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Fertilizer TDS Nutrition and Watering

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Candace

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I was very surprised that in another thread, Lance mentioned he fertilized in the 500 ppm range using R.O water. Although I'm happy with my plants growth and blooming, I'd like to hear more about this. I've been keeping my fertilizer in the 150-200 range for several years and have found this is the common range most people use. I've read and been told over the years that any higher than around 200 ppm will burn leaf tips in phrags and cause problems with root growth and a myriad of other negatives in paphs and other genera.

So, what is the ferlizer range you try to stay within? Why?
 

NYEric

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The TDS [total disolved solids] will not give you the amounts of fertilizing [salts] in the water. Most TDS are giving a measure of resistance.
 
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lothianjavert

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500 ppm may be high, but it is possible, depending on the ppm of the water, that much of it may not be fertilizer salts. TDS is "total dissolved solids" and includes fertilizer salts, as well as many others.

The water from our well is at about 150-200 ppm on its own. We need to do an analysis to figure out exatly what the dissovled solids are. However, our area is known for its iron concentration, so that is likely a large component.

I have NOT noticed any leaf tips browning or any other issues, and we have been watering and fertilizing with this water for 8 months now.

At our old house, we had an RO system hooked up, as even though we had "city water", the TDS were through the roof (800 ppm BEFORE fertilizer), and no matter what we did, the phrags especially were torched. The RO was a huge improvement.
 

Candace

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500ppm using R.O. water just seems very high to me from all the literature and what I've been "told" over the years. Oh, Lance...
 

gonewild

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Eric is right the testers read the resistance in the water.
Most chemicals used to make fertilizer mixes have a resistance when dissolved in water. When we talk about the ppm or tds or ec of the fertilizer solution we are talking about the amount of resistance in the solution.

Here is a "simplified" explanation of how the meter works:

The meter itself works just like a meter used by electricians to measure electric current it measures electricity in volts. Our water test meters simply use a mathematical formula to change the reading into something that relates to plants. The measurement is the same. But it would not make much sense to say how many volts is your fertilizer? 1 volt = 1 ec = 500 ppm

example

My fertilizer solution is "1 volt"
My fertilizer solution is "1 ec"
My fertilizer solution is "500 ppm"

Both the volt and ec are measures of electric current. We can't easily decide how many teaspoons of fertilizer to use per gallon of water with those measurements. How do we get 1 volt of fertilizer into that gallon of water?
But if see that 1 volt is the same as 500 ppm (parts per million) we can now use a physical tool to measure the fertilizer.

Sorry, it is not really simple and we must just accept that the meter works.
But meters need to be calibrated.
 

gonewild

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Candace said:
500ppm using R.O. water just seems very high to me from all the literature and what I've been "told" over the years. Oh, Lance...
This is what we will talk about. I want everyone to try to convince me I am wrong. Let's all learn together.

Start off with telling me (us) what literature you are going by.
What have you been told?

I'll tell you most articles are written by people who are quoting other people or other articles. We need to base our fertilizer knowledge on science and work done by horticulture experts, not persons passing on hearsay facts.

Rumors run wild. Someone figured out some particular orchid was sensitive to salt and now everyone is running around thinking you'll burn your orchids up if you fertilize them. A classic example of "Chicken Little".
 

gonewild

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Candace said:
I've read and been told over the years that any higher than around 200 ppm will burn leaf tips in phrags and cause problems with root growth and a myriad of other negatives in paphs and other genera.
Do we have some research that proves or even states that 200 ppm will burn leaf tips on phrags? Or is this just a number someone picked because they new it was safe?

Do we know if it is a high level of total salts that burns the leaf tips or is it one salt in particular that the plants are sensitive to?
 

gonewild

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lothianjavert said:
500 ppm may be high, but it is possible, depending on the ppm of the water, that much of it may not be fertilizer salts. TDS is "total dissolved solids" and includes fertilizer salts, as well as many others.
Correct, it depends on the water supply. But when I refer to 500 ppm fertilizer solution that includes any salts from the water source. in my case I'm getting 18 ppm from my RO water source.

The water from our well is at about 150-200 ppm on its own. We need to do an analysis to figure out exatly what the dissovled solids are. However, our area is known for its iron concentration, so that is likely a large component.
Yes and you need to know what form the iron is in. Excess minerals can cause problems with other minerals. Nutrient requirements of plants are not simple and an excess of one mineral may mean a deficiency of another and vice versa, a deficiency on one mineral may make excess of another toxic.
It is all about balance.

I have NOT noticed any leaf tips browning or any other issues, and we have been watering and fertilizing with this water for 8 months now.
Do you know what the ppm of your fertilizer solution is? (fertilizer in well water)

At our old house, we had an RO system hooked up, as even though we had "city water", the TDS were through the roof (800 ppm BEFORE fertilizer), and no matter what we did, the phrags especially were torched. The RO was a huge improvement.
It would be interesting to know if it was the 800 ppm total that "torched" the phrags or was it an excess of certain minerals?
 

gonewild

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Calibrate your ppm tester:

Mix 1 gram of table salt in 500 ml of pure (distilled or RO) water.
Dissolve thouroghly.
test with your meter.
Your meter should read 2000ppm or a little more if you used RO water.

