivity of the any nutrient solution will thus be directly proportional to the sum of the cation to anion charges in that solution. i.e. the number of anions and cations must match up. Extras do not count in the calculation.

Conductivity can be expressed in many different units, one of the most useful for growers is CF or the conductivity factor. The conductivity of a solution can be readily calculated from its composition, calculating the sum of the equivalents in mmol! litre, like this;

Cations Nh4+, K+, Ca++, Mg++, Na+, CF, EC
Concentration 0.5, 7, 3, 1, 0.25
mmols/litre
Multiply the ion charges by the respective Concentrations.
milliequivalents 0.5, 7, 6, 2, 0.25, 15 .75, 1.58

The conductivity of nutrient solution expressed in parts per million (ppm) can just as easily be
calculated by converting the ion concentrations to mol. Convert to mols by dividing the concentratic
ppm by the atomic weight of the nutrient. For example;

Cations Nh4+, K+, Ca++, Mg++, Na+, CF, EC
Concentration ppm 7, 273, 120, 24, 5.75
Atomic weight 14, 39, 40, 24, 23
Divide the ppm by the atomic weights to obtain the mmols/litre.
mmols/litre 0.5, 7, 3, 1, .25
Multiply te individual mmols/litre by the respective ion charge to obtain milliequivalents and add these together to obtain the CF.
milliequivalents 0.5, 7, 6, 2, .25, 15.75, 1.58

Conductivity Units

1 CF = 10 milliSiemens /cm normally written as the abbreviation 10 mS/cm
Another common unit is microSiemens/cm (uS/cm) :

 

[patlpp]

Thanks Fatman7574 - Spot on. While I was mixing up your favorite recipe (Lucas) My ppm was quite a bit off than advertised, so one thing has led to another. I may post your answer on another thread as reference. (will be reflected in footnote of course!) Thanks again.