Check My Math: Adding Disodium EDTA To Your HydroBuddy Nutrient Recipe?

[ExNavyInSTL]

@farside05

I was thinking about what you said regarding Potassium Silicate.

"Comparing your proposed mix to mine, you may be a little short on K. Adding in a Silica supplement (ie Potassium Silicate) would provide Silica and help bump that K a bit. You also have an abundance of Ca, Mg, and S. One of the benefits of having all the individual chelated heavy metals is that you're able to control the S more easily since they aren't combined with the extra Sulfates."

While researching it appears that Potassium Silicate doesn't play well with others at concentrate.

Considering this, I built a 1-gallon-based recipe around it to get 19 ppm of SiO2 and it added about the same in K. So, I took the recipe I like from before and lowered the Potassium Nitrate some, and brought it back up with a little bit more of Cal/Nit.

The amount of Potassium Silicate to get 19 ppm is 0.15 g p/gallon. That's easy enough to just add to the water that I am using in my reservoir recipe.

So, if I am topping off with another 5 gallons of nutrients, I would dissolve 0.75g of PS into a small bit of RO water, then place it in the reservoir. Then add in my concentrated nutrients and top up my reservoir until I get to the desired EC.

That sounds easy enough.

By the way, I had forgotten that when I bought all the other base nutrients I purchased a 1-pound container of Potassium Silicate.

 

[Delps8]

So, if I am topping off with another 5 gallons of nutrients, I would dissolve 0.75g of PS into a small bit of RO water, then place it in the reservoir. Then add in my concentrated nutrients and top up my reservoir until I get to the desired EC.

No mas on "topping off" for this Redleg. We know that EC does not measure what's in the nutrient solution - it just tells you how much electricity will pass through it. Given that different chemicals in nutes are taken up at very different rates, adding back nutrient solution can lead to nutrient issues. And imbalances are more often the driver of nutrient issues than are nutrient deficiencies (that's per Bugbee and I need to find the paper/video in which he states that).

Bugbee's paper "Nutrient Management in Recirculating Hydroponic Culture" makes a very strong argument to not top off using a standard mix of nutrients. He does discuss using ¼ strength Hoagland but, unless you're targeting specific chemicals in which the nutrient mix is deficient, he argues that adding nutrients will tend to lead to nutrient imbalances.

Between the cited paper and "Nutrient Solution Management and Longevity", I've switched to using RO for add backs and I replace the res when I've added back at least 50% of the size of the res or if pH starts to change radically.

Interestingly, and that's as far as I'll go because "the plural of anecdotes is not data", I got lazy a few weeks ago and I topped off using diluted nutes. EC went up, yay!, I got a little tip burn for my troubles (not yay). Sure that could well be a coincidence but, even if it was, it was a good lesson (and that is confirmation bias, of course!).

 

[ExNavyInSTL]

@Delps8

Thank you for that.

Some time back, I bought a wall-mounted EC & pH monitor

I have a 12-gallon (20-gallon arrives today) reservoir that the sensors stays in full time so I can look at the reservoir status at a glance.

Until your post above, I was doing the following:

• For my 5-gallon top-up, I would measure out how many grams (dry salts) for 5 gallons

• Then dissolve the A & B separately in a beaker in about 500ml of RO.

• After dissolved I would toss the two beakers into the reservoir with the agitator running

• This would spike the EC meter at (for example) 3.95 EC

• Then I would pump the reservoir with RO water until it came down to 2.1 EC (FloraFlex Veg)

• Then I would correct pH to 5.8 pH

If I am understanding you right, what I described above is "No Bueno?"

If so, I have no problem mixing up the whole 5 gallons (4 gals in this case because of bucket size) separately and then adding it to the reservoir. Then use much less RO water to correct E.C in the reservoir.

Although, that sounds like the same thing in a way. However, I trust Dr. Bugbee and you if that's what he says.

No mas on "topping off" for this Redleg. We know that EC does not measure what's in the nutrient solution - it just tells you how much electricity will pass through it.

 

[Delps8]

@Delps8

Thank you for that.

Some time back, I bought a wall-mounted EC & pH monitor

I have a 12-gallon (20-gallon arrives today) reservoir that the sensors stays in full time so I can look at the reservoir status at a glance.

Until your post above, I was doing the following:

• For my 5-gallon top-up, I would measure out how many grams (dry salts) for 5 gallons

• Then dissolve the A & B separately in a beaker in about 500ml of RO.

• After dissolved I would toss the two beakers into the reservoir with the agitator running

• This would spike the EC meter at (for example) 3.95 EC

• Then I would pump the reservoir with RO water until it came down to 2.1 EC (FloraFlex Veg)

• Then I would correct pH to 5.8 pH

If I am understanding you right, what I described above is "No Bueno?"

If so, I have no problem mixing up the whole 5 gallons (4 gals in this case because of bucket size) separately and then adding it to the reservoir. Then use much less RO water to correct E.C in the reservoir.

Although, that sounds like the same thing in a way. However, I trust Dr. Bugbee and you if that's what he says.

Based on what I'm reading, you top off with very strong nutes and then bring it down to 2.1 by adding RO. Seeing that N, P, K, and Mn are absorbed by the plants very quickly, every time you add more nutes, you're upping the concentrations of those chemicals even though the plant has already taken them in. That can lead to imbalances in the plant. I don't know how much this plays out in the real world, though.

Have you seen any kind of nutrient issues?

Are growers getting tip burn and just not noting it? I've had a couple of grows where there's simply nothing but green, the only blemishes on the leaves being when I drop nute water on them.

I think that's when I started using the RO add back approach but it's one of many changes I've made so that could be just a coincidence.

That's part of the message in the Bugbee paper but there's a huge amount more in the paper, to be frank. Reading his comments about Si made me a convert, for example. Many little data points.

Re. allowing EC to drop — I had the mindset of "gotta keep EC up" and realized that was potentially wrong because it rested on the assumption that all chemicals would be removed at the same rate. Very wrong. The other piece of the puzzle for me is that the plants need nutes of a certain strength. Again, very wrong. Even if a res has "only" 50% of a given chemical, that's still a whole lotta that chemical left.

Those two documents provide a lot of good info.