Now carefully measure out 250 ml of the salt water.
Mix it with 250 ml of pure water to have a 500 ml total.
Now your meter should measure this as 1000 ppm.

Now carefully measure out 250 ml of the last salt water.
Mix it with 250 ml of pure water to have a 500 ml total.
Now your meter should measure this as 500 ppm.

Now carefully measure out 250 ml of the last salt water.
Mix it with 250 ml of pure water to have a 500 ml total.
Now your meter should measure this as 250 ppm.

Now carefully measure out 250 ml of the last salt water.
Mix it with 250 ml of pure water to have a 500 ml total.
Now your meter should measure this as 125 ppm.

Keep doing this as long as it remains fun. But you cant go past 0 ppm :poke:

If your meter is accurate it should read the ppm for the concentrations above. If it is close but not exact don't worry.
 

gonewild

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I think the biggest misconception here is the measurement between total ppm and ppm of the nitrogen.

We'll use Rays recommendation of a constant feed of 125 ppm. That is meant to supply 125 ppm of actual nitrogen. To do this you end up with a much higher reading of the irrigation water because of the other minerals (salts) dissolved in the solution. You can't have a total ppm level of 150 and have 125 ppm of it being nitrogen. That is unless you are using a fertilizer that contains basically only Nitrogen.
 
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lothianjavert

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With the water at the old house, the water source was from the Susquehanna River at the head of the Chesapeake Bay-- so you had not only some salinity from the bay itself, depending on tide and water levels, you also had an incredible amount of agricultural runoff. The local treatment plants do not operate on RO, so all salts generally stayed. Water was clarified (particulates were filtered out and allowed to "settle", and chlorine was added, as well as a solution to raise the pH and buffer the water.

Hence, even w/o adding fertilizer, you already have a concentration of the salts, plus any resident salts from the bay. You know it's bad when at times the local newspaper advises those that need to watch their salt intake not to drink the water.

I do need to know what the iron content of the current water is, and in what form-- I understand that it's all about balance. Same thing w/ human nutrition. i.e. Vit. D is needed for calcium absorption, etc.

It'll either be sending away, or I'll check and see if my uncle can do it for me at his city's water plant, as they have a full lab there.
 

gonewild

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lothianjavert said:
With the water at the old house, the water source was from the Susquehanna River at the head of the Chesapeake Bay-- so you had not only some salinity from the bay itself, depending on tide and water levels, you also had an incredible amount of agricultural runoff. The local treatment plants do not operate on RO, so all salts generally stayed. Water was clarified (particulates were filtered out and allowed to "settle", and chlorine was added, as well as a solution to raise the pH and buffer the water.

Hence, even w/o adding fertilizer, you already have a concentration of the salts, plus any resident salts from the bay. You know it's bad when at times the local newspaper advises those that need to watch their salt intake not to drink the water.

I do need to know what the iron content of the current water is, and in what form-- I understand that it's all about balance. Same thing w/ human nutrition. i.e. Vit. D is needed for calcium absorption, etc.

It'll either be sending away, or I'll check and see if my uncle can do it for me at his city's water plant, as they have a full lab there.
Then the problem you had at the old place with your phrags being "torched" was probably due to a high sodium content level rather than the total tds in general.

So what I suggest is that maybe 800 ppm should not be assumed to be toxic just because it is a big number compared to 150 ppm.
 

Candace

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O.K. so how do we figure out what ppm of nitrogen we are using? I may indeed be underfertilizing as I've just added enough of whatever fertilizer I'm using to around 150-175 ppm. with my meter.
 

gonewild

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Candace said:
O.K. so how do we figure out what ppm of nitrogen we are using? I may indeed be underfertilizing as I've just added enough of whatever fertilizer I'm using to around 150-175 ppm. with my meter.
Read the label on the fertilizer. If it says it has 20% nitrogen then approximately 20% of the "salts" you are adding are pure nitrogen.
 

gonewild

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gonewild said:
Read the label on the fertilizer. If it says it has 20% nitrogen then approximately 20% of the "salts" you are adding are pure nitrogen.

Let me explain by example...

Fertilizer labels are as important to plants as food labels are to people.

If you start with RO water at 0 ppm and add enough fertilizer to make it read 150 ppm your total ppm is 150.

Now look at the contents of your fertilizer. If it is 20% nitrogen then 20% of your 150 ppm's is elemental nitrogen. When you do the math:

150 ppm x 20% = 30 ppm of nitrogen.

If you want to have 150 ppm of nitrogen in your irrigation water you need to add 5 times more fertilizer.

30 ppm nitrogen x 5 = 150 ppm of nitrogen.

This will make your fertilizer solution about 750 ppm.

This is an example only and not a recommendation. There are other factors involved depending on what else your fertilizer contains.
 

Candace

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Thanks for the explanation, Lance. By the looks of it, I've been underutilizing my fertilizers. If I like what I'm getting now, I'm hopeful I'll see even more growth and blooms if I up it a little. :drool: I'm going to increase it slowly and see what, if any results I see. And I'm going to use my MSU more regularly so I won't have to worry about any ph mishaps.
 
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